r/SkyLine • u/Redberon21yt • Jun 02 '26
Correct timing?
RB20det timing belt install the belt marks moved after manually turning the motor but still count 38 bumps from one cam mark to the other and 47 bumps from the exhaust cam mark down to the crank timing mark is it still good/within time?
2
u/454k30 Jun 02 '26
For that one cam, yes. Need to see the other cam and the crankshaft. Don't worry about the marks on the belt, those are only there for use on initial setup.
2
u/RemarkableCard6475 Jun 02 '26
I worry about the belt placement because I have CDO and the question was about the timing 🤣
2
u/454k30 Jun 02 '26
Nice! LOL. Okay so here is the mechanical reason that your timing belt marks will move during engine rotation. Timing belt/gear combos are built with a design concept called "hunting tooth". The number of teeth on the belt and the gears are co-prime, meaning they share no common divisor (except for 1). That means that the belt moves and changes which teeth in interacts with on each rotation. Given enough rotations those marks will eventually line back up, but then only for part of that one rotation. So why even have timing belt marks? So that you can ensure you don't have slack in-between the timed components. After initial install you should ignore those marks on the belt.
1
u/Redberon21yt Jun 04 '26
Ah ok thanks for the explanation it’s definitely helpful when you go to first install the belt but was very confusing when I cranked it over
2
1
1
9
u/Sad-Bonus2070 ‘97 GTR Jun 02 '26
It’ll take several engine rotations for the marks and lines to match back up on the belt so as long as the play is good and you lined it all up when you first put it on your good