Timing belt replacement

[Zennsx]

I have a question in regards to the DIY timing belt replacement writeup authored by Gay Kentosh. Specifically pages 21-22 where it states upon reinstallation to remove the pin punch from the rear exhaust pulley and advance the exhaust cam by 1/2 tooth. My question is how is it that the pin punch was in the rear exhaust cam upon removal , yet during reinstallation of the belt it must be removed?

What am I missing or overlooking? And I'm also a little foggy as to exactly how to remove the slack out of the new belt .

Thanks in advance, Chris.

 

[53heloFE]

I don't have the write-up in front of me but I used it along with the manual to replace mine last month. I had the punches out to break torque on the pulley bolt but kep them in after that until I needed to pre-tension the belt. I did initially have a hard time getting the teeth ligned up to get the new belt on, I think because of strecth from the old one. The cam is moved just enough to get the teeth and your marks aligned. You don't want the punches in when you are moving a cam, but I frequently checked to make sure everything matched up throughout the process. I am sure others on here will better be able to answer your question but I hope that helps for now.

 

[Zennsx]

I don't have the write-up in front of me but I used it along with the manual to replace mine last month. I had the punches out to break torque on the pulley bolt but kep them in after that until I needed to pre-tension the belt. I did initially have a hard time getting the teeth ligned up to get the new belt on, I think because of strecth from the old one. The cam is moved just enough to get the teeth and your marks aligned. You don't want the punches in when you are moving a cam, but I frequently checked to make sure everything matched up throughout the process. I am sure others on here will better be able to answer your question but I hope that helps for now.

So the cam wheel is adjustable and the punch is removed so as to not put any stress on the cam while loosening the exhaust cam wheel . I assumed the wheel was fixed and not adjustable. Boy I'm a dummy. :redface:

 

[Larry Bastanza]

The cam gears are not adjustable, they are fixed to the camshafts. When reinstalling the timing belt you MUST go by the book. Start with the crank pulley and install the belt in the sequence described.

When you go to put the belt on the rear exhaust cam it will not go on. You must advance the cam (using a 14mm wrench) about a half of a tooth(clockwise) to get it to go on, then retard it (counterclockwise)to tension the belt across the two rear cam pulleys. This is 99% of all the screwups on this service, if you leave the cam as is, and force the belt on, most likely the rear exhaust cam will be off one tooth. You will know immediately upon start up because at idle you will thjink you are listening to an SS Camaro. Unfortunately if that is the case you will get to do the job over.

As a safety precaution you can back off all the valve adjusters to make sure you have extra clearance in the case of being out of time, just remember then you will have the adjust them all, but that should really be done at this time anyway.

Let me know if you have any questions.

HTH,
LarryB

 

[53heloFE]

Larry,

I'm glad you were able to explain that better than I was able to...lol

 

[Zennsx]

I can see why this would account for 99% ot TB installation errors because the manual doesnt do a good job of fully explaining it. If I mark the new belt cogs in accordance with the old belt (tooth for tooth ) will these marks match identically with the rear exhaust pulley marks? I'm trying to have a complete understanding of this job before I attempt anything.

Thanks in advance, Chris.

 

[zahntech]

when doing timing belts on cars I have not done many on I like to take whiteout and make marks on the belt and pullys before removal of the belt, on a 4 cam motor like the NSX has, make a whiteout mark on each cam pully and matching mark on the belt so you will end up with 5 marks on the belt and one on each pully including the crank,,,then lay out the old belt next to the new belt and make corisponding marks on the new belt....after you put the new belt on rotate to motor 360deg and recheck that the marks on the engine line up with the marks on the pullys Note! your whiteout marks will no longer line up after you have rotated the motor.

as larry said ..follow the manuals direction closely and you will do fine..the cams may not want to stay where they are lined up after you remove the belt
so thats where rotating the cam slightly with a wrench comes in, in order to get the belt on correctly...happy hunting!