3.4 to 3.5?

[82-T/A [Work]]

Hey guys,

I have a 1987 Pontiac Fiero that I'm planning on dropping a 3.4 into. It's from a 93-95 Firebird. What I would like to know is... is it possible for me to install .040 overbore pistons in the engine? What kind of performance gains can I expect over a totally stock motor? I'm planning on going with an H272 cam, roller rockers, the usual stuff.

I'd like to slightly raise compression, and get as much displacement as I can while still having a motor that looks 100% stock (same as my 2.8 MPFI).

Would I be crazy to say that I could expect 5hp and 5lbs of torque?

Thanks!!!

[614streets]

Lol roller rockers and a 272 cam will net over five horsepower
Honestly though in addition to a custom set of 10:1 pistons you should step up to an speed or holley ecu and run a wide band meter. You could easily net 50 hp.

[v6h.o.]

.040 over pistons will not get you 3.5L's it will actually bring you up to 3.4L's. sadly the 3.4L in stock form is only 3.35 litres rounded up to 3.4L
you can easily overbore to .040 safely.

The rockers and Cam will net some good gains. moreso the camshaft. the rockers will be less of an actual gain compared to the cam but it all helps out.

As will already stated go with some 10:1 pistons.

I fully agree with his statement on the Holley Commander 950 ECU. I run one myself and the change over stock ECM to standalone is night and day.

[82-T/A [Work]]

Really? I didn't know that Holley sold aftermarket ECUs. Is this a simple replacement for my MPFI system? My goal is to give my Fiero as MUCH horsepower as I can possibly conceive of, but still have it look 100% stock.

By stock, I mean the car itself (interior and exterior) and the engine bay.

Like, my Accel 17lb fuel inejectors and my Accel ignition coil... I painted them black...

[614streets]

Dude you can get a new holley ecu and repin it to your factory harness for about 600 new and easily half of that used if you know where to look. Nobody will ever know and its the best mod you can do. It will ring all the tune needed to make the numbers.

Youd be very suprised , I do suggest the PRO commander and again, wide band. Run full closed loop.
I do.

[82-T/A [Work]]

Would I need a knock sensor? My current system does not have any provisions for a knock sensor. (no Fiero came with one).

Or a cam position sensor either.

Also, I am using a MAP sensor with a MAT sensor instead of a MAF system... is that a problem?


Thanks!!!

[v6h.o.]

]Would I need a knock sensor? My current system does not have any provisions for a knock sensor. (no Fiero came with one).

Or a cam position sensor either.

Also, I am using a MAP sensor with a MAT sensor instead of a MAF system... is that a problem?


Thanks!!!

No, Not a problem at all. I currently Still dont have my KS hooked back up on the car (long story) however the Holley does have a provision in hte ECU to wire up the KS, the Block *should* have a spot for a KS??? so you could easily wire up a KS.

You dont need a Cam position sensor, only SFI engines really need this, the Holley is only a MPFI style ECU. will not do SFI.l

MAP and MAT(IAT) setups is exactly what both 614Streets and I are Running.

[geoffinbc]

Yea his block will have provisions for a KS. It must the KS just screws into the collant drain plugs on the block. There should be 1 on each side.

[82-T/A [Work]]

Sweet! Thanks guys.... I'm going to remember all this. I'm going to build my engine first, put it together and install it. Then when I know it's broken in, I'll do the swap to the Holley Commander. That's pretty sweet, I didn't even KNOW they made a computer compatible with our motors.....!

[bszopi]

All standalone EMSs are compatible with our engines. You just have to know how to wire them up and then tune them.