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Question re: AFR head selection.


Guest zfan

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I am looking at purchasing a set of AFR heads and have a couple of questions for those with experience.

 

I have a built 350 30 over 4 bolt with a set of edelbrock rpm heads on her.

I am looking at putting better heads on her, preferably AFR 195's or 210's.

My compression is 10.3 to 1 with 64cc chambers currently.

 

I have two hyd. roller cams to choose from. The one currently in the car is a extreme energy hyd. roller 224/230-502/510 with 110 lobe seperation 4 degrees advanced. I have a 236/242-520/540 extreme roller cam in my garage I can use.

 

What would be the smarter combo? My intake is a Weiand stealth and my exhaust is 1 5/8" hooker super comp long tubes with 2 1/2" exhaust.

 

Mike

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One thing that really irks me about AFR is that if you go with anything but a hydraulic FLAT TAPPET cam, you have to upgrade the springs. They won't sell you just the springs, you have to add another $300 or so for the upgraded valves as well. That gets PRICEY.

 

Consider the Canfields. The 195s (PN 23-500) would be a good choice, and they come with springs that work with most streetable hydraulic roller cams, and the valves are high quality Ferea pieces even on the entry level heads.

 

Call Dave at Thunder Racing PRODUCTS (not Thunder Racing - F-body guys) at 330-792-2451. He can get you a set cheaper than buying straight from Canfield. I paid $1190 for assembled 215cc heads.

 

As for the cam, I have the solid flat tappet version of that one you have (the 236/242 one) and it's works great in my 327. I'd use that one.

 

If anyone has a good place to buy hyd roller lifters (retro) that don't cost $400, I'd love to hear about it.

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Note that the Dart 220cc heads that grumpyvette pointed out need .150" offset intake rockers, so if you already have rockers, you'll be buying 8 new ones. Most 23 degree 220+ cc intake port SBC heads need offset rockers on the Intake. That was one reason I went with the new PN 23-550 215cc heads - no offset rockers needed, they use standard rockers. I have money invested in my Pro Magnum rockers that I didn't want to looe.

 

BTW, the Canfield heads come with guide plates, but no studs. That's fine, since you usually want 3/8 or 7/16" studs and you can just buy them separately and install easily (use sealer - the intake stud hole breaks into the intake port).

 

FWIW, the Canfields I bought flowed better than quoted on the intake side, at 292cfm@.500, and 297/298 from .600 to .800. Low lift flow was also excellent. The exhaust flowed worse than advertised, but a minor bowl cleanup made them flow quite well. For quoted, as-is tested and after-porting flow numbers, see below:

 

canf215flow_1_summary.gif

 

Of course, the quoted and tested results differ some due to the different cylinder diameters used on the flow bench (4.125 for the quoted, 4.25" for the tests I had run). Both the Alan at Burtonsville Performance Machine and Ken at Canfield feel that will have a minor effect, maybe 6-8 cfm.

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One of my main concerns with buying new heads is buying a set that are to big. 210's or 220's seem like alot for a 350 or even a 383.

 

Originally I thought about 195's but my mechanic friend said 210's on a 350/383 are the only way to go. I also would like to keep the compression up on my build so keeping 64cc 's in mind, I don't see where AFR offers anything under 68cc's.

 

Do the canfields and if they do are they cnc'd at all? Thanks to everyone for the help!

 

Mike

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it might help a great deal if you understand that runner length and cross section area have a great deal to do with where the cylinder fill efficiency works best in the engines rpm range, on a 350-383 engine that runner length measured from plenum to the back of the intake valve distance should be about 10"-12" and the cross sectional area should be about 2.3-2.7 sq inches, but remember the DYNAMIC compression ratio,cam timing,(LSA/OVERLAP)displacement, stroke,rod length and exhaust header design also must match that same peak effective level for the best potential power! making the runners longer or the runners smaller in cross section LOWERS THE TQ PEAK, making them slightly shorter or larger in cross setion tends to RAISE the torque peak RPM

the exhaust primairys should be at least 18" long and not more than about 32" long before entering the collector and 1.625-1.875 in dia. the collector should be about 15"-22" long and about 2.75 in dia.

 

you might want to play with these calculators

 

http://www.newcovenant.com/speedcrafter/calculators/runnerarea.htm

 

http://www.newcovenant.com/speedcrafter/calculators/intake.htm

 

http://www.newcovenant.com/speedcrafter/calculators/intakecfm.htm

 

http://www.rbracing-rsr.com/runnertorquecalc.html

 

http://www.newcovenant.com/speedcrafter/calculators/compressionratio.htm

 

http://www.nightrider.com/biketech/calc_exhaustlength.htm

 

http://www.btinternet.com/~mezporting/exhaust_length.html

 

http://cochise.uia.net/pkelley2/Overlap.html

 

http://cochise.uia.net/pkelley2/DynamicCR.html

 

http://www.engr.colostate.edu/~allan/fluids/page7/PipeLength/pipe.html

 

try for about 4500rpm-4800 torque peak, a 7.8-8.2 dcr, and

 

these are the valve timeing overlap ranges that are most likely to work correctly

trucks/good mileage towing 10-35 degs overlap

daily driven low rpm performance 30-55degs overlap hot street performance 50-75 degs overlap oval track racing 70-95degs overlap dragster/comp eliminator engines 90-115 degs overlap

but all engines will need the correct matching dcr for those overlap figures to correctly scavage the cylinders in the rpm ranges that apply to each engines use range

 

for a 383 street strip engine that will be about a 210cc head,but the flow of the 190cc-195cc heads is close enought that the only real differance will be a slightly lower rpm range for the torque and power peak. a tunnel ram or stealth ram intake and about 11.1 CPR and a cam in the 240@.050-250@.050 intake duration range with about .600 lift and a 108-110 lsa as a good compromise for max hp but a slightly milder 230-240 duration @.050 lift and a slightly wider LSA in the 112-114 range will make the car much easier to drive, increase the torque rpm band significantly and only reduce peak hp slightly

look at this dyno chart, its a 350 with a crower #00471 cam , it makes 530ft lbs of tq and would make 450hp easily if it did not have a restrictive exhaust

 

torque.jpg

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Mike,

 

One thing your mechanic possibly has considered, that you may/may not have, is that the engine is going into a very light car (assuming your Z, yes/no?).

 

As a result, using your 210/220cc Ports in a hot street engine in a light car, you would delay the excessive power/weight factor by pushing the peak tq/hp up the rpm range, and this in turn would fudge your light Zcar's desire to spin the tires as airflow velocity in the cylinder heads will be minimal up to the point veh.speed is sufficient to support the peak tq/hp of your engine: did that make sence at all(?). Another thing, touched on in the previous posts above, is not to get to caught up in how large a port is-rather how much CFM that port flows at .010 lift increments.

 

Providing your DCR (Dynamic Comp.Ratio) is properly matched to your SCR (Static Comp.Ratio) then your larger ported heads would not be that detrimental to your engine's airflow velocity in a light Z-car's traction limited state at lower rpm's: instead it would actually compliment your package.

 

Are you familiar w/this process of matching your SCR to your DCR? Do you need help in making these choices(?), as all you have to do is ask 8)

 

Questions I would like to know are:

 

1) Have you already purchased your pistons?

2) What is the Advertised Duration spec's on both your cam's?

3) What is the intended purpose for this engine/car?

a) Mild Street, B) Hot Street, c) Mild Strip, d) Hot Strip, e) Dedictated Strip?

4) Are you planning on altering the diff.gear ratio?

 

As far as the Chamber Vol of you Cyl.Head are concerned: if you havent replaced your pistons & plan on doing so-then you can choose the pistons w/the correct dish/dome cc's to match whatever Cyl.Head Combustion Chambers available: thus the actual Cyl.Head Brand Name is not that big of a deal-as long as it suits your purpose.

 

Always remember that there is no single engine spec, Port cc's as an example, that stands alone. The secret to a good engine is an airflow velocity that matches your power needs within the rpm where it is needed most: you need it most in the rpm range you will find yourself in at least 60% of the time.

 

Along those lines, a good place to start your engine build, would be to match your SCR to your DCR. The DCR is a tool that indicates how much your cylinder pressure has been/will be bled off, due to a late closing Intake Valve, while your SCR is a tool in correcting the cyl.pressures that have been/will be bled off due to a late closing Intake Valve.

 

Still, the SCR & DCR themselves are not Islands unto themselves: but they are a great place to start.

 

Kevin,

(Yea,Still an Inliner)

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No I'm not that familiar with the scr and dcr numbers. The 64cc numbers are just the cylinder head numbers. I am relatively happy with the cars performance but would like a little more :D

 

The short block minus a cam change will stay as is for now as it is a fresh build. The Edelbrock rpm heads are holding me back as I have been told by several people. It runs 12.30's at 112 mph, the car weighs 2730 with me in it and a half tank of gas.

 

The current cam is a part number 12-423-8, the bigger cam I have is part number 12-433-8 both are comp cams extreme hyd. rollers.

 

You asked what I want the car for, well I do not daily drive it. It is a weekend fun car with an occasional street race but mainly trips to the strip when the need for speed arrives. Some car shows as well.

 

The rear gears are 3.70 lsd from an 87 turbo car with 235/60-15 drag radials. The transmission is a built 700r4 with a 2300/2500 B&M hole shot converter.

 

Like I said I'm looking to improve my cars performance with out building a new motor for now.

 

Any imput would be appreciated.

 

Mike

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Mike, I wouldnt take a chance on the bigger runners. Go with the 190 or 195s. What is your RWHP now? If your running 12.30s at 2730lbs, you should be pushing around 348 RWHP or so. I should be in the elevens with 380RWHP. I think you would be real happy with the 195s with your setup or the 190s if you dont plan on going 383...

 

CZ

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Mike...

 

Dyno Test Criteria

 

Horsepower: 500 HP

Engine: 383ci

Heads: AFR Street 190 Cyl. Heads

Compression: 9.5

Carburetor: Holley 0-4779 750 cfm

Ignition: MSD Distributor 36° Timing

Cam: Comp Cams 12-433-8 Hyd Roller Cam

Exhaust: 1 3/4" Headers

Fuel: 93 Octane Pump Gas

Engine built and dyno tested by American Speed

ultilizing an Edelbrock RPM Performer Manifold

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I agree with CZ. If you are not prepared to do a complete engine make over for an extra 100 tq/hp then you should not be thinking about a bigger cam change, instead go w/the AFR 195's and your power band will move up the rpm range 500 or 600 rpm's with a little extra tq/hp to boot.

 

This will achieve the effect I illuded to in my first post, yet on a mild level; that effect is to delay maximum tq from coming in too early-this leads to less wheel spin off the line while allowing your car to actually be rolling/moving fairly well prior to peak tq surfacing. This effect will also allow the car to act like a bat out of hell on the higher end. Less tq on the start with more tq/hp on the higher end is something our light Z-cars need.

 

If all you do is mostly street driving on the weekend with an occasional strip run & you are already running in the 12's then you have a serious Hot Street Engine 8) whose combo is perfect for your needs.

 

If you are going to make mod's I would suggest you do so in baby step stages. Start w/the AFR 195's w/out a cam or intake change. Your Cyl.Heads are the best place to start. Rpl the Cyl. Heads as their own modification. Then after you have done this and feel you still need a cam change or another intake, well at least this way you have a baseline to know what to expect out of any addt'l mod's.

 

Look at it this way: the AFR 195's are quite versitile as in they make great Hot Street Cyl.Heads and they can also be used for a Mild Dedicated Strip Car...it all depends on how you build your engine. However, providing you have decent Cyl.Heads you can always upgrade a cam/intake afterward, but if you dont have the better breathing Cyl.Heads to begin with then a Cam/Intake Upgrade is a moot issue as the better breathing characteristics are not there to begin with. You already have a decent cam: and your cam should compliment your AFR 195's Cyl.Heads.

 

Witout serious underbody mods our Z's are limited in space for an appropriate exhaust system for really heavy breathing engines: think about your exhaust system prior to ever choosing a heavy hitting big inch small block. If it cant exhale due to a restrictive exhuast then you will also be choking off the intake: if it cant exhale then it certainly cant inhale.

 

If you are not really prepared to give your engine a make over I would think you are right where you should be, performance wise. The slightly better breathing Cyl.Heads are a perfect addition to your engine: IMHO.

 

Kevin,

(Yea,Still an Inliner)

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.., No I'm not that familiar with the scr and dcr numbers.., Mike

 

What is needed to determine your actual DCR/SCR are the following from your current set up:

 

a) Swept Volume = Bore x Stroke

B) Block Deck Height (BDH) = Factory SBC BDH is 9.025"

c) Connecting Rod Length"

d) Cyl.Head Combustion Chamber Volume

e) Piston Compression Height

f) Piston +Dishcc's or -Dome cc's

g) Ring Land cc's = Assume 1.5cc for a SBC

h) Crushed Cyl. Head Gasket Volume

i) Bore of Cyl. Head Gasket (Slightly larger than Block Cylinder)

j) Seat to Seat Camshaft Duration Spec

 

Once you know these items then we can begin playing with the DCR/SCR#'s.

 

Kevin,

(Yea,Still an Inliner)

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I posted the links necessary above

the soiftware is at the lower part of the site

 

http://www.newcovenant.com/speedcrafter/calculators/compressionratio.htm

 

http://cochise.uia.net/pkelley2/DynamicCR.html

 

lets take my 383

static CPR is 11:1 on paper but 11.07:1 in the real world

MY cam is

 

http://dab7.cranecams.com/SpecCard/DisplayCatalogCard.asp?PN=119661&B1=Display+Card

 

my dynamic is 7.9:1

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  • 1 month later...

Well I got a deal to good to pass up so I went out and bought the Canfield 195/200 heads with 65cc c. chambers. I upgraded and got the double springs for roller cams good to 650 lift with 10 degree locks and they were also cnc'd.

 

I paid 1120.00 shipped to my door with studs and guides. What sold me on the heads is Chevy hiperformance stated they flowed better than just about all the heads at the critical 300 to 400 lift area. From .050 to .400 they out flowed all heads in the 180 to 220cc class.

 

Mike

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That's a great deal. Those heads do flow better than even the AFR's in general, if you can find someone who's tested both AFR and Canfield straight out of the box. And better at .300 and .400 as well. For the roller springs and studs included, your price is excellent. Adding up what it would cost to upgrade $1245 AFR heads for roller springs will add $300 at least.

 

IMO, AFR makes you pay for the name. Granted they are nice heads, but they make you pay more than you need to.

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