MPFI & 3.1 crank addition to s10 2.8 engine.

[johnc]

Can I put the heads, 3.1 crank and mpfi in/on to the s10 2.8 block? My '84 carb'd 2.8 has the one-piece rear seal. I am thinking a big issue would be crank sensors? I know this must have come up, so any ref's to a site or past post would be appreciated.
thanks,
johnc

[RacerX11]

No, not the crank. The '84 2.8 had the small-journal crank. You can't swap in the later large-journal cranks. The car 2.8's switched to the larger cranks in '85, but I think the S10's were small at least through '85. 614Streets could probably comment more accurately on the exact switchover point. Are the heads/MPFI iron or aluminum?

Marty

[v6h.o.]

yes... the old break a crank every year blocks...

one of the guys at teh old dealership where i worked put in 3 cranks in the 7 years i worked there in his 84 s-10, due to it was the old small journal crank. freaking things broke so easy.

it was either 85 or 84 for the small jounal crank's before they switched the larger ones.

[geoffinbc]

If he has a block with a one piece rear main seal than he has a large journal crank. I may not be the original motor. It was not until 1986 that ALL S-10's saw large journal cranks and one piece rear main seals. In 1985 it was still hit or miss.

[614streets]

I also belive that since you have a one piece seal that you may have the big main crankshaft. If you do have the Big main crankshaft , as said, yes you can swap in the 3.1 crankshaft. The later internal balanced 2.8 liters have the same disc minus the notches (timing referance). Make sure you use a nutral balanced flexplate/ or flywheel for your 3.1 crankshaft.

The only way you could have small mains and a one piece seal is if someone did the old chevette seal swap , highly unlikely.

Mic your current mains and you will know where to begin.

[Guest]

To save any confusion, I'd get an '86 or newer RWD (longitudily mounted) 2.8 or even a 3.1 block, this will save the time of finding out that you need a different block anyway. You could also continue to drive the truck while building your other engine.

But for simplicity sake, I would just get a 3.4 block from an F-body, since it will have a place for the crank trigger in the block already machined. To use the genII or genIII top end you will need to make a custom crank trigger other wise, that is using a 2.8 or 3.1 longitudily mounted block.

I have some pics of my hybrid build here: www.domesticcrew.com/raven/James

[johnc]

Mic your current mains and you will know where to begin.
I just did a quick mike, and it looks like 2.592" on the front journal. Anyone know the large and small spec?

[bszopi]

This is for the larger, from the website...

Crankshaft
Main Journal
Diameter - All: 67.239mm - 67.257mm
Taper - Max: .005mm
Out-of-round - Max: .005mm
Flange Runout - Max: .04 mm
Main Bearing Bore Dia: 72.155 - 72.168 mm
Crank Main Bearing I.D. : 67.289 - 67.316 mm
Main Bearing Clearance: .019mm - .064mm
Main Thrust Bearing Clearance: .032mm - .077mm
Crankshaft End Play: .06mm - .21mm
Crankshaft Flange Runout - Max: .04 mm

The dimensions you gave would convert over to 65.84mm, so it looks to be the smaller.

[johnc]

Thanks everyone for the info. Turns out the s10 2.8 got the one piece seal before the cranks were upgraded. Nice I got the straight info before getting a 3.1 crank.
johnc