heads

[1993blazerlt]

from what i understand CPI engines use a differen head than the TBI do one thing that is different is the CPI heads use a screw in rocker stud. I have seen screw in rockers studs on 92 and 93 4.3 CPI's. I have now had two 94 CPI engines a part and both did not have the screw in studs one was a blazer and the other a astro van. Is it likley that theses are just replacment heads or did GM put TBI heads with the CPI intke from the factory for some strange reason?

[Sparky2263]

The pre-96 heads are the same. The CPI made it's power with theintake and camshaft. Heads were the same.

Advice? Put 1.6 exhaust valves in them and port match (no deeper than 1/2" or so in the runners). That and a mild clean-up will give you an addl. 10-25 hp depending on cam selection.

Note, the 1.6's like more fuel. Read less mileage. Somewhat. Jury for me is still out on that as mine aren't on yet. Flow numbers are looking promising though.

[Matt 4.3 TBI]

The heads are the same? You sure about that? I've always heard the L35 heads are a bit better designed than the LB4 versions (190cfm vs 160cfm). 1993-1994 TBI engines make 5 more horsepower and ft-lbs since they usually have the L35 heads (if they have the plastic 'Vortec' valve covers).

[Maximus]

They are not listed as the same and Sy/Ty guys use the L35's over the LB4 heads all the time for more flow.My 93 TBI engine has screw in studs "non vortec composite valve covers"but the CPI heads in my garage floor are pressed in.Like Matt said the L35 heads are listed to flow more than LB4 heads.They also have totally different casting numbers between them.

[jjwalker]

Ever think of aftermarket heads? The OE combustion chamber design on those aren't all that great, and with aftermarket heads with modern swirl type chambers will reduce detonation, and increase thermal efficiency. It is just $$$$

[94s10]

after market heads for the 4.3 are crazy expensive. i would just stick to 96+ vortecs. theres flow number on another board where heavily p and p pre 96 heads still flowed worse than stock 96+ vortecs

[Sparky2263]

I've gone through the pre-96 heads and there's just not much difference between them. With the clean-up, 1.6 exh. valve, port match and minor bowl work they pretty much equal out.

I have no experience with fitting 96 and up heads nor their flow characteristics.

[Maximus]

No not much difference but some.Nothing big at all but just enough to matter.Now 96 up heads are awesome for flow.Can ya imagine a CPI intake with vortec heads.That would be a great combo.

[Sparky2263]

What is involved in doing that conversion?

[Maximus]

What is involved in doing that conversion?Don't know but give me time lol.

[j894]

http://www.tyclone.com/Vortec/

Need a spacer for the Cpi manifold to cover the taller
intakes ports of the newers heads.... and drill a few holes
..... or something like that

[03 Rado]

Vortecs flow 240 CFM@ .500 lift on the intake and 160 CFM @ .500 lift exhaust. Thats a 50+ CFM better than any intake made to date factory wise on both sides.
They need a 5/16ths spacer to go between the heads and intake to make up the width difference and then some hole modifactions for the intake to bolt to the newer head.
They DO NOT like to be toyed with on the intake side, valves, port, polish etc.
Exhaust side does like larger vavles and bowl work!