Sad to say it sounds as if the engine gave out at 101k miles. Took her to the shop and cylinder 4 and 8 have around 40 compression according to my local shop.

I had the heads machined and a valve job done and still have no compression.

Basicly i am wondering if a rebuild of the bottom end would and should solve this. If so wht would the cost be about and if not what should i look into?
its a 1991 350 tpi 5.7

 

Well its odd that 4 and 8 both have the same compression? Usually that happens in adjacent cylinders from a blown head gasket. Futhermore I would be very disappointed in the shop for not really doing the compression test. What i mean is yea they did the compression test but when you hit a cylinder with low compression your supposed to add a little oil to that cylinder and retest the compression to see if it improves or not. If it improves its the rings if not its in the heads. Because they didnt you spent good money to have the heads redone to not solve the problem. This is assuming no cracked block, the valve train is in good shape, stuff like that. Although at 110K i have a hard time believing that your rings are shot unless the car has been poorly maintained/overheated or something. Although like i said you can easily test to see if its rings.

 

Duplicate post

 

for what a shop would charge you to diagnose the problem you could have bought a manual and compression gauge and diagnosed the problem yourself. what happened to the car right before you had the problem?

 

A broken piston would also not be helped by adding oil.
I ran this test on a car I bought with a broken piston and ran it again on another one that I had melted.