THSCC Forums

Are there any Honda CRX Si (1988) cylinder head experts out there?

I got a chance to adjust my valves today and ran into a potential snag. I bought the CRX with 235k miles on it and I really don't have any idea of the history of the car. Something in the head was ticking like a time bomb (or a Miata ) and I assumed it needed a valve adjustment. Sure enough, most of the lash tolerances were *way* out and once I set them where they should be, the car seems to idle like a champ. I didn't get a chance to test drive it yet but it seems much more responsive just blipping the throttle.

The potential problem is that on one of the exhaust valves on the #4 cylinder, the adjustment screw had to be nearly bottomed out to get the lash within spec. All of the adjustment studs sit about 1/8" above the set nut (gotta be a joke in there somewhere) while the problem child mentioned above sits nearly 1/4" *below* the top of the set nut. If it was any lower there wouldn't be enough thread within the nut to tighten it properly.

I'm guessing this was the valve that was ticking so loudly. While the tick is totally gone, is this going to cause me a problem in the future? Any idea what would cause this one valve to be so far out of adjustment? About the only thing I can think of is that the spring has weakened over time and is sagging. I can't really see and other signs of physical damage to the rocker assembly but it wouldn't take much to throw it off I imagine.

I'm currently looking for another head I can rebuild in my spare time but it will probably take a couple of months. Well, unless of course I have to do something about this immediately.

Any ideas?

Thanks,

Jim

My guess - Slightly bent exhaust valve from someone breaking a timing belt - it's an interference engine. If the valve head has an edge (or shaft) bent, it won't seat all the way and would cause the adjuster screw to have to be turned down a lot, right?

I did it once on my CRX and that valve ticked ever after.

Check the compression? That should confirm a bent valve.

PS - I have just the opposite problem on my (formerly Karl's) MGB - valve recession, so the valves are sticking up too high.

_________________
Mike Whitney
whit32@gmail.com, 919-454-5445
V10, V8, V8t, I6, I6, V6, F4t, I4, I4, I4, I4, I2, 1, 1

Thanks! Off to find a compression gauge...

The car sure seems to run ok with a possible bent valve but I don't have much experience with these things.

If the timing belt broke, would it bend only 1 valve? It seems like more stuff would have gotten bent/broken. All the other valve adjustments were spot on.

I'm guessing if the just the shaft was bent it would still show good compression if I got the adjustment back within spec?

Jim

Nope. The valve would be "cocked" on the seat which is why Mike said the valve shaft is effectively "short".

You MIGHT be able to look through the spark plug hole to see witness marks on the piston top. However, since the engine was run a bunch since the possible incident any mark could be hidden by carbon.

If you can, do a leak down test since it can isolate where the "compression" is going if you have low compression.

Dick

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Dick Rasmussen

FS 50 2018 Mustang GT

I think it's possible all that happened was 2 bent valves with no other damage if the T-belt broke - those were just the only ones fully open. I'm working from theoretical knowledge here though.

You're right, I would expect the 2 valves next to each other to be similar. But who knows what bent which way IF the valves smacked the piston. Any weird marks on the cam at the bad one? If something is wrong, I wouldn't wait to fix it, since a bent lip is (1) probably tearing up the valve seat and (2) causing some pretty high (ie not designed for) forces on the valve and seat. Probably fine on a low-rpm street car but asking for trouble in competition use. IMO.

T-belt broke on my 90 CRX Si @ 83k in 1995(?). At the time I believe the service manual said to do it at 80k. I had a shop put on the new T belt (in college at the time) and it ticked but ran fine. Never did check the valves or compression - drove it another 50k and sold it in 1997.

_________________
Mike Whitney
whit32@gmail.com, 919-454-5445
V10, V8, V8t, I6, I6, V6, F4t, I4, I4, I4, I4, I2, 1, 1