75 or 164 Motronic crank pulley?

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mjr
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75 or 164 Motronic crank pulley?

Post by mjr » Tue Nov 08, 2011 3:22 am

Hi all. In the process of replacing front pulley on 2.5, for power steering. I came a cross a brand new 3 V belt pulley, with crank sensor notches too at the rear of the wheel. ie, no timing marks. The part number comes back as 75/164 3.0 Motronic crank wheel. Does any one know if this later pulley will fit the 2.5 engine without any clearance problems? obviously it's a lot thicker than the standard 2.5 unit, which only has one pulley groove. I have aquired it, since it obviously is ideal to go CAS set up too, and ditch dizzy at some point. i am aware of the balance issues, but that is a seperate issue. Just concerned with whether it will actually fit, without any modifications.
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Re: 75 or 164 Motronic crank pulley?

Post by Giuliettaevo2 » Tue Nov 08, 2011 9:35 am

The main problem you have is the fact that the pulley is balanced together with the crank and flywheel on the v6 engines. Using a 3.0 pulley on a 2.5 engine will get the balance off.

Secondly the grooves for the belts are located in different places so you'll need to change the mounts for the dynamo, the PS pump, the aircocompressor and teh waterpump. It will fit the crank perfectly.

75 v6 Motronic pulley is sought after and different from the 164 Motronic pulley which is a very common pulley. :?
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Re: 75 or 164 Motronic crank pulley?

Post by mjr » Tue Nov 08, 2011 10:19 am

I have spoken to 3 different alfa specialists this week here in the uk about getting the motor balanced for the 3.0 crank pulley. They build 75's and gtv6's, including 2.5 power steering conversions. All have said I am making an issue over nothing? AMZ and Jupe told me they have done countless conversions with 3.0 pulleys over the years and bolted them right up without any balance issues. I would have thought balance would be off too, but Im being told its not an issue!? i dont know which advice to take now :?

The positions are different for the pump and alternator? With the 3.0 engines I was looking at this week from 75's, the alternator and power steering pump brackets and pick ups on the block/head were identical to the pick up points on my 2.5 engine. I take it then that the Motronic 75 pulley is positionally different to the ordinary 3.0 pulley? I must admit I am starting to wonder if power steering is worth the pain the butt!! :roll:
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Re: 75 or 164 Motronic crank pulley?

Post by Duk » Tue Nov 08, 2011 7:33 pm

mjr wrote:I have spoken to 3 different alfa specialists this week here in the uk about getting the motor balanced for the 3.0 crank pulley. They build 75's and gtv6's, including 2.5 power steering conversions. All have said I am making an issue over nothing? AMZ and Jupe told me they have done countless conversions with 3.0 pulleys over the years and bolted them right up without any balance issues. I would have thought balance would be off too, but Im being told its not an issue!? i dont know which advice to take now :?
My guess would be that in a relatively short term (say less than 100,000km), it probably would be unnoticeable. But vibration takes its toll on bearings eventually.
Who is going to complain to a workshop about worn out bearings after only 10's of 10,000s of km, that'd be hard to prove it was from a 'less than ideally balanced pulley'!

Why else would there be differently balanced pulleys?

Scott Venables showed an excellent approach to being able to re-balance to original spec, the offset weighted flywheel after lightening. http://www.alfabb.com/bb/forums/milano- ... g-jig.html
Balance an offset weighted arbor with the original pulley and then put the new Motronic pulley on the arbor and add or remove weight to/from the pulley to correct its offset to the arbor.
Vwalla, 1 pulley that replicates the original's offset characteristics :D .

After all of that, why specifically, to you want to go to the trouble of using the 60-2 pulley? Surely there are easier approaches to tell the an engine management system where the engine is.
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Re: 75 or 164 Motronic crank pulley?

Post by mjr » Wed Nov 09, 2011 2:02 am

Hi duk thanks for the link, scotts solution ought to bring a pulley within tolerance. that's a nice solution actually. I dont specifically want to go to a 60 -2, but need a new pulley to drive the power steering, and pulleys are not exactly growing on trees here. this one was available brand new for next to nothing, so I took it. The euro gtv6's rarely came with air con, so most of them only have one pulley groove, hence why its no good for adding steering pumps.

You know the more I think about it, the more it makes sense what the garages are saying. Each engine being balanced with pulley and flywheel at the factory is not doable, it would have cost a fortune and slowed up the production too much. it makes more sense that Alfa established an acceptable tolerance for the engines and set a datum for the crank pulleys and flywheels to be set to. perhaps they had 2-3 balance factors for flywheels and front pulleys off of the shelf. I.e. engine builder would weigh all the parts as they went it, and using a table would tell him at the end to use flywheel A and pulley B. The workers would balance flywheels and front pulleys on mass in a different department, to say 2 different balance factors, taking care of engines that might be close to max or min weight tolerance. Since most engines would probably fall somewhere in the middle, then any wheel would be acceptable on the engine. These would then be fitted to every production engine, the theory being that the balance was close enough for each engine to last for what alfa would consider an acceptable lifetime. Im sure some engines ended up peachier than others using this method. This 75 motronic wheel I have is brand new and already has the counterweight and balance holes done. It is a stock item that could be bought over the counter at any Alfa dealer.

I bet there are certain combinations to stay away from, like fitting say a FWD pulley to a gtv6 or 75 for instance, but I bet you can fit any three litre 75 pulley to a 2.5 or 3.0 engine and still stay within an acceptable balance, where the engine is driven how it was intended to be driven, and not raced or red lined constantly.

any other thoughts? has anyone else had any direct results swapping pulleys,?
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Re: 75 or 164 Motronic crank pulley?

Post by Zamani » Wed Nov 09, 2011 8:15 am

My brother fitted an SZ pulley on his 164 engined 75. 13 years later no problems. Ideally you would want everything balanced. But is it practical for such a small part?

I put forged pistons in my car about 7-8 years ago, no problems. Now in this case, I would NEVER do this again. Since the pistons are not matched to the counter weights, the whole assembly SHOULD have been be balanced. But again, up till now no problems. And this engine is revved to 7K rpm, not the typical 6300 rpm engine.

Your pulley, in comparison to my pistons, is very insignificant, I would say go for it.

If the engine blows up within the next few years, chances are it would probably be due to a skipped belt, bad tensioner, dropped sodium-filled exhaust valve, failed oil pump and so on.

In summary, for a race car going to > 7K rpm, don't take any chances. Balance everything. But for a road car, why bother.
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Re: 75 or 164 Motronic crank pulley?

Post by mjr » Wed Nov 09, 2011 10:53 am

Well Z thats my thoughts too. I think a whole lot of folklore has built up around balance issues with crank pulley swaps, just like the same stupid stories with propshafts, which I have never had an issue with, with no marking up or keeping bolts in the same locations. I just don't believe that a main dealer would stock pulleys, which would then have to be rebalanced for each individual engine, it would be a recipe for disaster, knowing how stupid dealers could be at times anyway!

for racing use I can understand it, but not for road use. I rekon Im going to try it and see.
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Re: 75 or 164 Motronic crank pulley?

Post by kevin » Wed Nov 09, 2011 12:08 pm

We never swap pulleys without reballancing but thats because we build every to be raced . Out of interest the only way can tell the difference between a 3.2 gta motor and 3.0 166 motor visually is by the pulley . The counter ballance on the 3 .2 takes up half the pulley. There are no other visible marking on the engine. Our pulleys are reballanced same principle as scott. No need to take motor apart.
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Re: 75 or 164 Motronic crank pulley?

Post by WhizzMan » Fri Nov 11, 2011 11:56 pm

The Busso V6 engine used external balancing. That means that the crank itself isn't balanced to 0 grams, but was balanced to predetermined un-balance. Doing that, saved an enormous amount of weight on the counter-weights on the crank itself. This means that you do need the pulley and the flywheel off individual balance, to come up with a balanced trio.

Flywheel was balanced within 5 grams (most were below 2 grams even, but I have 5 grams factory tolerance in my head) to spec. The same applies for pulleys. No, there was no combined balancing of the trio, but due to the good balancing of the individual parts, this was not required.

messing with these will give vibrations that you will most likely not feel yourself, but that will either crack your crank (extreme case) or wear down your main bearing much quicker. Busso main bearings tend to last quite long, 200.000 km isn't an exception. If you mess up the balance of just the pulley, you're probably still looking at half of this.

it's not that hard to fix the balance of the 3.0 pulley, so I myself would get it done for peace of mind. If you want to balance your con rods to the gram, why not your pulley? It's more or less the same amount of unbalance per gram as a con rod, more or less the same location in the car and at the exact same speed of the engine anyway. Balancing con rods is done for exactly the same thing, lightening them is for relief of stress on the con rod bolts. The few grams difference isn't going to break those bolts, so why bother if you finish off your engine with an off-balance pulley?
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Re: 75 or 164 Motronic crank pulley?

Post by kevin » Sat Nov 12, 2011 11:56 am

I took a pic today of both my gta engines front pulleys and one has mallory added and the other is drilled. Shows there was no standard on the gta unless the mallory fell out on my other motor . One motor is brandnew still in crate , the other is in my sportwagon.
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Re: 75 or 164 Motronic crank pulley?

Post by kevin » Sun Nov 13, 2011 9:47 am

Check these two pics of GTA pulleys.
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