Hey, I'm a newbie to the forums but quite familiar with engines. I've recently tried installing a Y8 head on my D16 ('90 CRX) with little success...regarding compression anyway. Here's the story:

Before I touched anything, I tested the compression (cyl 1-4): 180-170-170-170. Sweet, the spec is 185, all looks good. I did the whole swap, took another reading and got like: 80-120-100-120. I figured my head was bad or something, so I reinstalled the original head, headgasket, and took readings again: 60-80-80-100. WTF!?! I've been doing different combinations of Y8 head to A6 gasket, A6 head to Y8 gasket, Y8 head to Y8 gasket. Each time I take care to tighten the head bolts properly and in order, make sure my timing is dead on, and that my comp. tester is fully tightened in the plug threads.

WHAT IS GOING ON!? My bottom end has to be fine due to the readings I received in the beginning and the fact that I haven't touched anything but the head this whole time. I would blame the Y8 but the A6 is getting crappy readings too! Anyone ever come across something like this? I need my compression back!

 

I would suggest performing a leakdown test... that will tell you for sure.

Were you very careful to make sure you aligned and installed the timing belt correctly and tensioned the belt correctly as well? If you installed the belt off a couple teeth, or you didn't tension it properly it could have skipped teeth... which would cause piston to valve contact resulting in bent valves and low compression (although I think that your numbers would be more consistently low throughout all the cylinders if you bent valves, but its worth mentioning).

Also, make sure that you perform the compression test with both underhood ECU fuses removed and with the throttle FLOORED.

 

I did the compression test exactly the same all times (with WOT and plugs removed). I've been extremely careful to align the timing marks each time, I've also removed the heads a couple of times now and could see no evidence of contact between piston and valve. A leak down test involves the valves correct? What is the general procedure involved and what will it "tell me for sure"? I've never done one, thanks for your suggestions!

 

A leakdown test just pressurized the cylinders with compressed air and then measures how much leaks past the valve seats and piston rings as a percentage. The lower the percentage, the better.

 

It also helps you figure out WHERE it's leaking 'cause you can usually hear whether it's leaking into the crankcase or into a manifold.

 

Ok, how will I ensure that the valves are closed on the cylinder that I'm pressurizing? On a side note, I'm ordering a new head gasket (Part# 12251-P01-004) because this one gave me my best readings, but I've been testing on a used one. Hopefully I'm just having a problem sealing the Y8 to the D16 with the '96-00 head gasket and the '88-92 will fix that issue.

 

You turn the motor over so that the piston in the cylinder you're testing is at tdc as well as the cams. Then you force air into the cylinder and listen to where it leaks out.