1998 Oldsmobile 88 Engine rebuild

HAMMONDD

MEMBER
1998 OLDSMOBILE 88
6 CYL
FWD
AUTOMATIC
185,000 MILES

Hi,

I want to swap my engine from 98 olds 88 into a 99 Pont Bonneville. Both cars have the 3.8L series 2 engine. I think these engines are interchangable, will this work for me?

I am having the heads rebuilt and valve seals replaced and I am going to replace all the bearings as long as I have the engine out. I did a compression test and the low was 165 the highest was 190 the rest were all around 175 or 180. So I am not planning on changing rings. The 98 olds engine runs great but does have high miles so some rebuilding is in order.
I want it to last 5 more years about 70,000 miles.

I think the only difference between the engines is oil presure. The 99 has a much higher oil presure pump than the 98 engine. Something like 80 psi in the 99 and 35 psi in the 98 engine which still runs fine on that presure.

Should I install a new higher oil presure pump in the 98 engine as part of my rebuild? Or go back to the lower oil presure pump desinged for the 98 or leave the pump alone and just use the same one already installed?

I do not want to use the oil pump from the 99 as it must have bearing material in it and it has over 250,000 miles on it.

The engine in the 99 Bonneville is junk thrown a rod, lots of damage. And the 98 Olds has been in an accident and is totaled body and frame damage severe.

1 Reply

JACOBANDNICKOLAS

MECHANIC
109,700 POSTS

The only thing I can recommend is to make sure to install the old sensors into the new engine. It should work since it is the same year and size.

As far as the oil pressure, stay with what the factory says is recommended for that engine. Also, since there is more than a 10% difference in compression between the highest and lowest cylender, make sure the valves are good and not leaking. With that much of a variation, you may end up with a slight rough idle. And since you are already going to have the heads off and the rods disconnected from the crank, pull the pistons, hone out the cylenders and replace the rings. It can't hurt, and they aren't nearly as expensive as one would think.

Let me know if you have other quesitions.

Joe