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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: mrnda on June 11, 2015, 04:21:05 pm
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1974 K20 pickup 350 automatic transmission 4wd
bought truck running rough, timing issue.
driving it home it died, while checking engine noticed distributor loose (hand loose)
got it home, adjusted timing and had it running went to tighten distributor and suspected the cap was not secured all the way around. The previous owner was messing with the idle when we bought it. Tugged on the cap and it came half way off, engine died. Will not start back up.
while checking things out, I had the distributor cap off and noticed the rotor will spin by hand?? it has an accel distributor on it top looks exactly like the pic that hopefully is posting with this. My assumption is this is the design? hopefully all I have to do is get engine to tdc, move the rotor to the #1 position and it will fire up. Before I proceed I wanted to consult the board of wisdom here.
Thanks and sorry for the long read.
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The rotor should not spin by hand since the distributor is meshed together with a gear at the bottom.
If the rotor CAN spin by hand it sounds like your distributor is not completely seated and you can confirm this by ensuring the distributor is fully seated against the intake manifold.
https://www.youtube.com/watch?v=O4WRL513Gx4
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thanks for the quick response, ill hit it when I get home. Much appreciated.
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could be the gear at the bottom of the distributor shaft if the distributor is bolted down.
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Thanks Irish, I will look into that as well.
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When you say "spin", how much?
There is a centrifugal advance just under the rotor. You should be able to turn the rotor about 15° but it should snap back when you release it.
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it can spin all the way around, there is tension on it the whole time and at one point there seems to be a relief with less tension. Took the distributor out and the gear at the bottom is fixed in place. The rotor can be turned without anything else spinning, the gear does not move. I held the gear at the bottom and was still able to turn the rotor.
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try pulling up on the rotor and see what happens
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RUNNING--
with the distributor out, firmly griping the lower gear and turning the rotor I could feel a point where there was a relief in the tension I figured that is where it is suppose to be sitting at, in that point of relief. reinstalled the distributor and set everything for what seemed to be TDC and it fired right up.
When I was initially working on the timing and noticed the distributor cap loose I must have thrown the rotor out of place when I tilted the cap back to see if the cap was not fully fastened down, which it obviously was not.
Thanks to everyone for the advice and quick responses it did help a lot.
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@ mrnda
The rotor is "fixed" to the end of the distributor shaft and should not spin when the gear is held stationary! The rotor will rotate a few degrees clockwise if the distributor has centrifugal advance, but will snap back to its original position when released. You expressed that you are using an Accel distributor...
- An HEI style rotor is retained to the distributor shaft with two screws. If this is the style of distributor that you have then the roll pin that retains the gear has sheared, or there's a problem with the assembly of the advance mechanism to the top of the shaft beneath the rotor. In either case there maybe enough residual friction to hold the rotor from spinning freely, but the problem remains and the rotor will drift.
- On the other hand, if the rotor simply presses onto the shaft and there are no screws to retain it, then the rotor isn't properly seated onto the shaft. With this style of rotor attachment there is an indexing slot in the top of the shaft that must align with a drive key cast into the base of the rotor.
Remove the distributor cap and snap a pic of the rotor as it is currently installed and post it.
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sorry for the delay. Here are pics for the distributor removed from the engine. really at a loss as far as what the next step should be. thanks again everyone.
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Grab the top of the distributor shaft with the attached advance mechanism in one hand and the distributor gear in the other hand. Twist the gear while firmly holding the shaft and pull the two apart. If the gear spins or pulls loose, either the the gear roll pin is sheared/missing or the distributor shaft is broken.
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alright, it will spin but does not seem like it wants to separate. what can be done to fix it or would we be better off just buying another one.
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what spins? the top part of the rotor or the whole shaft
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Use a pin punch and drive the gear roll pin out of the gear then remove the gear and thrust washer and slide the distributor shaft out the top of the housing. Clamp the flats at the bottom of the shaft (the oil pump drive key) in a vise. Grab the top of the shaft with the advance mechanism and try to twist it. Does it rotate around the shaft?
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Irish - the top part of the rotor is whats moving, I can hold the gear in place with my hand while spinning the the rotor.
bd - I will have to get to this this evening thanks for the instructions.
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so not even the top part of the shaft spins?. makes sense as to why it still intact but a new distrib sound like a likely outcome but its not that much money to replace under $50 (some around 35-40) on ebay
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Pull the rotor off
Try using pliers to spin the shaft
If you're using the plastic rotor it may just be the plastic stripped or broken inside
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partial update - grabbed a distributor from an extra engine in my garage and it works just fine, which is good. however on the test drive the engine started squalling after about 10 miles really bad and loud, the squalling would increase with engine speed. is makes the noise from the moment the engine is running from idle to drive speed.
I loosened the power steering belt and the alternator belt, lubed the distributor gearing, replace the rotor & cap but the noise is still there. I am thinking it is the bearings in the water pump?
advice, experience, and wild ass guesses appreciated.
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partial update - grabbed a distributor from an extra engine in my garage and it works just fine, which is good. however on the test drive the engine started squalling after about 10 miles really bad and loud, the squalling would increase with engine speed. is makes the noise from the moment the engine is running from idle to drive speed.
I loosened the power steering belt and the alternator belt, lubed the distributor gearing, replace the rotor & cap but the noise is still there. I am thinking it is the bearings in the water pump?
advice, experience, and wild guesses appreciated.
Random noises are always difficult since so many things are going. The alternator, power steering and water pump can make horrid noises.
Water pumps usually leak before making a huge noise tho. Any water around the lower weep hole?
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On the old distributor, I suspect what happened is the "tee" at the top of the shaft that anchors the advance mechanism and rotor to the shaft is loose and spinning on the shaft. On factory HEI distributors the tee is welded to the shaft and cannot rotate. I'm supposing that the aftermarket distributor you have uses a pressed on tee rather than being welded. In that case, replacement of the distributor is the most practical solution. Chucking the shaft in a vise and attempting to rotate the tee as earlier suggested would verify whether this is the case.
Regarding the noise, in addition to what enaberif posted, with the engine off, grab the fan blade and wiggle it fore and aft. If the w/p pulley wiggles too, the pump bearing is toast.
Or, remove the belts one at a time and run the engine to see if/when the noise disappears. Just don't let the engine overheat.
Or, use a 3' length of 1-1/4" rubber hose as a listening tube and move it around the engine to locate the source of the noise. Be careful to avoid getting caught in the belts and pulleys.
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no obvious water leak and there has not been a rise in temperature however I parked it as soon as was possible. I already took the belts off one at a time and that did not reveal anything, will try to wiggle when I get home. The part is extremely accessible and around 25-30 bucks may just change it and take that off the list of possibilities.
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water pump replaced noise is still there.
put old distributor back on the noise is still there.
any clue????
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Not to be mean, but quit throwing parts at it and diagnose where the noise is originating.
Did you try using a ~3' length of 1" or larger rubber hose as a listening tube as earlier suggested? Or, use a long screwdriver and move it around the engine touching one major component at a time with the free end of the screwdriver next to your ear - noise will telescope up the shaft so you can hear it. Do you have any means of posting a sound clip, so we can hear it? Is the engine running rough or any different than it did before the noise began? Any change in oil pressure?
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no offense taken, the only purchase was the water pump (25) the rest we had extra in the garage. I have not tried the listening techniques but that is our next step.
I will try to post a recording of some sort. performance has not been affected and I sincerely thank everyone for any input, no noticeable change in oil pressure but will look at that again.
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Take all the belts off and run it
It will be fine to run it a few minutes with no water pump
3-4 minutes max
If you still have the noise with ALL the belts removed
It's potentially a crank or rod bearing
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ssooooooo there were a couple of issues, I do appreciate all of the input about this going it alone is not very comforting.
Distributor was obviously broken, put in an extra one from the garage and magically the timing will hold. The screeching wound up being the shield plate from the engine and transmission, it was dangling on by one bolt so that was firmly reattached.
after reattaching that there was another screeching, slightly different. it would screech when running and for a second or two after the engine was cut off, made me think about the fan. WD-40 and it would take a couple of seconds to start screeching again after starting the engine, while running I sprayed the 40 behind the belt wheel on the fan and while I was spraying there was no screech. took all of that off cleaned the crap out of it and reconnected firmly and VOILA it runs like a champ.
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Happy to hear you got it fixed.
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What are the odds that the rotor is stripped out from careless installation?
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What are the odds that the rotor is stripped out from careless installation?
Zero. It's a married coil HEI distributor. The rotor installs only one way using two caged screws.
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Sorry, I thought it was an aftermarket Accel unit. I guess it uses the OE rotor?
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Correct