'69 383 driving us nuts...
11-26-2007, 04:06 AM
#1
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'69 383 driving us nuts...
A good friend of mine is building a '73 Challenger and has installed a '69 383 into the car. The engine runs like a clock, but it's got a strange metal-on-metal "chafing" sound coming from the upper front of the engine when it runs. It's driving us both crazy as we can not figure out what it is or what's causing it.
The engine had approximately 65,000 miles on it when he purchased it and he completely disassembled and rebuilt this engine before installing it into the car. He is very competent and meticulous about stuff and this was the fourth big block that he's rebuilt - I don't doubt that it is put together properly.
He pulled the pan to check for metal shavings and the oil is clean. The pan does not have a windage tray, so it's not a case where the crank is making contact with anything.
The engine starts right up, runs very well at high idle, but starts to lope, (badly), when the choke kicks off. It emits "the noise" at both low and high idle.
The only thing that we've noticed is that there is a very slight bit, (about 1/16th inch), of "run-out" in the harmonic balancer pulley, but this is negligable, and the belts are all running pretty true. Neither one of us think that this has anything to do with it.
The alternator is new and good. Power steering pump is fine. We stethoscoped the water pump, too, and it sounds fine.
My friend said that there was not any abnormal slack in the timing chain when he was reassembling the engine, and he doesn't believe that the chain is rubbing against anything. As well as the thing runs, I don't think that it has jumped time - but the lope at low idle has me wondering if it may have jumped a tooth or two.
He would like to avoid pulling the timing chain cover off if he can - but knows that this is going to be the next step, if it's not an "easy fix."
I suggested pulling the distributor and checking the shaft bearings first, as this is where the sound could be coming from, (where the drive gear would meet the cam), but I'm at a loss otherwise.
Any ideas or suggestions? This thing has us both completely befuddled.
The engine had approximately 65,000 miles on it when he purchased it and he completely disassembled and rebuilt this engine before installing it into the car. He is very competent and meticulous about stuff and this was the fourth big block that he's rebuilt - I don't doubt that it is put together properly.
He pulled the pan to check for metal shavings and the oil is clean. The pan does not have a windage tray, so it's not a case where the crank is making contact with anything.
The engine starts right up, runs very well at high idle, but starts to lope, (badly), when the choke kicks off. It emits "the noise" at both low and high idle.
The only thing that we've noticed is that there is a very slight bit, (about 1/16th inch), of "run-out" in the harmonic balancer pulley, but this is negligable, and the belts are all running pretty true. Neither one of us think that this has anything to do with it.
The alternator is new and good. Power steering pump is fine. We stethoscoped the water pump, too, and it sounds fine.
My friend said that there was not any abnormal slack in the timing chain when he was reassembling the engine, and he doesn't believe that the chain is rubbing against anything. As well as the thing runs, I don't think that it has jumped time - but the lope at low idle has me wondering if it may have jumped a tooth or two.
He would like to avoid pulling the timing chain cover off if he can - but knows that this is going to be the next step, if it's not an "easy fix."
I suggested pulling the distributor and checking the shaft bearings first, as this is where the sound could be coming from, (where the drive gear would meet the cam), but I'm at a loss otherwise.
Any ideas or suggestions? This thing has us both completely befuddled.
11-26-2007, 02:45 PM
#2
The very first thing to do is have a critical listen with a stethascope, although it sounds as if you may have. I'd try that again.
Second, or maybe even first, is to start with the engine cold so that you can run it a few minutes. Pull ALL belts, and try. Next, inspect carefully the balancer-to-timing cover. It might pay to pull the balancer out a little like maybe 3/8" and run a short time. Just a few seconds will tell. I doubt that the distributor is causing this, but you should be able to pull it out and rotate by hand, dissasemble, and find out.
Don't forget (dumbass) mistakes like the balancer/ pulleys rubbing AT cooler or PS hoses
Now, (in general) many engines had changes in timing drive components over the years. We once had a Ford 302 with a mismatched problem with the cam drive that allowed the cam to "walk" front and rear. This was a brand new assembly, and damn near ruined the cam. As I recall, the early/late cam drive components could be switched IF you had all the right pieces, IE you did not try and run a wide chain (Morse silent type chain) on the narrow sprockets. Roller chain, of course, either fits or not
If you can't find anything, suspect mismatched cam drive components. Are you running a windage tray? What's the chance that the crank is rubbing something, the windage tray, the oil pickup? Things DO get bent sometimes.
Are you ABSOLUTELY SURE it's in the front of the engine? How about the flywheel/converter/ bell cover?
Last, you DO HAVE a chain cam drive and not a gear drive?
Second, or maybe even first, is to start with the engine cold so that you can run it a few minutes. Pull ALL belts, and try. Next, inspect carefully the balancer-to-timing cover. It might pay to pull the balancer out a little like maybe 3/8" and run a short time. Just a few seconds will tell. I doubt that the distributor is causing this, but you should be able to pull it out and rotate by hand, dissasemble, and find out.
Don't forget (dumbass) mistakes like the balancer/ pulleys rubbing AT cooler or PS hoses
Now, (in general) many engines had changes in timing drive components over the years. We once had a Ford 302 with a mismatched problem with the cam drive that allowed the cam to "walk" front and rear. This was a brand new assembly, and damn near ruined the cam. As I recall, the early/late cam drive components could be switched IF you had all the right pieces, IE you did not try and run a wide chain (Morse silent type chain) on the narrow sprockets. Roller chain, of course, either fits or not
If you can't find anything, suspect mismatched cam drive components. Are you running a windage tray? What's the chance that the crank is rubbing something, the windage tray, the oil pickup? Things DO get bent sometimes.
Are you ABSOLUTELY SURE it's in the front of the engine? How about the flywheel/converter/ bell cover?
Last, you DO HAVE a chain cam drive and not a gear drive?
11-26-2007, 03:53 PM
#3
Also, if you have (a wrong) too thick front seal, or not seated all the way, the seal might be contacting the lower cam sprocket.
A tidbit: Did you know that on many V8's that when you install the cam drive, "on the marks" this does NOT set up no 1 ready to fire, but rather no. 6. This can be very unsettling on Mopar B engines, where you can install the cam drive, and right away put the distributor in also, only to have it puke up through the carb. I used to pride myself on being able to static time a new build, and fire it right up without putridity going on
A tidbit: Did you know that on many V8's that when you install the cam drive, "on the marks" this does NOT set up no 1 ready to fire, but rather no. 6. This can be very unsettling on Mopar B engines, where you can install the cam drive, and right away put the distributor in also, only to have it puke up through the carb. I used to pride myself on being able to static time a new build, and fire it right up without putridity going on
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