327 with 6 inch rods, and other crazyness

[Guest Anonymous]

I guess I need some sleep cause I am thinking stupid/pointless thoughts. Is there any particular reason that a person could not put a 6 inch connecting rod into a 327 assuming you had pistons that fit correctly...Normal 350 pistons do not fit into the 327 do they?

 

Onto something compleatly different... Is there any easy way to have EFI on a 327?

[Guest Night_rider_383]

The longer the rod the better. If you had the money for the custom pistons and aftermarket rods 6.00'' rods would work great in a 327.

 

The 302, 327, and 350 all share the same bore (4.000'') so yeah a 350 piston would fit into a 327, but the piston compression height would'nt be the same

[Mike kZ]

I have EFI on my 327! Check pics page 3 , press "WWW" button on bottom.

[Heavy Z]

Last month I read this article about a 400 block with a 327 crank, 6.209 rods, 11:1 compression that thanks to long rods ran fine on 87 octane gas:

 

http://www.airflowresearch.com/articles/article03/A3-P1.htm

 

That got me thinking about my 327 and whether I could do something similar. The response I got from Pete Paraska is as follows:

 

5.7" rod 327 pistons have a compression height of 1.675"

5.7" rod 350 pistons have a compression height of 1.560"

(0.115" difference)

 

6.0" rod 350 pistons have a compression height of 1.260"

 

With a 6.125" rod (available), you could put a 1.260" compression

height 350 6" rod piston on it and use it in a 327.

That's darned close to thte 6.209" Ford rod they used

in the 353 engine Davy pointed to, and the resulting

Rod/Stroke ratio works out to 1.885:1 instead of the 353's

1.910:1. Hardly worth worrying about.

 

You'd lose .010" of deck height, but that's usually the direction

you want to go anyway. (If you are using a .039" composition

gasket, you want zero deck height anyway, and the

combination of usual nominal piston compression heights, rod length and

half stroke work out to 9.000" anyway, where as the block

has a nominal 9.025" crank CL to deck dimension anyway.)

 

It may help you somewhat, just not as good as the engine in the article above. Maybe someone else will chime in with more info. If you do it, let us know how it goes.

[Guest Anonymous]

At the point this is compleatly academic to me, as there is a 2.4 Liter in my 240z that is at this point very happy, but I am an engineer in training (electrical) so I think I am allowed.

 

Any clue how much the connecting rods and pistons would run on the 327 with 6.125?

[Guest Night_rider_383]

I don't if you wanna build a small or large journal 327 (myself I would go with a small journal)

but here's some prices from competition products

 

large journal 6.125'' rods

 

eagle H beam $480

pro lite- ultra lite $430

not sure of brand H beam $350

howards ultimate duty $750

childs & albert alum $980

 

 

350 pistons for use with 6'' rods

 

badger hyper $100 flat top or dome (9.7:1 or 12.6:1 w/ 64 cc heads)

KB hyper 10.3:1 $250

KB hyper 11.5:1 $270

JE forged 2 valve relief flat tops $540

Manley flat tops $550

SRP 12.7:1 $500

SRP 10.5:1 $452

[ToplessZ]

I would love to hear some more comments on the engine build from the above article. How about an iron vortec headed version with the 305 vortec castings. The article is a few years old now and 6.300 rods can be had on ebay for not alot. I want to hear some input here or even something from someone who has done the same thing. IT would be a killer sleeper engine too. Im really stuck on the idea even after buying my aluminun 70 cc heads for my 383 plans.

[Guest Anonymous]

Are you reffering to something like this?

[ToplessZ]

Wonder if I can post yet. Yes those are the rods I saw but there were others too. I want input on this asap so I can start part sourcing.

[Guest Anonymous]

More crazy thoughts...

4.155 block (aka 400 cid .030 over)

6.3 rods

3.25 crank (aka 327 crank)

Pistons for a 400 with 6 inch rods

 

That would be .075 into the block by my calculations, which is probaly too much? Could the deck be shaved?

 

1.938461538 R/S

352.5 CID

[ToplessZ]

Read that above linked article that will answer those questions. 60 over on a 400 block most say is too much. 40 over is about the max there.but the difference in going 30 and 40 over wouldnt not hardly be noticable and then you have no room to go in the future. Yes it can be zero decked.

[Guest Anonymous]

My bad on my last post. I meant a .030 over block as I doublt there are many 4.125 blocks out there that do not need to be rebuilt.

[Guest Anonymous]

Looking around the internet the prices for 6.3 inch rods seems to be in the area of $1100. Is this for real?

[pparaska]

Try googling on the rod/stroke ratio thing. Check out Isky's site (tech articles), http://www.chevytalk.org tech section, victorylibrary.com.

 

R/S ratio is one of those things that seems real important at first, but after reading what really knowledgeable engine builders/racers say, it's not that big of a deal, IMO. The only really practical thing a larger R/S ratio seems to get you is less rod angularity which leads to less side loads on the pistons (among other things).

 

As far as detonation resistance, it's hard to tell what that 352 build with the AFR heads really had that made it that way. Consider that if the deck height is optimized for excellent quench, and a great chamber like the the AFR is used with .04-ish quench height, it's not that incredible to me that a SBC with ANY reasonable R/S ratio could run at 11:1 on 92 octane.

(I assumed the regular .041" 400 head gasket was used, and a zero deck with about 5cc of valve relief volume to get close to their 11:1 with the 56cc chamber 305 AFR heads.)

 

Maybe I'm trying to make myself feel better that I'm going from a 1.75:1 R/S in my 327 to a 1.6:1 R/S in my 406. But actually, I've been reading alot about R/S being the end all and it seems like one of those Internet legends after reading some of the tech articles above.

 

Here's a thought: Throw 26 (383) or 54 (406) more cubes at the motor and gain that typical 1.2:1 hp/ci that way, even lowering the compression ratio to 10:1 or 10.5:1 Sure, it'd be great to run on 87 octane, but gas is cheap compared to many things we have to buy.

[ToplessZ]

Well The seller for me is I want the Reliability factor to be high run on cheap gas and have a sleeper engine. I dont really want something that will wake the dead. I want something that sounds stock and surprises everyone dumb enough to fall for it. I would definatly like to hear more input on how to get the same detonation resistance in a different combo.

[Guest Night_rider_383]

You can get great detonation resistance out of just about any rod/stroke ratio engine.

 

The best things for detonation resistance are.....

alum heads

head chamber shape

tight quench

cam size

polished head cambers, piston tops, valve faces

the right total timing for the engine combo

[pparaska]

The November 2003 Popular Hot Rodding magazine has another great article by David Vizard - "The Power Squeeze - Maximizing the compression ratio delivers more bang for the buck than you can imagine."

 

Topics include:

 

-Static compression ratio,

 

-Expansion ratio,

 

-Cylinder pressure vs piston position for high and low compression,

 

-Static Compression Ratio Power gains as a function of original vs new CR

 

-Dynamic Compression Ratio (yes johnc, he really uses that term - defines and explains it's importance ), (i.e., effect of Intake Valve Closing point on low rpm cylinder pressure)

 

-Compression Pressure

 

-Lowering Fuel/Air Charge Temperature for Detonation Resistance:

--Reduced head water jacket temps through lower thermostat ratings,

--Cool intake air to the TB/Carb,

--Intake and Exhaust valve thermal barrier coatings,

--Combustion Chamber polishing (or better yet, thermal barrier coating)

--Intake manifold and cylinder head port thermal barrier coating

--Exhaust port coating (to minimize heat transfer through the common Exhaust/Intake Port wall near the valve seats - especially on AL heads with no water between the Exh and Intake ports - and to keep heat in the exhaust and out of the water jacket.

--Piston thermal barrier coating to keep hot spots at bay

 

-Fast Burn Chambers (mixture motion/agitation)

-Staying away form chamber cavities with the smallest dimension in the .06 to .012" range (e.g., proper quench height)

-Minimum quench clearance and chamber volume to obtain desired compression ratio

-Stay away from domes larger than 0.1" high (text says .001", but I believe he meant .1")

 

-Ignition

--Ideally burn the mixture from 5 deg BTDC to 15 deg ATDC

--fast burn means less ignition advance needed - optimized advance means less advance than for slower burning chamber/port configurations.

--Use "more than enough" ignition system energy to fire the higher pressures.

--High current, multiple spark ignition may allow less advance and allow for more compression to be used.

--An overkill ignition system allows colder plugs to be used, for better detonation resistance.

--Plug Side electrode should cover only half of the center electrode looking straight down the center of the plug.

--Round off end of Side electrode to remove this source of hot spots

 

Vizard states you can run as much as 11.2:1 static compression ratio on 93-octane pump fuel, with a small safety margin - too small for hot, humid weather.

[pparaska]

Joe (rags here on HybridZ) agreed with a comment I made to him the other day at the Convention track event - 327s seem to be pretty detonation resistant even with 5.7" rods. I've had a few in the 10:1 and 10.5:1 compression region with lopey cams and double hump heads and I've NEVER had a problem with detonation on 93 octane.

[Kevin Shasteen]

.., I am an engineer in training (electrical)..,

 

PeteP,

 

I have not read Vizards latest article...I will have to go buy it when I get a chanve. Thanks for the heads up.

 

Fearlessrogue,

 

Regardless if you are an electrical or mechanical engineer-if you wish to know the differences in rotating assemblies: con.rods, Piston Comp. Heights (PCH), and Crank Strokes, then you need to understand the Slider Crank Mechanism & how to create your own personal Crank Angle Charts.

 

As stated by other in this post the connecting rod alone is not going to "Make Your Engine". An engine is a total package, no one component stands alone.

 

If you were to look at the Crank Angle Chart comparisons between a Stock 350 and the 350 (actually a 352) that Chevy Should've built you will see there is very little difference.

 

Keep in mind that this articl utilized a Comp Cam's XE270HR10: this cam has an Intake Valve Closing (IVC) of 61* ABDC. When we speak about the IVC we are dealing w/the amount of volume still remaining after the IVC-which is a reference to the size of the actual Cylinder Displacement that gets Compressed. In other words, "How much of the Bore x Stroke Remains after the IVC"...this remaining volume after the IVC is the Cylinder Volume that we plug into the Compression Ratio Formula in calculating our Dynamic Compression Ratio (DCR).

 

The DCR is the spec that ties our Total Chamber Volume to our SCR for your level of required/desired performance (also, sorry JohnC-but the math doesnt lie).

 

Stock 350:

4" Bore

3.48" Stroke

"B x S" = 716.93 cc Cylinder Volume

5.703" Con. Rods

1.560" PCH

1.64 R/S Ratio

11:0.1 SCR = 71.7 cc Total Chamber Volume

IVC @ 61* ABDC = .802 (Percentage) of Stroke remaining after IVC

IVC of 61* ABDC = 575 cc Cylinder Volume

575 cc Cylinder Volume + 71.7 cc Total Chamber Volume = 9:0.1 DCR

 

352 SBC Chevy Should've Built

4.155" Bore

3.25" Stroke

"B x S" = 722 cc Cylinder Volume

6.209" Con. Rods

1.190" PCH

1.91" R/S Ratio

11.0:1 SCR = 72.2 cc Total Chamber Volume

IVC @ 61* ABDC = .793 (Percentage) of Stroke remaining after IVC

IVC of 61* ABDC = 572 cc Cylinder Volume

572 cc Cylinder Volume + 72.2 cc Total Chamber Volume = 8.9:1 DCR

 

The entire point for the article, "The 350 Chevy Should Have Built" was to show the important of airflow velocity. They built an engine that keeps airflow velocity high and allows the piston to dwell longer in the TDC range. This means the Piston remains longer at TDC during the ignition phase of the Combustion Stroke. Therefore-the spark is applied to the combustible gasses for a longer period.

 

The important factor is to not focus only on the Con. Rods-but also the Cyl.Heads the article utilized.

 

It is a complete package-no one component stands alone.

 

You should be able to look at the remaining Cylinder Volume of each engine and clearly see that there is not that much difference between a .802 and .793 percentage of stroke.

 

So, if this doesnt make that much difference then why bother? You have to see the 352 for what it is: it is a large bore moderate displacement Small Block. The engine utilized smaller Cylinder Head Intake Ports with an Intake Manifold to match-this keeps the port pressures high leading up to the Cylinder for combustion. High Port Pressures means good/high Cylinder Pressures (which JohnC was correct on ).

 

The article on the 352 also utilized a 270 cam.....NOT A 290 cam! So there was still enough Cylinder Pressure after the IVC for a decent idle and power to boot: the perfect street engine!

 

It is a total package-no one component stands alone.

 

Kevin,

(Yea,Still an Inliner)

[Heavy Z]

One drawback to using long rods was brought up by a sprint car racer/mechanic friend of mine. He says that the shorter pistons needed to use long rods have a tendency to 'wobble' more because the rings are closer together. He says that yes the long rod idea is good for power, just not to expect the piston rings to make it to 150,000 miles. I thought some of you may find this interesting.