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recent engine build results could interest to some of you


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#1 grumpyvette

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Posted 10 January 2004 - 12:40 PM

SBC 407
· Block, 509, +30, Zero deck, Blanked water passages, Clearanced oil ways, Lifter valley vents, ARP main & head studs, Durabond cam & Clevite 77 main bearings.
· Crank, Scat 4340 forged steel, 3.75”, internal balance, Pioneer SFI balancer + ARP bolt.
· Rods, Comp. Products 6.00” H beam bronze bushed + ARP bolts Clevite 77 bearings.
· Pistons, SRP #4032 flat top, 5cc relief, Speed Pro plasma moly file fit rings.
· Complete rotating assembly balanced. Including - Flywheel, Clutch, Balancer & Crank pulley.
· Heads, AFR 210 Race Ready, 76cc, 2.080/1.600 valves, drilled for steam. FelPro #1014 gasket.
· Cam, Comp. Cams ‘Magnum’ #12-450-8 (286HR) Hydraulic roller.
230/230 @ .050, .377 lift 110 LSA 106 ICL.
· Pushrods, Howards Cams heavy wall 5/16” 7.4” long.
· Rockers, Pro Magnum roller, 1.6, 7/16” stud.
· Lifters, Pro Magnum hydraulic roller. AFR Hydr-Rev kit.
· Comp Cams Springs #950 + #740 retainers installed at 1.875”
· AFR rev kit, AFR stud girdle.
· Lube, Melling M99HVS pump, Canton 7qt 5 trap pan with inbuilt windage and scraper, Cooler, Accumulator, oil stat, remote filter.
· Holley 800cfm #4780C, 1” spacer, Victor Jr single plane.
· Static CR 10.32, Dynamic CR 7.9.
· Quench 0.0415” (Gasket .039” + .0025” down hole).
· MSD Pro Billet Street Dizzy, MSD 6AL, MSD Blaster 2 coil, MSD 8,5mm leads.

After several pulls followed by adjustment and re-jetting we arrived at:-

RPM BHP Torque
3800 367.3 507.7
3900 384.0 517.1
4000 395.1 518.8
4100 407.9 522.5
4200 418.9 523.8
4300 429.4 524.5
4400 439.6 524.7
4500 449.6 524.7
4600 462.1 527.6
4700 467.4 522.3
4800 476.6 521.5
4900 485.4 520.3
5000 489.2 513.9
5100 498.5 513.4
5200 496.0 501.0
5300 506.1 501.5
5400 508.4 494.5
5500 508.7 485.8
5600 505.6 474.2
5700 505.8 466.0
5800 505.8 458.0
5900 494.6 440.3
6000 491.9 430.6

its not my engine but I thought you guys would like the combo and results info

notice that hes not running a huge cam, or crazy high compression, or extreme lift, but he is running a good set of high flow heads and a well matched combo like the last post I had suggests with a dynamic compression ratio close to 8:1 and the cams durration matches the rpm range, damn similar to the cam Im running, (but closer LSA since hes running a carb not EFI )
Id like to point out something here!
LOOK CLOSELY AT THE TORQUE CURVE


RPM BHP Torque
3800 367.3 507.7
3900 384.0 517.1
4000 395.1 518.8
4100 407.9 522.5
4200 418.9 523.8
4300 429.4 524.5
4400 439.6 524.7
4500 449.6 524.7
4600 462.1 527.6
4700 467.4 522.3
4800 476.6 521.5
4900 485.4 520.3
5000 489.2 513.9
5100 498.5 513.4
5200 496.0 501.0
5300 506.1 501.5
5400 508.4 494.5
5500 508.7 485.8
5600 505.6 474.2
5700 505.8 466.0
5800 505.8 458.0
5900 494.6 440.3
6000 491.9 430.6

Id like to point out something here to those of you who keep insisting that your required to run small ports sizes and dual plane intakes to make decent mid range torque
look closely at what the combo uses


Heads, AFR 210 Race Ready, 76cc, 2.080/1.600 valves, drilled for steam. FelPro #1014 gasket.
· Cam, Comp. Cams ‘Magnum’ #12-450-8 (286HR) Hydraulic roller.
230/230 @ .050, .377 lift 110 LSA 106 ICL.
Holley 800cfm #4780C, 1” spacer, Victor Jr single plane

[b] like IVE CONSTANTLY SAID, ITS THE CAM AND PROPERLY MATCHED COMPRESSION RATIO THAT HAS THE LARGEST EFFECT ON THE ENGINES TORQUE POTENTIAL, while its true that smaller ports can increase the volumetric efficiency at low rpms, they are not always required, and the tend to hurt the high rpm performance, you also don,t need a great deal of duration in the cam you pick,if the heads your useing flow decently, notice hes only running 230 @.050 lift
LARGE ports matched to the correct compression ratio and cam can make very good torque.
as always its the total combo OF PARTS and how the parts match the displacement and intended rpm range, NOT the result of a SINGLE PART choice!


" IF YOU CAN'T SMOKE THE TIRES FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!"

#2 Michael

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Posted 10 January 2004 - 08:34 PM

Grumpy,

I was wondering if you could please post an analogous set of specs for a 454. You've posted links to 454 builds in the past, but most were either 496 strokers, boat engines, had custom-ported stock-casting heads, or some combination of the above. There's also a list of "big block combos that work" over on Chevytalk, but those are almost all race motors. For instance, last year you (if I recall correctly) posted this:


Displacement: 468ci
Compression: 10.0:1 Static Comp.Ratio
Heads: World Products Merlin Iron, Oval Port Intakes
Intake Manifold: Weiand Team G
Carb: Demon 850cfm
Cam: Crane PN# 139651 Hydraulic Roller
Advertised Duration: 306/318 In/Ex
Duration @ .050": 244/256 In/Ex
Lift: .632"/.632" In/Ex
Lobe Separation Angle: 114

That's something to think about, but way too high-rpm-oriented for me.


Right now I'm looking at the following:

* stock 454 2-bolt block, bored 0.030", decked 0.022"
* stock 6.135" rods, resized, with ARP bolts
* Speed-Pro hypereutectic (cast) pistons, 0.090" dome
* stock 4.000" cast crank

With the machining to-date, with this combo the pistons stick out 0.001" above the deck. Compression ratio with 119cc chambers and 0.040" head gasket comes out to around 9.12:1.

The rotating/reciprocating assembly has been balanced with my damper, flywheel, and clutch. So that set of components is now fixed. I also have a Performer RPM (oval) intake, 4160-style 750 cfm carb, and an exhaust tract based on slightly modified Hooker block-hugger headers.

What I need to buy is: cam, lifters and the rest of the valvetrain, and the heads. I've run numerous simulations on Desktop Dyno, but I am profoundly disappointed with the program's assumptions and results. So I would rather rely on the advice of experience.

My current cam choice is something like the following (custom grind, hydraulic roller): 0.557"/0.557" lift, 227 deg exhaust, 221 deg intake (at 0.050"). The purpose of the roller cam is to avoid lobe-wiping - that's what killed my original engine 3 years ago. I would certainly be open to the idea of a mechanical roller, if I could find a cam small enough for my application. And that is, diesel-like torque below 3000 rpm and a never-exceed rpm of around 5200 (I hate high rpm!). Yes, I'm aware that this is too conservative in terms of piston speed limitations, but I drive like an old farmer.

Thanks.

#3 Kevin Shasteen

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Posted 11 January 2004 - 10:33 AM

Your small oval "Truck/Peanut" port cyl.heads are perfect performers as long as you dont wish to exceed the 5k rpms.

Not knowing your Piston Compression Height or your Total Chamber Volume cc's everything here on out is just an assumption.

Let us say your Total Chamber Volume cc's amounted to 130cc.

Since you mentioned earlier this is a 454 .030 over then we are looking at a 460 BBC.

Take your 460 / 8 cylinders

460 / 8 = 57.5 cu. in

Now multiply this by 16.387 to get cylinder displacement in cc's

57.5 x 16.387 = 942.25 cc

Now, back to your assumed 130 cc Total Chamber Volume.

Let us say you want your Dynamic Compresion Ratio to be 8.0:1; what you do is deduct 1 full unit of compression from the 8.0:1 and then multiply that by your Total Chamber Volume...like so:

130 x (8.0 - 1.0 ) = 910 cc

This will represent your Cylinder Displacement after the IVC has taken place. The next step would be to convert your Cyl.Displ. after IVC to a lobe duration. We do this by dividing your Cyl.Displ. after IVC by your actual Cylinder Displacement of 942.25

910 / 942.25 = .965

If you look at a Crank Angle Chart for a 454 w/stock 4" stroke and stock Piston Compression Height-you will see that the .965 corresponds to a cam lobe duration of only 26* IVC ABDC.

This is not a performance cam in anyway shape or form: and a cam I hope you wouldnt want. I think the cam you are looking at would be perfect for low rpm tq-hopefully someone else w/more experience in BBC's will chime in.

What most folks miss is that as cylinder displacement increases so too does that engine's ability to utilize a cam w/a longer duration w/out harmful side effects....hence the ole saying, "There's no replacement for displacment".

I would say your secret to power, regardless of rpm range, is in the cylinder head. So if you want power down low, make sure your cyl.head's intake ports are upper middle of the road but not quite in the "Street/Strip" range as far as port sizing goes. This will compliment your 9.12:1 SCR.

BBC Cyl.Head Port sizes:
1) Small = 225-295cc
2) Medium = 295-325cc
3) Large = 325-460cc...and on

You will also want your Intake Manifold Port's Cross Sectional Volume to be slightly less than your Cyl.Head Port's Cross Sectional Volume as this will ensure high airflow velocity at lower rpms which equates to peak torque in the 2500-3500 rpm range.

Make sure your cam's LSA (Lobe Separation Angle) resembles that of a Tow Truck....hence, you need to keep the Overlap to a minimum. This also ensures high cyl.pressure at lower rpms as a minimal of Cyl.Press. bleed off occurs, of which also equates to peak tq/hp at lower rpm's.

Controlling Airflow Velocity is the key to knowing where in the RPM range your tq/hp will surface and understanding how Displacement effects airflow velocity is the key to hitting your projected taget in the bulls-eye.

Hoped my .02c's worth helped....I still think someone more familiar w/BBC's needs to chime in.

Kevin,
(Yea,Still an Inliner)

#4 grumpyvette

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Posted 11 January 2004 - 12:32 PM

"Right now I'm looking at the following:

* stock 454 2-bolt block, bored 0.030", decked 0.022"
* stock 6.135" rods, resized, with ARP bolts
* Speed-Pro hypereutectic (cast) pistons, 0.090" dome
* stock 4.000" cast crank

With the machining to-date, with this combo the pistons stick out 0.001" above the deck. Compression ratio with 119cc chambers and 0.040" head gasket comes out to around 9.12:1.

The rotating/reciprocating assembly has been balanced with my damper, flywheel, and clutch. So that set of components is now fixed. I also have a Performer RPM (oval) intake, 4160-style 750 cfm carb, and an exhaust tract based on slightly modified Hooker block-hugger headers.

What I need to buy is: cam, lifters and the rest of the valvetrain, and the heads. I've run numerous simulations on Desktop Dyno, but I am profoundly disappointed with the program's assumptions and results. So I would rather rely on the advice of experience.

software is only good for trends, it falls short on predicting exact hp/tq altho it can give you a good ballpark in some cases

My current cam choice is something like the following (custom grind, hydraulic roller): 0.557"/0.557" lift, 227 deg exhaust, 221 deg intake (at 0.050"). The purpose of the roller cam is to avoid lobe-wiping - that's what killed my original engine 3 years ago. I would certainly be open to the idea of a mechanical roller, if I could find a cam small enough for my application. And that is, diesel-like torque below 3000 rpm

you need to realize that diesel engines normally run much higher compression ratios than gas engines,....torque is the result of a combo of the expansion ratio, cylinder pressure,surface area on the pistons and leverage due to crank stroke and rod length geometry, plus the volumetric efficiency and number of cylinders PLUS THE NUMBER OF POWER STROKES PER SECOND
your NEVER GOING TO GET DIESEL LIKE TORQUE AT COMPAREABLE RPM LEVELS BECAUSE YOUR LACKING A GREAT DEAL OF CYLINDER PRESSURE POTENTIAL in a gas ENGINE combo

Ill post a combo useing your base parts shortly

" IF YOU CAN'T SMOKE THE TIRES FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!"

#5 grumpyvette

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Posted 11 January 2004 - 01:39 PM

have a long talk with both BRODIX and CRANE before buying parts



http://www.paceparts...39&1=242&3=1215
first look this over, IVE HIGHLIGHTED A FEW THINGS IN THE DESCRIPTION
Detailed Description
The 454 HO offers tremendous value in a big block crate engine. Based on the GenVI block, this 425 horsepower iron head engine is a great choice for that muscle car in the garage. We've heard of several of our customers replacing their rare matching number 396, 427 or 454 with our 454 HO in order to drive their car on today's gasoline without fear of destroying their classic engine. The HO stands for high output, it also stands for big valves, rectangular ports, forged pistons, forged steel crankshaft, forged connecting rods and four bolt mains. Sounds a lot like the performance big blocks of the late 60's doesn't it ? When you add in the steel roller camshaft, shotpeened rods, windage tray, one piece rear main seal and high speed single roller timing chain, it sounds more like the performance big block of the 90's. And it is ! The 454 HO makes 500 Ft/Lbs of torque with its rectangular port open chamber cylinder heads. With 118cc combustion chambers, the modest 8.75 to 1 compression ratio loves today's pump premium and has no appetite for lead, octane boosters or other fuel additives. Its 2.19" intake and 1.88" exhaust valves and high lift .510"/.540" roller cam let it breath with the best of the early muscle car motors.With your carburetor, HEI distributor, exhaust system and bright red '67 Corvette coupe (sold separately 31 years ago), you've got a muscle cruiser worthy of your time, effort and expertise. And, if you want to use your muscle car's fuel system with a mechanical fuel pump, you can because the 454 HO GenVI block has a conventional style fuel pump boss.The 454 HO is not intended for marine use, and should only be used in 1973 and earlier pre-emissions street vehicles or any year off road vehicles.Technical Note: For manual transmission applications use flywheel #14096987 and a suitable 11" clutch assembly.


now we can use your slightly higher 9:1 compression or better yet boost it to 10:1 with small chamber aluminum heads and more efficient oval port intake matched to those oval port heads to beat those figures with the correct cam choice. I think Id be looking at a set of small brodix oval port heads with 105cc chambers(CHECK TO MAKE SURE THEY WORK WITH YOUR PISTONS)

http://www.brodix.co...-2/page1-2.html
• Chambers Offered as Small as 100 cc

Posted Image

id pick a crane hydrolic roller cam #139731

http://dab7.cranecam...B1=Display Card

add your intake and carb and you should have close to the results your looking for( my software and some prior experiance says youll be closer to 550 ft/lbs than the 500ft lbs the stock engine makes with the increase in compression and better head flow

[b] have a long talk with both BRODIX and CRANE before buying parts

" IF YOU CAN'T SMOKE THE TIRES FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!"

#6 Michael

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Posted 11 January 2004 - 07:16 PM

Grumpy –
Thanks for the advice.

One issue that comes to mind is the tradeoff between better-flowing heads and a smaller cam, vs. worse-flowing heads and a larger cam – assuming comparable port volume and flow path geometry in all cases. The advantage of the former, in my view, is the more benign valvetrain dynamics. Also, as the instantaneous valve curtain area starts to approach the size of the port cross sectional area, flow rate begins to really taper off, in which case the difference between static (flow bench) and unsteady (in the actual engine) flow data gets even larger than “usual”. So, what I’m really asking is, why the recommendation for Brodix heads, which have among the worst flow bench data on the market, and a relatively large cam (0.610” lift)?

BTW, my comment about diesels was mostly figurative, to stretch the point that my preferences lean toward the absolute opposite of those who need or want an engine build that emphasizes high-rpm hp over a narrow rpm band.


Kevin –

I do value your contribution to the discussion, but would like to mention that elementary arithmetic isn’t always the best avenue of advice. There is a tremendous difference between theory and practice. Lack of a firm footing in the workshop – that is, the practical experience – does not imply naivete in basic engine theory. Practical choices for what to buy are especially difficult in today’s market, where so many similarly-spec’d and similarly priced products are available, and every manufacturer makes great effort to tout his product as superior. And as Grumpy noted, amateur software simulations and paperback textbook rules-of-thumb have their limitations. Two-phase viscous compressible flow with unsteady boundary conditions and curvature that makes the quasi-one-dimensional assumption inappropriate is, I think, a complex enough problem that even good familiarity with the theory is of minor help with making practical choices. So, I am looking to duplicate, as far as feasible, an existing engine build.

Those peanut port heads, by the way, are history - they got cracked during the process of pressing in new valve guides.

#7 Kevin Shasteen

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Posted 12 January 2004 - 10:35 AM

.., BTW, my comment about diesels was mostly figurative, to stretch the point that my preferences lean toward the absolute opposite of those who need or want an engine build that emphasizes high-rpm hp over a narrow rpm band..,

I think, a complex enough problem that even good familiarity with the theory is of minor help with making practical choices. So, I am looking to duplicate, as far as feasible, an existing engine build.

Those peanut port heads, by the way, are history - they got cracked during the process of pressing in new valve guides.


Michael,

Multiple things to think about here; for starters Complex issues upon first glance appear to be chaotic, yet as Chaos Theory has taught for ages-out of chaos recognizeable patterns will emerge.

A Diesel's torque is not solely determined by its Static Comp.Ratio. If you have ever had a diesel's cyl.head off and noted the size of it's intake port then you will have witnessed why most diesels come on the cam early in the rpm range. A daily driven gas engine, w/acception to the diesel's higher SCR, can mimic the early rpm peak power.

Forgive me for not homing in on my initial post's point earlier: BTW-the math was simple upto the point where the "Cyl.Volume after IVC" number was transformed into a "Cam Duration Spec" ...this is not simple as it involves a Crank Angle Chart. So IMHO either you understood this and are smarter than the average bear or you misunderstood it all together. The fact that you are asking for assistance in purchasing these engine components tells me you dont understand airflow velocity.

I'm only going to such efforts here so that when you do speak to a tech line, which grumpy suggested-and was correct in doing so, you will be a more educated consumer and wont have to rely entirely on someone else's opinion/suggestion. Afterall, being an educated consumer is where the fun really begins.

Because I understand the confusion that comes w/purchasing cyl.heads and cam's, allow me to babble for awhile. As stated earlier-out of chaos recongnizeable patters will emerge. This begs the question, "what recognizeable patters are there in engine building?" After all, why are you looking at an engine sim if you are not also trying to recognize patters? Why have you gone to such efforts to calculate your Static Comp.Ratio yet you dont even have a set of Cyl.Heads nor a Camshaft? These patterns in your approach express to me that your confusion lies in your inability to understand how to manipulate Airflow Velocity to your satisfaction. So, having a basic understanding of Airflow Velocity is the first step.

BTW: I too agree that engine sims, especially the cheaper ones, are not acurate enough....this is why I dont use them. When utilizing calculations it is always helpful to know what calc's are useful -vs- useless: true none are absolute yet some are close enough to almost being absolute. I have found the trick to being accurate is to mimic the calc's of the experts. David Vizard, Peter Burgess, and David Gollan and a few others offer excellant calc's for a theorized paper engine. Just like you wanting to copy a known BBC engine build so too will I copy the experts known calc's.

When attempting to understand the airflow velocity in your engine the first step is to recognize that your peak power numbers will continue to rise or fall in the rpm range based on the point in time that your airflow goes supersonic....the sound barrier. This also begs asking, "How do you go about manipulating the point where your airflow goes supersonic?"

You or I, or anyone building an engine, will be designing this "Supersonic" limitation into our engine out of knowledge or out of ignorance: I always choose to do so out of knowledge (educated consumer). This limitation is know as the "Limiting Port Volume". Grasping these points of interest are mandatory if you wish to make the correct decisions in component purchasing, and they are:

1) Optimum Airflow Velocity equals Optimum Cylinder Filling
2) Excessive Airflow beyond what your Cyl.Heads can Flow equal Supersonic airspeeds.
3) When the Sound Barrier, 1200 feet per sec, clashes w/the thermodynamics of an auto engine, said sound barrier occurs at .55 to .60 of the spped of sound.

So, again, what causes airflow to go supersonic and how do you control it? A lot, but I'll attempt to keep a complex issues simple. Remember, your intent for your engine is to have your power peaking at or just prior to the 5000 rpm range.

The size of the Cyl. Head's Intake Port, directly adjacent to the push rod tunnel, is the port that determines what your engine's peak rpm will be just prior to your airflow velocity going supersonic: one of the calc's for determining this Limiting Port Volume's peak rpm is:

LPV = (.00353 x RPM x S x B^2) / CA

LPV = Limiting Port Volume
RPM = Revs Per Minute...engine speed
S = Stroke
B = bore
CA = Minimum Cross Sectional Area...in sq. inches

CA = (RPM x S x B^2) / 190,000

Maximum HP RPM:

(CA x CONSTANT) / S x B^2

Constants:
1) 177,780...for Flat Tappet Cam
2) 184,136...for Endurance Race Roller Cam
3) 195,558...for Pro Stock Drag Race Endurance Roller Cam

This size of your Cyl.Head Port works in conjuction of your Port Volume, this was my purpose for initially giving you the Small, Medium, Large sizes of BBC ports in my first posting...for it is the size of your ports leading up to the cyl. for combustion that determines where in the RPM range your peak power will surface and if your engine will be peaky or broad. Your cam duration, LSA, and LCA assist in this factor but mostly these cam spec's decide the characteristics of your power band and not its intensity; your airflow velocity at a specific rpm decide the intensity of your cam spec's characteristics.

The LPV of factory BBC Cyl. Heads
1) Large Square Port = 2.5" x 1.75" = 4.375 sq.inches
2) Large Oval Port = 2" x 1.75" = 3.5 sq.inches
3) Small Oval Port = 1.5625" x 1.4375" = 2.2 sq.inches
4) Symmetrical Port Bow Tie Head = 2.59" x 1.74" = 4.5 sq.inches

*Now these only represent factory BBC port volumes and not the Aftermarket.

So, if all these theory calc's are just theory-then why do the mfg's go to such effort to offer Cyl.Head's w/different Port sizes? This is the first step into recognizing an Airflow Velocity Pattern.

Your Intake Manifold's Port Cross Sectional Volume needs to be .80 of your LPV of your Cyl.Head's Intake Port Cross Sectional Volume for good Airflow Velocity on a NA Steet Engine, and .90-.95 for a Dedicated Racer.

To obtain your 5000 rpm Peak Power we need to know our LPV. Since we dont know this figur yet we will have to calculate our CA first then use that data to calcualte our LPV, such as:

CA = (RPM x S x B^2) / 190,000
CA = (5000 x 4" x 4.281"^2) / 190,000
CA = 366539.22 / 190,000
CA = 1.93 sq.inches

Now input this 1.93 into the LPV forumula to ensure that this figure will place your Airflow Velocity into the "Supersonic" arena for your 5000 required peak power rpm.

LPV = (.00353 x RPM x S x B^2) / CA
LPV = (.00353 x 5000 x 4" x 4.281"^2) / 1.93 sq.inches
LPV = 1256.08 / 1.93
LPV = 650.82 fps

The Sound Barrier is 1200 fps, so divide this into your LPV:

650.82 / 1200 = .54 percentage...slightly under the .55 preferred range.

Another point is that you probably will not find a BBC cylinder head w/an CA of 1.93". This is why you will need to increase your Static Compression Ratio to the 10.0:1 range as this will increase the port aifrlow velocity and ensure said airflow velocity reaches supersonic prior to/just at your 5000 required rpm range.

To ensure that your cam doesnt bleed too much cyl.pressure off you will want a cam whose overlap "LSA" is minimal. If your cam duration bleeds to much Cyl.Pressure then you will have delayed your Airflow Velocity from going Supersonic and as a result your peak power now supercedes the 5000 rpm range...and if you really choos your cam wrong-your desired 5000 rpm peak power will turn into 6000 rpm peak power. WHY WOULD YOU DO THIS IF YOU NEVER PLAN ON GOING BEYOND 5000 rpms?

As stated earlier, we all design this "Supersonc" barrier into our engines..some of us do it out of knowledge while most of us do it out of ignorance.

Common Overlap -vs- Peak Power Max rpms are:
1) 10*-35* = overlap for Acceptable Mileage/Tow Truck
2) 30*-55* = overlap for Daily Driver, good low rpm power
3) 50*-75* = overlap for Hot Street Performance
4) 70*-95* = overlap for Oval Track Performance
5) 90*-115* = overlap for Dragster/Comp.Eliminator Engines

If you truly want peak power by 5000 rpm's then you must get a cam whose overlap ensures this peak power rpm range. Do you know what your cam's overlap is? If you dont know it then you need to. Otherwise you are probably pushing your peak power rpm beyond 5000...which is something you dont want to do.

You also need this camshaft's duration to allow atleast .80 of Cyl.Volume Remaining after the Intake Valve Closing (IVC)...enters the Crank Angle Chart. In order to obtain 80% Cyl.Vol. after the IVC you will need a cam whose IVC occurs in the 60-65* ABDC....couple this with the overlap between 10*-55* range.

You, as an engine builder, will move this "Supersonic" wall lower in the rpm range when your build your engine such that port pressure is increased and Cyl.Bleeding is minimized; whereas the opposite effect occurs-in that you will move this supersonic wall higher in the rpm range when you build your engine such that port pressure is minimized at lower rpms combined w/excessive Cyl.Bleeding.

Do you have Ed Staffle's book on Modifying BBC's? You should get it-he also talks about the DCR and SCR issues: this will shed immense light on how you should go about building an engine for any desired rpm peak power.

Hope this helped you to make a more educated decision. Good luck-hope you get what you need.

Kevin,
(Yea,Still an Inliner)

#8 ToplessZ

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Posted 12 January 2004 - 12:02 PM

I like the math. :)
~Dream huge and you'll finish big...~

#9 Michael

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Posted 12 January 2004 - 11:37 PM

Kevin -

Quote: “...not so simple as it involves a Crank Angle Chart.”

Actually, this is pretty simple – it’s just the crank-slider model. Sophomore engineering Dynamics class.

Quote: “ ...peak power numbers will continue to rise or fall in the rpm range based on the point in time that your airflow goes supersonic.”

This is not true. The airflow in the intake tract is NEVER supersonic. With a large enough pressure difference (around 8 psi at standard atmospheric conditions, for isentropic expansion; you’ll need an ever larger pressure difference for the real-life conditions) the flow will be choked (sonic) at worse. For it to actually go supersonic, a converging-diverging nozzle is necessary.

Careful flow measurements in actual running engines have shown that the maximum instantaneous velocity attainable inside the intake port is limited to a Mach number of around 0.5. Jim McFarland’s articles (“Performance Professor” on the web, former Hot Rod contributor) point out that about 240 ft/s (about 0.2 M) MEAN flow rate is a good practical upper bound for flow rate at the peak torque (peak volumetric efficiency) point.

Heat addition (which happens as the flow goes toward the combustion chamber) does result in an acceleration. Total (stagnation) temperature is increased, which for a calorically perfect gas in subsonic conditions will tend to drive the mean flow toward sonic. Of course, an air-fuel mixture (with trace water vapor and combustion products from reversion into the intake) is not a calorically perfect gas, so the equations of motion have to be integrated numerically to arrive at the “proper” result (simply put, the constitutive equation for anything but a calorically perfect gas is too complex).

The full answer comes from integration of the Navier-Stokes equations – for multiple species, with the “appropriate” turbulence model, and proper description of inflow and outflow boundary conditions. Specific models have been developed for internal flows, but they’re basically just educated guesswork. Commercial CFD houses such as Fluent will sell you a software package that attempts to calculate this, but it’s still largely voodoo mathematics – which they will themselves admit.

Characteristics (infinitesimally weak rarefaction and compression waves) move at the local drift velocity, plus or minus the speed of sound. So in a coordinate frame relative to the local drift, they are actually sonic. It is management of the characteristics – understanding their geometry in an x-t diagram – that’s responsible for phenomena like ram tuning – but that’s another topic.

Quote: “3) When the sound barrier... occurs at 0.55 to 0.60 of the speed of sound”.

The statements about sound barrier are not accurate, but you’re right that the practical “speed limit” inside a port is around 0.5 of the local speed of sound.

Quote: “LPV = (0.0353 x RPM x S x B^2)/CA”

Well, if CA is an area, then the units for LPV come out to velocity, not volume.

Quote: “Your intake manifold’s cross sectional volume needs to be 0.80 of your LPV of your cylinder head’s intake port cross sectional volume...”

“Cross sectional volume”? Perhaps you really meant “cross sectional area”?

Quote: “CA = ... = 1.93 sq. inches”

Using your formula, the units for CA now come out to a length cubed per unit time – in other words, a volumetric flow rate – and NOT an area.

However, consider the following: we want to relate the engine’s airflow needs to port cross sectional area and port averaged velocity, right? The engine ingests air only when the intake valve is open. Since we’re talking about port velocity and port area, and have left the valve curtain area outside of the discussion, we need to make some assumptions. Ideally we would calculate the area under the curve for the valve opening event (if we had data from the cam manufacturers on valve opening amount vs. cam angle, and typically we don’t). That area is conceptually equivalent to holding the valve open at a larger, constant lift, but over a much shorter duration. That larger lift would give a valve curtain area larger than the port cross sectional area. Calculating the right equivalent duration is difficult, because it’s not enough to consider steady-state effects; we need to consider unsteady gasdynamics. But we’ll guesstimate. My guesstimate is an effective “duration”, for a street cam, of around 70 degrees, or roughly one fifth of a revolution. An experienced engine builder will have a more accurate guesstimate, taking into account precise details of the cam lobe shape! THIS IS PRECISELY WHERE EXPERIENCE IS SO IMPORTANT, and theory is insufficient!

Anyway, to continue – a V8 with 460 cubic inches at 5000 rpm (2500 intake strokes per minute) and 85% volumetric efficiency ingests about 1.18 cubic feet of air/fuel mixture per second. But our fictitious valve is only open for one fifth of a revolution per revolution, so that 1.18 cubic ft/s is equivalent to around 5.9 ft^3/s during the fictitious equivalent valve-open event. So let’s conserve mass: volumetric flow rate equals cross-sectional area times mean (integrated) velocity. A typical moderate oval-port head will have, as you point out, about 3.5 square-inch port cross sectional area. So we get 242 ft/s. That happens, by pure serendipity, to coincide with McFarland’s advice; meaning, if I want a torque peak at 5000 rpm, and IF my guesstimate for effective equivalent valve opening duration is any good, then the 3.5 square-inch ports are just right. But in all honesty, my guesstimate is too crude to be of direct practical use for head selection.

But the real lesson here is that the main limitation really isn’t dealing with too fast a flow speed through the intake port; it’s about keeping for flow velocity high enough. Low flow velocity leads to poor intake conditions in the combustion chamber, and poor VE. At low rpm, those heads give a really low intake velocity – at some point, too low of a velocity. But how low is too low? Ah, here again we need experience!

Also keep in mind that port shapes are different! A longer, more contorted port might have a higher port volume than a shorter, straighter port with a larger cross-sectional area. Port volume data, by itself, is not very useful. And unless you cut up a cylinder head on a band saw into sections, you really won’t know the internal port shape or the area at the narrowest point inside the port. Big block heads have larger port volumes that small blocks, only in part because they have larger port cross sections; they have much longer runner lengths, too.

#10 Kevin Shasteen

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Posted 13 January 2004 - 08:45 AM

.., Quote: “LPV = (0.0353 x RPM x S x B^2)/CA”

Well, if CA is an area, then the units for LPV come out to velocity, not volume.

Quote: “Your intake manifold’s cross sectional volume needs to be 0.80 of your LPV of your cylinder head’s intake port cross sectional volume...”

“Cross sectional volume”? Perhaps you really meant “cross sectional area”?

Quote: “CA = ... = 1.93 sq. inches”

Using your formula, the units for CA now come out to a length cubed per unit time – in other words, a volumetric flow rate – and NOT an area..,


Michael,

You are absolutely correct Michael. So, you are smarter than the average bear. Freudian slips....most folks dont understand that-you did understand so good for you.

Good points about the curtain area-I thought about mentioning this yet my previous posts were too long as it is. Also-most engine builders dont have as much of a grasp on Fluid Dynamics as you do. I have read at least a dozen or so times in my readings on camshafts/Compression Ratio's that most engine builders have experience in building engines-but their experience in choosing a camshaft are not based on theory but trial and error experience. So, in the theory area your understanding far outweighs most engine builder's knowledge in engine building...something for you to think about.

Even though the Crank Angle Charts are simple Soph/Junior HS Trig-connecting that principle into an engine and ensuring your Dynamic Comp.Ratio optimum Static Comp.Ratios compliment one another when it clashes w/your Airflow Velocity within the port is not always as simple...even though it uses simple math in a slightly more complex manner: which brings me to my next question:

"If everything is so clear to you then why are you asking for assistance on purchasing Cyl.Heads/Cam?" Keep in mind, this thread is not about who knows more than whom: it has turned into a quest for a Hybridz member who wishes their peak hp to occur prior to 5000rpm's.

I am just an auto math flunkie wannabe :wink: , yet I understand how to go about purchasing a set of Cyl.Heads or cam and how to make those components match the airflow velocity that brings about a peak rpm in the rpm range I want. So, I am lost as to why you would ask for assistance when your auto IQ far out weighs most of us here: including myself(?)

I still say you are making this way too complex: really Michael-you have everything you need to make your purchase-except confidence in yourself. Understanding what the experts have written in their books, including their formula(s) are very relevant. The experts theory, not mine, are very on point. If you want any engine to run in a particular rpm, then you have to know how to manipulate that airflow velocity in such a manner that accomplishes your goal. You do this by understanding Crank Angle/Cam Duration, Port Volume/Port Flow coupled w/your Dynamic CR/Static CR: it is a simple process if you look at each variable as individual variables...then you have to connect the dots.

Providing your Intake nor your Exhaust are the limitations in Airflow Velocity and your Valve/Curtin area are the only limitations in airflow: then your 5000rpm max can be achieved by building your engine with the following: Your cyl.heads need to be in the 240-280cc range, the port entry needs to not exceed the 2.5 sq.inches, your cam needs to not exceed the 60-70* IVC range, and your cam's overlap needs to not exceed the 55* overlap: and your cam needs to have an LSA of 112*-114* since you will require your peak hp to surface at the 5000rpm point...NOT 5200rpms nor 5300rpm's: but 5000 rpms. If you choose cast iron cyl.heads with the cam description given your Static CR needs to be around 8.5-9.0:1 and if you choose alluminum cyl.heads then bump your Static CR to the 9.5:1-10.0:1. I may not have hands on BBC exp but I do know what I have read and am very good at applying that knowledge....hence, I believe that you are making this waaaay to complex. No offense intended.

You have everything you need to make a purchase...so dont hesitate and dont doubt yourself. Are you doubting yourself due to lack of actual hands on exp in building engines or just a lack of useful data in approaching those purchases? I'm only asking because I dont know your situation. I have only built a dozen or so engines in my hobbyest lifetime-yet from my past experience and what I know now I would have to say you certainly have enough of the concepts of Airfow Velocity down to make a purchase?

FWIW-if your hesistation is due to lack of engine building-dont doubt yourself: you have more tools (mentally) than most of us ever had when we made our choices. Research as much as you can-but at some point....you have to turn your Theory into a little R&D/Test&Tune. Believe in yourself and make the purchase based on what you aleady know.

If you are looking for cyl.head flow numbers-have you checked out Stan Weiss's website?

http://users.erols.com/srweiss

He has most of the current flow numbers for newer and older cyl.heads: except for AFR's.

As a comfort zone: dont get hung up on thinking you have to get the "Perfect Cam". Camshapfts and Intake Manifolds are basically cheap in costs. Even the experts dont ever limit themselves to just one cam or just one intake. So, perhaps you might entertain experimenting w/two or three cams/intakes manifolds.

Good luck in finding what you want: let us know how it all turns out.

Kevin,
(Yea,Still an Inliner)

#11 grumpyvette

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Posted 13 January 2004 - 01:35 PM

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THIS 265cc oval port head WOULD WORK VERY WELL ON THAT 454
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the AFR bbc flow numbers you wanted
keep in mind you can,t use most of the potential if your only spining the 454 to 5000rpm, its kinda like hunting mice with 10 gauge slugs
" IF YOU CAN'T SMOKE THE TIRES FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!"

#12 Pyro

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Posted 14 January 2004 - 07:24 AM

Mike,
A little note on big block chevy cam wiping.

My 454 was doing the same thing. And I did the same fix as you are planning (roller cam). However, after reading a bunch of stuff and talking with some local speed machine shops I have come to the conclusion that Big Block chevys stuffer from "lifter bore alinement problems" and the cure is to re-bore the lifter bores and install sleaves which are bored into the correct position. This is a $450.00 job.

I think my engine has a very bad case of this. After eating 3 cams during the "break in" I finally went roller. However, the roller didn't solve a little lope/miss that the engine SHOULD NOT have. My cam is only a 208/214 duration H-roller so I expect a good idle. I think that some of the valve events are off because the alinement is so bad. ????

This is just my latest threoy. This engine has been killing me over the last 3 years! And this is the last thing to try and the promising thing is that an old speed shop guy thinks this could be the case. This shop even has a special machine to correct the problem! If you are interested in talking to him call Bill at 210-333-7150 (kendrick automotive, SA Texas).[/u]

#13 Kevin Shasteen

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Posted 17 February 2004 - 12:50 PM

.., LPV = (0.0353 x RPM x S x B^2)/CA.., we want to relate the engine’s airflow needs to port cross sectional area and port averaged velocity.., Since we’re talking about port velocity and port area, and have left the valve curtain area outside of the discussion..,


Michael,

I recently came across this site about the Valve Curtain Area.

http://rgmracing.free.fr/luc/heywood1/

It takes both the Valve Curtain Area and the Cam Angle into consideration and has some techincal math formulas. Thought you might be interested in it.....AND since you are much more adept at the technical math I was curious as to what you thought.

When this thread first took place I forgot about another math equation I had come across sometime ago. I forgot about it up until I came across this site. After my mind was jarred I searched till I found it. It addresses the same phenomenon as the formula listed at the top of your "Quote"; it is the formula that David Vizard gives for calculating the peak HP of a Cylinder Head by utilizing the Cyl.Head's Intake Port Area.

The formula I am about to give is similar in that it also addressed the Cyl.Head's Intake Port but instead of looking at the Intake Port adjacent to the push rods: this formula utilizes the Bottleneck in the port just before the top of the intake valve....the point where the Intake Valve Guide protrudes into the Intake Port just above the valve.

So basically it is looking at Port Limiting Velocity also; it is just doing so from the opposite end of the Port. This second formula also utilizes mm instead of sq.in.

The example offered is on a Ford 2000cc SOHC engine

V m/s = ((L x N) / 30000) x (D/d)^2))

V = Velocity m/sec
L = Piston Stroke mm
N = Engine Speed RPM's
D = Bore of Cyl mm
d = Port or Valve Throat Diam mm

[x] = ((76.95 x 5500) / 3000) x (90.8 / 38 )^2))
[x] = (42335 / 3000) x 2.389^2
[x] = 14.1075 x 5.707
[x] = 80.516 m/sec

Convert your m/sec to f/sec by the multiplying the appropriate constant of 3.2808399

80.516 x 3.2808399 = 264 f/sec :-D

Hope this offers some insight into the airflow velocity at the valve as it is tied into the Valve Curtain Area.

Kevin,
(Yea, Still an Inliner)




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