Lets see

Car started sounding like a subie when I went into boost a bit then notice loss of power

Did compression test cylinder 3 was holding 70 psi, all others were around 140-150

Some people say I bent a valve but a local tuner said your psi would be zero if that were thr case

He suggested I broke a land ring or melted a piston

Head is coming off tomorrow but need opinions

 

i had a bent valve and a bad valve seat and i was doing 80 on the 4th cylinder and all 3 others were doing 170, so it might be the case of a bent valve. Does it started to do it without any other problems ?

 

Well regardless the head is gonna have to come off, so not too much point speculating.

 

Well the head is off so here is what im trying to figure out

If it was a bent valve a local tuner said you would have zero psi from the compression test because its leaking i was holding 70

If it was a headgasket would that affect all cylinder pressures?

Or would it be the rings of the piston just barelt holding pressure but still stable?

I would prefer not to pull the piston out just to save time but need help, if I need to pull it then so be it

 

I had 2 bent exhaust vales on cylinder 2,3. Compression was 120 on those two cylinders and 155 on 1,4. Brought the head to the machine shop for rebuild. They told me I bent two exhaust valves and the valve seat needed to be redone

 

Ok so it held the pressure not sure why I was told it would be at zero psi, I'll send it in because it does need it anyways before putting it back on

 

Who ever told you it wouldnt read any pressure on a compression test was wrong. The only way it would read 0 is if you straight dropped the valve or there was a big hole in your piston. Either of those would have been really obvious when you pulled the head.

 

ok I better not mention who said that then... he has a really good reputation down where I live lol


Ok sounds good thank you

 

I had bent valves that held water for 2 hours in the head upside down that had zero compression. It is possible without it being obvious. Don't use water use a solvent like PB Blaster or WD40 to check valve seal.

 

I mean if your valves are so bent that they never open at all then you could read 0. Thats pretty bent though and you would be able to see that. It is not a case of bent valves = 0 compression though. How bent am i talking about? Bent enough to probably throw the rocker off.