Just did a compression test 100 psi on every cylinder how bad is this?

[MR.chris]

I just bought this motor from a local guy and did a compression test today. Every cylinder was at 100psi cold. I dont know much about motors but this looks bad to me. The motor has 264 cams and a tomie 1.2 hg would this make any differance?

[rc1honda]

Motor is no good do not buy. Even a cold compression should be around 130psi. Sounds like the rings are fried. If u do buy be ready for a rebuild.

[MR.chris]

I bought it six months ago and just got it running. But it runs like crap. I am screwed!

[rc1honda]

Recheck the compression after the motor has run awile and gets warm. if it's still at 100psi pour a little oil into the spark plug cylinder, if the compression goes up after the oil then the piston rings are fried and you will ned to rebuild the bottom end.

[OM3GA]

Well the thicker head gasket would definitely bump the compression down some. Definitely check it in different states as rc1honda has stated. If you can ask someone that knows the formula to calculate what the compression numbers should be after that hg has been installed then maybe you can get an idea.

[MR.chris]

I will definitely recheck the compression again but I wont have time to work on the car until next weekend. If the motor is bad can I drive it around on low boost for a while or should I have it rebuilt right away? I dont want to cause unnecessary damage to the motor.

[OM3GA]

Well it depends on how its running, obviously check your oil and stuff like that. I mean seriously try to calculate what the compression should be at with that HG and go from there, also ask if there is low comp pistons etc. Any of these things will drop your numbers and appear to be giving you a bad compression reading even though they are set up for the stock specs. Basically the lower the compression the higher the boost can be without knocking as long as everything is in good shape.

For example if your compression is low because of a leaky headgasket but it still runs that does not mean you can boost it more. However with mods such as thicker HG and lower compression pistons it will give the same effect but everything will be good to go. Find out what all is done to the engine internally and go from there. If its nothing other than the HG thats been replaced find a way to calculate what the compression numbers should be. Thats what i would do.

Good luck!

[canary-s14a]

the manual says to do the compression test with the engine well warm, and with the throttle completely opened. The min value is 128 psi, the optimal i think is aroun 150 psi

If you test it in cold engine probably the rings wont be well tight and 100 psi maybe is normal...

test in wam condition and you will know

1,2 is stock height so the head gasket wont be the problem...

[MR.chris]

I drove the car around last night and it runs pretty good no smoke or anything. But it will not idle on its own (for about one minute) until it gets warm I have to keep my foot on the gas pedal and then it runs fine. Anyway I read that if the timing chain is off by a tooth that the compression will be low on all cylinders. Well I have the day off and I will test the compression again today.

[MR.chris]

I warmed the motor up and did another test and I had 121psi on the first three cylinders and 123psi on the fourth. Im just going to drive the car untill it dies. From now on I will allways get a compression test done before I buy. This was an expensive lesson to learn. How long do you think the engine will last if I dont drive it to hard ???

[nuts510]

Read check the cam timing being off one tooth makes a big difference in how they run and the compression. The factor some variance in the compression does indicate weak rings

[Thrasher068]

Just did a comp on mine as well. i am at 150 - 160 PSI. If u have bad rings you may want to rebuild sooner then lettin it blow. Trying to save money now may cost u $$$$ later due to block damage

[OM3GA]

Just did a comp on mine as well. i am at 150 - 160 PSI. If u have bad rings you may want to rebuild sooner then lettin it blow. Trying to save money now may cost u $$$$ later due to block damage

+1 it sucks but it is usually better to rebuild upon the first sign of failure.

[MR.chris]

I removed the valve cover and the exhaust cam definitely looks like it is off by one tooth. Plus the CAS is not centered and I think that is an indicator that the cam angles are off but I am not sure. I think that I will pay someone to fix cam angles and timing.

[OM3GA]

Makes complete sense, hopefully it all works out.