Timing Belt Questions

ChesterCRD · **Posted:** Sun Oct 30, 2011 10:29 pm

I'm getting ready to tackle the timing belt job. I plan to replace the idlers and check the feel and appearance of the tensioner and water pump. So, my questions:

1. Thoughts on the Gates timing belt versus OEM? Gates is about 50% the cost of OEM and I haven't any experience with them. I would hate to break a timing belt due to saving ~$80. Then again, maybe the Gates is a better product that OEM. Opinions welcome.

2. Tensioner function...is this a wear item other than the bearing? I'm wondering if there is a spring type setup similar to the serpentine belt tensioner where it really should be replaced after 100K.

3. How difficult is it to turn this motor over by hand (to check alignment with new belt)? Anything special other than just turning the lowest pulley? Should an 18 or 24 inch breaker be sufficient?

Thanks in advance for any insight.

Sir Sam · **Posted:** Mon Oct 31, 2011 11:56 am

1. I've used both the OEM and Gates, either is fine, both are equally difficult to install when new. For my money I've save the $80 and spend that elsewhere.

2. There is a spring in the tensioner, and there is a bearing. Personally I think the tensioner is fine at 100k. The TB idler pulleys tend to be the ones that show more wear on the bearings. I'm thinking a 200k interval for the TB tensioner is a good idea.

3. Long breaker bar will do it. When you hit a compression stroke just hold it and let the pressure bleed down, then keep turning.

papaindigo · **Posted:** Mon Oct 31, 2011 1:34 pm

Just spent a happy weekend with geordi and lgoodbar helping out on lgoodbar's TB job so they may want to add info. Things we found that immediately come to mind.
1. On both TB and serpentine belt the tensioner doesn't "relax" quite enough, at least with Mopar belts, so the trick is to route the belt over all of the "things" with outer lips for the belt to clear and do the final install on an idler pulley. On the TB even that was not quite enough as we had to relax tension to the max and install the final idler pulley using its bolt to carefully pull it behind the belt. URGENT NOTE, I'm sure geordi will want add more but under absolutely no circumstances try to install the TB tensioner last as for mysterious reasons known to no one both geordi and lgoodbar's engine, the latter untouched since the factory, had an oversized bolt hole, which had been helicoiled, for the tensioner bolt. If you make this mistake the helicoil will be damaged and it's off the the parts store.
2. we left the original idler pulleys and water pump alone even though replacements were at hand. All of those had rock solid bearings and zero sign of losing lubricant. NOTE TO FORUM for thought - short of leaving the semi-useless dust cover off the engine is there any feasible way to create view windows in that dust cover, perhaps with hardened plexiglass so one can actually see at least part of the belt and pulleys?
3. I'm not sure I'd recommend a long breaker bar to turn the engine unless it has a rachet head just because of the necessity to reposition it. geordi did ok with a medium long regular rachet handle but it was a bit of a tug; we did mark the crank pulley so we could see the rotation count and did a temporary reinstall of the cam locks just to confirm all was still aligned after 2 rotations.

Sir Sam · **Posted:** Mon Oct 31, 2011 4:24 pm

IMO the cam locking pins are near useless when trying to determine the correct timing between the cams and the crank.

papaindigo · **Posted:** Mon Oct 31, 2011 4:37 pm

Sam I'm not sure I follow your point or perhaps we are talking past each other. We started with a running engine with the original factory belt, rotated everything until the cam locking pins and flywheel pin would go in, marked a bunch of stuff, locked everything down with the big cam tool, did the install, removed the cam locking tool, manually rotated the engine twice until all the marks came back to the same place, checked the TB tension mark, then for a final extra check that we were back to the cam position where we started made sure the cam locking pins would go back in which they did. I looked back over your right up and except for the last locking pin check we did essentially the exact same steps you did including the initial cam locking pin install.

Now if we had started with a disassembled engine or one that was already out of time I'm not sure how one would go about setting the correct cam to crank timing in the first place.

Sir Sam · **Posted:** Mon Oct 31, 2011 8:58 pm

papaindigo wrote:

.....We started with a running engine with the original factory belt, rotated everything until the cam locking pins and flywheel pin would go in,

Now if we had started with a disassembled engine or one that was already out of time I'm not sure how one would go about setting the correct cam to crank timing in the first place.

If the crank pulley is off by one tooth it is possible to insert the flywheel pin and have it go through a hole other than the crank pin tool hole. This is why marking the crank accurately in an important step that should not be neglected.

This is also why it is possible to have a vehicle with a skipped timing belt that appears to be correctly timed, the crank pin will go through a hold other than it was intended to.

Retiming an engine from scratch proves to be exceptionally difficult because of this fact when the flywheel is not visible.

naturist · **Posted:** Mon Oct 31, 2011 10:39 pm

Given the labor costs of a timing belt job, with or without tensioners, idlers, water pump, etc. and given the costs of catastrophic failure if you guess wrong, and in light of the small costs of the individual pieces, I think it's being penny wise and pound foolish not to replace all that stuff at once. I mean, it's not like a tensioner is made of gold, already.

papaindigo · **Posted:** Tue Nov 01, 2011 8:21 am

Sam - I get your point and one thing we did that I negelected to mention when inserting the flywheel pin (FYI used a 6mm hex key per the FSM not the Miller screw in pin as the threads were rather dirty) was to insert the pin and tap the flywheel around where the hole should be so we knew were going into, when the pin was centered up, a small hole in the flywheel and not something else.

I'll cheerfully admit it would be nice to be able to "see" what the various pins are going into and if the various gears/cranks had usable factory marks not to mention cam gear keys. Made me long for the old days when lining up various marks at top dead center in a timing chain/gear job guaranteed that you had it right.

ChesterCRD · **Posted:** Tue Nov 01, 2011 9:01 am

Thanks for all the input folks. Right now I'm planning to use the Gates timing belt and plan to check it at 150k. I'll buy the tensioner and idlers now and decide whether to replace them based on how they look/feel when I get in there.

Sir Sam · **Posted:** Tue Nov 01, 2011 12:26 pm

papaindigo wrote:

Sam - I get your point and one thing we did that I negelected to mention when inserting the flywheel pin (FYI used a 6mm hex key per the FSM not the Miller screw in pin as the threads were rather dirty) was to insert the pin and tap the flywheel around where the hole should be so we knew were going into, when the pin was centered up, a small hole in the flywheel and not something else.

I'll cheerfully admit it would be nice to be able to "see" what the various pins are going into and if the various gears/cranks had usable factory marks not to mention cam gear keys. Made me long for the old days when lining up various marks at top dead center in a timing chain/gear job guaranteed that you had it right.

Been there done that, I even have a broken 6mm hex key from messing around with that.

And yes my threads were dirty too, I gave up on getting the miller crank pin to thread in. The 6mm hex key just lets too much play in the crank, even with that in place its possible to get it misaligned.

The best solution I have found for the crank is to use a drill bit very close in size to the miller tool diameter, I forget what size that ended up being right now, but I had better luck with it holding the crank in place than the miller tool or a hex key.

geordi · **Posted:** Tue Nov 01, 2011 2:02 pm

That may be your mistake Sam, the flywheel pin isn't meant to hold anything in place, it has to cross almost an inch of open space between two narrow partitions of metal to do its job. The flywheel is thin, and the coverplate where the threads are, is also thin. As such, any misalignment will pull the pin out of horizontal easily, and if you are using the Miller pin, possibly rip up those small threads.

The key that you have the crank in the proper position is the pulley bolt holes on the front - They will be in a 12/6/3/9 o'clock position layout when the crank is in the right spot, AND the pin goes in so you can tap around it's small hole on the flywheel (for verification of the right hole) but seat it properly horizontal against the cover.

The crankshaft has enough "weight" that you won't move it by accident unless you are a gorilla installing the belt. Just leave it there at 90 deg ATDC for the moment and move on with the job.

For installing the belt - Papaindigo is correct about what we discovered - DO NOT INSTALL THE TENSIONER LAST! The belt is a difficult beast to get installed, but with that helicoil in the tensioner's hole... The way I got it to seat properly was to remove the idler pulley above the tensioner on the left side, and use THAT to supply enough slack room to set everything else.

Start with the water pump or the cam pulleys, and work your way around clockwise to each pulley. The cam tool will keep them completely secured, so that is a good starting point - When perfectly seated, there should be ZERO slack between the two cams at the very top. The teeth should line up perfectly. When they do, it might be helpful to slide in a couple of 1/4" extensions across the top of the belt just to help retain everything there. If you scribed the fuel pump (I marked two different teeth with one in the middle, and the cover opposite) you will know that the pump was right where it had been. Pull the belt tight against the idler, and into the teeth of the pump. Down to the crank... Where you might find it a half-tooth off. This is to be expected, and where a little finesse comes into play.

Since the top cams are still pinned and locked with the tool, you don't have a lot of wiggle room here, but luckily you only need about 1/4" or so of travel. Rock the crank counter-clockwise just a hair until the teeth of the belt seat, then pull it back clockwise to vertical - See how it stops exactly at vertical (looking at the bolt holes) and the belt is now slightly tensioned? It won't hold there on its own, so you don't want to let go. Having a helper is VERY useful at this point. You aren't hurting ANYTHING to move the pistons that little, dont forget that they have to reverse their direction hundreds of times every minute in operation, and you are only moving it 1/4 inch or so. Nowhere near enough to find a valve with a piston. If you need to move it more than 1/2 a tooth... Something else is wrong, go back and check the belt for proper alignment and seating on the other pulleys.

Now you are back to the tensioner, which is in place, but loose... RIGHT? Good. Put the belt around that, and the water pump (which has no set position, unlike the fuel pump) and now you should have a nice big loop of empty belt, just waiting for another idler pulley. This is the tough one. You need to get the bolt of that idler to line up with the hole so you don't cross the threads. But since there isn't a helicoil in that hole, it shouldn't be too difficult to do. This is also where "pre-tensioning" the belt on the fuel pump side helps you, it gets you a tiny bit extra wiggle room to get the idler into place. Crank that into position behind the belt, watching that the belt slides along the face of the pulley and doesn't get trapped behind it. It shouldn't tho.

NOW, you are ready to do a final feel of the seating around all the pulleys, and tension the whole thing. Rotate the tensioner into position with its tool, watching that little "window" and the wire behind. When it is in the right spot, you will basically not have ANY more you can get out of it. Its tough, push hard to get there. Lock the tensioner down with the correct torque, 312 INCH-pounds on my wrench is 26 lb-feet. Its not much.

Pull your pins and locking clamp from the top and give the whole thing a rotate with your big wrench - it helps to scribe the top of the crank here so you KNOW that you got it around twice... I went ahead and looked at both my scribes and the cam pins for double-super confirmation... but it is the tensioner window you are really looking at. If the wire is in the center of the window... You are done!

At this point, you can start the motor without the accessory stuff in place (it will run just off the battery for a few seconds) to confirm everything runs great like we did... Breathe a sigh of relief, and start closing it back up. If we didn't have to run to the parts store for the helicoil, the whole gig would have been about 3.5 hours. Not too shabby.

Timing Belt Questions

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