Bent Valves? During Belt Change

[gijoe985]

Not my car, but I thought I'd ask.

Timing belt was being changed. The engine got tuned over with the belt off, or something along those lines. The belt was reinstalled. The car ran rough. The belt was reinstalled 2 more times because it was assumed that it was off a tooth. Compression reads moderately low on a few cylinders ( I don't know how low, but lower than normal) Car is getting a Random Misfire code.

Sound like a few valves got bent? Solution, take off head, take head to machine shop, have them pressure test?

Thanks

 

[4pistons]

The engine got tuned over with the belt off,

Turned over with the starter or by hand??

The belt was reinstalled 2 more times because it was assumed that it was off a tooth

Assumed?? Whoever did the job didn't know? Timing belt replacement is a very exact procedure on a 4G63, it's not something left to chance or guessing.

Compression reads moderately low on a few cylinders ( I don't know how low, but lower than normal)

If the valves were bent enough to cause the car to run rough then compression would be close to zero on the cylinders with the bent valves.

Solution, take off head, take head to machine shop, have them pressure test?

Do a cylinder leakdown test while everything is still assembled. DOUBLE, TRIPLE check the timing belt install.

Rick - '91 GSX

 

[alansupra94]

Yeah considering that these are interference motors when I am setting the timing, I am making sure I am dead 100% sure on the timing.

 

[gijoe985]

Turned over with the starter or by hand??

Well it has been run since then... so if they were off, they have run it.

Assumed?? Whoever did the job didn't know? Timing belt replacement is a very exact procedure on a 4G63, it's not something left to chance or guessing.

Well it was running so bad, that is all they could assume was wrong. Ran fine before, replaced the belt and it ran like garbage. So it was a logical assumption. I don't know if they were thinking about bent valves.

If the valves were bent enough to cause the car to run rough then compression would be close to zero on the cylinders with the bent valves.
Do a cylinder leakdown test while everything is still assembled. DOUBLE, TRIPLE check the timing belt install.

I'll get them the stuff to do the leakdown test. I've ran into something like this before. On a mazda protege. The valve was just barely not seating, so it still had like 90psi showing up on the compression gauge. But a leakdown showed that one of the exhaust valves was definitely leaking...