90 4.3 reman

[Bobcat07]

New to me. Nice interior, trailer, house, driveway, yes I assumed the motor was well kept. Caveat emptor.
Idle nice, think kitty cat.
Off idle vibration.
Outdrive is smooth, u-joints, coupler, gimbal bearing seem OK. Alignment seemed front high a bit.
I pulled the motor to change plugs, wires, original coil. Did a comp check and I've got 120,110,140,150,160,175. Gonna do a leakdown test next weekend.
So now I know my vibration I'm thinking....
My Question
Would you run it around a weekend or two and get it rebuilt or a reman in the works for next season or... do it NOW so I don't have oily motor pieces in the bilge.

 

[Bondo]

Ayuh,.... Welcome Aboard,..... The '90 4.3l is a pre-balance shaft motor,.....
It's gonna vibrate,......

This winter, swap in a post-'96 4.3l is yer best bet,.....
Post-'96 has the vortec heads,.....

 

[Bobcat07]

Bondo, I was hoping you'd reply! Thanks!
I am just starting my journey with this project so you'll see (read) me around.
The previous owner said he froze it 15 years ago and had the engine replaced. I see 10172756 on the block casting itself and 12 bolts holding the intake manifold down.
I am still new to Merc info sources so I'll have to search a bit.
My neighbors son is an engine builder and he's so good at it he's booked prty full but maybe....

 

[Lou C]

Vibration? Yes the non-balance shaft units do vibrate more, but not excessively, I've had one 21 years. I'd want to know about the cyls that only had 120 & 110 psi. Mine normally is 165-170 both before and after a top end overhaul.
If you go with the Vortec, you'll need an 8 bolt Vortec intake, and a carb that has an electric choke (if you want to use a choke) because the Vortec intake does not have an exhaust cross over for the choke thermostatic coil spring.
Exhaust is the same for both pre Vortec and Vortec, and you would have to add an electric fuel pump with the safety switch and wiring. No provision for a mechanical pump on the Vortec.

On the one I have the vibs you feel are between 1700-1800 rpm not right off idle. You only notice it if revving it in neutral otherwise I never feel it. They do have the even fire crank with the split main journals but it doesn’t take out all the vibs.

 

[Bobcat07]

A lot of good info there, thank you thank you.
You are correct, about 1800 rpms and nothing major. I didn't run it long as, again, it was new to me and once I saw the original, 30 yr old coil I assumed I had a weak spark that was blowing out as the compression increased coming off idle. I'm much more inclined to believe it's just the natural vibration now instead of something ready to die.
The seller seemed like a straight shooter but so do con-men... hahaha
Thanks again for the info/advice. I will update in a week or so after a leakdown test but I think I'm going to run it and look for an upgrade to the balanced vortec design no matter what.
I can't wait!!!