difference in 3.1 and 3400 heads

[z24cavaliercaleb]

alright i've decided to build my 3.1L with 3400 internals but next will the old intake fit on the 3400 heads or would i have to use the 3.1l heads if i used the old intake. i don't really like feedback about the 3400 gaskets and i don't want to rewire the injectors... so i was wondering if anyone knew if there is a difference before i get too far and find out the hard way.

[SappySE107]

Metal 3400 gaskets trump all and the 3400 top end outperforms the 3.1 by a lot. You would have to keep the 3.1 heads to use the 3.1 manifolds as they are not compatible.

[Superdave]

um, the 3.1 and 3400 use the same exact crank and rods, pistons are too big and the cam won't work... so not sure what you mean by internals.


3400 heads, are only compatable with 3100 and 3400 lower intake manifolds, only 3100, 3400 and 3500 plenums fit as well. None of the gen2 stuff will fit.

read the hybrid guide here: http://www.domesticcrew.com/hybrid.html

[z24cavaliercaleb]

well what i'm saying ill have motor work done to the 3.1l block to get the internals from my 3.4... i would just use my 3.4 but then i have to fabricate allot of mounts and i'll try spending lil more money here to save headaches there.. so the machine shop will bore out my block... not the first motor i've owned that i bored out.. i have a motor that i bored 120 thousands over. started with a 289 v8.

[SappySE107]

What does a 289 have to do with a 3.1 exactly? You can overbore it .120 if you want but its not going to be very strong.

[montess408]

yeah if you want to keep your 3.1 to save the trouble to make the mount's that is good but i would keep the overbore to a minimum as it dont give that much extra power (but i have heard of a.i.r motors boring out a 3.1 .100 over b4 to make close to a 3.4)
and i would use the 3400 top end as it has been said it just flows better you can keep your 3.1 injectors and just tune for them or get some bigger accel ones

[z24cavaliercaleb]

What does a 289 have to do with a 3.1 exactly? You can overbore it .120 if you want but its not going to be very strong.

The studebaker 289 was a motor with two types of v-8 blocks full flow and semi flow block and i used a semi flow block because there is allot of room for boring. i think max is like .200 but i went for lil more then half to be safe. and these motors are fully forged from factory so they are tough motors.. i've talked to the motor shop and they said that they can get it to a 3.3 and exceeding that would be kinda dumb so ill just go with there word.

[z24cavaliercaleb]

ok now for bigger injectors i decided on these. http://store.summitracing.com/partde...749+4294782213

but computer programing what exactly would i need? would the chip on
wow-tech.com/store work, or what would i need to buy to correct this problem?

srry im new with fuel injection engines.. im used to working on engines with carbs and distributers..

[geoffinbc]

3.1L injectors and ecm will run a 3400 just fine. I have done it before and it actually ran a tad rich at stock fuel pressure. Once in closed loop however it ran perfect. There is no need to re wire anything just use the 3.1L injectors in the 3400 fuel rails.

[Superdave]

It's possible but on the stock tune it does run lean at WOT above 4K RPM and really bad close to 6K.


I'd use stock 3100 injectors, the computer will try it's hardest to compensate at idle and WOT fuel will be a bit closer. Real tuning would help out for sure.

[geoffinbc]

We ran it on a stock 3400 and it ran great even at WOT. We checked and it was not lean. We used a Caspers adjustable fuel pressure regulator to dial in the fuel pressure.

I suppose if you had some mods or a descent cam it would throw that out the window though.

[Superdave]

the VE is alot different... did you run a stock 3.1 bin file?

here is a stock 3.1's VE tables ($A1, adder and main added together)



and a 3400 swapped '90 cavalier that i've been working on.



Look how much more fuel is needed to keep the o2 voltage in the .9-1V range VS stock.


I won't say it dosen't work, it does but still.. propper tuning will always bring the most out of the car.