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GMC V6 and V12 Engines Engine repair and rebuilding

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  #1  
Old October 31st, 2021, 09:11 PM
Mike Caldwell Mike Caldwell is offline
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Default Stuck engine -- Now what???

I've got a 401 out of a New Idea harvester that's been sitting in my shop for too long and now I'm getting ready to restart the project.

Grabbed my 18" breaker bar and socket and tried to turn it over and -- double oof later -- no luck.

What should I try first? Penetrating oil in spark plug holes? other tricks?

Problem is I don't want to tear it down and have to hunt replacement gaskets, etc. and create more work than I need.

So what can I do to free up the engine? If I can't get it running without major overhaul I may give up on it and and let someone else adopt it.
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  #2  
Old October 31st, 2021, 10:49 PM
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AZKen AZKen is offline
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Default Re: Stuck engine -- Now what???

Mike, I don't blame you for not wanting to tear it down. There is a good chance you can get it to move BUT FIRST,
1. What is the history? was is running when you got it or what? Why was it being sold?
2. What is it mounted on now?
3. Is there a transmission attached?
4. How are you trying to rotate it? What accessories are still on the belts?
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Old October 31st, 2021, 10:57 PM
Mike Caldwell Mike Caldwell is offline
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Default Re: Stuck engine -- Now what???

Don't know if it was running, been too long. I think it was free. Guy was scrapping the old harvester.

Mounted on pallet now; headed for engine stand.

No transmission attached.

Tried 18" breaker bar; I'm a fair-sized fellow and when engine started rocking on pallet I backed off. Using socket on nut on front pulley; nothing on flywheel to grab but I could make longer bar that would bolt up.

No accessories; bare engine.
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Old November 1st, 2021, 02:57 AM
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Default Re: Stuck engine -- Now what???

Quote:
Originally Posted by Mike Caldwell View Post
Don't know if it was running, been too long. I think it was free. Guy was scrapping the old harvester.

Mounted on pallet now; headed for engine stand.

No transmission attached.

Tried 18" breaker bar; I'm a fair-sized fellow and when engine started rocking on pallet I backed off. Using socket on nut on front pulley; nothing on flywheel to grab but I could make longer bar that would bolt up.

No accessories; bare engine.
I remember this topic being discussed a few years ago too. I think you're on the right track using penetrating oil and a longer breaker bar. Repeating the process over a period of days, attempting to turn the engine over in both directions may free it up for you. Try using a pipe extension on your breaker bar too, and hitting the end of it with a big hammer.
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Old November 1st, 2021, 06:50 AM
BobBray BobBray is offline
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Default Re: Stuck engine -- Now what???

This is the way I usually do it: First, remove all the spark plugs and spray in a good amount of a penetrating oil, something like PB Blaster, Liquid Wrench, or Kroil (which is the best but expensive). Let it sit for a few days, spraying a little more in each day. When you are ready to try turning it again, drain the oil and filter (if the filter is a canister type drain but don't replace unless it's full of sludge, if it's spin-on, dump it out and put it back on). Put a few quarts of cheap 30W in the engine and pull the distributor and valve covers. Prime the oil pump, you can use a long slotted screwdriver with the handle cut off chucked in a drill down the distributor hole, turn the pump slowly clockwise until you feel a bit of resistance. Look for a little oil coming out of the rocker shafts around the rocker arms. Spray a little more penetrating oil in the spark plug holes, then take your breaker bar and try turning the engine clockwise first. Yes, you might have to hit it. If you get it to move a bit, then try back and forth working it until it's free. Get a longer breaker bar, 18" isn't much. Good luck! Let us know how it turns out.
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Old November 1st, 2021, 06:54 AM
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Default Re: Stuck engine -- Now what???

Quote:
Originally Posted by Ed Snyder View Post
I remember this topic being discussed a few years ago too. I think you're on the right track using penetrating oil and a longer breaker bar. Repeating the process over a period of days, attempting to turn the engine over in both directions may free it up for you. Try using a pipe extension on your breaker bar too, and hitting the end of it with a big hammer.
Agree with Ed on most of it but not the longer pipe and hitting with a hammer. That would probably work if pistons were just a bit locked by rust, after soaking. But if valve train/valves are stuck or timing chain jammed, etc. that would create more damage. Use measured caution until you detect some movement after soak. Rock the crank back and forth, mostly CW. Plugs need to be out during turning.
Since history is unknown, you may want to:
1. Take valve covers off and inspect valve train/springs. I've seen folks bang on top of valve end of rocker with rubber mallet to see which valves are stuck and won't spring at all. They smack it hard enough to overcome the spring tension. Slightly.
2. Be sure starter pinion is not jammed into fly wheel.
3. Soak with almost anything and a combo if you want MMO, kerosene, rust penetrant, carb cleaner........ down each plug hole, down the valve train.
4. Back and forth on the crank shaft, steady as you go, eventually is will make a whole revolution. It will take awhile.

Last edited by AZKen; November 1st, 2021 at 05:44 PM.
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Old November 1st, 2021, 05:48 PM
Jim A Jim A is offline
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Default Re: Stuck engine -- Now what???

I like the finesse answers over the brute force ones.
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Old November 1st, 2021, 06:19 PM
Mike Caldwell Mike Caldwell is offline
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Default Re: Stuck engine -- Now what???

Sounds like what I had in mind was the way to try. Thanks for the help.

Next trip to town I'll get a gallon of PBBlaster, etc and a "spark plug compressed air" adapter. Pull spark plugs, pour in some penetrating oil, compressed air for a while, repeat five more times.

Will listen closely for air escaping

Meantime I will find a long piece of steel and adapt it to bolt to flywheel and see about applying some torque to the crank. Might even set it horizontal and hang some weights on it for long term pressure.

Thanks for the help and hope for the best!!!
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Old November 1st, 2021, 07:02 PM
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Default Re: Stuck engine -- Now what???

No no no, Mike! Here's whatcha do. (chews toothpick)
First you getcha some marvel mystery oil. Squirt exactly half a drop in each spark plug hole.
Then ya getcha 1 big wrench. A plumber's wrench is good for this.
Finally, you getcha a pipe. About 12 foot long is good.
Now you put the wrench on it so the handle points up to 12:00. Poke the pipe on the end of the wrench handle.
Now go out to your pickup and get a rope. You need a good stout one. Tie that rope real good to the trailer hitch and the top of that pipe. Tie it good or it'll slip down and just pull the wrench off and you won't get to experience the wonders of modern fisicks.
Ok, back up now until there's just about a foot of slack in the line, then NAIL IT!
I mean just jump on that accelerator. You should hear all four wheels squeal in a 2wd truck. If not, you did it wrong and i can't be held responsible for any damage done to your engine. Don't use a 4wd. They're made to fix snow and dirt, which won't help with engine repair.
That should crank it right over like pull starting a lawn mower. It'll start up and run like a top.
Good luck! Have the wife make a video of the whole thing too so we can see how it goes!

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Last edited by FetchMeAPepsi; November 1st, 2021 at 08:11 PM.
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  #10  
Old November 1st, 2021, 08:23 PM
Mike Caldwell Mike Caldwell is offline
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Default Re: Stuck engine -- Now what???

That reminds me of a hired hand dad used on the farm once.

Watched him smoke a cigarette with one hand while bleeding vapor from a butane tank with the other. Quietly walked away . . .

NOTE on my last post about air compressor fitting -- yes, I'll have to do something to make sure valves are closed.
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