I have a freshly built B18C1. Went to go break it in today and somehow it managed to jump timing, tested slack by hand cranking engine previously. While driving and monitoring my A/F ratios the car stalled and left me on the side of the road. Got it towed home and found my belt somehow shredded on the outboard side and jumped timing on my intake cam.

Anyway I reset the timing and put on my old belt to compression test the cylinders, I do not have a leakdown tester at home, compression is reading (cold) around 205 psi on all cylinders with relatively unsealed piston rings.

With those numbers do you think I am safe or should I go get a leakdown test performed since the piston rings are still breaking in as well and may throw off the test?

 

I'd just pull the head. Takes a couple of hours and a little money for a new head gasket, but that way you know whats going on. That is just the way I would do it, you don't have to.

 

I will probably end up having to do that just to be safe. My compression numbers previously cold where quite similar though. Wouldn't in theory indicate that the valves are still sealing properly?

 

don't pull the head.... if your compression numbers look good go with it .... your only looking for bent valves which would leak the compression and be obvious..

 

I am more curious as to what caused the belt to jump. Belts cannot jump unless the belt was excessively loose or out of time to begin with. Given you describe only one cam out, I would vote in favor of the timing belt not being installed correctly.

External belt shred would be due to installing the timing belt guide washer in backwards, or not at all. This would show wear on the cover if it were missing. Those two washers are the only parts that control the position of the belt, assuming of course that the bearings and pulleys are straight and in good condition.

Your numbers indicate good sealing. In the event of valve leakage it would be very evident. I would be curious, if you had a bore scope, to look at the intake side of the piston. BTW, did the cam skip forwards, or backwards?

 

The intake cam advanced a few teeth if I remember correctly. Honestly I did not count how many teeth as I was more concerned with getting it back in time and checking for bent valves. Forward guide washer was installed correctly (concave facing away from the belt), it is an 01 so the rear washer is built onto the timing pulley. Apparently a timing bolt fell into the lower timing cover and got lodged in there I am assuming between the crank pulley and timing cover. A friend who was helping me failed to mention that he had dropped a bolt in when he was putting the timing cover back on. I found it when removed the timing cover.

Compression numbers look good and I checked the valve lash which seemed fine.

New belt and timing cover is installed, by myself, and it sounds like it is running fine. I think I got very lucky. I will end up doing a leak-down test just to be safe.

 

*Slight update* I do not recommend using the Actron compression tester "hose" that is just a straight piece of metal that is intended for deeply recessed spark plugs. I found out last night that the part that threads into the cylinder also is threaded into the rod (not one solid piece). I went to pull it out of the warm motor and the threads that go in the rod backed out and left the part that threads into the cylinder stuck the head. Waited for the motor to cool overnight and put blue locktite on the rod and luckily I managed to get the whole thing out.

Moral of the story is use the regular rubber hose and not the long metal rod.

Pic below is the part I am referring to.

 

That's good to hear. FYI, a pulley will always retard when it slips. No pulley can ever spin faster than the force that supplied said force, unless it did a full 360 before re-engaging, in which case you would most likely cause permanent damage.

The belt wear requires a real explanation. A belt does not shred unless something hits or interferes with it. Please explain.