I disagree. the timing gear is attached at the camshaft centerline which is completely unaffected by the cam profile...a stock cam and an aftermarket cam will have the exact same centerline do you agree?? If that is the case then the only way the cam profile can affect the timing belt is through engine velocity.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jerseykid609 &raquo;</TD></TR><TR><TD CLASS="quote">know how many hod rod guys use oem belts. Seriously ive never seen one issue with a timing belt sanping on low 9 high 8 sec cars i mean seriously who here on this bord is gonna take there motor to 10k and have it hang there for more then a few sec's ?</TD></TR></TABLE>

um, NHRA dragcars are based on the chrysler 426 hemi and they use gear driven timing sets...there's no BELT or CHAIN involved. What you see spinning on the engines is the roots style supercharger drive belt. Some modified stock drag cars use "dry-style: timing belts similar to those used on most imports but they are re-inforced and metal guided.

hell, even nascar engines only use double roller timing CHAINS...and yes, timing chains stretch over time due to stress...

 

I think at this point I'd also like to point out that I just realized I'm talking about sohc engines while you're talking about dohc engines....well, at least that's what I think I was just able to gather...

 

You have what is called a "moment" created around the centerline of the camshaft. The camshafts will have the same centerline, but its the duration and lift of the camshaft that will create a moment into the camshaft, which is translated into the cam gear. This moment that is created cannot be ignored, and the moment will grow with increase in lift and duration. So you have a positive moment acting into the cam gear, translated into the camshaft. You have the opposite moment created through the camshaft translated into the cam gear. The force and moment balance will show that the contacting points of the timing belt teeth to the cam gear teeth will have a opposite normal force to the normal force at the same position created by the crankshaft. The result is a tensile force generated onto the camshaft. The fluctuation of the opposite moments created by the camshaft is purely dynamic situation, ie varying with rpm. This is where the dynamical situation occurs. If i had the time I would draw out a nice free body diagram of the situation.

 

damn...this is getting intense...either way, my timing belt has stretched...and i need to change it soon

 

most people forget that most aftermarket cam gears are made of aluminum and their teeth wear down faster the stock causing any timming belt oem or aftermarket to become loose after a cetain amount of miles...

jun cam gears are made with oem metal cams gears just modified center portion.