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Timing Belt Phuck Up

SS#eater

By SS#eater,
in Engines & Forced Induction

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SS#eater Collaborator

SS#eater

Posted
Posted

hey all

i need some help....i am changing my water pump...easy enuf (r33gtst)i took the timing belt off marked its positon 1st..... belt and cam gears crank pulley etc...but i have accdentily rubbed out my mark off belt and now im stuffed, the crank nor cams moved during the water pump install when i went to put the belt back on i noticed my marks gone....now i matched the marks i made on the cam gears up and just pulled the slack around the bottom "cog" to the tensioner side...and put tention on it....and i manually turned the motor over just to make sure nothing was going to foul.....im not confident that its 100% it could not be more than 1 tooth out but what im thinking is that nothing moved so by right if matched the marks on the cams to the ones on the belt (my own marks) and just pulled it arond the bottom cog it should be right?????? how do i check that my crank and cams and timed right? i am putting a new belt on now...... so just say i took a belt off and for what ever reason some one turned my crank and cams randomly and i had to re-align them all how do i do that.....

thanks for anyhelp

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monster Contributor

monster

Posted
Posted

*phew*

Ok...

Turn the crank until #1 piston is at TDC (easy enough to find by taking the spark plug out, VERY gently putting in a long screw driver and keep turning until the piston is right at the top) Then tuen the cams until they both line up with the timing marks on the back plate.

Put the belt on and try turning it 1 full rotation to see when it comes around again, if all the timing marks line up (once you have turned it, the marks on the belt will not line up to the pulleys) with TDC on the crank and cycle 1 on the cams.

I hope I explained ok :D

doo doo Proficient

doo doo

Posted
Posted (edited)

your belt should have makings on it that match the markings on the cam gears and the crank belt gear. It only fits on one way, make sure the arrows are in the right direction. If there's no markings then you could download the workshop manual which will tell you how many ribs are between the marks on each gear. I had to move the crank around a small amount to fit the belt and have enough slack for the idler and tensioner but just always check it's on the right tooth before you tension it. To align your gears the crank mark is at about 4 o'clock and the cam marks are at about 9-10 o'clock on the inlet and 2-3 o'clock on the exhaust- there's even matching dots on the backing plate behind the cam gears. If they're not close to this (in relation to each other-don't forget the crank travels at twice the speed of the cams) and the belt is off i wouldn't be moving anything very far by itself. if they're close enough then put the belt on then count the number of ribs between the marks or where they would be if in contact with the belt (and you know this by having counted how many ribs between the marks for each on the belt) should tell you if it's out. I, being rather anal about this sort of thing, would then move the gears into the right positions for the marks, take the belt of and put it back on with all the belt and gear marks in the right place.

Actually that's for GTR, I think the RB25 is the same?

Edited by doo doo
SS#eater Collaborator

SS#eater

Posted
  • Author
Posted

thanks for the quick reply guys...will have to look at it after work tommorow hopefully my new belt idler and tentioner will be here and i can put her back together:)

thanks again let you knnow how it went!

Fry_33 Proficient

Fry_33

Posted
Posted

The direction arrow on the belt is only there to assist installation. The belt doesn't have to operate in that direction. However, if you do take a belt off and put the same one back on you should keep the arrow pointed in the same direction. The timing marks on the belt are there to assist installation too. As long as the alignment marks on the cam gears and crank all line up with their marks after the belt is on and they line up again after it's rotated through you should be fine. Just make sure that you are looking at the timing marks straight on to remove any errors by looking at the marks from an angle. If you can't see the crank mark line up with the mark on the block easily then you can always use a camera.

abu Grand Master

abu

Posted
Posted

The marks on the belt are only to help you line up the cam gears and crank cog, as long as your cam gears are lined up with the backing plate marks, crank cog is lined up with the mark on the oil pump then just throw the belt on but make sure the arrow is pointing in the right direction

Make sure you don't over tension the belt either

doo doo Proficient

doo doo

Posted
Posted
The marks on the belt are only to help you line up the cam gears and crank cog, as long as your cam gears are lined up with the backing plate marks, crank cog is lined up with the mark on the oil pump then just throw the belt on but make sure the arrow is pointing in the right direction

Make sure you don't over tension the belt either

I don't agree as you can be out a tooth from the exh cam to the crank quite easily in the process of getting the belt on the idler pulley (you can't put the tension required in the belt for the marks to line up using just your hands) - use the marks, it's going to mean it's correct. Tensioning the belt just requires rotating the crank twice (clockwise) then holding the tensioner pulley in that position with an allen key and doing up the nut (32-43 ft-lbs). Again this is GTR spec.

Fry_33 Proficient

Fry_33

Posted
Posted
make sure the arrow is pointing in the right direction

The arrow on the belt is only there to assist installation. There is nothing structurally different in the belt that requires it to go in a certain direction. But if you're reinstalling a belt keep the arrow pointing in the same direction as it wsa when you took it off.

blind_elk Grand Master

blind_elk

Posted
Posted

It's not rocket science! You don't need to mark the belt at all.

TDC marker on the crank aligned with the timing marker on the timing case cover. Indent mark on inlet cam wheel aligned with inlet-side mark on cam wheel backing plate. Indent mark on exhaust cam wheel aligned with exhaust-side mark on cam wheel backing plate.

Install belt. Adjust tensioner.

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