Anyhoo...
I have a Iron headed LT1 and a set of aluminum heads.

I've heard that an engine can be raised one full point
when you go to alum. can somebody confirm this?

Iron 58cc, .03 gasket, .022 down, 5cc eye brows = 10.7:1
Alum 51cc, .03 gasket, .022 down, 5cc eye brows = 11.7:1

And no I don't want to run a .050 gasket, the 72 quench is
badddd.

If the corn-senses is no then I'll just hold off on the alum.
heads till I build a 383 and get reverse dome pistons.

 

Well the general rule of thumb is that aluminum heads can handle about 1 point of addition compression over cast iron heads. That being said Ide say your right on the rasors edge. My gut tells me I think you might be able to just squeak by but its so close i don't know if ide recommend trying it.

 

if you run a decent sized cam to keep dynamic compression down abit, you should beable to run 92 on that compression.

I've heard of guys running closer to 12 to 1 on a bigger cammed LT1 motor on 93 oct just fine. Wouldnt recommend it but anything under 11.5 to 1 is typical for an LT1.

 

LT1's aren't even really at their full potential untill they are over 11:1... there are lots of LT1 guys running as high as 12.8-13.0:1 CR on pump gas.

As long as you have the proper cam for it, your LT1 will work very well with an 11.7:1 CR. Your LT1 will love you for bumping up the CR that high

www.camaroz28.com is loaded with great LT1 info and knowledgable members there. Best place around for LT1 building info IMO.

 

yes, you can go up one more point when using aluminum heads because of their cooling advantage over cast iron. with a decent cam and keeping running compression down youll be fine on premium. you can always port alittle out of the combustion chamber

 

I wanted to keep the cam and just swap on the heads. That
said, I might get 2cc out of the chambers and valve reliefs
dropping it to 11.4:1.

I'll read somemore on camaroZ28 as Air_Adam sugested.

 

As was suggestedy Orr, do you have the cam specs so that you can calculate your dynamic compression ratio? That will be the true measure as to whether you can run that static compression ratio or not.

 

my thoughts exactly. I also like the idea of just very minorly porting the combustion chamber wouldn't hurt plus you would decrease compression slightly as you already found.

although i'm with the above poster in those reguards as well, with the right camshaft and quench you can squeek 13to1 by on a pump gas motor.

 

LT1 engines can typically handle unusually high compression ratios (for the camshaft being used) without problems if the tuning is done right. I don't know if its the cylinder head design, the fantastic cooling system, something else or a combination of the above, but LT1 engine really do LOVE really high compression ratios. Almost everyone who knows LT1s, with even a mild performance cam, will build the shortblock to 11.5:1 or more. If the cam you are using is anything noticeably bigger than stock, I wouldn't worry about it too much. It will be fine if its tuned by a competent tuner (I would avoid a mail order tune for this).

 

"I don't know if its the cylinder head design, the fantastic cooling system,"

Reverse cooling. The cylinder heads get the cooler water from the radiator first. Helps in controlling detonation.

 

The cam in it is the stock 96 B-body cam.
Every where I look doesen't list the valve events for that
cam just the duration and lift, so no dynamic number.

I ported the heads, valve job and did a few things I will not
mention till I can get a set on a flow bench.

Does anybody make a .018 steel shim for the LT1?
I could run the iron heads (which are ported too) and a
shim would give me a .040 quench and be right at 11:1

I was hoping to run a stock 96 LT1 computer for now.
I got a 94 Camaro computer but I have not figured every
thing out to run it in the 96 OBD2 car

What cam's are you (Flaming-Ford, Air_Adam) refering too?

 

11.7:1 is probably too high for a stock LT1 cam, whether it be an F-body, Corvette, or full size LT1 cam. 11:1 would be ok, but any higher would probably be too much. Thats pretty close to what a stock LT4 was running (10.8:1 CR and a cam very similar in specs to the aluminum head LT1 cam).

I wasn't refering to any cams specifically. All I was trying to say is that if you build a gen 1 350 and an LT1 using the same camshafts, you may be limitted to (jst to pick a number for arguement sake) 10:1 compression with a Gen 1 350, but the LT1 could be just fine with 11:1 or 11.5:1 with the same cam and otherwise similar engine build.

For a given camshaft, and LT1 can typically handle a noticeably higher compression ratio than a similar Gen 1 engine.