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HELP!! Mechanical tensioner slipped Leakdown test show no bent valves low compression

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GSTurbo1

10+ Year Contributor
610
1
May 2, 2012
Pickens, SC, South_Carolina
Ok this has been a long drawn out process and I should have had my car on the road two months ago. After a fresh rebuild new pistons bearings and everything, head decked checked for warpage I got it all together and switched over from hydraulic to mechanical tensioner. First turn of the key the car started right up and idled perfectly, then I went and sat in the drivers seat watching all the gauges. The car began to lobe real hard then just died, I tried to start it back up without thinking. While trying to start I heard a metallic pinging with every stroke of the piston, then I got out and walked to the engine and saw that the timing belt was practically off of the camshaft sprockets. Instantly I thought bent valves, I put the car back in time and could not get it to fire. A couple of times I heard like a fireball, sort of off time combustion that made me think bent valves too. So we did compression check and showed 90psi on 1,4 and 20 to thirty on 2,3. I pulled the head took it too Dover cylinder heads and they said it had no bent valves but I think they just didn't want to work on it. SO I took there word for it and put it all back together and compression test showed same thing but leakdown test showed low 15-20% leakage only past rings like normal. So I said screw it and bought a completely refurbished and restored head from nwcylinderheads, plus I have some stripped threads on the head I pulled.

The car has been professionally timed multiple times so It was not me struggling to get in time.

I installed OBX stage 1 cams in the car, the car ran so I don't think it would be the cams causing this problem. I'm hoping its slightly bent valves.

I did the test where you turn the head upside down, put solvent on the top... if it has leaky valves the solvent will leak through, I had nothing leak through.

Any theories will be taken seriously, cross your fingers and say a prayer that this new head will be a god-send.

The block and pistons are perfect a couple of light cirecles on the pistons can't tell if it is from me tapping it down with rubber mallet handle when installing in the block or if its from valves hitting.


FIXED::: I have bent valves! I took the exhaust manifold off and noticed that there was gas on the mating surface and gasket. Previously I had done the solvent test with gas... So I preceded to put the head on its side... intake facing down and exhaust facing up. Then, filled each exhaust port up with seafoam immediately valves from 2nd and 3rd cylinder began to leak sea foam the numbers 1 and 4 began leaking shortly after. I then flipped the head over and did the intake ports... immediate leakage out of all the ports. Problem FOUND!!! But why would the leak down tester not show this? I guess I didn't have enough psi to show the correct %.

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