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383 spun main?

RebelRider

RebelRider

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A little back story........
1970 Plymouth Roadrunner 383/TF
I got the car in 1999 to drive to high school. In 2000 the number 7 rod bearing spun. At the time I did not have the knowhow to rebuild it myself. We pulled the engine and brought it to a reputable local builder. It had to be punched 60 over and the crank turned. He had it for over a year before I got it back. By this time my mind had started to wander and I got the car running again and parked it in my dads shop. Over the past 20 years, I have had it running a few times, but nothing more. Always sounded great.

Fast forward to now. I have finally settled down and have dove into it. I just got finished putting electronic ignition, along with a new edelbrock 600cfm. I changed the oil and got it running decent. While idling, it developed a bad belt squeal. The alternator alignment has always been a little off, so this was no surprise. I figured I’d just pull the alternator belt and see about fixing the alignment later.
Squeal is still there. I then pulled the PS belt. Still there.......no belts on the engine at this point. A sharp constant screeching coming from up around the balancer. Spun main?
 
what's the oil look like? what pressure is it running at cold/hot? is the distributor shaft bushing spinning?
 
I’ll have the check on the number, but had plenty of pressure. What bushing are you referring to? Oil looks fine with no glitter.
 
RebelRider said:
I’ll have the check on the number, but had plenty of pressure. What bushing are you referring to? Oil looks fine with no glitter.
Click to expand...
there is a bushing pressed into the block that the distributor shaft rides in. I've seen them freeze on to the shaft and spin. easy way to check is simply pull the distributor out and make sure there is no bushing attached to it. mark your distributor position on the base and the block first, and don't spin the shaft 180* out
it's just a thought, without hearing it myself and without the belts on, I'm not really sure what else it could be.
 
Well, I wouldn't assume it's a main bearing- yet. My plan would be to methodically test everything that moves in the engine, in hopes of finding the rough spot, starting with the easier stuff first... you tried it with the accessories disconnected, excellent first move. Like the guys said lift out the distributor and oil pump driveshaft and check where the shaft and it's gear ride on the bushing (you'll see it once the shaft is out). Pull off the valve covers and check rocker arms and shafts for any signs of galling or dry running. At this point, I might go ahead and spin the oil pump (counter-clockwise) with a drill and long piece of 5/16" hex shaft, while slowly turning the crank, to verify oil gets up to the top end. Unbolt the flexplate from the converter and see how the converter spins by hand to rule out any possible trans or converter noise..should spin free and easy. Hopefully you've found a possible trouble spot by now. No? Then move on to pulling the timing cover (yeah damper and water pump=sucks I know) inspect the chain and sprockets and look for any signs that the oil slinger (if installed) was making contact, with the chain OR the front seal area. At this point, if all is good, time to dig deeper. I'd pull the rockers, pushrods and timing chain and see how/if the cam spins by hand. We're all in now. With the plugs removed, engine unhooked from the trans, and no timing chain, the crank should turn fairly easily with no grinding or scraping noises/feelings, and no hangups or binding. Good luck!

I shoulda mentioned---We have some dang sharp members down in Texas, if the situation starts to go sideways you could always put up a call for help in the general forum and maybe just maybe someone's close enough and available to give you a hand---folks around here have been known to do crazy stuff like that!
 
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WP29440SE said:
there is a bushing pressed into the block that the distributor shaft rides in. I've seen them freeze on to the shaft and spin. easy way to check is simply pull the distributor out and make sure there is no bushing attached to it. mark your distributor position on the base and the block first, and don't spin the shaft 180* out
it's just a thought, without hearing it myself and without the belts on, I'm not really sure what else it could be.
Click to expand...

Not quite this simple. But a good thing to check. Bushing (if I’m thinking the one you are) is on the oil pump / distributor drive shaft. Distributor will never come out with anything on it. Once out stick a BIG screwdriver into the slot in the middle of the gear and turn left, maybe a little back and forth. If it moves or starts to “unscrew” the bushing is fine, if it won’t move it may well be that bearing.

I’ve never heard a main/rod bearing “scream” as you describe. Usually just a knock them destruction.
 
Unbolt the crank pulley & try running it....
 
Thanks for everyone’s suggestions. I have it on the lift right now, so I’m going to look around the balancer in the morning.
 
Nate S said:
Not quite this simple. But a good thing to check. Bushing (if I’m thinking the one you are) is on the oil pump / distributor drive shaft. Distributor will never come out with anything on it. Once out stick a BIG screwdriver into the slot in the middle of the gear and turn left, maybe a little back and forth. If it moves or starts to “unscrew” the bushing is fine, if it won’t move it may well be that bearing.

I’ve never heard a main/rod bearing “scream” as you describe. Usually just a knock them destruction.
Click to expand...
oh yeah ya ya my bad , for sure I meant siezed on the oil pump / distributor drive shaft , I don't know what the hell I was thinking , I've seen / replaced them a thousand times, long Monday at work today lol
 
Last edited:
Nate S said:
Not quite this simple. But a good thing to check. Bushing (if I’m thinking the one you are) is on the oil pump / distributor drive shaft. Distributor will never come out with anything on it. Once out stick a BIG screwdriver into the slot in the middle of the gear and turn left, maybe a little back and forth. If it moves or starts to “unscrew” the bushing is fine, if it won’t move it may well be that bearing.

I’ve never heard a main/rod bearing “scream” as you describe. Usually just a knock them destruction.
Click to expand...
How much force should I have to put on this thing to move? I can’t get it to turn at all. The center “screw” should turn, correct?

image.jpg
 
That’s not a screw - it’s the drive slot for the distributor. The gear won’t turn while it’s engaged to the cam gear. You have to wiggle it up while turning it (forgot which direction, but one way will make it climb and the other drop).
 
68gtxman said:
That’s not a screw - it’s the drive slot for the distributor. The gear won’t turn while it’s engaged to the cam gear. You have to wiggle it up while turning it (forgot which direction, but one way will make it climb and the other drop).
Click to expand...
So the distributor keeps it seated?
 
It will ride up to cam gear counter clockwise but stops. I’m assuming it shouldn’t come all the way off? Should I be feeling for something?
 
RebelRider said:
It will ride up to cam gear counter clockwise but stops. I’m assuming it shouldn’t come all the way off? Should I be feeling for something?
Click to expand...
before you take that all the way out mark the corresponding teeth so it goes back exactly in the same spot, or the rotor will be in a different position if it goes back in somewhere different
 
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you should be able to spin that out while pulling up with a big flat blade screwdriver
 
It feels like it hitting a stop halfway up the gear.
 
With the description of the squealing, if it’s moving at all that’s probably not the problem. The fact that it doesn’t really want to come up more than a little bit might indicate shaft wear or contamination on the lower shaft. I rebuilt an old sludge monster and had to drive the thing out from below with a steel rod and hammer.

Being that this hasn’t seen many miles since rebuild I’d be inclined to just leave it alone. The fact that it moves tells us it’s unlikely to be the problem.
 
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