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Low Compression

shrike

By shrike,
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shrike Apprentice

shrike

Posted
Posted

Ok so i have a rb25det neo in my 32 long story short some di*k tried to nick my rad cap and I didnt notice so car overheated bad head gasket went and compression as follows

1st cylinder 30psi

2nd cylinder 0psi

3rd cylinder 0psi

4th cylinder 60psi

5th cylinder 31psi

6th cylinder 121psi

engine was a 80000km import motor with a range of 150-147psi

so I got the head skimmed 25thou och

new gasket etc all torqued down

got a mate to do the timing (may still be out will be getting reset asap)

car wouldnt turn over

redid the comp test on the first 3 cylinders and gave up as the results where the same

there is no water in any of the cylinders so I know the head gasket is sealed

before I replaced it there was no oil in the cooling system or water in the oil

pistons dont seem to have shrink and pretty sure rings are ok

could the timing cause compression issues?

any other reasons this could be happening ?

otherwise I may just get the engine rebuilt or buy a long block (grrrrr)

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SargeRX8 Grand Master

SargeRX8

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Posted (edited)

Timing can cause compression issue but it can't be that bad.... A cylinder might never be able to compress if one of the valves is open but if your timing is that far out, I would be surprised if you didn't bend your valves and they aren't sealing. Adjust the timing your self if you know how. Remove belt and slowly line up all markings to 0 degrees. Do a leak down test so you can source the leak. did you inspect the head when you replaced the gasket? Reading your thread over you seem to have over looked the head completely...

Edited by SargeRX8
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shrike Apprentice

shrike

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Posted

When I ripped the head off I got it skimmed and I checked all the valves etc and everything seemed ok (valves went up and down fine etc)

I didnt get it vac tested so im guessing it will be the head hoping not however :s

im taking it to my mates dad whos a mech and going to get him to set timing and do a leak down test to see whats up im guessing head will need to come off and be rebuilt or replaced

if it needs replaced id have to buy a long block as finding a neo head is near on impossible

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