Bill Ball

I'd like to know the "stretch" in timing degrees after the belt has "settled" in. I've never noticed any "stretch" with the standard Gates, but I may not have been looking close enough.

Doubling the valve spring pressure may require a stronger belt.

Bill Ball

Oh, I see Ken has looked at this and found 2 degrees "stretch" with a regular Gates belt and none with Gates Racing on a motor with stock valve springs, I assume.

https://rennlist.com/forums/10428821-post54.html

danglerb

What do you suppose will be the compliant element if a bit of debris gets between the belt and gear?

Gary Knox

What do you suppose will be the compliant element if a bit of debris gets between the belt and gear?

Well - if the car has a PorKen Tensioner, there is compliance in that!!

G--

mark kibort

ive seen no stretch, but maybe like bill, i havent looked hard enough.
certainly no failures (yet) and ive used the conti for over 15 years now just because it was what the supplier always sent me at engine build or rebuild time.

PorKen

The gears.

I ran w/o covers on my OG '81. The gears wore down really fast because of all the grit that gets on the belt.






Post 8000!

PorKen

I'm starting to think about adding some retard to the static cam timing for the Racing belt.

With standard belts, I think there may be some high rpm retard as the belt reaches its compliance limit. (Variable valve timing! )

The Fixer

My only concern with the racing belt is setting the belt tension, seems the belt would change the forced required to twist it thus making my tensioning tool useless

ROG100

Gates engineers are very specific about this question - same tension setting as the stock belt.

GlenL

But how did the Gates engineers expect the tension to be measured?

The twist approach (Kempf) is more dependent on belt construction than the bend approach (9201).

danglerb

Twist or bend, what is measured is the force to displace the belt some amount which makes me think two things:

Belt that doesn't stretch as easily will measure higher at the same tension as stretchy belt.

A compliant tensioning system, like Porkens, will have roughly constant tension, so it will measure lower at the same tension as on a non compliant tensioner system.

ROG100

Belt construction is the same - only the grade of the material has changed.

There are at least six manufactures of this belt that I can think of and they all use slightly different materials and maybe different construction criteria. But we all use the same tools and settings to tension them.

Mongo

Two degrees???? The Conti belt we took off my car had the same amount of stretch.

The Fixer

Checked my belt and mine was very tight, but since it has been fine all these years i left it.

Gary Knox

Fixer,

I don't 'believe' the racing belt has MORE reinforcement, it just has better reinforcement. The OE belt is reinforced with fiberglass, while the Racing belt is reinforced with Kevlar. Kevlar is a synthetic polymer, developed by and produced by DuPont (our neighbor to the south, and my former employer). Kevlar cord is like any fabric cord - nylon, polyester, polypropylene, etc. in that it is highly flexible, and in the Kevlar case, it is very difficult to cut compared to other polymer or natural fibers. Tying it in a knot has very little effect on it's strength - try that with fiberglass! It will survive many times more flex cycles than fiberglass, and it has essentially no stretch until it is near the tensile breaking point.

IF you were into automobiles in the '60's and '70's, you may remember when fiberglass was used as a belt in bias (and even a few radial tires). It deteriorated quickly, as the fiberglass in the belts broke. I was involved in the evaluation of Kevlar in radial tire belts, from passenger tires all the way up to the giant mining tires. Never any problems with the Kevlar breaking - it was just too expensive to commercialize. It also has high temperature capability vs both fiberglass and the other polymer fibers, and is unaffected by moisture.

Thus, in automobile applications where temperatures to 250+ degrees, and moisture (hoses), or high flexing no stretching conditions (belts), it is an ideal reinforcement for rubber. Again, the products containing it are more expensive, as the fiber is significantly more expensive. The mfg process is VERY complex and technically challenging.

Actually, when you get right down to it, when you consider JUST the reinforcing material, the Kevlar is MORE flexible than the fiberglass!

Gary Knox