hey everyone,

I've got this 86 trans am that i love to death, the only problem that I'm having with it is the stock LB9 TPI engine leaves a lot to be desired in terms of power. Who the hell wants to drive a slow car with a v8 anyway?

So I got this crazy idea. I've heard of guys putting the 305 heads on their 350s to raise the CR, so I thought about putting some aluminum 72 cc 350 heads on my 305 and lowering the CR. to about 8.7, then finding the thickest possible head gasket, flipping the exhaust manifolds upside down and running dual t3 turbos with some custom intercooler piping.

im still debating on whether to stay EFI or go carbed. if i go EFI im definitely getting at least a modded LT1 intake because at high rates of flow the TPI runners suck. if i go carbed, i already have a 4 bbl intake sitting around all id need is heads and carb, and i could recoup some of the money by selling the tpi setup.

does anyone have any suggestions as to which stock gm cars came with 72 cc aluminum heads that flowed well? carbed or efi, if efi maybe the vortec truck heads and intake? also, is the 305 a destroked 350 or a debored(lol) 350? cam suggestions? im wanting to rev this thing pretty high and i will have a strong valvetrain no matter which route i go.what's the thickest head gasket that they make for the small block? were there heads made that will fit the 305 with a bigger chamber than 72 cc?

any suggestions/criticisms are welcome and much appreciated i just had to throw this out there and hear what some of the GM experts on the board think about it.

 

unfortunately you can't use 350 heads on a 305...atleast without a whole lot of work. The bore sizes are different, and you can't fit the bigger 350 valves in the 305.

I don't know that there are any 72cc aluminum heads... I don't know that there really are any stock aluminum heads that you're going to be able to pick up cheaply either. Aluminum L98s sell for way more than they are really worth, and fastburns and things like that aren't going to come too cheaply.

 

well that killed my hopes and dreams...thanks though. heh

 

people have been getting good results from L31 vortec 350 heads on 305's. 72cc is to big anyhow, the L31's 64cc chambers will more than get you where you need for compression.

 

"people have been getting good results from L31 vortec 350 heads on 305's. 72cc is to big anyhow, the L31's 64cc chambers will more than get you where you need for compression."

so are there no bore problems with putting these heads on a 305? what compression would i end up with? im shooting for 8 at the highest. also, what intake and computer will i have to run with the vortec heads? will i have to get the scoggins dickey intake and use my tpi computer? thanks.

 

what Im trying to say is that the smallish cams selected used typically with a 305 performance application are small enough to prevent the valve from hitting. the 1.94/1.5 inch valves used in the vortec heads are the same as the old highest performance head for 305's known as the S/R 305 torquer head. It also had these size of valves.

To know what lift a vortc can acheave lift wise on a 305 a set of checker springs would be needed, I suspect it is probably pretty good.

To see what people are doing and of what they are capable of I present to you:

THIS


as far as compression, using a set of 64cc heads on a 9.5:1 motor previously equipped with 58cc yields a very boost friendly 8.85:1 compression if the same gaskets are used. GM used a very thin head gasket on most 305's that I have disassembled that is very prone to blowing. using a regular head gasket will likely yield another few thenths compression into the 8.7 to 8.5 range which would be very nice indeed. My personal boosted project I am building is considered the low side of compression for a boosted performance motor at 8.6:1

switching to 72cc heads with the thin "easy blow" gaskets yields a 8.1 to 8.0:1

using regular, nicer, performance head gaskets gives you a yield of about 7.9 to 7.8:1 which is probably a bit too low.