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Discussion and questions related to the course How to Degree a Cam
Hi just degreeing in some Barra cams using lift at TDC spec.
Example: I set intake cam at 2.92mm lift at TDC with 0 lash solid lifter.
Problem is every time I rotate the crank a full cycle to TDC again to re-check the spec it’s off and varies between 0.1 to 0.3mm lift then sometimes it will land on spec.
I suspect the timing chain has a stretched spot in it that’s giving me these results?
Does this sound correct?
I'd be very surprised if it was the timing chain, that would also be throwing off the exhaust, which you don't mention?
Are you still using the variable timing mechanism as that's more likely to be moving a little?
Setting to zero lash is quite tricky, have you tried at 2 thou', or there-about, and seen if the timing/lift variation is still there?
What results do you get for variations at BDC [EDIT - bit of a typo' there]?
Thanks for your advice, I haven't moved onto the exhaust yet as I was having problems with intake cam
but yes it makes sense to see if the exhaust one is doing the same as well.
Will check at BTD as well.
Using Atomic Vernier gears
my understanding is even if the lash is not 100% 0 it should still give consistent readings? (will follow your advice and try 2 thou lash anyway, Cheers)
Finally got back to this engine I replaced the cam chain and sure enough it wasn’t the problem… I also checked the exhaust cam and I had the same problem there just to a lesser degree.
I found that if I was super consistent with the way that I rolled the crankshaft up to tdc the measurements where a lot more accurate. Following this as I was checking the Piston to valve clearance I found that I had little-to-no valve stem seal to keeper clearance. So I think this is what was the main issue. Trimming valve guides and fitting low profile seals is the next step now.
Had the valve guides shortened and fit low profile seals. modified a set of rockers to make the easier to adjust my adjustable solid adjustable checking lifters to get 0 lash. Checked valve stem seal to retainer clearance… all good
seat valve timing with no problems.
defiantly had a clearance problem that’s was giving me the inconsistent readings.
cheers for the advice
Glad it all came together!