My current 350 has a 8.5:1 cr stock, with its 76cc heads. i used the cr calculator that was provided in another post, and i see that somewhere around a 58cc head would give me aoubt 10:1 maybe a little more. Does anyone make an aftermarket head this small, or do i need to purchase a 62cc head and just have it milled down? I wanna run a lunati voodoo cam - something about this.....Duration 284/292, Lift .525/.546 110 LSA, does anyone have any suggestions..maybe a differnt cam that would work better? And with aluminum heads, i should be ok on pump gas with this compression i beleive??? Thanks Josh

PS. on top of the engine is a team g intake and a 750 edelbrock carb. 700r4 and 4.10 rear.

gm had a head with 58cc

what pistons do you have? Flat tops and 58cc would give around 10.5:1. 64cc heads would give you around 10:1.

They are stock pistons with 4 reliefs (sp?) i was told about -7 or -8cc. They are approx. .025 in the hole. I know gm made some 58 and 60 cc heads, but i was wondering if anyone aftermarket performance heads around this size.

What head gasket are you figuring on using?
FYI...GM sells a .028" composite gasket that is reasonably priced...and there's always the .015" shim gasket thats works well too.

i planned on the .028 gasket. It helps to bump my compression a few points higher. I dnt wanna use the steel shim gasket, becuase the block is factory, it is not as smooth as the heads, and i have heard problems of leaks occuring if the block is too rough.

50cc heads. http://www.racinghead.com/Products/Heads/PA-SBC.asp

car craft did a story on this, you have to clearance hte pistons for the valves because gm put hte valve reliefs in the wrong places..

How gm does something like that i dont get..so how do i clearance the pistons? or does this need to be done professionally?

Does the cam play a factor in figuring out the clearance issues?

Thanks for all the help on this guys, i appreciate it!

A stock, L-48 350 motor used 64 cc double-hump heads and .020" thick steel shims and was right at 10 to 1 even if it was spec'ed 10.25 to 1 CR.

NOTHING wrong with shims at all. GM installed them on millions and millions of motors SB and BB through the years!!

pdq67

http://cgi.ebay.com/ebaymotors/SBC-DART-IRON-EAGLE-49CC-HEADS-215-RUNNER-NEW_W0QQitemZ8042513479QQcategoryZ33617QQrdZ1QQcmd ZViewItem

Yes they're real.

Obviously I know nothing whatsoever about the seller, I'm not "recommending" them or anything; just using their ad for what information it contains.

Didnt the 305 heads have 58cc chambers?

the 305 heads were 60cc i believe, but some were smaller valves, also im trying to get a little better flow then a stock gm head. I guess if there is no other way, i could have them ported but i would rather an aluminum head neways, since i want some where in the 10+ compression range.

Also, anyone have anything to say about the cam i was planning on using? The specs are in my original post up top. Anyone input about it will be taken into consideration, im not very familiar with cams. Thanks again- Josh

305HO, -601 heads range from about 53 to 58 or so..

The ones with the 1.84"/1.50" valves hardened seats, double quench closed chamber and right at 160 cc intaker ports. Nice heads!

Mine measured 53 and 55 cc's!

You gotta cc them to know for sure..

pdq67

Dart iron eagle heads are availbe with 49cc chambers

85 up Corvette aluminum heads are about 58cc if I remember.......

http://www.chevyhiperformance.com/techarticles/46359/

Read the article.......

I have a set of dart IE that are 52cc for sale. I just sold a set of pro toplines that were 54cc.

World products sells the cast iron S/R torquers with a 58cc chamber. I would hope these are a bolt-on deal as S/R stands for stock replacement. Another option is summit carries an aluminum trick flow head with a 56cc chamber. Both these heads are intended to keep the compression up in smaller displacment engines ie 283, 305, 327. But I don't see any reason they wouldn't work well on a 350 also. My guess is the trick flow is more of a performance head, but some of the magazines have used the S/R head and produced pretty good results with it also (for a more mild buildup).

The embossed shim from Felpro will be worth considering in order to get your quench area at .040" to prevent detonation. I have used it on stock blocks without problems. One thing I do for prep. work is WD40 and a fine FLAT wetrock on the block. I pull the dowel pins and completely cover the deck with the stone from top to bottom and work it front to back with very very light even pressure to ensure smoothness and knock down casting ridges.

I would recommend sticking with a 64cc head in case you ever decided to further modify your engine. If you were to add a stroker kit, you would be hard up to get the CR back down as flattops will yield about 10.9:1 with 64cc heads, which is streetable on pump gas with proper quench.

One thing I might add is that small chambers shroud the valves on stock 23 degree heads, which can hurt flow.

One thing I might add is that small chambers shroud the valves on stock 23 degree heads, which can hurt flow.


what does that mean, shroud the valves??

Imagine if you will, a 3.9" intake valve, in YOUR engine. Sounds like it should flow pretty good, eh??

Now imagine putting it in a 4" bore. What just happened?

That's shrouding. If the air can't get around the valve margin because it's too close to something, including but not limited to the bore or the chamber wall, it won't flow; no matter how big the valve, no matter how carefully ported the port, no matter how far you open the valve, and so on.

Standard practice for high-flow heads is to lay back the chamber wall away from the intake valve especially, particularly on the spark plug side. That's where the flow is; along the roof of the port, and through the plug side of the valve throat into the chamber. It does no good to open a valve .600" if the air then has to squeeze through a .300" crack.

Basically, the chamber wall should be at least as far away from the valve at any given lift, as the valve is open.

That involves removing material, which enlarges the chamber, which lowers compression. There's no such thing as a free lunch. Everything is a trade-off.

One thing I might add is that small chambers shroud the valves on stock 23 degree heads, which can hurt flow.

I think that should be a "can" shroud the valves. Both the topline 50cc and the Dart 49cc heads I've had had the chambers layed back to unshroud the valves. With old GM heads it was common practice to do this while installing larger valves.