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Discussion Starter · #1 ·
Hey Guys, Planning on doing a top end swap onto my 3.1L 91 Z24 just wondering if alot of people have done this and what I all need to make it work, or even if it would be easier to swap a full 3400 in. Just throw some idea's at me, I would really like to do the top end swap.
 

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Alright, now for those who don't want to do a full swap, any tips/tricks or is this a direct swap? Are the IM's interchangable? Which exhaust manifold will be needed?

P.S. Thanks Brian for the link!
 

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The question you need to ask your self is, getting a mount and extra 10hp~ vs taking the engine apart to find that u gained 15hp not worth your time. Ive done it and I scraped my cavy and bought a new one and droped a 3400, big difference.
 

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Yup... You will actually gain minimal power with a 3400 top end... I have been comparing stock 3.1 with the 3400 over the past couple weeks and the heads are mostly identical, same shape and size. And the upper intake manifold has slightly larger ports, obviously matching up to slightly larger ports on the top of the lower intake manifold. The throttle body is a few mm bigger as well. But the heads have the same size valves only difference is rockers and D shaped exhaust ports. Also it would probably end up the same price to buy a whole 3400 engine as opposed to pieces for the hybrid...
 

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satern13 said:
Yup... You will actually gain minimal power with a 3400 top end... I have been comparing stock 3.1 with the 3400 over the past couple weeks and the heads are mostly identical, same shape and size. And the upper intake manifold has slightly larger ports, obviously matching up to slightly larger ports on the top of the lower intake manifold. The throttle body is a few mm bigger as well. But the heads have the same size valves only difference is rockers and D shaped exhaust ports. Also it would probably end up the same price to buy a whole 3400 engine as opposed to pieces for the hybrid...
the heads are ALOT different..

revised intake port shape, revised short side radius, raised ports, larger intake valves (iirc). completely redesigned exhaust ports. The LIM is drastically different with it's larger equal length runners and better designed bends. The plenum is also again completely different.. larger runners, better distribution, larger TB etc...

3400 top end on a 3.1 with 0 other mods will net like 20-25 more HP.. add in a cam, some P&P work, higher comp pistons and a bigger TB.. then you are looking at some decent power, probably 50-60 HP+ @ the crank (around 200 ish on a 3.1)
 

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whitelightning2 said:
satern13 said:
Yup... You will actually gain minimal power with a 3400 top end... I have been comparing stock 3.1 with the 3400 over the past couple weeks and the heads are mostly identical, same shape and size. And the upper intake manifold has slightly larger ports, obviously matching up to slightly larger ports on the top of the lower intake manifold. The throttle body is a few mm bigger as well. But the heads have the same size valves only difference is rockers and D shaped exhaust ports. Also it would probably end up the same price to buy a whole 3400 engine as opposed to pieces for the hybrid...
the heads are ALOT different..

revised intake port shape, revised short side radius, raised ports, larger intake valves (iirc). completely redesigned exhaust ports. The LIM is drastically different with it's larger equal length runners and better designed bends. The plenum is also again completely different.. larger runners, better distribution, larger TB etc...

3400 top end on a 3.1 with 0 other mods will net like 20-25 more HP.. add in a cam, some P&P work, higher comp pistons and a bigger TB.. then you are looking at some decent power, probably 50-60 HP+ @ the crank (around 200 ish on a 3.1)
Werd!

The intake vales are larger in the 2000+ 3400 and 3100 heads.

The genII heads are VERY different than the gen II heads, a lot of it isn't seen at a glance, and some of it you really have to investigate what is different.
 

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Discussion Starter · #13 ·
Thanks for the Info guys, really appreciated.

I decided to go for the full swap, my buddys gf has a grand am gt and its got the 3400 I drove it a few times and I want the power in my car... lol Now for my 3400 search
 

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straight from GM

Gen III cylinder heads are used on late model V6/60? engines for improved performance. They feature an increase of 0.040" in intake valve diameter and a reshaped port for a flow improvement of 16.7% at 0.450" of valve lift. The exhaust port has been reshaped into a "D" port configuration for a flow improvement of 31.7% at 0.450" of valve lift.
those are some nice improvements... :)
 

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isaachayes said:
IIRC all 3400's had the larger valve, and then in 2000+ the 3100's did too cause they have the 3400 heads and intakes.
Thats what i thought too, but who knows.. i'll have to do some more research before i decide what to do... and i'm not doing anything till i get the damn thing started! lol

I started tearing it back apart the other day but havent been in any real hurry since my cherry picker isn't here anyways and i've been working alot.. hopefully i'll get to drive it before winter hits again! Atleast it won't be a 8 month winter like it was in Michigan!!!
 

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Well... The odd thing is that I purchased some 3400 heads off a 2000 grand am. The valves fit identically into my 3.1 heads and vice versa. The intake ports on the heads are almost the same shape as the 3.1 ports. The exhaust does have the D port which is different, but the heads I have are mostly identical. The coolant passages are slightly different shape, but in the same place. And then of course the rocker mount has a little slot.

I do agree that the lower intake and uppper intake are slightly larger and probably have better flow, which can be seen just by design.

But I am confused as to how I have a set of 2000 heads that are the same size valves....
 
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