Do I have bent valves?

[HartmanMS]

My harmonic balancer separated the other night. I replaced that. I then found out that I was out of time slightly. So I took the time to take apart the timing side of the motor. I reset the timing belt etc. After I get finished up, I start the car…only to find out that my idle is lopey and rough, my vacuum at idle is merely 8mm-Hg, and I have a major higher rpm vibration . Do I have bent valves? What else could cause this? thanks guys.

 

[HartmanMS]

I am going to try a compression test tomorrow. I think that will tell me if the valves are bent or not.

 

[blue92laser]

Well, Ill tell yah what...

the higher rev. engine vibration is because your oil pump sporcket is rotated the wrong way. And if you managed to do that you might have also missed a few teeth on the timing marks. But most like is bent valves due to the jump in timing.

 

[HartmanMS]

When I reset my timing belt I set the oil pump gear at its white marks, perfectly lined up, as well as the balance shaft gear, the crank, and the cam gears. I did everything right there, unless the oil pump can be out a full turn, 360 degrees..., lined up is lined up on the oil pump gear, isn't it? Then I did the 6 turns to check tension etc. and then let it run for a few minutes (idling like crap of course), and rechecked the timing, still 100% perfect. I will do the comp. test tonight, and post the results.

 

[HartmanMS]

I will also add that before the compression test I am about to do, I checked timing once again, and once again it was perfect. I decided to give it a low rev and hold it there (about 2500rpm) the vacuum increased to about 14-15mm/Hg. More evidence towards my bent valve theory. And I noticed that on a short rev to 4500, I heard a slight metal "ting" . I of course let off the throttle and pulled back into the garage. I will do a compression check as soon as my friend gets here with the kit.

 

[TurboGeoff]

Iam almost positive you have a couple bent valves.

4g63s have very high tolerances, usually skipping just 2-3 teeth will bend a valve.

I skipped 5 teeth on my 3000gt and bent all of the valves.

-Geoff

 

[Defiant]

I did everything right there, unless the oil pump can be out a full turn, 360 degrees...

Bingo.

Were the dowels in your cam sprockets UP when you put on the belt?

 

[HartmanMS]

I had the cam gears' timing cut marks with the white lines aimed directly at each other and parallel with the cylinder head. The pins on the cam gears would have to be up then, wouldn't they? All of the other timing "line-up" marks were dead on at the same time also. This is what I did... -2g timing belt vfaq link- figure 6 shows it.

UNLESS you are talking about number 24. "It is possible for the oil pump sprocket timing marks to be properly aligned, and have the balance shaft out of phase. This could result in a SEVERE engine vibration."

Although my balance shaft gear lined up with its timing mark also when all the others did when I set the timing...I guess tomorrow after school, I will take the belts, pulleys, covers, etc. and find out if the oil pump gear is 360 off. Thanks Defiant for leading me to this. Hopefully that is most of my problem.

The compression test isn't happening till Thursday. I guess I'll have to wait for that.