Crank only spins about 180 degrees on partially rebuilt motor

[PeterC]

My son has been working on his LY7 and got to the point of replacing the heads on the block after swapping camshafts. He placed the heads on the motor and torqued them down without moving the crank into the correct timing position. Now wen the motor is rotated it stops at two points with a hard metallic noise is if it hits a pin or something, prior to the heads being put on motor spun freely. We took the camshafts off still same problem, we tapped tops of valves and none seem stuck down (all springs extended, look same height by eye). We took sump of looked at crankshaft looks ok. However I suspect that WD40 usage on the big ends may have siezed one of the shells so it rotates and then stops, is this possible? Or is it possible a valve bent if a piston was at TDC when heads torqued?

 

[_R_J_K_]

Pay attention to this thread - https://forums.justcommodores.com.au/threads/alloytec-wont-rotate-by-hand.283154/

 

[Not_An_Abba_Fan]

Pull the heads off again and have a look. Anything else bolted on at the same time as the heads?

 

[shane_3800]

I highly doubt you would bend a valve as the piston should move.

 

[PeterC]

Pull the heads off again and have a look. Anything else bolted on at the same time as the heads?

We think you're correct (we're going to have to take the heads back off), my son wanted to avoid this as it is expensive for him as needs new bolts and gasket when doing so. The only other thing was the oil pump but we took that off, no change. I wondered what would happen if piston at TDC (my thought was that there would be a low chance the piston was exactly at TDC and that it would move out of the way too, unless perhaps two pistons opposing each other).

 

[shane_3800]

We think you're correct (we're going to have to take the heads back off), my son wanted to avoid this as it is expensive for him as needs new bolts and gasket when doing so. The only other thing was the oil pump but we took that off, no change. I wondered what would happen if piston at TDC (my thought was that there would be a low chance the piston was exactly at TDC and that it would move out of the way too, unless perhaps two pistons opposing each other).

You don't need to replace the gasket. If you know the torque of the bolts when doing the angles you can get away with reusing the bolts too.

 

[losh1971]

Couple of HGs is not expensive and bolts are cheap too. I can get a set of bolts for my engine for $70 the lot. Why risk it for that price. If I had a V8 it's cheaper again. IIRC Alloytec parts were cheaper than Buick, when I was looking.

 

[delcowizzid]

Are the chains on the cams and timed correctly

 

[PeterC]

Are the chains on the cams and timed correctly

The cam chains weren't on, cam shafts were free to move independent of the crank. If it's bent valves it's weird.

 

[PeterC]

The issue was that the spaces in the head gasket for the cylinders was about 1mm in diameter too small, my son suspects that the gasket was for the 3 litre engine. Ebay not so good in this case.