0 psi on cylinder 3 after swapping in rebuilt/machined head.

[Javier395]

My car is a 1991 LX, original f22a1 with 217k.
Failed to check the timing belt when I got it, it ended up snapping on me one day on the way to work, and, believe it or not, it was the original T belt from 1991, insane.

Either way, I ended up buying a junkyard head out of a 90 f22a1 with same miles, new head gasket and studs and when it is done, all cylinders were on 175 and cyl 3 used to be 75psi, ran okay despite that. Fast forwarding the story, yesterday I got my head from the machine shop, installed it, torqued everything properly and the car runs worse than before, and this time 178psi on 1-2, 0 psi on 3 (dry and wet comp test), and cyl4 came to 150. Checked injectors, retorqued the head down to 79lbs instead of 78, checked valve lash, intake manifold gasket, vacuum lines, and even tried playing with timing a bit until I got it 100% lined up in TDC on both the crank and the head with zero slack on the belt, pretty much so perfect it cant mess up.

Even after those adjustments, cyl3 does not get any compression, engine turns on but runs like crap, when accelerating it you could hear cyl3 being inactive, the car does not stay on by the way, and if it is put under load forget about it, not enough power, car is pretty much undriveable at this point.


What could it be, ... cyl3 piston rings? small hole or crack in piston? impossible but vent valves again?
I checked that piston and it looked great, cyl walls were in amazing shape. Any pointers would be great.

[Raf99]

Smoke... , get a smoke machine on that if possible. If you can push smoke down the spark plug entrance and test with valves closed, you should either see smoke coming out of exhaust or air intake area (or other). Obviously if it's a piston ring then smoke will go in and not come out of exhaust or intake, maybe seep past and come out of oil cap hole.

Only thing I can think of....

[Javier395]

Alright, I will see if I can try that out as well as a leak down test of some sort to see where is the air going.

[Fleetw00d]

Was the cam already installed in the head before you installed it? If you didn't have both the cam and crank at TDC for #1 when you installed the head, you could have bent a valve(s) when installing it. If you set it on block without lining it up properly, you could have set it on an open valve and bent it.

[Javier395]

Yesir, the head was complete when I got it back, I set it to TDC by hand before installing it, and I also set the block (or crank as per say) to the white TDC mark at the flywheel, #1 piston all the way up and #1 valves on the head closed.

[Fleetw00d]

Yesir, the head was complete when I got it back, I set it to TDC by hand before installing it, and I also set the block (or crank as per say) to the white TDC mark at the flywheel, #1 piston all the way up and #1 valves on the head closed.

OK. You lowered the head straight down on the block, correct? If so, then you're back to the smoke and/or leak down test. I'm assuming the shop checked the head for cracks and flatness (although if cracked, I would suspect you'd have at least some compression)?

[Javier395]

Funny thing is, when I had the junkyard head in for a while, cylinder 3 had 75 psi. Now it has 0 which is strange, and still getting good comp on all other cylinders. Im still going to try a leak down test which I havent done, maybe recheck my valve lash on each cylinder, and lastly a smoke test. Not really in the mood of taking out the motor although that would be my last resort if so.

[Javier395]

Funny thing is, when I had the junkyard head in for a while, cylinder 3 had 75 psi. Now it has 0 which is strange, and still getting good comp on all other cylinders. Im still going to try a leak down test which I havent done, maybe recheck my valve lash on each cylinder, and lastly a smoke test. Not really in the mood of taking out the motor although that would be my last resort if so.

All of this just because your boy here did not bother checking the timing belt
haha

[Rilas]

Was it out of time, and you bent some valves? I'm assuming.

[wtfisafleek]

I agree with the leakdown.

So just to be clear, when you installed the cylinder head onto the block, the rocker assembly was already installed?

[Javier395]

Was it out of time, and you bent some valves? I'm assuming.

Before the original belt snapped the engine was perfect.

[Javier395]

I agree with the leakdown.

So just to be clear, when you installed the cylinder head onto the block, the rocker assembly was already installed?

Correct, and before I installed the head back I put the UP sign facing upwards by hand, then the crank on the white TDC mark so both the head and crank are at TDC on cyl# 1

[Chrizzly92]

could've also been a slowly leaking valve seat and now an exhaust valve has a hole burned in it. that would also explain why the 3rd cylinder still had some compression left in it and now its totally gone. i don't think its a timing issue and if he put the crank and the cams in at their tdc mark and then turned them only by hand, bent valves are probably not an issue.
start the car and open the oil cap and loosely put it on top of the filler hole. if it gets blown away, piston rings in cyl3 could be bad, if thats not the case, its not piston related. if other cylinders are fine in compression, its not a timing belt issue. due to the fact that the cylinder still had ab bit compression, i would highly suggest a burnt exhaust valve as the reason for the issue.
it could also be a rocker thats too tight and keeps the valves open a bit. have you checked that?

[Javier395]

could've also been a slowly leaking valve seat and now an exhaust valve has a hole burned in it. that would also explain why the 3rd cylinder still had some compression left in it and now its totally gone. i don't think its a timing issue and if he put the crank and the cams in at their tdc mark and then turned them only by hand, bent valves are probably not an issue.
start the car and open the oil cap and loosely put it on top of the filler hole. if it gets blown away, piston rings in cyl3 could be bad, if thats not the case, its not piston related. if other cylinders are fine in compression, its not a timing belt issue. due to the fact that the cylinder still had ab bit compression, i would highly suggest a burnt exhaust valve as the reason for the issue.
it could also be a rocker thats too tight and keeps the valves open a bit. have you checked that?

I mean the head is freshly machined and most of the originally bent valves were replaced, the good ones were cleaned up and valve stem seals and some other stuff are freshly new, so I dont get how it could be a burnt valve now. Some people have told me that it could be they over shaved the head or did a bad valve angle job on some of the valve seats.

When I had the temporary junkyard head, I put a bit of oil in cyl3 to see if compression woul raise from 75psi but it stayed the same.

I have pending the following: to re-check valve lash, if that fails, a leak down test, or a smoke machine test to see where the leak is.


I will keep yall posted.

[Raf99]

Smooookkkeeee it

go buy a cigar and blow it in. I think there are better things you can buy too that just give off smoke constantly. Blow it in through the spark plug hole. Dam, someone must vape near you. May take a bit to make it to the exhaust outlet though haha