can you swap a 3.1 top end on a 3400SFI block?

[Superdave]

aah, ok.. I usually go with .040 of preload. As long as you measured and it all works out then it'll be fine. Plus with the adjustable rocker arms it'll work out better.


for the guys that do the reverse of what you did they have to get longer pushrods because the Gen3 ones are pedistal mounted. Their pushrods always vary in length due to how much preload they want to run, if their heads have been shaved, headgasket thickness and what cam they are using.

[ForcedFirebird]

aah, ok.. I usually go with .040 of preload. As long as you measured and it all works out then it'll be fine. Plus with the adjustable rocker arms it'll work out better.


for the guys that do the reverse of what you did they have to get longer pushrods because the Gen3 ones are pedistal mounted. Their pushrods always vary in length due to how much preload they want to run, if their heads have been shaved, headgasket thickness and what cam they are using.

I just bought a set of Gen2 pushrods to do the "opposite" lol.

I'll check pre-load, lifters are soaking in oil now to be installed tomorrow.

What is the pre-load procedure for the roller-fulcrum rockers? 1/2-3/4 turn after the rods stop spinning - like the Gen 1's? I could use the thread pitch to calculate the turns, but it's easier to ask


I'm surprised the 3400 rods worked since the 3x00 heads are much taller, and really doesn't make sense to me since the iron heads have equal length rods and the 3400 has unequal lengths. If you use the cam and lifters from the iron head block and the matching pushrods, you are OK. Weather or not the length can be adjusted for with the adjustable rockers prevailant on the iron heads is up to the builder, but again it surprises me that the 3400 pushrods work.

I agree with the others, you could have used the complete 3400 and had the same power as the 3.1 iron head turbo. If it's the idea of having a turbo the intregues the customer, tell him that would be extra. I too have had a 3.1 iron-head turbo (although with a much larger turbo) and they are not that fantastic in my opinion - compared to the 3400 I installed a turbo on (same turbo as my previous setup).

[Superdave]

the 3.1 turbo he's using is a Gen2 engine.. Aluminium heads.

[ForcedFirebird]

the 3.1 turbo he's using is a Gen2 engine.. Aluminium heads.

AHH, sounds better now. The roller lifters are still longer than the flat tappets.

The Gen2's use the same bolt pattern as the iron heads, correct? I remember using some FWD gaskets for headers...

Yes, then the manifolds would need the bolt holes notched and ported to work on the 3400 heads. Too bad, though, the 3400 turbo is a screamer (ask Loner).

[pontiacjeff]

That is correct, I am using gen2 3.1 turbo as pictured above, but it is modified for a T3. The engine made 200whp on only 5psi boost non intercooled, stock injectors. There is NO stock n/a 3400 that will make that at the wheels, sorry. I built a Magnuson s/c 3400 and it made only 190whp on 7psi with an extra .3L of displacement and the better heads. Granted, turbo is better power, we all know that.

The car is a Sunbird with a 5-speed Getrag. We intercooled it after we dynoed it and upped the boost to 7-psi, but I was out of fuel with the stock 3.1T injectors, probably about 225-230whp, don;t know for sure b/c we never got back to the dyno. So I turned the boost back to 5psi and let him go. He spun a rod brg recently. I have this 80K mile 3400 out of my wifes Montana (put a 3800 Series II in it). That's why I wanted to do this top-swap. This guy has no money, this is a totally junkyard budget for a totally junkyard car. Yes, the 3400 pushrods are a tad too short, but with the adjustable rocker modification, they are in allowable range. I would not use them if they were near the end of the valve tip.

All this talk about small port 3.1 heads on the 3400... what about the guys who use the iron head 2.8 Fiero stuff on the 3.4 Camaro engines? Now THEM'S is some small ports! LOL! Those engines run like a bat out of hell, lot's of torque...

[pontiacjeff]

AHH, sounds better now. The roller lifters are still longer than the flat tappets.

The Gen2's use the same bolt pattern as the iron heads, correct? I remember using some FWD gaskets for headers...

Yes, then the manifolds would need the bolt holes notched and ported to work on the 3400 heads. Too bad, though, the 3400 turbo is a screamer (ask Loner).

If that 3500 top swap in for your Firebird, you're gonna need a much bigger turbo!

[3400-95-Modified]

I think they were saying use the whole 3400 with the 3.1 turbo stuff on it... that would make more power. But then your looking at possibly maxing the injectors on the normal 5lbs of boost. Either way your working with what you have since its a budget build for him.

[Superdave]

That is correct, I am using gen2 3.1 turbo as pictured above, but it is modified for a T3. The engine made 200whp on only 5psi boost non intercooled, stock injectors. There is NO stock n/a 3400 that will make that at the wheels, sorry. I built a Magnuson s/c 3400 and it made only 190whp on 7psi with an extra .3L of displacement and the better heads. Granted, turbo is better power, we all know that.

That's funny.. Damon's 3400 5 speed sunbird put down 191 WHP with only an intake and decent exhaust, all stock internals with 90,000 miles on it.

Different dyno then you used obviously.. although it was a Dynojet.

[pontiacjeff]

5-speed = alot less power loss than a 4T45E. Most 3400's make about 120-130whp stock. Add about 15whp for a 5-speed. That's still hard to believe an intake and exhaust picked up ~45whp to = 191whp. That's like 60hp in boltons. Hard to believe. I bet they double corrected. Alot of shops do that and it really pisses me off. The dyno makes auto corrections for air conditions at the time of each run. Alor of shops will take that number and correct it again using a chart ot other reference.

But back to topic. I finihed putting the engine together today. I had to soak all 12 lifters to get them unstuck... after 80K at about 60-thou preload, the valves were all stuck in place. All there was was hyd (oil) bleed. That's why I thought the pushrods were too short after checking the second time. The reason they weren;t laching is b/c the lifters were partially collanpsed! Now I have all the valves lashed with the stock jamb nuts in place. The exh preloaded about .020, the intakes about .015. I had to modify the roller lifter retainers to clear the 3.1 intake gasket (valley pan) by cutting off the top "bridge". Then I had to tweak the gasket just a tad more to get the ports to "come down" in place. It al lined up static and bolted down great. Tomorrow it will run again, but with the stock 3.1T injectors for now, and on the same 5psi, till he gets more money for injectors. Thanks everyone for helping.

[ForcedFirebird]

If that 3500 top swap in for your Firebird, you're gonna need a much bigger turbo!

For the 3.4/3500 I'm planning on using a pair of to4e's (t3/t4 hybrids).

[torq455]

check your PM's Jeff!!! I'd like to hear from you.

[loner666]

the 3400 turbo is a screamer (ask Loner).

That it is. Thing still scares me at times if im not paying attention. Its also a 4t60e killer as I think the one I just put in is having problems already as well

[G-U-NOT]

I sent you a PM Jeff.... let me know!!

[RedBird]

5-speed = alot less power loss than a 4T45E. Most 3400's make about 120-130whp stock. Add about 15whp for a 5-speed. That's still hard to believe an intake and exhaust picked up ~45whp to = 191whp. That's like 60hp in boltons. Hard to believe. I bet they double corrected. Alot of shops do that and it really pisses me off. The dyno makes auto corrections for air conditions at the time of each run. Alor of shops will take that number and correct it again using a chart ot other reference.

i really feel that i should just stay away, not add fuel to this fire, but i can't help myself.....

last i knew, 3400's in the vehicles they came in were making closer to 150whp bone stock. a well maintained 5 speed 3.1 will make 120whp, but every 3400 vehicle i lined up against when i had a 3.1 was whomping my ass :P

I'm going to quote myself from over on v6z24, in a thread from several months ago talking about this exact thing

Bottom line in this discussion - All of our custom tuning for maximum power, with a 5 speed, a good exhaust, and a good intake, is much better than GM's tuning for maximum fuel effeciency/comfort, with a power-hogging automatic and restrictive intakes/exhausts.....

tuning makes a difference

[blackbombshell95]

check your PM's Jeff!!! I'd like to hear from you.

Same here(emails X bazzilion)