Hey everyone, I just got my head back from the machine shop and i am trying to get the timing chain back on. I have all my timing marks matching up, but here is my ? why in the hell when i crank it over does the timing chain jump off the marks. I have all the tensioners tight where the chain does not move, but its still like the chain is jumping off. Is there any special trick to do this other than getting the marks matched up.


Thanks for all the help.....

 

Don't worry, your fine, lol. It's because the crank gear is so much smaller than the cam gears. The marks are going to jump around. More links on the chain than teeth on the gear. Just make sure you have them all aligned up the first time, and you will be good.

 

here's something taken of a j-body

Now to time it the white dot on the crank (on the toothed gear one tooth has a white dot) goes straight down, the diamond on the intake cam goes toward 2 o'clock mark, triangle on the exhuast cam goes towards 10 o'clockthere are 3 colored links on the timing chain, rotate the chain intill the 3 colored links line up with the 3 timing marks (white dot tooth on crank, diamond tooth on intake, triangle tooth on exhaust) Personally heres how I do it... line up the crank mark on the chain, then line up the exhaust cam mark and the chain, take the intake cam gear off, and line it up on the gear then roate the gear upwards to the cam.... if it doesn't seem to reach either turn the crank counter clockwiseon the exhaust cam clockwise, either way just a very little bit, by doing this you put all the slack in the chain on the side of the intake cam, then slide the gear on, a 15/16 wrench comes in handy to physically turn the cam itself just a litte bit to get the teeth to lock in. (The cam gears will one fit ONE way, they are notched so you can't really put the gear on wrong) once you have the gear back on check to make sure the all the links are lined up with the timing marks, if the aren;t go back and do it again, if they are lined up gently turn the crank just a tiny bit clockwise, becarefull because it WILL jump teeth how it sitting at this point, you bump the crank over to takeall the loose tension in the chain and put it on the back side of the engine, it will make it a million times easier for the next step which is puting the chain tensioner bolt back in the head. Triple check the colored links and the timing marks and just to be safe turn the engine over by hand at least 2 full crank revolutions.


!!!!!! IMPORTANT NOTE !!!!!!

once you turn your engine over by hand the colored links and the timing marks will not line back up after spinning the engine over... there is a ton of links on the chain and very few teeth on the crank..... comon sence would tell you if you spin the crank which has (MAKING UP A NUMBERS JUST TO GET THE POINT ACROSS) 20 teeth .... that the the chain that has 300 links is not gonna make a full roatation, its only gonna rotate the 20 links it took for the engine to turn over.... eventually if you spin the engine long enough they will come back and line up but don't sit there expecting them to. Seems like common sence but I get asked that ALOT by people.



there's a full write up that guy did on the full cam install i'll try and find it

 

Wow...this boggles the mind! The crank sprocket has 23 teeth, the cam sprockets have 46 teeth, and the chain appears to have 148 slots/links for the teeth. This still means that every two crank revolutions the cam gears must line up -- but the timing marks will not align again every 2 revolutions -- I can't figure out how often the crank should turn before the marks should align again! I just tried 6 revolutions and they still didn't realign -- they're still in proper time -- getting the marks right the first time is VERY important!

 

right....valvetrain spins half the speed of the crankshaft. So every two revolutions of the crank gear and the cams and crank will be lined up. The marks on the chain however will not.....you need to rotate like 30+ times or something like that for the marks to line up again.

 

Replaced timing chain. While making revolutions my chain starts out tight then becomes loose very briefly then tight again. Unsure if this was normal. Replaced chain, guides, tensioner

 

Is the tensioner compressed or extended?

 

I assume you are looking at the chain in between the two cam sprockets? If so then yes this is normal, when turning over by hand, because the of the difference in resting positions between the two cams. The spring force in the tensioner is not enough to overcome this.