OK so I thought fitting a new timing belt was "simples" as they say, having changed a belt on my 1980 S in 2016, my 1986 S2 in 2019. Now I am wrangling a Gates belt onto my 1989GT. Backstory;
- Removed belt to investigate intermittent belt tension warning light, then discovered additional TLC was required
- New steel crank gear
- New steel oilpump gear
- New cam gears [aftermarket from Roger]
- Both fitted with keyway at midpoint of slot in the gear. Both fitted with timing slots aligned to backplates
- Rebuilt original tensioner
- Crank at O/T [previously at 45BTDC whilst assembling]

I have reread the WSM, Dwaynes guide, RL posts, JD CDs etc. so think I have a good handle on the ins and outs of the job;
- fit idler pulley and route belt under idler pulley but over tensioner pulley
- start seating belt at the crank
- feed belt over oil pump
- keep tension and feed over drivers side (LHD)/passenger side(RHD) cam gear
- clamp gently in place
- feed under water pump
- release any tension in the tensioner
- feed over passenger side (LHD)/driver side (RHD) cam gear

Then tension/check etc.

Sounds good yes? Only the belt will not stretch over the 2nd cam gear whatever I do. I have gently sash clamped the tensioner arm towards the compressor to collapse the spring fully and allow maximum belt slack but still no joy.

I recall one of Greg's posts recently about belts now arriving without prestretch - could this be the case and is the window really that small between fitting and not fitting?

David
'89GT

 

No idea if it will help you at all but I use a wrench on the 5/8 sprocket hex washer to help tension the first section of belt and have never had an issue.

Given you have new sprockets that will also make things that bit tighter.

Presumably you have the tensioner bolt backed out such that the piston does not travel any further to slacken off?

If all else fails you might try to see if you can get the old belt back on for comparison purposes.

 

Hi Fred

Yes tensioning bolt backed out fully. I forgot to add in my original post that I changed my tensioner out for an identical casting number/date item as the fill nipple sheared on the original one. I calliper measured all the internals and they checked out the same. Even checked the plunger that holds the belleville washers, seated in the base part. I think the combination of new gears and tight Gates belt is the issue. I managed to get it to fit by removing the tensioner body leaving just the arm and rollers in place. With the belt strung I managed to fit the tensioner body by heating up the washer stack to collapse it and sash clamping the tensioning roller 7 O'clock position to water pump body 2O'Clock. Gave me just enough slack to fit the tensioner body bolts. Still slightly perplexed by the whole episode.

- I think I can rule out any differences in the tensioner assemblies - checked and measured identical
- I think I assembled the belleville washer stack correctly; 7 sets of 5 like this; OPEN END <<<<< >>>>> <<<<< >>>>> <<<<< >>>>> <<<<< PLUNGER END

Now to check the timing, how hard can that be!

David

 

David,

As long as you get there all well and good but you should not have to go through that turkey dance with the tensioner.

How are you going to do the timing- clock gauges or with the 32VR kit?

 

Hi Fred

Yes agreed. Total malarkey. I turned the engine over a couple of times after and the belt between the cam gears went very slack. Adjusted tension again maybe it got caught up somewhere but i couldn't see any issue. I have rotated the engine several times and rechecked and it seems comfortable and tension consistent. I will be checking (and rechecking) timing using a dial gauge but may need to get/fabricate something to get alignment on the valve. Feels like im making heavy weather of this - maybe out of practice!

David

 

If forgot that the UK did not get 32 valve motors until the S4 arrived so presumably the 32VR is no use on what I presume will be a 16 valve motor. No idea about cam timing on those models.

Edit - Brain fade- you are talking about a 89GT. 32VR kit definitely needed!

 

On cars with the double lower roller, there's a little piece of the inner belt cover (about 30mm wide), between the crank gear and the oil pump gear.
This "tab" needs to be on the outside of the timing belt, when installing the belt.
It's common for people to "trap" this tab on the inside of the belt.
This can cause.....issues.

I continue to have problems with the factory timing belts quickly stretching after the initial install. (This makes more work, for us, since we have to go drive the cars ~50 miles, let them cool down, and retention the timing belt, before we can give them back to the owners.)
I have not used a Gates belt, for quite some time, so I have no idea if they have the same issue.
Seems like Roger should know.....

 

Yes definately 32v. More intimidating than the 16v I am more used to. I heard of the 32vr kit/tool and need to look into it

 

Hi Greg, yes first time I strung the belt loosely using the old belt, i caught that exact tab but i know it was clear when i did the new belt install. This is my first gates belt too having used Contis in the past. Do you think the gold standard is a Porsche belt?

I did wonder about using the old cam gears and a weight haning on the wall to precondition the belt but havent calculated/found datapoints for weight necessary. I will pay special attention to post install retension checks.

I took the opportunity to swap the double roller for a single one. New 6201RS bearing of course

 

Hi David I'm puzzled by this, as on my 32V MY91 I found (new cam gears too) that the Gates belt bought from Porsche was much easier to fit than the Continental. The Conti was a struggle but the Gates slipped on pretty easily.

 

David,

Cam timing is a breeze with the 32VR kit and its complimentary Bumpstick kit that is nice to have but not absolutely necessary. It is the kind of kit that a group of owners can purchase and share useage given the limited need for use. Once the sprocket covers are off cam timing is literally a 10 minute job once one is comfortable with the process as is advancing or retarding the cam timing and no requirement to remove the cam covers at all.

My cams were set using the factory method and when I acquired my 32VR kit the cam belt was fully run in with the initial stretch completed. When I tried out the 32VR kit the settings were exactly where Ken's manual said they should be so my cams were obviously very accurate and I would expect [hope?] all cam sets to be that accurate thus peace of mind as it were.

 

Hi Adrian
yes I am still headscratching. I am checking timing but there is a surprising change in belt tension as the engine rotates by hand as it goes through valve opening cycles. Once i have timing established i will take a view as to whether i am happy to go live or consider backtracking. Trying to get the car running again so i can get the 951 in the bay for work to get it ready to drive to Italy in August

 

Hi Fred

Yes that tool looks good. For now I amtrying to go old-school and use a conventional dial indicator as i wanted to take a peak at the cans and chaian tensioners anyway. Quite a palava to remove the cam covers I must say!

D

 

I found it helps get the 5/8 cover off after removing the engine removal bracket. One of the good things about timing conventionally is that if and when you acquire access to the 32VR tool it gives you confidence about the calibration.

 

I don't think that there used to be much difference between the Porsche belt and the Gates belt, since they were both made by Gates, on the same drum.
Now that I'm having issues with the Porsche belt stretching a bunch, initially, I'm no longer certain.
If the current batch of Porsche belts are somehow different, does that mean that the current batch of Gates belts are the same way?
I have no idea, since I don't use Gates timing belts, any longer. (Porsche lowered the retail price of the factory timing belt, significantly and the reason to use the Gates belt simply disappeared.)
You would need to ask the people who sell lots of Gates timing belts this question. (Assuming that they have inventory from the same period as the current Porsche belts.)