Thread: 327 rebuild

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I have a 1969 327 block for rebuild. would it be more beneficial to put 350 heads, 76cc (1.94 intakes) vs 60cc heads with 1.74 intakes? if so, what can is the max I have the heads milled ?

Depends on what pistons you are running and how far below the deck surface they are.....

they're flattops with valve recesses flush with deck.

Not trying to be a smart ass, but with the information you provided at this point, the best answer anyone can give you is as Dave said...."depends". The small valve/small chamber heads will increase compression and the small valves will make better bottom end torque but run out of steam quickly above 3500-4000 RPM. The small chamber heads could potentially raise compression too high to run on pump gas. The bigger valve heads will breathe a lot better but the compression drop may make the engine a real pig.

I would start by figuring out what the compression ratio will actually be with various combinations. To do this properly you will need to know the actual volume of the combustion chambers. Do not go by what the factory advertises the chamber volume as these old heads they are usually anywhere from 2-6 CCs larger than claimed. It’s best to actually CC the chambers to find out…..and you will need to do each chamber, as they will vary within the same head. Although not as fancy as some, JEGS and Summit both sell economy CC kits that will suffice for doing this

http://www.summitracing.com/parts/po...1155/overview/

JEGS Economy Cylinder Head CC Kit - Free Shipping on All Orders @ JEGS

After that you will need to figure out the volume of the piston valve reliefs and if the edge of the piston is beveled what that volume is along with the volume based on how far down the piston is in the cylinder at TDC. Do not assume the pistons are flush with the deck. You will normally find they are a few thousands down in the bore. The way to find this is with a depth micrometer or in a pinch a straight edge and feeler guages.

Finally you will need to know the compressed thickness of the head gasket.

With those values in hand find a decent on line calculator and plug in the numbers to come up with the real static compression ratio. From that point you can play with different thickness head gaskets and milling (figure .007” per CC as a ball park figure for milling ) to fine tune the compression.

The final step would normally be taking the real static compression ratio and plug that along with proposed cam profile into an online calculator to determine dynamic compression.

Sometime in this process you will also need to determine what grade fuel you will want to feed this thing to determine what you target compression ratio should be based on how you want to use the engine.

The Second Option

Go eeny meeny miny mo, bolt a set of heads on and see what happens.


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By the time you prepare a set of used heads, you would be far ahead buying new. I used World Product S/R Torquer heads on a 327 some years ago, and they worked great.They a S/R (stock replacement) heads are made for 327's: 2.02 valves, 67cc chambers. Here is the link:

http://www.summitracing.com/parts/wr...60-1/overview/

Or you could go with a set of Chevy Vortec heads. They would also be a good choice, although you would need a Vortec intake manifold. You can't beat the price on these:

http://www.summitracing.com/parts/na...make/chevrolet

Lynn also has a good point, building a old set of heads properly is not a real cheap proposition.....although depending on what you have to pay for the old heads it might still be slightly cheaper to do old castings. That will depend on the labor rate of local machine shops and the quality of their work.

I did a pair of "60cc" Power Packs earlier this year. After cleaning, milling, hardened valve seats, new valves (I upgraded from 1.72 to 1.94s) deshrouding the intakes, milling, new springs, retainers and keepers the bill was around $700 not counting the cost of the heads to begin with.

The heads Lynn lists are probably still a bit better as they likely have bigger runners and the combustion may be a lot closer to the claimed volume than the heads I started with. (On the Power Packs I started with, after milling .015 off, the chambers still ran between 62-64 CCs).


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I measured 76cc on the heads +/- 2. I have an edelbrock manifold and carb that needs to get used so I'm kinda stuck with the 882's instead of buying a couple others that need a different intake. ile b using pump gas so maybe I should b building to the max compression that precludes pinging. ive heard 9/1 to over 10/1. is there a number I should target?

With flat top pistons and 76cc chambers, you are looking at around 8:1 compression which is okay for an average driver. With 67 or 68cc chambers you would have about 9.3:1 compression, which would be much better for a performance application. However, static compression is not as good of a guide as dynamic compression which takes in your cam specs, gasket thickness, etc.

if I build for 10:1 will the engine ping on unleaded gas? also, how much can I shave the heads b4 taking away too much head strength? btw, thank you all for the info. I really appreciate your time and expertise. Ron

Originally Posted by ecreek

if I build for 10:1 will the engine ping on unleaded gas? also, how much can I shave the heads b4 taking away too much head strength? btw, thank you all for the info. I really appreciate your time and expertise. Ron

I'm running 10.3 static and need 91/92 octane, preferably without ethanol because it will lose seven or eight octane points over a few weeks sitting idle. If I were building it today I'd be down in the 9 to one range shooting for 87 octane.

Please delete.

Originally Posted by ecreek

if I build for 10:1 will the engine ping on unleaded gas? also, how much can I shave the heads b4 taking away too much head strength? btw, thank you all for the info. I really appreciate your time and expertise. Ron

Looks to me like you just have an old 327 that you will freshen up a little bit and use for a daily driver. Nothing earth-shattering, just a motor.

None of the early iron heads will make any kind of power compared to the heads available to us today, so it really does not matter which heads you use, they're all junk. I might opt for the 882's simply because of the low static compression ratio they produce. As Lynn said, you'd be just over 8:1 static compression ratio. You never know what fuels will be available in the near future, so don't paint yourself into a corner with a high-compression ratio motor and then not be able to buy fuel for it tomorrow. There is nothing wrong with an 8:1 daily driver, but you will have to run a stock camshaft with it. Any hot-rod cam you bolt into the motor will want and need more than 8:1 static compression ratio.

Here's a tutorial I wrote for the wiki on another site. It explains the relationship between static compression ratio and the intake valve closing point @0.050" tappet lift. Cams must be matched to your combination. You cannot just reach out into thin air and grab any cam that you think looks good to you. You must build for it.
http://www.crankshaftcoalition.com/w..._compatibility

To answer your question about what static compression ratio to use with pump gas, generally use up to 9.5:1 with iron heads and up to 10.5:1 with aluminum heads. You can, however, use up to 15.0:1 static compression ratio with E85 fuel. Problem is that you have to use such a radical cam to support that SCR that usage on the street is very limited.

Use a cam something like this....
Crane Cams 114102 2010 Hydraulic Flat Tappet Camshaft and Lifter Kit Chevy 262-400 V8 57-87 RPM Range: 500-4000, Duration @.050": 184/194, Lift: 0.
I'm not saying you should use a Crane cam, I'm just showing you the cam timing you need to use with a low-compression motor. Use this cam timing to aid your search for the brand of cam you want. Be very careful about the quality of flat tappet lifters. There is some junk circulating out there, but if you buy a quality name brand like Crane or one of the other major cam makers like Iskenderian, Crower, CompCams, Lunati, etc., etc. and you buy their lifters with the cam, you should be OK. Alternately, toddle on down to your local Chevrolet dealer and belly up to the parts counter. Order a bone-stock cam and lifters for a 1980 Camaro 350 LM1/Z28. Those motors had an 8.2:1 static compression ratio and the cam designed for them will work well in your 8:1 motor. Again, buy cam and lifters together, from the same supplier.

Here's a tutorial that I wrote concerning using a flat tappet camshaft with the crankcase oils that are generally available off-the-shelf today. You must exercise extreme caution with them.
http://www.crankshaftcoalition.com/w...ips_and_tricks
Sidestep the nightmare of a flat tappet cam by moving up to a hydraulic roller cam or solid roller cam. You can get into a Howards cam and lifter retro-fit combo for about 600 bucks, that eliminates all the mumbo-jumbo in the tips and tricks article.

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again, thanks for the wealth of info. last question; How much can I mill the old heads b4 excessive iron taken off weakens them too much?

Originally Posted by ecreek

again, thanks for the wealth of info. last question; How much can I mill the old heads b4 excessive iron taken off weakens them too much?

Most fellows will limit head surfacing to about 0.030" (thirty thousandths of an inch). On a small block Chevy head, each cut of about 0.006" (six thousandths of an inch) represents reducing the chamber volume by one cc.

If this were my build, I would limit cutting the heads to only the amount required to get a good, flat surface on the heads, like maybe 0.005" to 0.010". Do not cut the heads thinking that you will make a race motor. You won't.

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Ditto what Tech said - just get a nice square surface. Milling heads has introduced a lot more problems than it has solved. All things equal, you're better off going with a thinner head gasket.