Guest

Well, I'm gonna start on my 3.4 heads (iron, same as 2.8 & 3.1)
and was wondering if there's any interest in me doing a thread as I go?

micktroup2

That would be great! Are you going to do a 'before and after' on the flow?

Base91

iTrader: (1)

Are the 3.1 and 3.4 heads exactly the same? Does the 3.4 have bigger valves for example?

Guest

All the '85-up HO 2.8 heads had the bigger valves. Third gens and Fieros got them, but S-10 TBI 2.8s did NOT get the bigger valves.
I already ported the 2.8 heads and bolted them to my 3.4, which is now in the car but hasn't yet started.
I worry that I made one spot in one exhaust port too thin, and I fear it may crack. If so, I want to have this pair ready to swap on.
So far as I can tell, these '93 3.4 heads are identical to my '86 2.8 heads in every way that would affect performance / fitment.
I should do some "before" numbers on a flowbench, but funds are ultra tight these days.
I think it enough to know that doing the 2.8 to 3.4 swap, with a 204/214-112 cam, has been shown to drop the RPM of peak HP down by at least 200 RPM, and that this is gaining nearly 25% more cylinder under each combustion chamber, so 25% more port area is no problem, and 25% more flow is needed.
I doubt I'll gain 25% of anything, but it really can't hurt, and should be some help.
I did well with my 305 heads on my '86 IROC-Z, I could feel much more low-end torque, and it suddenly created a very fun new traction problem.
I'll start posting pics tomorrow.

-JMAN-

I was actually thinking about doing this once i get goin with my camaro.
love to see how it turns out.

Base91

iTrader: (1)

Me too. I just got the 3.4 long block. Pretty dirty at the moment. Is the lower intake manifold the same on the 3.1 and 3.4? What about with aluminum heads? Is the lower intake different?

Guest

I found some obvious difference in the LIMs, so I ported and re-used my 2.8 version. Pics of that porting are in my other thread.

Six_Shooter

iTrader: (2)

This is wrong, after '85 there are no "H.O." heads, since they are all the same, and would be the same as the earlier H.O. heads. Since there was only one version of the heads the H.O designation was dropped. The S-series most certainly got the same heads after '85, using the larger valves.

Guest

It's okay that you hate me, but don't lie to everyone else. TBI versions never got the big valves. Period.

project89

iTrader: (1)

umm tbi did get the large valve heads carbed engines are the only ones that got the small valve heads

Six_Shooter

iTrader: (2)

I didn't know I hated you? Just stop posting incorrect or inaccurate/skewed information.

TBI most certainly got the large valve heads.