My friends car stripped the timing belt and bent valves. We pulled engine apart and used another set of heads with good valves to get the car running. Now it runs, but runs very rich and makes less than half it's power. It has higher than normal compression, and is getting good spark. The ECU is reporting code 55 so all the sensors are working. The one thing that was quite strange when we were reasembling was the the front head timing gear would never line up with it's timing mark, it was always 1/2 tooth off, either forwards or backwards. It lines up with the marks on the belt, but not the rear timing cover. That head was off a Z31 engine, but everything seemed identical. Can anyone thing of a reason why this head would be throughing the timing off. The cam, cam gear, lifters, rockers, and distributor are from the original Max engine. We are really scratching our heads on this one, and hoping someone has an idea of what to check. Sorry for the long post, thanks for any replies.

 

Anyone have any ideas?

 

I'll take a stab but you probably know more than I do since you guys did all that. All I have done is the timing belt myself but mine didnt line up at first either.

What I learned was that the front cam and the distributor are gear linked, while the rear cam and crankshaft arent except for the timing belt. So if you had the front cam out 180 degrees that could be a problem, or if the crankshaft and or rear cam were out 180 degrees that would also cause a problem. In other words you could have things lined up but 180 degrees out of phase. Although it should not run well if it does at all. Hopefully cylinder 1 (on the rear bank) is at TDC (according to distributor location) when all three line up with the cover, the belt marks are only used when installing the belt to ensure the correct nummber of belt teeth between the front and rear cam sprockets. After they are on and you rotate the crankshaft by hand with plugs out you can check for any interferance and to see if all the sprockets line up with their marks on the back of the cover. You will notice that the belt marks will not line up again or only on every X number of cycles. This is only my understanding and I could be wrong. Hopefully others with more experience could confirm or deny and help you out. Good luck.

 

Well, just to let you know, if you line up the cams with the timing marks and the crank with the timing marks it's not possible to be 180 degress out of phase. It is possible to install the distributor 180 degrees out of phase if you base it on TDC of the crank alone. This whoever would cause the car to not run at all. We installed the distributor when the timing belt was installed so we are sure everything is at the correct TDC.

We starting pulling the front head apart today to switch the valves and put the original head back on. We found that the intake valve for #6 was not opening. Not really sure why, the lifter was fine and the rockers seemed normal. But the intake port on the head was full of gas. So that would explain the loss of power and the gas smell. We are hoping that with the original head, all the marks will line up the way they are supposed to and everything will work this time. I will post a reply when it's all done.

The really strange part is that even though the intake valve was not opening, the cylinder still got compression. I guess it was sucking air back in through the exhaust valve or something.