2.5 to 2.8

[Mr_Efficiency]

I've been looking for a very specific truck for a while now. An older boxy S10, short cab, short box, 2.8 and a 5 speed. I have found an 1989 short cab short box, 5 speed S10 (GMC version tho.. forget what its called S15 something) the only problem is it has the 2.5 iron duke in it. The body is mint, no rust at all, the truck only needs a windshield (cracked) and possibly fix the parking brake since the wheels are blocked so it wouldnt roll away, lol

Swaping a motor is no big deal to me, what are the specifics of puting a 2.8 into this truck? will the 2.5 trans bolt up? will it hold the power? I plan to do some towing and possibly a 3400 top end swap since I'm swaping the harness anyways.

Also I need a rwd 2.8 correct? I have a fwd one here but im guessing its not good to me for this truck, correct? What about motor mounts? wiring issues?
Anything at all would be helpful, I'm just trying to get an idea what I'm getting myself into.
thanks

[geoffinbc]

It is a pretty easy swap. The older 4 bangers got the 7.62" rear end later than the V6 trucks but the T5 transmission was just as strong. Yes the 2.8L will bolt to the trans but You will have to change engine mounts, exhaust system, radiator and some other minor accessory stuff. The swap would be simple though just time consuming.

[Mr_Efficiency]

thanks,
What does the compression come out like with the rwd 2.8 and the 02 3400 aluminum heads? I saw somewere on here it was 12:1 or something but i cant find that thread. Can i run that on 89 or 91 octane safley? also are the rwd 2.8 and 3.4 pistons the same? I might go with a 3.4 if its all i can find but i'd prefer a 2.8.
Also what can i look for donar car wise, i know the s10 and some Fbodies came with the 2.8 in rwd format but is there anything else?
And what about the crank trigger on the rwd 2.8 and 3.4 is it the same as the trigger for fwd aplications (3.1). I plan to run this with a cavalier harness and ecm.
thanks

Edit: what about the flywheel? will i need one for a 2.8 or 3.4 depending what i go with, or will the 2.5 one work?

[geoffinbc]

Compression will be around 12:1. I doubt you would get away with is on 89 or 91.
2.8L and 3.4L pistons are completly different.
S Trucks and F Body Cars were the only RWD Applications.
There is no crank trigger on a RWD 2.8L. The 3.4L and FWD applications are the same though.
You will need a 2.8L Flywheel.

[Mr_Efficiency]

would i get the same 12:1 compression with a 3.4 and 3400 heads? or would it be any lower?
Where can i buy a external crank wheel if I end up going that route?
If i go with a 3.4 would a 2.8 or 3.1 flywheel still bolt up with the crank? I'd imagine so but i want to be sure, would hate to find out the hard way.
Also how would pushrods and such work out for this, would it be the same as any other hybrid swap?
Sorry for all the i'm sure newbie questions but im new to the hole rwd thing and i cant find any threads on this kind of conversion.
thanks

[geoffinbc]

A 3.4L and 3400 heads would still have high compression.
The store has external triggers.
A 2.8L or 3.1L flywheel will work. However since you are using a Truck T5 then you need a flywheel from a 5 Speed 2.8L truck.
Pushrods from a Gen II motor will be the correct length for the GenIII heads on a Gen I block.

You seem to be going for a smaller displacement motor. If you want, try and get a 3.4L engine and use a 2.8L crank. This way you will get the crank trigger provisions and short stroke but still maintain good performance and gas mileage. You will have to get custom pistons though. Or who knows there my be something out there that works. Or perhaps someone has oversized 2.8L pistons already.

[Mr_Efficiency]

Yeah i would like to stick to a 2.8 but wouldnt mind a 3.4 if i came acrossed one given the problems it would save with the crank triger. I'll just have to wait and see what i come acrossed.

Is there any way to lower compression to something reasonable like in the upper range of 10:1. Thicker head gasket? maybe even a 3500 head gasket cause of the larger piston diameter. Or should i just have the piston or combustion chamber machined?

So far my only real road block is going to be a flywheel. whats so diffrent about a fwd flywheel? Cant i just use the fwd flywheel and pressure plate with the rwd clutch? cause i'm guessing the input shaft on the trans is diffrent for fwd and rwd cause of the tranny makes (borg warner/getrag)

Unless i just get lucky and find a rwd 2.8 with a 5 speed but i doubt it since everything around here is auto.

Its to bad i cant just rig up a fwd 2.8 to work, lol

Thanks for all the responses so far, youve been a really big help.

[geoffinbc]

The FWD Flywheel is a different size. It wont work with the RWD starter. It is not a problem getting a flywheel. They are pretty cheep. You can even get one from a junkyard and have it cleaned up. You could use a FWD flywheel with a T5 Truck transmission as long as it was on a FWD block.

[Mr_Efficiency]

thanks, so I just have to match up the starter to the motor and im fine. sounds easy enough.