Engine screams above 3000 rpm

luigi164

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I know it's difficult to diagnose a noise made by the engine by looking and hearing a video.
This is what my engine ( a stock 383 2bbl ) does when reved up at 3000 rpm. Below that no noises. My first thoughts were the belts but after adjusting them a little tighter ( the alt/ac was a little loose) it made no difference.

Anybody here recognises this noise ?

 
Try taking the tension off all the belts, you probably have a dry bearing someplace. Spin the alternator, is it quiet? Next spin the water pump, does it turn freely and smoothly. Spin the idler pulley, if it sticks or rattles as you turn it, it is toast. Next check the A/C pulley, it should turn freely without any resistance and minimal noise. If you can not find any thing using this method, try reinstalling the belts one set at a time to see if you can isolate which item is causing the noise.

Dave
 
Typically on those AC equipped big blocks, the fan and water pump belt is tensioned with an idler pulley. They're notorious for failing and screaming while doing so. Mine did exactly the same thing.
 
For good measure, check the air gap on the a/c compressor clutch. Definitely a metallic slippage sound. What about any slop in the fan clutch?

Keep us posted,
CBODY67
 
Taking belts off 1 at a time like mentioned will show you. Before that you can check to see if ac clutch is slipping or chattering. Turn ac on and off to see if it changes
 
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After some research I found out the idler pulley bearing is toast. Ordered a new one from RA and it came in today. New problem/question: I have to use the old bolt and nut cause the new pulley is without those. How do I get the old bolt out ? I thought it was a dustshield and I've tried to hammer it of but ..
 
I think you probably have the wrong pulley, the OEM style you have does not come apart. www.manciniracing.com has the reproduction pulley, but they are pricey.

Dave
I've seen the one on Mancini and it is indeed pricey. So I thought the one from RA is oke, thinking I could use the old bolt. Mmm, searching for a suitable bolt an option ? Are they available?
 
I've seen the one on Mancini and it is indeed pricey. So I thought the one from RA is oke, thinking I could use the old bolt. Mmm, searching for a suitable bolt an option ? Are they available?

The mounting bolt is usually slotted and something of a mopar only item. Some of the York after market A/C systems used the type of pulley you have. The mounting stud has a machined collar that keeps the pulley away from the bracket. You would have to drill out your bracket to make the conversion.

Dave
 
Or get rid of the idler pulley and go with a dual water pump pulley
 
Or get rid of the idler pulley and go with a dual water pump pulley

That's an interesting idea, have you seen this done? I'm trying to picture it in my head, I sort of see it working on a non-A/C car. Do you think it work on an A/C car like his?
 
You can find the oem version cheaper on ebay, or swap meets

The only tensioners there would be from the alternator and from the power steering pump bracket
 
Thanks! Why don't more people know about this! Better question, why didn't Chrysler just do this in the first place?

Back in the days of v-belts, there was an orientation that "essential units" would get a dedicated belt to run them. In this case, the water pump, which makes sense. If all of the other belts fail, the water pump would still be operational. The original Z/28s used a dedicated belt for the water pump sans tensionser, but used special deep groove pulleys to accomplish that. Plus you also have to remember that v-belts can stretch with age and use. There are some recent GM a/c compressor belts which are untensioned, with ONE belt that runs them. Talk about a pain to change the belt on, if needed! Obviously, v-belt quality control is better, decades later, than "back then".

Remember, too, that with the dedicated-length belt/pulley arrangement, if the belt goes and no exact replacement is available, not a good position to be in. Especially in a world with land-line phones and no "pay phone change" in your pocket . . . at 10pm at night . . . away from the larger city. Much better to "have options" of making something different possibly fit and work well enough to get you back to civilization or your normal repair shop!

Before getting all "excited" and asking questions (in the current time) as to why they designed something the way they did (in the "model-year" time, minus 3 years), you have to remember the way things were done back then and WHY they were done that way. It's those side issues, "two levels below the surface" that usually explain things better than what's seen on the surface, in current times.

Another side issue would be Chrysler's huge law enforcement vehicle business. In that area, having a vehicle that can go 24hrs/day is important, no matter what. So finding a rouge belt that would work would be more important, ultimately, than having to have the EXACT item itself. That business was extremely important to Chrysler, even if it might cost them a few dollars more for the belt/idler arrangement for the water pump belt. Further solidifying the "one belt/function" general orientation for essential engine accessory drives. In this case, the water pump would be an accessory, just as the alternator or power steering pump would, just that the alternator or power steering pump would not be essential to engine operation and its longevity.

As time progresses and later re-designs happen, other options did appear as parts quality did improve.

Just some thoughts,
CBODY67
 
Replaced the idlerpulley at last. As posted before I ordered one from Mancini. First thing I noticed it wasn't a exact reproduction of the OEM one as you can see on the pics. The new one is a bit wider so the belt is deeper now. It works, only thing now is that the adjustment is almost at its end...At least no more screaming anymore :thumbsup:

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