Hello everyone, got a question and need advice, so working on my 73 coupe I discovered that it has two different heads on the motor. Passenger side has #3927186. GM 13 Driver side is #3927185. GM 54 1A180. So it turns out the drivers side is 74CC head and the passenger side is 64CC How much does this make a difference in how the engine runs.

thanks
scott

 

Bubba strikes again. It obviously works and kept the car running and on the road. Is it delivering the best performance, likely not. Look at the bright side, install another decent 64cc head and you’ve certainly corrected the compression imbalance and improved the engines performance potential. I’d be wondering what other mismatched components lay beneath the surface in your engine though.

 

Yup unfortunately when you buy a c3 these days it like a box of chocolates you don’t know what you got till you open it.
it looks like the wrong front grill frames are different also

 

How does it run/rev/idle? I’m really curious. Half the cylinders are probably 9.5:1 and half are 8.5:1.
maybe Bubba was more clever and used two different thickeness head gaskets to make up for the difference in combustion chamber size.

 

Well it really hasn’t run in over 15 years been in storage. But with that said I just replaced gas tank, carb, shocks, But it seems to run alright the odd side does smoke when it’s running. My concern is what’s it doing to the engine.

 

Can't be pushing evenly on the crank. But that said maybe Bubba did put a shim gasket on one side? A simple compression test could give you an idea. A new set of matching Aluminium heads might be a great idea!

 

Any suggestions on a pair of replacement heads Aluminum or cast iron Would like to stay with 64 cc

 

Lots of opinions and options out there. Really depends on what you want and how much you want to spend. I think edelbrock estreet heads are great in terms of price/quality/performance. Same with trick flow heads.
AFR heads are the best performing but also most expensive.
I think all around aluminum heads are better than cast iron.

 

I run the Edlebrock E street heads, 64 cc's. Much better flow than stock heads. Come setup pretty nice for the buck. Basically setup for a flat tappet cam.
Been on my car for over 6 years. Absolutely no issues.
I did need to buy head bolts and pushrods. Everything else fit like factory.

 

Any of the big name heads use good parts. AFR, Brodix, Trick Flow or Edelbrock are the big ones. You definitely get what you pay for. Without upgrading your cam you are looking at a 180 to 185 intake port volume. A rule of thumb is doubling the flow for the given HP you are looking for. But that is a very general rule. Some of the cheap chinese ones use cheap parts and if a valve lock fails or you snap a valve head off you will be looking for a replacement head or engine rebuild at a minimum. Depending on what your future engine goals for horsepower are and whether or not you are going to rebuild it anytime soon I would not go larger than 64cc and would be looking at 62 and 58cc heads as well. With the upgraded heads you have an opportunity to upgrade your cam as well since the lifters have to be removed. JUst remember the flat tappets lifters have to go in the same spot they come out of if you werent aware of that. Also use a high ZDDP oil so you dont wipe out that tappet cam. IF you want to keep it a mellow motor then the 64 cc would be a good choice as you can upgrade your pistons to domes if you do rebuild it in the future. IF you go smaller cc chamber now you are going to limit yourselff to smaller domes or flat tops, but some people would say thats a better choice for flame travel.

Almost any aluminum head will give you flow benefits over the very heavy and poor flowing cast heads. They are also a benefit in detonation besides the weight reduction

 

If you purchase any set of complete aluminum heads, check all the components that come installed on the heads.
I purchased a new set of complete Edelbrock Performer RPM heads.
The heads are beautiful and were ready to bolt on.
My engine builder double checks everything and he disassembled the heads to insure they were perfectly straight, they were.
He found that the valve springs on the heads were rated at a higher spring rate than what my cam and lifers were rated for.
The springs were great for a racing applications but to high of pressure for the street.
So I paid for assembled heads, including all the components, then paid for them to be disassembled checked, replaced the springs and reassembled.
In the future I will only purchase bare heads, have them checked then install the components instead of paying twice for parts and labor.
I’m sure in most cases complete heads can be bolted on out of the box, but my engine builder is very critical about checking everything.

 

wow
I am with you on "what it is doing,,,"

guess find a stock head to match?

 

So I’ve been looking for heads, cast iron vers aluminum, if I go with a new set of aluminum heads will that detract the price of the car. Although it’s not the original engine it is time era period correct for the car. Used cast iron heads that I have found would have to be completely rebuilt. Which adds to the cost of the heads. Like I had mentioned it’s got one 64 cc head and one 70 cc head. I don’t believe it has an upgraded cam in it so I am assuming it’s basically stock with a set of headers on it. I would prefer to keep time period correct heads on it. But with that said still trying to make a decision.

thanks for all the advice
scott

 

Get the aluminum heads and enjoy the power. Get another 64 cc head someday and throw it in the closet for the next guy. The original motor is only worrh about $4k appraisal wise and you ain't got it so it doesnt matter. Its never going to be a "numbers matching car " again.

 

With all the accessories with stock intake , valve covers and air cleaner bolted up you almost can't tell if they're aluminum heads or not , paint them the same color as the engine block and it's even harder to tell

 

If the engine is running good, I would go with the set of Edelbrock E Street heads and matching intake manifold.
If you want to keep and run the original QJet carburetor, which are actually amazing street carburetors, then get it rebuilt by Lars and make sure you order the correct intake.
If you want to get a little additional zip out of it Edelbrock also offers up some nice cam kits that are excellent quality and include everything you need for a good valve train.
You didn’t mention what you are running for exhaust, but a set of headers and dual exhaust will really wake it up.
These upgrades and the cam kits are awesome for the average street machine and you will really feel a difference in performance and if you do it right maybe even improve your fuel economy.
If you want the original look in the engine compartment, just paint the intake and heads and unless someone is really looking, nobody will know the difference.

 

Here is the 357ci small block I have mentioned many times on this forum, it is in a 69' car........it has Trick Flow 175DH heads, a 2701 Edelbrock intake, 650 Classic DP Holley, Crane roller rockers, Howards Hydraulic Roller Cam, 10.6 to 1 compression.....plus a bunch of other sneaky stuff, like the 2.5" C2 exhaust manifolds, the L46 fuel filter and line setup........this is in front of a TKO 5 speed......this car will run high 12's easily.......has 13 inches of vacuum.....and sounds great but not too radical.....kind of like a stock LT-1.......it is a ton-o-fun...and with the 14" chrome factory style air cleaner...and the ignition shielding....no one can tell the difference except the well informed......






Jebby

 

IF it really matters Speedway and Trick Flow both make the camel hump fuelie heads in aluminum that a rattle can will make stock old school...

https://www.speedwaymotors.com/Chevy...ad,379621.html

https://www.summitracing.com/parts/tfs-30210002

 

Hello rescue rogers, thanks for the links i looked up estreet heads which run around 1,200 to 2,400 dollars. I found a set of cast iron heads for 300 but they were bare heads no springs or valves and they would need valve guides and seals which brings the price up to around 900. So i think new aluminum heads are in my future. Thanks for all the advice.

scott

 

you will be very happy and you wont have to have them ported to perform well which you would have had to have done to the cast heads