Head Gasket Replace and NO COMPRESSION ????

[toofortyowner]

I recently purchased a 1995 240sx. The owner told me that the car had a bad head gasket. His daughter said that it over heated and she immediately cut it off and they let it cool added coolant and drove it home.. It then just sat until I purchased. Before I purchased the car, we were able to get it started after about 15 minutes of cranking. And it ran pretty strong when it was running. I would over heat after about 10 minutes of driving.

So I purchased it, towed it home and pulled the head off of it. I took it to the machine shop where he said that the "head got really hot" he machined it a couple time to get it strait and gave it a valve job. I took it back placed it on and purchased NEW head bolts. As I was torquing the, I broke the heads off of one of the bolts. I realized that I was torquing them too tight ( I was using NM vs ft/Lbs) I figured I would continue on any way( with one missing/broken bolt.) I I got it all back together( with the exception of a couple intake manifold bolts) and tried cranking the car. The engine spun freely as if there was NO compression. it did not even seem as it was trying to start. So I removed the cams and removed the head again to get the broken bolt out of the block -- I took one of the old bolts and used that one instead. I got a new gasket and reset the head. This produced the same result. No compression. This time I put a gauge on it. NO COMPRESSION. ( Or it would jump to like 30PSI and and immediately go back down to 0 on every cylinder. I again pulled the head and went to buy a used head and slapped it on with the bolts. ( used a new gasket this time) I ultimately got it to start but it took about 20 minutes of cranking for it to start and it would immediately would shut off. It also would backfire. ( Timing off?)

I am at wits end....I am not sure whats going on -- as far as timing is concerned -- I think I set it correctly -- cam lobes are at 12 and about 2/3 or so. The piston #1 was at TDC as well. -- I also lined up the distributed to hit on cylinder #1. The only thing I can think of is buying new bolts and torquing them to spec as I have used these bolts -- the first set I over torqued -- and I did not reuse those -- the second set were the original bolts which I dont know if the previous owner over torqued them or what.

What are your thoughts. It seems that the head still is not sealing the chambers...with the used head or with the machined head.

Thanks for your help

[FlipCoupe]

Pretty sure those bolts stretch once torqued so you should never reuse OEM head bolts. Also the cam lobes should not be pointing to 12 at TDC, there are a few threads on here that show how to properly set the timing of a KA.

[toofortyowner]

Thanks on the bolts...what I meant by Cams was the little dot not the actual lobes..the lobes are pointing away from each other almost straight at the to of the head rim

[Lobo240sx]

Check the mechanical timing.

[toofortyowner]

Ok -- so I did a compression test and cylinders 1-3 are reading 150 each and cylinder 4 is 0 (zero) -- this is an improvement from zero across the board.

As far as mechanical timing goes...I think I am doing it right but not sure. What would cause one cylinder to be zero. It moves NONE. Could timing be off 90 degrees. Or is there a post on how to set mechanical timing when you have a complete rebuild.

[OutToWinPAHC]

New bolts yes ( DO IT) , not that it matters here but do you know how much was milled off the head and did you get the proper sized gasket? And did you check the block at all, if the head was that bad you could have a bad decking or problems with that cylinder (rings, ring lands, scoring).

And yes
how-to-remove-cylinder-head-from-ka24de ... 17356.html
1991-1994-240sx-replacing-timing-chain- ... 55023.html
zerothread?id=62997

[toofortyowner]

The block was good and the head I have on there now is not the one I got milled. Its the used one I bought. I have compression now but in one cylinder...and it is reading ZERO. Would bent valves give you ZERO. With a bent valve would it read at least low? Prior to install I did the liquid test to see if the valve sealed and it was good.

[OutToWinPAHC]

Bent valves would not seal

[FlipCoupe]

When my cylinder 1 read 0 psi it was my rings. Full rebuild and I had compression back, unfortunately I over tightened a rod cap and that was the end of that project lol.

[StryfeS13]

Yes a bent valve will give you 0 compression. Even something stuck on the valve preventing it from closing will give you 0 compression.

Pour a cap of oil in the cylinder and see if the compression raises, if it does, it's your rings, if not, it's something else.

[OutToWinPAHC]

Yes a bent valve will give you 0 compression. Even something stuck on the valve preventing it from closing will give you 0 compression.

Pour a cap of oil in the cylinder and see if the compression raises, if it does, it's your rings, if not, it's something else.

If the rings were that far gone where you had 0, well oil wouldn't help

[IanS]

Compression test will show you a symptom. A leakdown test will tell you the cause.

Do a leakdown test and report back. That will tell you if its leaking into the crankcase, cooling system, intake, or exhaust.

[toofortyowner]

Just coming in for the night...I think I will try a leak down test tomorrow. I ended up redoing the timing I rotate the cams a little. They were set perfectly as I have read in other post. Also my chain have the silver links to help you and I originally set them to that.

I moved it a tooth and reset the distributor. Now I have 30psi in the 4th cylinder and it cranks -- it runs really rough but it started and I have compression. I figured that the cam timing must have been leaving the valve open on the compression stroke. I still dont know why its so low but maybe the leakdown will tell me.

[FlipCoupe]

Yes a bent valve will give you 0 compression. Even something stuck on the valve preventing it from closing will give you 0 compression.

Pour a cap of oil in the cylinder and see if the compression raises, if it does, it's your rings, if not, it's something else.

If the rings were that far gone where you had 0, well oil wouldn't help

When I did the oil test I went from 0psi to about 20psi, it definitely raised it even with blown rings.