Yet another timing belt question...

Hey guys,

Doing a lot of work on my 91, including the timing belt. I've got a quick question that I already posed to LB, but I'd like to get more feedback from you guys that have done this.

I've finished the tensioning procedure and with the crank at tdc, the pin holes in the cams all line up, and the cam marks on the gears (cam side) line up, but they are a bit below the plate that you use for reference. Have you seen that they are a bit below or should they be more exposed and visible?

Thanks in advance guys!!

Can you show us a picture?

After looking closer I found that I was off a tooth. Re-did the belt and finally got it. Took 4 tries to get the belt perfect. Got her fired up last night, purring like a kitten.

hope did you do the valve adjustment you should have since you were right there

Lude_2_NSX said:

Hey guys,
I've finished the tensioning procedure and with the crank at tdc, the pin holes in the cams all line up

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pin holes all line up really? I thought on the earlier cars there was some misalignment on them from factor.

Once i lined up the cam marks perfect, the pin hole was a bit off on the rear intake, but the others actually lined up pretty well.

so no comment on the valve adjustment? this needs to be done everytime the timing belt is off. if not even though the pins lined up there is still some play and valves get bent then you need to redo everything again. but this time replace all the valves etc.etc. etc.

but its your car so do what you will.

Hmmmm. I didn't do the valve adjustment, didn't have the tools. If all of the marks were lined up, how could valves get bent? Is the tolerance really that tight?

Lude_2_NSX said:

Hmmmm. I didn't do the valve adjustment, didn't have the tools. If all of the marks were lined up, how could valves get bent? Is the tolerance really that tight?

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I think Shawn meant it's scheduled valve adjustment. I'm not sure of the interval but these require occasional valve adjustment just like any other scheduled maintanance.

I agree David, but I doubt valve damage would occur due to a lack of adjustment...

In case someone uses the search feature for the same topic, for the reference, if you own early 91 model engine, the pin hole won’t line up at the Front bank Exh cam.
The 5mm pin punch will hit the top surface of the front exh camshaft without allowing it to go any further.

Once the TB tension is adjusted, the pulley markings will line up as follows;




Front bank





Rear bank


Even with the cam pulleys set at the wrong timing such as just one tooth off or even two teeth, the piston won’t hit the valve. Never tried three teeth off though…..
Unless you turn the crank without the TB, you won’t bend the valve even with the incorrect valve clearance.

I think Shawn’s advice is related to the fact that when the #1cyl is at the TDC, the [URL=http://www.nsxprime.com/forum/usertag.php?do=list&action=hash&hash=2]#2 cyl[/URL] is at the intake stage and the [URL=http://www.nsxprime.com/forum/usertag.php?do=list&action=hash&hash=3]#3 cyl[/URL] is at the exhaust stage that both camshafts at the rear bank are under tension.
This means that the cam shafts could rotate themselves on their own if not locked properly while removing the TB although both #2 and #3 pistons (as well as #4 and #6 ones) are miles away from the TDC so none of the valves at these cyl will hit the piston head.
Obviously, when the #1cyl is at the TDC (compression), #5cyl is at the exhaust TDC so that’s the risk.

Kaz

Thanks for the clarification! Timing belt is still on after about 250 miles!

question.. is everyone using the tool to hold the crank pulley? I have airtools and other cars, i was able to break the bolt with no issues or the pulley moving.

3/4 drive impact works about 95% of the time. Still need the tool to tighten it back up.......

My $.02

Regards,
LarryB

3/4 impact

Hey Larry ,hope all is well ,is that impact still working?
Ralph

Hi Ralph,

Like a champ.....

Regards,
LarryB

I used impact, worked perfect. You do need a pretty strong gun however.

ya i have a 1000lb 3/4 that i've used for every timing belt I've done.

glad to hear it , something to be said for the WAY tools used to be built !

I give up.. Cant pop the bolt. It snapped my 3/4" drive extension

Every once and a while I do get a really tough one. Then I go to "manual" mode: 3/4 drive breaker bar, 5ft pipe..... this is assuming you have the tool to hold the crank pulley......

Secretaznsauce said:

I give up.. Cant pop the bolt. It snapped my 3/4" drive extension

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I seem to recall an impact deep socket worked for me, and I didnt need to use an extension. I could be wrong however. I know you can lose alot of torque with extensions...

Lots of heaths a 10 ft breaker. Job done. Got zoomzoom