First off I'll explain my situation. I own a 1989 S-10 Blazer with a 4.3L V6 in it. I am getting a 305 from a 1986 K5 Blazer (fullsize) and am going to be rebuilding it to swap into my S-10. The 305 is currently carbed so I'll be ditching the heads/intake for a TBI setup. The easiest car to find 305s at the wreckers is F-Bodies, specifically 3rd Gens. My question is is there any particular year I should be looking for to get the best flowing setup? Or were the heads all the same throughout these years. Thanx for the help!

 

the stock tpi heads for the LB9(i thik thats what it is) 305 is probably your best bet at the bone yard if you want direct fit. You can get 350 heads from an l98 but i belive youll have to have them machined to get the right compression w/ a 305. Youll want to get the 86 and up heads b/c the older heads have different intake bolt angles and a few acc. bolts missing.

 

so the TPI heads will accept a TBI intake?? if so thats great.

 

they sould accept it w. no probs. The intake face and bolt patterns should be the same (87 and up)

 

hopefully I can find all the parts I need for a decent price. Then port/polish them and it'll all be good.

 

The bolt patterns changed mid year 87, not in 86. So just to be certain you get the right set grab an 86 set.

 

i think its the other way around... He wants tbi + tbi intake. But slade is right, the pattern changed mid year. Look at the heads and the 4 center bolts should be at a shollower angle than the other bolts on the corners of the heads. Those are the heads you want for your tbi setup.

 

See if you can find a set of L98 alum. corvette heads. They have the same size combustion chambers as a 305 (58cc). Then use an aftermarket dual plane intake with a tbi adaptor plate. That should make your S10 rock. You'll be looking for traction help next.

Steve

 

The 58cc was designed to work on a 350 because of heat dissipation. You would have to mill the heads to 54cc to make them retain the 9.3:1 comp ratio you have now.

 

I dont agree with that, at all. The 305 heads are supposed to be 58cc, same for the corvette heads. I know in reality both cc lower than that, but the compression ratio will be the same with either head. I think you are talking about an entirely different subject, which has nothing to do with static compression ratio.

 

So you dont agree than that GM would put 64cc combustion chambers with iron heads on 350's and 58cc chambers with aluminum heads on 350's to obtain the similar compression ratios? If you bolt on 58cc aluminum heads on a 305 you will lose compression but maybe not a huge amount.

 

No, I dont agree. You change the combustion chamber size from 64 to 58 without changing anything else, the static compression ratio will go up. Thats just how it works. Head material (aluminum or cast iron) has absolutely nothing to do with what the static compression ratio is.

 

You are wrong , it doesnt matter if the heads are iron or aluminum the compression ratio willl be the same if the combustion chambers are the same size. Aluminum dissapates heat better and enables you to run a little higher compression ratio without detonation but the material itself doesnt change the ratio.

 

I know you can run a higher compression ratio with aluminum without dentonation, but Ive been told many times before by engine builders at the track that during the normal engine operation the aluminum transfers/dissipates more heat lowering your effective compression ratio.

 

for the price its gonna cost I'll probably just go pick up some heads from the local engine shop and then put them together myself.. Then they're already done and wont require cleaning or anything.

 

Compression ratio is a constant. You take the volume at BDC and at TDC. (volume at TDC)/(volume at BDC)= compression ratio. How different materials may make the engine actwith the different ratios still doesn't change the ratio because its a constant.