Double Roller Timing Chain Cam Advance Retard

supervel45 March 16th 2016, 9:09 pm

Be careful on the chains if yo don't know the origin and you are not degreeing your cam. The Zero (0) can be misleading. Make sure it is in line with the gear tooth are it is likely a retard late model chain.

supervel45 March 20th 2016, 3:05 am

https://www.fordmuscle.com/archives/2007/04/DontBeRetarded/index.php
So did Comp Cams mis-grind their cam or were the timing gears mis-marked? Seems like something was way off.

Dave De March 20th 2016, 11:32 am

I interpret the term "straight up" as equal to degreed in on zero degrees. Anyone with a performance build should dial in the cam no exceptions.
Considering the tolerance stack up that goes into angular degree error there a may be a huge error.
Look at it this way, each component has its own tolerance and they can all add up but most likely there will be some that are plus and some that are minus.
Angular tolerance stack-up
Crank key to rod journal
Crank Gear to tooth
Chain length
Cam gear pin hole to tooth
Cam pin to lobe

These are 6 individual tolerances that if each is +/- 2 degrees as being reasonable there will be a maximum variation of 12 degrees from true zero. Probability wise most will be within +/- 3.5 degrees for normal distribution.
I overly simplified this not accounting for a crank error of 2 degrees will only yield one degree of camshaft error because the cam is half the rotation. Using a 2 degree tolerance the maximum limit is 8 degrees camshaft error.

supervel45 March 20th 2016, 12:59 pm

^^^^^^^Very well stated. I could see the zero playing with a lot of guys heads on the late model after market chain if they did not know about the keyway lining up with the center of the gear tooth. and the dot. Kind of caught me off guard when I first looked at the two gears side by side and slowed down a second to think about it and I have seen the pictures before. The advance keyway on the late model gear lines up with the old gear 0 keyway. I think that may be what the guys in the article went wrong. First time I have ever had two 3 way keyed gears like this in person to compare, and always wanted see exactly what was up. Another member also told me roller chain replacement chains on late model Fuelie 460's will not work with after market gears, and if the third gear in the picture is from a fuelie chain, there is a difference between the teeth.

rmcomprandy March 20th 2016, 1:11 pm

In the high performance engine business, "straight-up" means "as the cam was initially ground".
Stack-up can make things vary from that, greatly.

"Fuelly" gears WILL work with aftermarket "PLUS" roller timing gear sets but, NOT with "True Roller" timing sets. The pin width and size is slightly different.

supervel45 March 20th 2016, 4:55 pm

Thanks Randy. I was looking on Rock Auto at replacement chains only no gears and they had quite a few, it was kind of hard to figure what fits what. On some of the old muscle car cam specs it will show a 112 LSA with a 112 ICL unlike Comp cams and many others that show a 112LSA at a 108ICL which I believe is like 4 degrees advance cut in when it is installed there, could be mistaken though but I believe that is what you where referring to. Yes I know the LSA is ground into the cam and can't be changed by were it is degreed in at.

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Double Roller Timing Chain Cam Advance Retard

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