So this has happened 3 times to me now. Different conditions, different timing belts(both a GReddy and a Toda), new tensioners, different cam gears. It doesn't seem to matter if the car is being driven hard or easy. The first 2 times resulted in no engine damage. Since the third just happened I can't say for sure if there is any damage.

The cam gears are off by anywhere from 90 to 180 degrees.

Setup is in sig. The motor just shuts off and I coast to a stop. No bang no loud noises. Nothing. Anyone have any ideas?

I know 100% this last time the belt was installed properly and setup right.

 

didnt you have belt stretch and tension issues last go around. have you done a compressio. test yet

 

the timing gear on the crank shaft, is it in operable condition? I can only thing of this timing gear being damaged, or the timing belt is too loose. Perhaps the deck of the block/head were milled too much where you have too much slack? but Id assume you tighten the belt enough. Why not an oem belt?

 

The issue was the Gates Blue belt being to long. I switched to the GReddy belt and the marks lined up where they used too. The car then went on the dyno and made 529. This started happening about a month after I switched to the GReddy belt. I really don't think the compression is off. The car feels as strong as ever and pulls just as hard in 3rd gear as it always has. I have acceleration datalogs to prove it.

I have used a degree wheel and the cam timing is off a little over 2 degrees due to head/block milling/decking.

With all the times I have been under the timing cover I have never looked at the timing gear on the crank. I have never heard of one wearing out, is that possible? It's def something I can look at.

Up until recently I had used OEM belts but went to the GReddy/Toda since I figured they were less prone to stretching since I have heavier valve springs. I wouldn't think these belts could be the problem but I guess anything is possible. I have a new OEM 1 I could try. I'm out of ideas at this point.



Now that I think about it I think each time this has happened the engine has been in a decel condition. First time was a 2nd to 3rd shift at low speed and light throttle, second time it happened I was in 4th gear at light throttle, about 45 mph shifting to 5th, and today I was hard on the brakes after a hard pull in 3rd gear. I was thinking it was due to acceleration but maybe its just the opposite.

 

If you have stiff springs, you need to remove ALL slack out of the timing belt, if you leave any slack in it, it will show. Have you ever tried to crank the motor the wrong way, and looked at the timing belt below the exhaust cam and above the crank timing gear? this is what I believe is happening when your motor is de-accelerating with stiff springs and with a belt with slack.

 

I'm going to pull the cams out when I get home from work tonight to see if there is any scaring on the cam journals. If not then you are probably right the belt was too loose (but I find that hard to believe). I am starting to wonder if I had the belt too tight. Causing the cams to bind up during decel, jumping the belt when it has the most tension.

 

i do a half inch of deflection

 

with a toda and greddy belt, I don't see them jumping teeth from being too tight, those belts are extremely stiff/tight as is. its important to ensure there is -ZERO- slack with stiff springs or you're asking for trouble. I push the tensioner up to release all tension from the springs attached to the tensioner and I tighten the bolt. I do this multiple times while doing 5-10 rotations per tightening.

 

Not sure if your still using Tuner 1 cams or another cam but a high duration cam can cause belt flap upon decell and cause the belt to skip. The Endyne Timing belt tentioner is one of a few tentioners used to eliminate belt flap and prevent belt slip..

 

with the motor hot or cold?

I use the gates blue with super tech 85lbs the belt is loose and flaps when the motor is cold but its tight not super tight but it doesn't " whine" when hot. I always idle the car up to temp before driving.

I was also under the impression that too tight/ no slack can wear the cam caps and such. ..

 

This happened to me quite a few times on my turbo LS right after I got it back from the machine shop. The issue ended up being the timing belt tensioner. I had one from auto parts international at the time. I replaced it with an OEM honda tensioner, and didn't have the issue again.

 

cold, then i recheck deflection after its normal temperature

 

Thanks for all the responses, I'll answer each as I get a chance. I've replaced the tensioner each time and only used OEM.

 

I have been following the Helms manual and I'm still using the Tuner 1s. This last time I was barely able to push the belt down or lift it up with my finger between the cam gears.

When I got home last night and pulled the VC the belt was loose. I would turn the crank by hand and the crank would rotate but the belt would pop over the cams. I pulled the belt off and the cams rotate fine. Then I pulled the cams, the cams look good. There is a bit of an edge on the inner side of the intake and exhaust cams on the belt side but nothing major. Looks like normal wear to me, it's close to the edge too, not really in the journal.

 

Can I get an Un ******* believable

I think I figured out the issue. Looking at what happened this last time I figured the belt had to come loose. So that points to a tensioner. I know I have used 3 brand new OEM tensioners. Only thing I could think was my torque wrench. I tried using a different wrench and low and behold the torque on the wrench I had been using must be at least 10 ft/lb off. So instead of 42 ft/lb the torque on the tensioner was probably closer to 30 ft/lb.

Let this be a lesson boys and girls, have your torque wrenches calibrated often. The last time I had the one I had been using calibrated was like 5 years ago. Jesus I feel so stupid.

 

Yea I know its bad but I dont use a Torque wrench on this specific bolt I just tighten it good...I know my limits on how far I can crank certain size bolts

Ive had good luck with stock tensioners and belts

 

craftman 3/8 drive fits perfect...never had a problem with is coming loose

 

That's what my wrench is. I have a Craftsman 3/8 and a 1/2 and the 3/8 is the one that's off. It's old and I haven't used it in forever. I should take it to Sears and have them service it. I'm sure it's that simple.

I use my 1/2 all the time and it is great. Guess I will need to try to use the 3/8 more once I get it back.

 

Wow, I think you are really lucky nothing got damaged

 

I know. My pistons are dished and have valve reliefs cutout so I'm guessing that saved me. I feel very fortunate the motor is still in 1 piece.