Another Timing Belt question - rear cam alignment

[I Grok NSX]

Morning all,

I'm in the process of installing a new timing belt and have been using all the information found here at NSXPrime plus I do have the manual.

I have pins installed in the cam shafts to prevent movement. All is well.

I had the timing belt installed earlier this morning and double checked the alignment. I noticed that the rear cam markings were in conflict with what is presented in the manual.

On the rear exhaust cam on page 6-25 of the manual, it shows (and tell) that the timing mark be 1/2 tooth past (below) the timing mark of the intake mark. As stated before, I have used pins in the cams to prevent movement of the cam shafts. The pins are still in place. My cam shaft alignment mark is 1/2 tooth above the intake mark. If I move the cam to the 1/2 tooth below (past) the intake mark (as shown in the manual), the pin for the exhaust does not fit.

Edit: Also, there are pink paint dots on each cam. The paint dots DO align when the pins are in and the timing mark on the exhaust is higher (1/2 tooth) that the intake mark.

Edit 2: I went ahead and put tention on the belt and tightened it all up with the rear cam ABOVE the other cam mark and the cam pins fit just perfect. Infact, the rear exhaust cam pin fits very deeply, like the forward exhaust cam pin. Very puzzling. I'm going to disassemble the belt and move the rear exhaust cam to the Lower position (as indicated in the manual) and see how ever thing fits. Be back soon.


What is the deal? Any help is appreciated.

By the way, I've also replace ALL of the cooling hoses and that is a bigger job than the timing belt in my opinion.

 

[Zennsx]

I think in the DIY written by Gary Kentosh and co authored by Larry B it mentions having to remove the rear exhaust pin to achieve this alignment.

 

[I Grok NSX]

I think in the DIY written by Gary Kentosh and co authored by Larry B it mentions having to remove the rear exhaust pin to achieve this alignment.

Thanks. I read that post during my search. I guess my real question is why did the pins fit before I started ... and now the rear exhaust pin won't.

 

[Briank]

Until you turn the engine around a couple of times and tension the belt the pins will not fit. Just takes a little time for the new belt to seat and relax into position. When I did mine is seemed that there was a problem when first installed also.

 

[Gerard van Santen]

Thanks. I read that post during my search. I guess my real question is why did the pins fit before I started ... and now the rear exhaust pin won't.

Perhaps the old belt was stretched due of aging?

 

[Larry Bastanza]

Based on your description the rear cam is retarded one tooth. You need to ADVANCE the cam in order to get the belt to go on. But then you should set it back by using a 14mm wrench on that cam.

The pin will not fit, until things are proper and you have turned the crank another 720 degrees to tension it up as stated above. With the crank at TDC, USING the arrows on the crank gear and engine block, the cams should be dead nuts with a new belt.

When I do this I pull the pin, set the cam, then test after a 720 degree rotation of the crank. If you are not 100% sure do not button it up.

IMPORTANT NOTE: Make sure the timing belt tensioner pulley is tensioning the belt and LOCKED in place BEFORE you turn the crank.

HTH,
LarryB

 

[I Grok NSX]

Hi again,

I'm looking for the symptoms for a mis-timed timing belt. For example, if the rear bank exhaust cam was either retarded or advanced one tooth, how would the engine run?

Would it be hard to start?

Would it back fire?

Would it hesitate during acceleration?

Looking for any symptoms of a timing belt change gone wrong.

I've fired up my NSX and it started immediately. When it warmed up, it has a nice idle and when I blip the throttle, it revs up quickly. I haven't got the alternator or some of the other engine components on yet, but when I do finish tomorrow or Wednesday, I'll take it for a test spin. I'll be looking for any symptoms posted here for a mis-timed belt.

But so far, it seems as everything is as it should.

I'll post in a couple of days for the results of the test drive.

Thanks for your post and help.