2.8 top end swap
02-24-2019, 09:12 PM
#1
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2.8 top end swap
Hey, guys!! I have an 81 Chevette that I just picked up a tbi 2.8, 700r4 and s10 rear end for and was thinking about a 3500 top end swap before I put it in the car. The original plan was just to drop it in and go, but I was unable to get the computer and wiring from the guy so it got me thinking top end swap and microsquirt. Is it worth it or should I just swap in a 3500? I know there is a lot of info on here and other forums, but it seems scattered and incomplete. Big thing I am wondering about is what crank trigger to use. What do you guys think?
02-24-2019, 09:31 PM
#2
Re: 2.8 top end swap
The 3500 heads won't work on the 2.8. The 2.8 bore is too small for the 3500 combustion chambers. You'd have to use a 3.4 block to use the 3500 heads. The bore of the 3.4 is JUST large enough to work with the 3500 combustion chamber.
This is not even considering the static compression ratio you'd have by just swapping the 3500 (or other FWD aluminum) heads onto an iron head 2.8, which would be between 12 to 12.5:1.
IMO, the full 3500 swap is a better way to go. To keep the throttle body aspect easy though, use a 3400 UIM and throttle body since it's cable driven, or get an adapter to use a 3.5 "Shortstar" throttle body on the 3500 UIM. I went the former and am happy with the results.
As fas as teh crank trigger is concerned, if you're going Megasquirt the easiest way to buy the 36-1 trigger wheel and use that.
This is not even considering the static compression ratio you'd have by just swapping the 3500 (or other FWD aluminum) heads onto an iron head 2.8, which would be between 12 to 12.5:1.
IMO, the full 3500 swap is a better way to go. To keep the throttle body aspect easy though, use a 3400 UIM and throttle body since it's cable driven, or get an adapter to use a 3.5 "Shortstar" throttle body on the 3500 UIM. I went the former and am happy with the results.
As fas as teh crank trigger is concerned, if you're going Megasquirt the easiest way to buy the 36-1 trigger wheel and use that.
02-25-2019, 08:48 AM
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Car: 1985 Firebird
Engine: 3.4 turbo
Transmission: Auto
Axle/Gears: 3.42
Re: 2.8 top end swap
it's just a matter of time before that ol 2.8 bottom end lets go anyway. especially throwing alum heads at it. i'd find a 3.4 and build it with 3400 pistons and use the 3500 heads.
02-25-2019, 08:52 AM
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Car: 1985 Firebird
Engine: 3.4 turbo
Transmission: Auto
Axle/Gears: 3.42
Re: 2.8 top end swap
3500 block is nice and would make more power. roller cam and such, but a 3.4 block would be easier.
02-25-2019, 05:42 PM
#6
Re: 2.8 top end swap
Yes, you can use FWD aluminum 2.8/3.1/3100/3400 heads on a 2.8 block.
I honestly wouldn't just do a top end swap on a RWD short block, at least not without some experience with frankenstein 60 degree V6s, and knowing exactly how and why the high compression would work the way it will.
I agree with the above, use FWD pistons if you're going to use the FWD top end. While it may not be double digit SCR, it will still be plenty more power than any iron headed version will get you. SCR doesn't have nearly as much effect as increased flow of the heads does.
I honestly wouldn't just do a top end swap on a RWD short block, at least not without some experience with frankenstein 60 degree V6s, and knowing exactly how and why the high compression would work the way it will.
I agree with the above, use FWD pistons if you're going to use the FWD top end. While it may not be double digit SCR, it will still be plenty more power than any iron headed version will get you. SCR doesn't have nearly as much effect as increased flow of the heads does.
Last edited by Six_Shooter; 02-26-2019 at 09:35 PM.
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