No compression in 4 of the 6 cylinders in a 95 3.1l engine

I have a 1995 Buick Century that overheated and blew a head gasket. The vehicle ran and I pulled the heads and had them resurfaced. When I installed the heads and tried to start it it did not run. It has gas and spark. I checked the compression on the front 3 cylinders. They have 0 compression. I pulled the valve covers and checked the pushrods on the rocker arms. The push rods are in the proper location. I checked the compression on the back 3 cylinders and 1 and 3 have 120 PSI and # 5 has 0. I am thinking the timing chain and sprockets have jumped a tooth or 2. Any ideas.

I have a 1995 Buick Century that overheated and blew a head gasket. The vehicle ran and I pulled the heads and had them resurfaced. When I installed the heads and tried to start it it did not run. It has gas and spark. I checked the compression on the front 3 cylinders. They have 0 compression. I pulled the valve covers and checked the pushrods on the rocker arms. The push rods are in the proper location. I checked the compression on the back 3 cylinders and 1 and 3 have 120 PSI and # 5 has 0. I am thinking the timing chain and sprockets have jumped a tooth or 2. Any ideas.

did you tighten the bolts in the pattern there supose to be when replacing?

If its just the valve timing, then all the cylinders should still have a similar reading.

Try spinning the engine over with both valve covers off (by hand is best) and observe the valve gear. Do all the valves go up and down the same amount?

Also, take a close look at the top of the valves and springs. Make sure the valves and keepers are still in place. It's possible some of the valves have dropped.

Yes I tightened the head bolts as per OEM recommendation with new head bolts. The valves all open and close. I can not index #1 cylinder to verify TDC. I have backed the rocker arm nut of a little on the 0 compression cylinders and they jump up to around 150 psi.

How much did the machinist remove from the heads? If it's much more than a 0.020" cut the push rods may be too long. The Chevy V-6 has a very sensitive valve train, an lifter plunger travel is only about 0.080" total maximum.

If the cut was lighter than tah, your lifters may have pumped up. They should self-adjust once the engine is running and oil flow/pressure is normal.

Dont know how much was cut from the heads. If the cut was more than you specified how can I compensate for this?

I have run into that many times. Seems the lifters get pumped somehow with the pressure off. Take the front valve cover off and losten the rockers a couple turns. engine should start, tighten each rocker slowly as they start to tick back down to their stops. will run rough for about 5 minutes then smooth out and all good after that.

Thanks for the input everyone. I have heard of lifters collapsing but not pumping up. I will give it a try.

Does any one know what causes these lifters to pump up and hold a valve open?

Not sure what causes it but I have done tons of those head gaskets and it just seems to happen 1 out of 10 times. Did that fix it?

I finally got a chance to work on this car today, I finally got it running, the only problem now is 1/2 the lifters are not oiling the rocker arms. Ran it about 10 minutes, changed the oil and ran it for another 5 minutes still no oil to these same rocker arms. I would put it back together and run it but Ii need to ensure the rocker arms are oiling.