96 3400 with fiero heads

[bob442]

better flowing upper and lower intake IIRC, the 00 stamp on the lower intake is what would be more desirable, i recall ben saying something labout that to me. i could be wrong

[Ray Hamilton]

Use 3400 DOHC pistons, flat top with valve reliefs. That's what I did.

[ericjon262]

Use 3400 DOHC pistons, flat top with valve reliefs. That's what I did.

or just keep the better flowing top-end, power, and fuel econ of the stock 3400...

[newfiefiero]

I was thinking about doing that, but I figured it would be harder to find DOHC pistons than doing a bit of extra wiring.. Plus I don't have the time to do any internal work right now. It's good to know tho just in case I decide to go for the stock look later!

[ericjon262]

I was thinking about doing that, but I figured it would be harder to find DOHC pistons than doing a bit of extra wiring.. Plus I don't have the time to do any internal work right now. It's good to know tho just in case I decide to go for the stock look later!

My vote would be to make the 3400 look stock.

[newfiefiero]

Another question about this swap... I want to keep the air conditioning, can the old compressor mount up, or could I use the newer one?

[LZeppelin513]

Another question about this swap... I want to keep the air conditioning, can the old compressor mount up, or could I use the newer one?

You would need to fab a bracket and figure out how to swap the pulley to match new belt. Easier would be to use the late fiero duke AC compressor as it uses the right accessory belt, but you would still need to fab up a bracket. Probably easiest is to use 3400 pump and have AC hoses built at a shop.

[LZeppelin513]

As for wiring, you will have to decide between OBDI or II.

I decided to go OBDI with my 3400 and 3500 swaps. Grab a 7730 from a yard and follow instructions from Ryan's website to re-pin for the 7730: http://www.gmtuners.com/files/index.htm. Its easy you just need to take your time and not mix anything up. Wiring on the engine side means splicing existing fiero wires to pigtails on 3400 sensors/etc. Probably best is to get at least this iron http://www.amazon.com/Weller-WLC100-.../dp/B000AS28UC and solder/ heat shrink each joint. It takes some time and seems a bit overwhelming looking a a big rat nest of wires but is a fun/ rewarding/ very doable project. Make sure you have and familiarize yourself with fiero and 7730 wire diagram. Remember, you just have to make the ECM happy, give it the sensors it needs. Eg. the cam sensor screwed into the 3400 is just cut off and not used because the 7730 doesn't use it. Also you will need a tune for 3400. I contacted Ryan from the website I posted above and purchased a tune from him. He was helpful reasonably priced and the tune was great while I had the car. I could get up to 35 MPG cruising, 26 city. There are others that you can get a tune from on this site as well. Expect to pay around a hundred bucks for a mail order tune. Other option is tune your self. More time involved and big initial investment but then you have the equipment. If you ever turbo or make significant upgrades it is usually a better option to be able to tune yourself. This time a round with my 3500 I picked up a wideband and Moates emulator.

All gauges work fine. Reuse 2.8 Fiero oil pressure sender in 3400 block, speedo gets signal direct from stock tranny, tach works, you will need a 3 wire coolant temp sensor, I think i found mine on a 91-93? sunbird. This is because one input goes to 7730 and one to the fiero gauge. Alternator is up to you. I went with modern alternator, but you have to notch the decklid a bit to fit in stock 3400 location. Some have figured out a low mount solution, usually on AC side. When I was thinking about putting the alt in stock 2.8 location I didn't think it would fit due to 3400 shallow timing cover design. Part of the fun is coming up with your own solutions for the little problems you will encounter along the way. Not a weekend project unless you really know what you are doing and have the equipment. I had no mechanical experience at ALL and very limited tools when I took on my 3400 swap and it was a great summer project.

Edit to add: After owning 2.8 fiero and 3400 fiero, I would never choke the 3400 with a fiero top end even if it was cheaper and easier. To each his own.

[newfiefiero]

Well, its been a long time since I've posted here, and many things have happened. I just recently had my third child and things are pretty hectic at home now! Also, I never did get that grand am motor, but I did buy a 02 pontiac Montana off of a friend of mine!
I was wondering, is the montana computer worth using in my swap? I haven't found a lot about this computer (not sure of the exact P/N, as the van is in a snowbank, and I'm on Baffin Island right now), so I don't know which route to take. The 7730 OBD1 seems pretty promising, but would I be better off with the OBD2 computer that comes with the van?

[ericjon262]

I'm using a montana computer with my swap, although, I haven't driven it yet. it'll work, but the swap is a little bit more involved to go obd2.

[newfiefiero]

Are you getting the computer reprogrammed or using it as is?

[ericjon262]

I'm reprogramming it myself, using a DHP powrtunr. you'll need a few parameters changed up for it to work in a fiero.