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Balance belt

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balance belt
6K views 34 replies 8 participants last post by  Hernando 
#1 ·
Hello

A couple of weeks ago I proceeded to change my 156 2.0 2002 twin spark engine belts (cam and poli V), but i decided to leave it w/o the balance belt. Some people claim that is a good option at the expense of a little increase in vibration. The thing is that the engine now vibrates in kind of an unpleasant way. The car has lost some finesse IMO. I can sometimes even feel a small vibration on the throttle pedal.
Other than that the car performs normaly, and the engine, even if more rough, has very good power.

I was wondering about the experience of other members on this matter. I am considering to refit the belt (obviously with a new one)

BTW, any one aware if this belt and the tensor are available in europe? I am heading to Spain in october. Maybe going also to Germany. German site Autodoc does not have it.

Thanks in advance
 
#2 ·
AutoDoc should have it. I got mine from them, though as part of a Gates timing belt kit.
 
#3 ·
I was wondering about the experience of other members on this matter.
My experience is that removing the belt does result in some slight increase in vibration, but not to an objectionable degree (at least not to me, but others may be more sensitive...). Deleting the balance belt results in the engine vibrating similarly to other two litre in line four cylinder engines that are not fitted with a balance belt, and there are very many such engines.

This is one of the reasons why, pre the invention of balance shafts, that four cylinder (in line) engines were almost never larger than two litres capacity, i.e. larger than two litres and the vibration started to become unpleasantly noticable. With the introduction of balance shafts it became possible to produce smoother four cylinder engines with capacities larger than two litres.

It is my understanding that Mitsubishi owns the IP related to counter rotating balance shafts, and that all other manufacturers using them pay a royalty to Mitsubushi.

Regards,
John.
 
#7 ·
If the balance belt breaks, which it can as it has teeth on both sides. It will 'take out' the normal timing belt.
Hence the low 36,000 mile belt change recommended by Alfa.
Hence, without the balance belt there isn't as much chance I think of having cam belt failure, at low mileage.
That is only my opinion.
The 2.0TS engine is 'super' smooth with the balance belts. So, I would rather have the belt and change it every 36,000 miles.
It is as smooth as any six with the balance belt. Makes driving the spider a pleasure. It is a great car to drive.
 
#8 ·
I am just in the process of replacing the engine on my 2.0 TS following big end failure at high revs. I had only just completed 300 miles after full belt service. During the disassembly of the damaged engine I noticed that the upper balance shaft was very stiff and I am wondering whether it was a contributory factor towards the engine failure? My replacement engine has only 50k miles but I have decided that the balance shafts to be removed.
 
#9 ·
The balance shafts cannot be safely removed, AFAIK as there are oil feeds to the balance shaft roller bearings.

When I deleted the balance shaft function in the TS, I used washers and refitted the bolts. I think this was to ensure the shafts stayed in the correct position so oil flow and pressure to other engine bearings would not be lost. That way I simply fitted new seals and plugs for the balance shafts but they do not rotate and no longer have pulleys.

I had the crankshaft and flywheel balanced (flywheel lightened first) to help minimise vibration. There is a difference between primary and secondary vibration (which the balance shafts reduce). Some people have opined that balancing the crank assembly does nothing to reduce vibrations but my 2.0 TS now has similar/slightly less vibration to a 1.8. It may not be quite as silky as a 2.0 with balance shafts but quite frankly I no longer notice much difference in vibration in my JTS using balance shafts and TS without.
 
#11 ·
Oil flowing to the balance shaft bearings is some small degree of oil flow / pressure not available to feed the other engine bearings, so if the balance shafts are no longer used it makes some sense to remove them and block the oil feeds. This also lightens the engine slightly.

Not necessarily with Alfa engines, bit I've heard of this being done with blanking sleeves, i.e. metal plugs machined to be a tight fit into the balance shaft bearings, so the plug prevents oil from exiting the bearing feed hole. I've also heard of people threading the feed holes and inserting small bolts / threaded plugs into them (sealed and secured with a high strength thread locking compound). I haven't ever done this, and expect it would awkward considering access to the feed holes would be tight. I expect there would be traps for the unwary, so due diligence required (for both methods above).

On the other hand, leaving the disabled non rotating shafts in place would mean that the other engine bearings still get the same oil supply as a standard engine will, so I doubt there is any imperative to delete the balance shafts and blank the oil feeds.

It occurs to me that it ought to be possible to machine two grooves into and near the edges of each bearing journal, into which O-rings could be fitted. Oil would still flow into and fill the space between the bearing shell and the shaft journal, but couldn't escape the bearing because the edges are sealed with the O-rings (so no pressure / flow is lost).

Machining such grooves should be relatively easy to do (just turn the shafts in a lathe), probably easier than making blanking plugs or trying to thread the oil feed holes, but you'd miss out on the weight saving of removing the shafts (a rather minor weight saving, is it worth it for this reason...?).

Regards,
John.
 
#12 ·
Thank you John. It will be much easier then to just run the engine without the shaft belt but I did read I think on the 145 Forum that the shafts would need to be somehow fixed into a position to stop them from rotating randomly and thereby causing dangerous vibrations? Also, thinking ahead.....I do have a spare 1.8 T.S engine for the 'future'. Could it be re-bored to fit 2.0 TS or larger racing pistons? Another option I have been offered is an early 155 8v block to use with a spare 2.0 TS 16v head but I understand from Fruity that configuration would not work. I am curious why I have been offered it!
Regards,
Dino
 
#17 ·
There is no matching head gasket to allow that type of pick and mix. The piston deck height is different by about 5mm so there is no cheap way to make it work. The only way is bespoke pistons and/or rods but even then you risk excessive rod angularity and that is for a track car. It would be a good way to quickly wear the thrust side of the cylinder bore. How many thousand pounds do you want to throw at it?

Disabling the balance shafts is a tried and tested way of not using balance shafts. I think the modification I did was a couple of bolts and repair washers which cost about £2. 50k after rebuild it still works perfectly.

I appreciate you want to know but the guidance given really is good and the alternatives are just really complex headaches which will only be good for emptying your bank account.
I'm not trying to dampen enthusiasm either.
 
#20 ·
There is no matching head gasket to allow that type of pick and mix. The piston deck height is different by about 5mm so there is no cheap way to make it work.
If the pistons protruded from the deck by that 5mm (I don't know which way this would go, pistons too high or too low), then I think it should be (might be) possible to insert a spacer plate. Of course this may then require two head gaskets, one above and one below the plate.

Having said that, many years ago I had a custom HG made (for an A series BMC engine), because the machine shop had skimmed the top of the block way more than I had requested. This resulted in the pistons protruding by about 0.5mm from the deck, which was an issue, of course. The custom gasket was thicker than the stock gasket so the pistons wouldn't whack into the head. It worked well for a long time, but one day the engine suddenly lost compression on two cylinders and I heard a wierd 'tinkling' noise passing down the exhaust pipe. A small section of the gasket (where two cylinders are very close to each other and the gasket lacks width), had broken free and been passed out of the engine through an exhaust valve. I think the extra thickness of the gasket had made it weaker at this point, and it also probably ran a bit hotter than ideal (locally at this point).

Problem was solved with a home made solid copper plate cut to the same shape as a head gasket, but thicker. This plate was then fitted using 'silver frost' paint as a sealant, with no gaskets (but ensuring that the plate was fully softened by annealing prior to fitment). Never had a problem with this 'gasket', but it was a lot of work to make.

The only way is bespoke pistons and/or rods but even then you risk excessive rod angularity and that is for a track car. It would be a good way to quickly wear the thrust side of the cylinder bore. How many thousand pounds do you want to throw at it?
It's my understanding that if a shorter conrod is used then the secondary imbalance will also tend to get worse. I don't know how significantly...

Regards,
John.
 
#18 ·
When the engine is separated from the gearbox, both balance shafts can be removed. As you stated the upper one is stiff to turn there may be some sort of issue. The balance shafts run in ball race bearings and the only drag on them should be the bearings and the timing belt oil seal.

It may be worth removing the affected balance shaft and ensuring it is all ok. The bearings should not be wear prone but wear is possible which is why some high mileage cars have them disconnected. That said, I see no reason why the shaft bearings cannot be changed.

If the shaft and bearings are damaged, only then would I consider having an engineering fabricator make up a blank to plug the oil feeds and locate properly into the oil seal and not have end float or it foul its fitting plug at the flywheel end.

You would either have to take very careful measurements yourself and specify exact dimensions for it to work or take block, shaft, seal and plug to a fabricator.

Hopefully the shaft and bearings are ok though for my £2 modification to work.
 
#27 · (Edited)
I found that there might be, maybe just, with a tailwind, on a good day, being optimistically hopeful, perhaps just a tad more power detectable with the belt deleted. I put it down to placebo effect...

I noticed slightly more vibration at idle, but also at higher rpm. The engine is just a bit more 'buzzy' (for want of a better description). I don't find it objectionably harsher, but I can feel the difference, mostly through the steering wheel.

Note that my car has a modified engine brace (the brace at the top / front of the engine), with one of the rubber bushes replaced by a solid 'spherical rod end' ('solid' insofar as it has no rubber to isolate vibration, but it does articulate angularly). So, my engines' increased 'buzziness' might be more than if it had the standard two rubber bushes in the brace (instead of only one rubber bush).

The rubber bush was replaced to reduce the engine rocking back and forth on / off power. The reduction in engine movement makes the engine feel more 'connected' to the chassis, with a sharper feel to power changes (on / off throttle). It feels like a slight improvement in throttle response.

This modification also causes an increase in engine noise transferred directly into the chassis structure. I was surprised to find that after replacing the rubber bush (with the rubberless rod end) that I could much better hear the engine (without that bit of rubber further insulating the chassis from sonic 'intrusion'). In particular, induction roar was much more apparent from within the cabin, but also various 'mechanical' noises could be more clearly heard (i.e. camshaft whine and subtle gearbox and / or differential sounds).

To some people this might sound like a bad thing, but personally I found it to be very much an improvement to what was (IMO) an overly quietened motor. It now sounds a lot 'sportier' without being too intrusive when cruising (others may not agree).

Lots of people change exhaust systems primarily to increase engine noise. I found that replacing this one rubber bush with something less sonically insulating had a somewhat similar effect, but nicer, and with the advantage of the increased 'noise' not being embarrasingly apparent from outside the car (the engine is not actually louder, but the noise it does make is not so isolated from the cabin interior). I have also removed the various resonance chambers in the induction tract, which are designed to quieten the induction system (God knows why, isn't this car supposed to be at least a bit 'sporty'...). The TS engine does make nice noises, but IMO they are overly 'subdued' in the standard 147 form.

Regards,
John.
 
#29 ·
John, the engine top mount needs replacement on my car - that is the small one that looks like a dumbell. Is this the one that you have modified with a spherical joint(s)? Coincidentally, I also need to replace the rear exhaust silencer. On a separate note, the engineer who is preparing my engine says that if the shafts are to be retained they must be isolated in a fixed position and not allowed to turn. Also,
I have been unable to identify an off-the-shelf balance shaft delete kit from UK based tuning specialists.

I found that there might be, maybe , with a tailwind, on a good day, being optimistically hopeful, perhaps just a tad more power detectable with the belt deleted. I put it down to placebo effect...

I noticed slightly more vibration at idle, but also at higher rpm. The engine is just a bit more 'buzzy' (for want of a better description). I don't find it objectionably harsher, but I can feel the difference, mostly through the steering wheel.

Note that my car has a modified engine brace (the brace at the top / front of the engine), with one of the rubber bushes replaced by a solid 'spherical rod end' ('solid' insofar as it has no rubber to isolate vibration, but it does articulate angularly). So, my engines' increased 'buzziness' might be more than if it had the standard two rubber bushes in the brace (instead of only one rubber bush).

The rubber bush was replaced to reduce the engine rocking back and forth on / off power. The reduction in engine movement makes the engine feel more 'connected' to the chassis, with a sharper feel to power changes (on / off throttle). It feels like a slight improvement in throttle response.

This modification also causes an increase in engine noise transferred directly into the chassis structure. I was surprised to find that after replacing the rubber bush (with the rubberless rod end) that I could much better hear the engine (without that bit of rubber further insulating the chassis from sonic 'intrusion'). In particular, induction roar was much more apparent from within the cabin, but also various 'mechanical' noises could be more clearly heard (i.e. camshaft whine and subtle gearbox and / or differential sounds).

To some people this might sound like a bad thing, but personally I found it to be very much an improvement to what was (IMO) an overly quietened motor. It now sounds a lot 'sportier' without being too intrusive when cruising (others may not agree).

Lots of people change exhaust systems primarily to increase engine noise. I found that replacing this one rubber bush with something less sonically insulating had a somewhat similar effect, but nicer, and with the advantage of the increased 'noise' not being embarrasingly apparent from outside the car (the engine is not actually louder, but the noise it does make is not so isolated from the cabin interior). I have also removed the various resonance chambers in the induction tract, which are designed to quieten the induction system (God knows why, isn't this car supposed to be at least a bit 'sporty'...). The TS engine does make nice noises, but IMO they are overly 'subdued' in the standard 147 form.

Regards,
John.
 
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