Ok guys a little recap. I have heads on my 454 BBC that are peanut port heads (346236 casting numbers). I have been told tat these heads are not very good for performance. I have been looking for the "better" heads. I went to racing junk and found two sets of heads.

For more recap, check out my previous post (http://www.chevelles.com/forum/ultimatebb.php/topic/4/21849.html) . It starts about 5-6 posts down with slpin making the suggestion about the 781 heads. Ends on the 8th post down. After that it goes into a gear swap.

One is 3931063 which I was told are 68-69 396/402/427 Oval Port Closed 101cc Chambers. Would the smaller chambers increase my compression too much?

The other is casting number 336781. I was told that these would be a nice swap, even though they would drop my compression a little bit. These are 73-85 Oval Port Open 118cc chambers.

My question is which one of these heads would be better and would I see any gains? I was thinking the 427 because of the different flow numbers, but I do not know a whole lot when it comes to motors, so I am just going on numbers.

I will get the heads that I get ported/polished and just generally went through.

Thanks in advance,
Chris

the 781 will flow better because of the open chamber design... you wouldnt need any port/polish to make power on either head.... get rid of the peanut ports... bolt either of those on, and you can expect a power gain.

your old heads were 113cc right? you could mill the 781 down to that cc, check your piston down to hole too, so you could run a shim headgasket which would raise your compression about half point and give you a good quench.

Alan,
did you edit your post or am I going crazy. Didn't you say something about the two different types of pistons or does that really not matter? O also, you lost me when you said the pistion down to hole and everything after that? I get the headgasket, but whats quench? And the pistion to hole thing.

As I said, I know very little about the techinal parts of motors.
Chris

heh yeah, i did edit it... there are like 2 things you could do....

you could get the 063 and bolt it, and that would be the wisest choice if you have flattops... it would bring your compression to around mid 9:1, and with a cam like a comp XE to build cylinder pressure, it will make the car run REAL well.

but if you dont have flat tops, you could take advantage of the flowing charastics of the open chambered heads... the 781 could be milled down to ~113 cc which would give you the same compression as you have right now... but if you currently have flattops, that would mean your compression is in the 8:1 range... great for 87 octane, but i think you would want more compression for more performance. ;)

piston down the hole is how far deep the flat part of the piston is under the surface of the deck (at tdc). the stock is usually around .025 and with a shim headgasket that is .02 thick, it would bring your quench to .045 - having small quench will make it not as easy to detonate. but you cant go tooo small on the quench or the piston will hit the head... and.. thats not good.

using shim headgaskets also mean the surface on the deck and heads needs to be flat... i took mine out because they were leaking, and im still deciding whether to try the steel shim again and run at 10:1 or go with a composite gasket and have 9.5:1.... big difference in compression just with headgaskets, eh?

Thanks Alan. Now my question is is there anyway of seeing the piston type without pulling the heads. I know its a really silly question, but I don't want to pull the heads, look at them, tell the guy I will but them, wait for them to come and get a chance to put them on. Stupid question, but I figured there is different ways of doing things.
Chris

i dont think there is a way of checking pistons without taking the heads?

you only need to take off one side though...

Red,

Please do yourself a favor and buy a copy of HPBooks "How to Hotrod Big-Block Chevy's" and Ed Staffel's book "How to Build Max. Performance Chevy Rat Motors" b/c both books will bring you up to speed real quick if you take the time to read them and think about what is being said!!

I look through my old copies all the time b/c they are both great reference books.

One last book is the Hot Rod Volume 10 Technical Library book by CARTECH, "How to Build Monster Chevy Big Blocks". Also a great book but more about building BIG BB motors!!

I throw this out b/c I knew zero about BB's when I laid down the money for my 454 P/U core motor and had to read these to figure out what's going on with the BB's b/c I was always a SB guy up until that point....

pdq67

Thanks pdq, I will look it up tommorow. As for the pistons, I hope to be able to find out before the weekend is over.
Chris