Low compression after new head gasket Any ideas?

[chrisagu28]

I put in a ka24de swap into my 89 240sx, It fired right up but yet a few moments before I drove it, white smoke poured out, it blew a head gasket. So I took it all apart, surely enough gasket was done for. Put a new one on and put it back together, now it won't start. Got fuel and spark. Come to find out I have too low of compression. I am getting roughly about 95 on each piston. I know it is suppose to be 150+. So any ideas why such low compression?

[sommmatt]

deck the head/block? piston rings? valve seals?

squirt some oil into the cylinders and redo your compression test.

[chrisagu28]

Alright I will do that. I think I might have messed up. When I put on the new head gasket, I reused the head bolts not thinking about it. I was reading if you reuse the old bolts it won't make a good seal at all and cause a low compression and possibly head gasket leak.

Do you think that might be the cause?

[240sxmech]

your timing might be off by a tooth or so recheck your timing marks.

[chrisagu28]

at first when It would not start I thought it was the timing, so I redid the timing chain various times. I did it so many times. Everytime lines up where it is suppose to be at TDC and the lower and upper chain are all set correctly.

thanks for the response though.
Modified by chrisagu28 at 5:29 AM 11/15/2008

[DubsSuck]

dumb question but did you zip the head bolts in sequence and let the gasket set?

[240sxmech]

really dumb question ,what do you mean by let the gasket set?? lol

[chrisagu28]

Yes in swquence and I torqued them down, but I did not put oil on them Like I was suppose to. I read that you are suppose to dip it in oil, torque down once then untorque them then retorque them once again. Weird.. I just torqued them down dry.

What do you mean let the gasket set?

Well today I found a good bit of gas in the oil and you can smell gas like crazy in the head and on the dip stick. So I am thinking the gas ruined the piston rings and it is not causing compression like it should. I would have to rebuild the whole engine at this rate.

[DubsSuck]

really dumb question ,what do you mean by let the gasket set?? lol

you're acually supposed to torque the head bolts twice once to set the gasket so it can seal, and the second to secure the head.. thats how chilton tells you to do it... thats how i did it.

[480sx]

Kinda seems like cam timing. You might have made it so that the upper chain lined up, but you could still have the lower chain messed up.

[chrisagu28]

I mean, I found your post timing and how to set it after a head gasket change. I used it and lined everything up. I will probably take this motor out and put it aside. Put a running one in and build up the spare motor or something.

[s13_maJiK]

I mean, I found your post timing and how to set it after a head gasket change. I used it and lined everything up. I will probably take this motor out and put it aside. Put a running one in and build up the spare motor or something.

Step 1: Make sure timing is correctStep 2: Leak down test- If you see the coolant bubbling in your radiator or reservoir, you have a bad headgasketStep 3: If you don't have coolant bubbling and it isn't holding the compressed air, Possibilities could be rings, valves etc as stated earlier. (To test for rings, do a wet compression check by squirting oil in to the cylinder, as stated earlier, if your compression goes upyou have bad rings.

[fitofitin]

Try to see if there is another cylinder giving you problems.

This is what I have learned. A simple step to find it: run the car and start to unplug the spark plug wires, one by one.

The idle speed will diminish strongly, and the smoothness too, with each wire removal, this is normal.

But when you have a bad cylinder you will notice very little or no change at all. When you unplug a wire and that occurs, then you found the bad cylinder.

For that cylinder you should perform these tests in different stages: ignition test, fuel test and compression test.....

Compression shouldn't be a problem since the gaskets are new, though.

When doing a compression test and you detect problems, the most likely causes here would be a leaky valve (probably an exhaust valve since they run much hotter than intake valves and usually fail or "burn" first), a blown head gasket (which shouldn't be the actual problem this case), or a rounded or badly worn cam lobe.

Also perform a leakage test. Air leakage through the exhaust port would indicate a bad exhaust valve. Air leakage back through the intake manifold would indicate a bad intake valve. Air leaking into an adjacent cylinder would indicate a blown head gasket. Minimal leakage would indicate a rounded cam lobe.

Leaky valves would require removing the cylinder head and having a valve job performed. A leaky head gasket would require removing the head and replacing the gasket (and probably resurfacing the head to restore flatness, so check this out for your new gaskets. Are they sitting properly?). A cam problem would require removing and replacing the camshaft and lifters (old lifters should never be reused with a new cam).

Hope this helps. Good luck

[s13_maJiK]

Try to see if there is another cylinder giving you problems.

This is what I have learned. A simple step to find it: run the car and start to unplug the spark plug wires, one by one.

The idle speed will diminish strongly, and the smoothness too, with each wire removal, this is normal.

If you do this make sure you ground the wire

[needmorenissan]

the same thing happend to me it was the piston rings on mine could be the timing on yours did u machine the head or block?