well as you may know a few people reported snapping timing belts when running bigger cams and firmer valve springs. Oddly enough it seems to have happened more with Toda cams than others, but it was enough to concern me as I am running Jun cams. My initial thoughts were that running too much tension (too tight) on the timing belt could be just as bad as running too loose. I have a good friend who builds Honda race motors for a living and he supplies the engines for race applications only. His engines probably get re-built more often than our street engines but they do operate at very high stress conditions, operating range for the engines is 7000-10000 rpms on the track. I know he uses many big cams in his engines, from his own custom grinds to experimental work with Toda Spec C and even Crower, he does a lot of development work with cams and engines in general. Being worried about my timing belt I had a chat with him. With all of the race motors he builds he doesn't apply excessive tension to the timing belt and he uses stock timing belts, and he has never broken a belt. I spoke to him about applying tension to the belt above what the factory calls for, and he did not think that was a good idea. His comment to me is that increased tension is usually applied to the belt on a cold engine, then when the engine heated up in operation, the distance between the center of the cam gears and to the crank increases causing even further tension to be applied, this can cause the belt to snap prematurely over time, particularly with constant stopping and starting (much what you would see on a street driven motor). He also mentioned the increased wear that can occur on the crank mains, but most people know about that. All he recommends is that tension be keep on the crank when the tensioner bolt is tightened , this will ensure that any unnecessary slack is taken up, but won't apply too much tension. He only applies the factory recommneded tension, but he does maintain pressure on the crank pulley while tighening the tensioner bolt, this is a two man operation but he highly recommends it. Just some info to share from what I have been told, I am sure every engine builder has their own opinion on this issue, and who knows what the correct answer really is. But I really believe over-tightening the belt can be just as problematic as having one that is too loose.
just my opinion and info. to share. hth.

Joe


[Modified by JSIR, 10:07 AM 5/13/2002]

 

I think the biggest factor in timing bely failures has to do with large non-VTEC lobes. Mainly Toda Spec Cs and Bs. Since it is like always being on VTEC, these cams cause much more wear and tear on the valvetrain. Just my $.02

 

mmmmmm Toda C's

 

yeah that is my feeling also as most of the recent failures we have seen have been on Toda B/C cams .

 

I think i'm still going to get a power enterprise belt just to be on the safe side.

Craig - Who has enough problems and a broken timing belt would make it 10x worse.

 

not just that, but it's also the fact that the loping stresses back and forth at idle...

but to quote D: "it's a wear item."

 

hahaha... thats what he told me about my bumper cap and lca fawker

 

Just raise your idle...my gears were set at +5. -5 and had a very small lope...not like the other toda B's that I've seen...and fuel management really helped the idle out.
Austin