Was wondering if anyone else has seen a timing belt go this quickly ? I've got one of the Feb 2003 Evo8's and am in the process of completing a cam upgrade ... my timing belt was a bit stretched and has been replaced. Obviously pulling more @ the wheels than what it was shipped with @ the crank is gonna put a strain on it ... but 2 years, 22K miles? If the tuner shop (shameless plug www.gothamracing.com) hadn't spotted this it might ... I don't even want to think about it.

happy holidays,
dave

 

Raymerd -
How do you know it was stretched? Wheel horsepower doesn't have that much bearing on T belt strain, except when you have to fight stiffer valve springs simply to run the car. The 272's require a bit more work to rotate, but not enough to prematurely stretch the T belt, IMHO.

 

it is made of rubber it will stretch. I replaced my belt when I put the cams in. to me it is a no brainer.

 

Since belt removal is not a routine part of camshaft R&R, what caused the tuner to suspect that there was a problem with belt stretch? Was it due to low tension? If so this can be caused by other mechanical factors that will surface again after new belt settles in. Did they remove and measure the belt, and if so, how far out of spec was it?

Curious to hear the details.

 

More likely is improper installation...I have seen this loads of times now were belts jump teeth not because of stretch but because of the method gears and cams have been installed
belts do not stretch they fail across the teeth...yes they are made of rubber but inside there is corded plys that snap when the belt fails
No, the amount of power the engine produces has no relation to tension put on the belt...
My 2c
Argue if you like!!!

 

Andrew -
You're The Man! I'd still like to know how it was determined that the belt was failing, unless there were teeth gone . . .

 

Sorry for the late reply, but I've been traveling to my mother's house for Christmas. The belt had clear stretch marks at the junctures of several of the teeth, you could clearly see striations/stretch marks where the "teeth" met the belt proper. they were perpendicular to the belt, that is, cut across the belt from underside to topside. Comparing it to the new belt is was noticeably "longer".

I don't subscribe to the theory of it being an installation issue (it wasn't jumping teeth) the guys at gotham know what they are doing and their 4G63 guy is nothing short of an absolute expert.

I was chatting with a Mitsu service guy, and he commented that one of there customers that drives a GT3000 VR4 has gone through many belts, and at the last go around replaced it with a kevlar belt ... anybody know anything about kevlar timing belts ?

cheers,
dave

 

How much "longer" was the old belt? Gearbelt drives do not generally fail due to stretch, but rather from catastrophic failure, ie. the belt breaks. I guess some stretch could be expected and is probably normal as long as it's a very small percentage of the overall length.

I agree with Andrew about the "jumping teeth" failure mode. It seems to be due to improper installation of cams/belts/cam gears. The biggest problem is not belt failure but tansioner failure. I was told that Buschur for instance, never reuses the tensioners.
"Once the pin has been pulled out, we throw them away"...... Oh yeah, I had one of those "jumped teeth" after Busted Solutions installed cams and cam gears in my '03 GSR...... I was lucky and there were apparently no bent valves or other damage, but the car would not start. Andrew diagnosed it and repaired it

 

Raymerd -
Kevlar belts are around - do a search for timing belts here on EvoM. If I can dig it up, I'll post.

 

I had a problem with my timing belt at about 18k miles. I was getting my car tuned on a dyno and I was not putting down the power that I should. Initally, we thought that we had cylinder damage in one of the cylinders. We checked the compression after the car was safely tuned and it was 150 in all four cylinders. No damage to any of the cylinders. After talking to several Mitsu reps, I learned that standard compression is 162, but they will not look at it unless it falls below 138. I figured that I had a weak Evo and nothing could be done about it. A few months later, I was having cam gears installed and figured I would replace the timing belt with a kevlar one. The technician noted that the stock belt had a good amount of play in it, but it was not slipping and showed no signs of damage. Once the gears and belt were in place, we checked the compression again. The tighter kevlar belt brought the compression up to standard compression in all four cylinders. We held the two belts up to each other and the stock belt was either slightly longer or it stretched considerably. I posted this on dcevoclub.com back in the spring if you want to do a search for it.

 

Evo -
I'm having a hard time with your compression improving after a change in cam timing belt. Can you explain to me exactly how this works?

 

 

...Or your kevlar belt is smaller than stock. Something's amis if your compression raised with the new belt.

 

Mabey you did your first compression test with a cold motor or with the thorttle plate closed and your second one with a warm motor and/or with the throttle plate open. That could easily account for a magical increase of 20psi.

Shiv

 

Come on people lets think about this rationaly...If a toothed belt is noticeably longer as claimed the pitch of the teeth must have changed making it impossible for it to mesh on the cam gears/crank gear ect maybe it grew a few more teeth....could you count the amount of teeth on the longer belt please
And as for the compression changing that idea is flawed on so many levels that I can't even begin to respond to it