Effects of chain tension on Camshaft Timing

[tpepmeie]

As I was finishing up my latest 427 build, a thought occurred to me. To time the cams, you first tension the secondary chains using the manual tensioners. Get the timing perfect, then remove the manual ones and install and fire the hydraulic tensioners.

Would seem to me that if the tension you impart on the manual tensioners is tighter than the hydraulic tensioners, the camshaft timing will be different under running conditions. Anybody else have an opinion here? There is really no spec for how tight to tension the manual tensioners. I generally just give it a few degrees with a small open end wrench, but no real torque beyond a little more than finger tight, so to speak.

If the hydraulic tensioners apply less force, wouldn't that have the same effect as chain stretch, and retard the valve events?

Love to hear what others who've done this think. I know Graham and Marc are on here from time to time, they've done it hundreds or thousands of time.

Just thinking out loud today, before heading to the speedway!

[A26B]

My thoughts;
The hydraulic tensioner force will be variable, increasing from low rpm oil pressure to high rpm oil pressure. The lbs-force applied to the chain could be calculated by PSI x Area in2. In2 cancel & the remainder is lbs-force.

The force applied by the manual tensioner could likewise be calculated but has variables like thread friction that you could leave out to get an close-enough force and resultant torque requirement to use.

FWIW, My experience with Corey has been more force from the manual tensioner than what you describe. I've always been under the impression that the objective is to get ALL of the slack out. There is no chance of stretching the chains.

[Paul Workman]

The critical cam timing factor, far as chain tension goes, is the chain length between the cam and secondary sprockets - on the tension side of the chain. So, as long as there is enough tension applied sufficient to remove any (practical) droop between those sprockets, then "enough is enough" and more (tension) is superfluous where establishing timing is concerned.

Beyond setting the initial cam phasing, the tensioner is relegated to managing the chain slack.

Other factors to change that critical length include subsequent chain wear or sprocket wear, etc., resulting in changes in cam phase changing over time.