3400 fiero swap questions

[Velox65]

First off, hello! New on here.
Now to business haha, I have a 85 fiero 2.8 I'm looking to put a 3400 in it and retain my factory heads and intake. Now with my iron heads and the 3400 pistons will drop compression like crazy so what pistons should I use (dohc or rwd?) also can I put the 2.8s cam and lifters in place of the 3400s(bad cam) I'd like to avoid having to get custom pushrods as this motor is a get me by thing till I get the parts for my 3800 swap later.

Thanks in advance

Travis.

[mtownfiero]

If your just using the motor to get you by until you get a 3800 and your not worried about the motor itself looking stock why not convert to the 7730' ecm using the stock fiero harness and keep the entire 3400 setup. You would have to figure out the exhaust and some other small things but i think it would be much easier than tearing a motor apart to make a new one with less power.

[2.8-350TBI]

You know, it would be easier to swap in the whole 3400 than build a hybrid the wrong way.
Plus, you have the added advantage that you dont have to lift the heads off the block and that saves you some cash for when you change the cam. Plus you get heads with awesome flow characteristics, a great fuel managenent and a roller cam. But if you already have the block, I see your reasoning.

You can use either 3.4DOHC or RWD 3.4 pistons, which have 3cc's less dish, which increases compression ever so slightly...

[Velox65]

I'm not wanting to mess with the wiring, I'm gonna have to do that when I do the complete 3800 swap, I'd rather not do it twice, also I don't have the complete 3400 setup all I got was the block(75$) with a bad cam and a bad head gasket so I have to pull the heads anyways. That's my reasoning. So use dohc pistons and I'll buy a flat tappet cam and lifter combo, it'll be better than the anemic 2.8 for sure. With the 3400 oil pan what timing cover should I use (88?) and use the dohc flexplate and a remarked 3.4 balancer correct? I get conflicting info on those.

Thanks for the replies guys.

[Velox65]

Bump, also can I put a flat tappet cam(like in the 2. on this 3400? If not someone point me to a good wiring guide for a dis swap I suppose

[2.8-350TBI]

Nope, the 3400 uses a roller cam. There are many aftermarket rollers for the 3400 tho!
I wouldnt know how to help you on dis tho.

[mtownfiero]

go to www.gmtuners.com or something like that or the 7730 ecm conversion on fiero.nl. this will let you convert to the newer 7730 ecm just by changing pins at the ecm and adding a few wires.

[Velox65]

Bump well it looks like I'll be needing pushrods, I'll be ordering from smith bro's. I'll be needing 5.85" length and oil through and the standard diameter(5/16?)but what's the wall thickness I need? I can't figure this out.

[Fierobuffoon]

I'm not wanting to mess with the wiring, I'm gonna have to do that when I do the complete 3800 swap, I'd rather not do it twice, also I don't have the complete 3400 setup all I got was the block(75$) with a bad cam and a bad head gasket so I have to pull the heads anyways. That's my reasoning. So use dohc pistons and I'll buy a flat tappet cam and lifter combo, it'll be better than the anemic 2.8 for sure. With the 3400 oil pan what timing cover should I use (88?) and use the dohc flexplate and a remarked 3.4 balancer correct? I get conflicting info on those.

you can use the neutral balanced v-6 flywheel/flexplate, they are mostly the same.. but why bother just drive a different car until you get that 3800.. 3.4 balancer needs to stay with 3.4 crank.. for what matters you can use a 3100 cam and lifters.. much better than flat tappet profiles for a 2.8

[Velox65]

Because my 6.0 ls bird drinks the gas and is now to nice to drive "daily" it's a weekend car, the 3800 may be year or so away, but I have a 3400 sitting and ready so why not. Looks like I'll be needing a 87-88 fiero timing cover also

[bob442]

you want to only do things once, so just do things once...? if the 2.8 doesnt run worth a crap or is blown up i can see the point, but it it runs fine, i'd leave it till the 3800 motor is ready.

[Velox65]

you want to only do things once, so just do things once...? if the 2.8 doesnt run worth a crap or is blown up i can see the point, but it it runs fine, i'd leave it till the 3800 motor is ready.

That's the thing the 2.8 has a spun rod bearing and this is the quickest route to running