So I have a 2004 Honda S2000 with 156 K miles. Recently my timing chain snapped but no damage was done I rebuild the head anyways and car drives fine but when I check compression it is low 180 previous the rebuild I check the compression it was at 240-235. Any idea what can cause the problem

 

Using the same gauge? Took test both times when the engine was at same temp? Hot engine wont read the same as a cold one. Throttle open or closed?

 

use a different gauge. This time I tried it on hot engine I'm not sure about last time before rebuild but I'll try both ways also closed throttle

 

Sounds like several variables. A different gauge will almost always read different to some amount. Some quite a bit for what ever reason. People report it all the time. 180's is pretty darn low though. Wondering if the gauge is leaking?

With my gauge I have tested two of my motors. A F22 with 50k miles read in the 220 range and a F20 with 80k miles reads in the 210 range. Same gauge, same conditions, cold engine, throttle open.

 

I agree, numbers can only really be compared using the same gauge and conditions.
My car came back as 200 / 200 / 210 / 210, but leakdown shows 6-8% in the front two and <2% on the rear two.

Either way, leakdown is what you want to do. Short of that, you can skip the leakdown tester and just pressurize each cylinder at TDC and listen closely. I'll bet on hearing air out the intake or exhaust.

 

Cold I get 180 warm I get 230. Thats a brand new cylinder head and 90k block/rings. Cold makes a massive difference.

-Paddy

 

Yes it does.

 

Typically the cheap gauges read like crap, you need to use a good craftsman, snap on, etc a 150-200 dollar compression gauge will give you the best reading.

I know some of these AutoZone/walmart testers showing 110-120 on every car u ever test lol