This winter/spring I had the cylinder head off the car. The head was sent out to get ported, valves cleaned, GSC beehive springs, etc. I then put Kelford 272 cams in it. Car was reassembled, and as my buddy and I were setting the timing I noticed this:

With the stock cams and springs, if I would turn the cams (assuming the cam gears were removed) there was like 4 positions. If I turned the cams in between 2 positions they would spring back to the closest one. With the Kelford cams and gsc springs the cams just stayed put no matter where I turned them. I probably should have questioned this more, but I just assumed it was because of the new springs.

Anyway, so I tried to start it up tonight and the motor was spinning WAY too fast and making a vibrating noise. I then took the upper timing cover off and noticed the cam gears were exactly at TDC. I glanced at the dowel pin on the crank sprocket and it was nowhere near where it should have been. I took the pulley off and sure enough, the crank sprocket was just slipping and tore the teeth off of the timing belt. The tensioner seemed to be working properly, and there is lots of tension on the belt.

Anybody know if the cams should still lock themselves into certain positions regardless of aftermarket springs?

 

Take it to CBRD they are right down the road from you.

Josh

 

It sounds like the cam timing was off... i.e. valves resting on pistons. This keeps the cam from turning. Springs won't change that, maybe make it a little harder to turn

 

I'd like to take it to CBRD, but $100 per hour makes for a pretty steep bill. The pistons can't be touching the valves because when I try to start it the crank spins, therefore the pistons are spinning as well. If the pistons hit the valves it would make a pretty loud smack. It's just like something else is froze up or something, not allowing the timing belt to move.

 

Get new timing belt, install it, turn everything by hand before starting the engine (which your supposed to do after you do some kind of head work like this to make sure you have clearance with the valves before starting it.)
Hopefully nothing got damaged

 

Thanks for the ideas guys. Yeah I know you should turn everything by hand, and I had every intention of doing that.. but unfortunately I had a few projects going on at once combined with an extremely bad memory and forgot. Either way, there's no point in installing a new timing belt until I figure out the reason the first one got chewed up. I was just wondering if anyone had this problem before.

 

I was just thinking to set the timing up again and turn it by hand so you can see where it is binding up and you might find your problem.

 

True, you make a good point. I do have to change the belt anyway. I turned the oil pump sprocket by hand, so I know that's not locked up. Besides the tensioner pulley I can't remember anything else the timing belt touches besides the cam gears. This leads me to believe it's in the valve train somewhere. Maybe I'll just take out a loan and trailer it to CBRD. Then they can fix it and tune it right there..

 

First off, a run-in cam will move more smoothly through the bearings and over the lobes. Also the stock lobes are narrower in design and probably more pointed, thus less open duration at max lift, so they might tend to snap to a more valve closed position if the peak of the lobe is not exactly centered on the valve (follower/lifter/shim).

Aftermarket performance cams will have more lift and more duration, with the peak area, generally, much wider than a stock lobe. Additionally the friction surfaces (both lobes and bearings) are still fresh and will not slide as easily until some usage has occurred. So it is not at all surprising that the new performance cams do not snap to a new position. Naturally I'm assuming that the new cam bearings have the proper clearance and that nothing is fouling or jammed.

Do the cams rotate with a proper amount of torque? Or are they very tight to rotate?

If the valves were opened and not properly synchronized with those moving pistons the first time you cranked the engine over, then some or most (or perhaps all?) of those weak valves are now bent as the pistons think nothing of smashing a valve head out of it's way when it moves up. After all, these are interference engines, yes?

Most likely if a valve is bent, it will not close sufficiently to close the cam between the base lobe and the valve follower/shim. So be sure to check these. if you find a tappet clearance much higher than expected, that is say 0.10"+ instead of 0.010", then you have found a bent valve.

 

100 bucks an hour is a hell of a lot cheaper then a new motor

 

Unlikely but could be cams with oversize journals.

 

How many miles on your timing belt?
Did you leave a punch/screwdriver in the balance shaft alignment hole?

 

Sorry to hear about your issue.

The 4g63 is an interference motor. If the timing between the crank and the camshafts (valves) is not correct, the pistons WILL hit the valves. If you turned the motor over with the starter and it spun "fast" without the timing being right, you'll probably need to pull the head and check the valves to see what their condition is now.

It sounds like something went wrong in the install. Maybe you switched some cam caps or got the wrong parts, but the cams should turn easily in the head, subject only to the effect of the higher rate springs, which will exaggerate the feeling that you have to push to a certain point and then the "snap" from the springs.

Did you bleed your lifters?

Good luck.

 

Cam bearings?

 

Yes I did bleed the lifters, but the timing was "eyeballed". The cam caps were all removed and set aside in the exact order. Then reinstalled accordingly. It is entirely possible that I messed something up on the install, as this is my first head removal/installation on a car. I just can't remember doing anything wrong. I'm contacting CBRD now to see if I can just trailer it to them.