Hello all, I have just put the new belts and the Hill Engineering tensioners on my 1985 QV and have been following 'Birdmans' giude on the net and some treads on the forum. My question is the tension on the belts. I have done the 'Verell' suggested technique with the cam locks in place, putting a forward pressure rotation on the crank nut/bolt, plucking the belt to see if you get that musical note and then tighteing down the tensioners to the 41 ft lbs. My issue is that when I release the pressure on the crank bolt the belt on the rear bank has a nice high pitch twang to it and is still quite tight yet the belt on the front is not as high pitched, more of a low 'E' (to those musical guys amongst us LOL).....and is definetly not as tight. I am on TDC, pointer on flywheel lines up, belts marks all line up, camshaft mark under oil filler cap dead on etc. I even took the cam locks off and rotated the engine by hand many times and brought all the lines on the belts and pulleys to line back up (dont ask me how many revolutions to do this, I lost count) And still it seems the front bank belt at TDC is a little looser than the rear belt. Or is the rear belt too tight? I disasembled both tensioners and cleaned them out, little grease inside etc. Is this something I should be worried about or am I being major paranoid? I dont want one too loose but I dont want one too tight either that may age the belt or take out a pulley bearing. Any thoughts?
If all your marks are on.....leave the tensioner bolts (which carry the bearings) loose and turn the engine slowly by hand (to avoid tooth skipping while the tensioners are loose). I turn mine four revolutions...but more is no biggie. If your tensioner mechanisms (springs and sliding surfaces) have been cleaned and lubricated (it sounds like they have), the bearings should ride freely against the belts as you turn the crank. You'll see the bearings ride along on the belts and adjust themselves. Once the bearings settle into the belts, bump the crank one last time with your wrench (I just gently hit it with my hand). That should snug up the long run of each belt (the non-tensioner side) and allow the tensioners to take up any final slack. You can then tighten the tensioner bolts. It is quite possible to drive yourself crazy over belt tension (it's one of those topics with "scare the **** out of you" potential, but it shouldn't). The main thing is to let the tensioners take care of it all by themselves, without any additional pressure or "help". The only way that you can really over-tighten it all is if you push on the tensioners or add additional pressure prior to tightening up the bolts. I've got about 2000 miles on my Dayco Isoran belts and Hill bearings (thank you, Ricambi) and it's all rock solid.
Just because you're paranoid doesn't mean someone is not out to get you. However, in this case, you should be OK. It's the same procedure I've used multiple times without any incident.
OK, so it sounds like I have done the right thing via the correct procedure, any ideas on why the rear bank is tighter than the front bank at TDC? Is it odd to see the washer under the tensioner bolt not sitting perfectly round on the top of the bearing surface? I have posted a picture, pretty sure the old bolt sat like that on the old tensioner (a little askew) when I took the cam cover off. I have a picture of both. How do you guys like those solid oak homebuilt cam locks! Image Unavailable, Please Login
I think you worry needlessly, and you'll be surprised how "loose" the belts will feel after a few thousand miles use If you had the cam locks in place on both sets of cams when you did this: having a slight difference in the loads on the belts would be almost unavoidable IMO (unless you get lucky) because there is no physical reason for the load to be shared equally by the two belts (because of slight distance differences in the load path from the gear on the crank to the now locked cam sprockets). You'd get a more consistent result if you had one set of cams locked up and one set free -- so that the forward pressure you put on the crank nut would only be resisted by one belt (and slightly extend that tensioner plunger outward), then tighten that tensioner down. Then remove the locks from that set of cams and move it over to the other set of cams, apply the same amount of forward pressure to the crank nut, and you should get the same tension in the other belt (and slightly extend the other tensioner plunger outward). Just a thought...
Mr. Steve said it If you have locks in place, you're bound to see a difference in tension. Not so much once you release everything. And yes, that slight offset of the washer is normal. Tighten it up, fear not and enjoy your car.
If you pluck the long run of the belts as you rotate the engine you will find the tension in the belts (and hence the note they produce) varies and is not constant as you turn the thing over. At TDC one belt produces a much higher pitch note than the other but as you turn the engine you should find that both will produce the same note, just not at the same time/point in the cycle.
I've been worrying about this since I did mine. I thought that an excessively tight belt had ruined the bearing because of a noise that the engine makes at really low revs, say 500 rpm, a low hum. It sound like a loose exhaust shield or even a bad thermostat. Now instead of immediately tearing into the belts I'll slowly go over everything like the cam covers, shields, etc. It was a real pain when the engine was running poorly--that turned out to be a block in the #4 idle jet. Anyway, thanks for saving me from myself.
I agree with Steve Magnusson, I generally do the very finall tensioning by loosening 1 lock & so that only the belt I'm tensioning is locked, then I release that lock & tighten the other lock for the final adjustment of the remaining belt. (One of those things that's hard to explain in a write-up). After multiple rotations, the reason that when on PM1-4 TDC one bank's belt will have a slightly different tension is that the cams for each bank are timed differently due to the 90 degree difference in the piston positions, thus are putting slightly different tension on the belts. ie: The rear bank belt tension when the crank is on PM1-4 of a stroke should be very close to the tension on the front bank belt when the crank is on PM5-8 of a corresponding stroke. The tensioner bearing washer is off-center because the tensioner bolt is screwed into the head, while the tensioner washer is centered on the tensioner. While the tensioner's position is determined by slack the belt system, not the tensioner bolt.
Thanks to all the replies, I did what Verell suggested and released the one set of locks after adjusting that teniosner and moved to the front one and voila, that nice musical note. I then rotated threw a few evolutions and both belts at different times had the same tension coming up on TDC. So it looks like all is well, Merry Christmas and Happy New Year to all.......
