Forum » General Engine Building Discussion » Timing belt stretch

Timing belt stretch

General Engine Building Discussion

Talk about engine building here. New products, tricky questions or showcase your work - If it's engine building related it's welcome here.

= Resolved threads

Page 1

Many of us are aware of timing belt stretch/deflection on moderate to high power engines. Most notable on Nissan's RB platform. Andre has even talked about this before if i'm not mistake. On this particular platform iv'e seen reports of up to `7* variance between cam and crank position in higher than stock HP applications, when logging both.

I suppose my questions are pretty straight forward:

1) Do kevlar belts help with the stretching of the belts?

2) Does a solid timing belt tensioner solve the stretching issue?

I would be inclined to think the answer for both is no. Thoughts?

Hello, you are correct,

They do not help the only way to correctly sort it is to run a crank trigger, I have tested a few different types of tensioners and some engines gave more timing issues do to the harmonics increase from solid tensioners.

For many years we have tuned around the issue on RB engines, and done a pretty good job of it too.

it is also interesting and a little off topic but I have measured a few engines from the front of the crank to the rear and have been really surprised by how much twist there is in some engines crankshafts

Regards Ross

Wow that is impressive Ross. I believe it! Crankshafts aren't as robust as we'd like to think. And yea the crank trigger kit is what i'm getting after. Iv'e fitted a 24-1 cam trigger kit in replacement of the factory CAS, but haven't driven it yet, or been back to the dyno. But from the reading iv'e been doing even a proper cam trigger isn't ideal.

Camshafts can have more torsional flex than crankshafts - one of the reasons for the early crank trigger conversions for drag raced Chev's, which had the distributor driven off the rear of the cam'.

With the longer, thinner six cylinder camshafts, I wouldn't be surprised if it's even worse.

Interesting discussion. Would you say the RB26 AEM 24-1 disc cas trigger with a compatible ECU is better than the stock disc? Obviously not as good as proper crack/cam sensors. A kind of half way house??