Belt drive Cam Retard?
 

Just curious if anyone knows how much a belt drive will let a cam retard at start-up? I realize there are many factors that would influence the answer to the question. If you have any experience with this could you please post the setup. Looking for some informative data so I can make an educated decision.

depends on the belt drive system used... Jesel is the most accurate and low and behold almost twice the price of everyone elses... Ya get what ya pays for.. lol as for retard IMO about 1 degree at the hit but once rotating back to set point...(on a new belt... )

now my question to you is why are you concerned? the advantages of a belt drive far outweigh any timing issues you'll encounter... just askin?

I have to clearance rods on even bank. I know when you start it will retard which will give more clearance. I ask cause if the belt will retard xxx degrees at start-up if there is a situation where the motor is shut down abruptly at some point the cam will advance which in return will give less clearance.

if your clearance is so close that 1 deg either way will cause interferance you may have a problem.

No but I bet 5 degrees in either direction will make a big difference.

maybe but unless the belt is streatched and ready to brake i don,t see that happening.

Jesel says 2-4* of backlash is acceptable.

Have you tried turning it over with a bar and see how much play is there ?

2 degrees of backlash is = to 1 degree either side of setpoint

I'm curious as to what combination you're using that is so tight in clearance, in order to create this concern...

4.75 stroke crank Callie's ultra xd(xtra clearance) I beam's 55mm cam. Just not going to spin without some extra work.

I'm waiting in the belt drive. Using old timing chain setup for mock up purposes. I new going in this was going to be an issue. It's not my first go round with long stroke stuff. I just want to cover all my bases cause I'd rather not have a situation where the motor clearances itself. The cam is degreed where it needs to be I will clearance the rods so it will spin. Then I will back it up 6-7 degrees spin it if all is good I will advance it 6-7 degrees and check clearance. It was recommended by the rod manufacturer to use a long zip tie to measure cam/Rod clearance... Feeler gauge is a no go.

I will be doing a detailed build thread at some point so I can share with my fellow OSO'ers the joys of building a big cubic inch motor. It's a whole lot of putting together and taking apart.

Ok, is the backlash in a timing chain that is not brand new any less, or more than a belt?

The chain set I have (which is very tight) moves the cam as soon as the crank turns. This is using a degree wheel and dial indicator.

Where it gets very interesting with a standard cam core and roller springs is how much the front of the cam turns before the back. When you put any kind of spring pressure on a standard cam it twists it up like a pretzel.

Have you checked it yet? The XD rod will sometimes clear a 55mm with a 4.75". If it hits, the clearancing will be very minor. Here is the interference on an Oliver rod, which has a bigger shoulder then the Callies. [ATTACH=CONFIG]539260[/ATTACH][ATTACH=CONFIG]539261[/ATTACH][ATTACH=CONFIG]539262[/ATTACH]

Wow. Looks like the Oliver Rod is close to clearing. Mine isn't even close with the XD rods.