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GMC V6 and V12 Engines Engine repair and rebuilding

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  #1  
Old February 21st, 2022, 12:47 AM
MoscowMule MoscowMule is offline
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Default Internal parts aveability

Hello we did a compression test on our 65 305 E today.A few cylinders were 100,103. Several were 95 ,but one was 75. Take it I'm not sure how much it has been run before we purchased it. Hoping the valves may just be gummed up.It starts right up idles and runs good.No engine noises. We plan on pulling motor in the next few weeks and tearing it apart.I have a complete gasket set.My question is how available is internal parts for these motors? Where could I purchase valve seals,rings,and bearing if needed?
I really want to keep this motor. Hoping it's nothing major,but my pockets aren't that deep to have a unlimited budget either.
Thanks Moscow Mule
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  #2  
Old February 21st, 2022, 01:38 PM
James James is offline
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Default Re: Internal parts aveability

A word of warning: if you don't know how old the fuel is then drain it out, flush the tank, and fuel lines. Old fuel will make all of your intake valve stick (open, close, or part way) and cause bent push rods. Then the valves will have to be hammer out. If the fuel smell odd compared to fresh fuel don't use it.

That 75 is not that bad. I would change the oil and filter and drive it for 1,000 miles, just to give the engine a chance to clean itself out. Then I would suggest you do a cylinder leak down test. This will tell you where you are losing the compression. It won't be a lot of air flowing out (with a warm engine you should see vapor coming out) due to the fact the tester is a low pressure version (automotive). If it is the valves (it would be blowing air out the carburetor or the exhaust pipe). Valve lash could set too tight causing the valve to be cracked open, causing a low reading. If it not the valve lash then all you have to do is to pull the heads. If it the rings (air blowing out the oil filler hole) then the whole engine would need to be pull. But with your numbers I would not change a thing, I would just drive it.

If it not broke don't tear it apart. These engine are design to run several hundred thousand mile between overhaul. Beside parts are hard to find.

This is what I been using for a cylinder leak down tester: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Chances are your engine is fine the way it is, just drive it.

The only thing I suggest you do is pull the valve covers and remove the rocker arm assemblies. The shafts usually fill up with sludge. Make sure the oiling hole (in the shafts) for the rockers is clocked in the right location when you reassemble them. Valve lash is adjusted with a hot engine. While your at it change the thermostat and anti-freeze (8 gallons) after flushing out the cooling system.
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Old February 21st, 2022, 04:54 PM
Jim A Jim A is offline
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Default Re: Internal parts aveability

I think James' advice is right on the button.
A very conservative approach will pay off.
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Old February 22nd, 2022, 12:48 AM
MoscowMule MoscowMule is offline
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Default Re: Internal parts aveability

Thank you so much James.That's the best news I've received all day.I do not feel the gas is very old.The guy we bought it from used it on his ranch.We haven't drove it much.Just up the road about 1/2 mile and back.We pull it in and out of the shed a few times.We are in the tear down and rebuild the whole body process so we aren't able to put a 1000 miles on it at this point.We need to pull the motor anyhow cause someone installed a aftermarket oil filter setup on the driver's side fenderwell.It has original canister filter still.This one on the fenderwell has no filter or return hose on it.However the oil pan is leaking where they drilled the hole with a hose going to this housing.So we are going to weld that shut and clean the motor up and repaint it to original red color.I'm praying everything well be good on the inside,cause it runs so good and sits there idles perfect.Thank you again
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Old February 22nd, 2022, 01:55 AM
James James is offline
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Default Re: Internal parts aveability

Quote:
Originally Posted by MoscowMule View Post
We need to pull the motor anyhow cause someone installed a aftermarket oil filter setup on the driver's side fender well. It has original canister filter still. This one on the fender well has no filter or return hose on it. However the oil pan is leaking where they drilled the hole with a hose going to this housing. So we are going to weld that shut and clean the motor up and repaint it to original red color. I'm praying everything well be good on the inside, cause it runs so good and sits there idles perfect. Thank you again
I use to have that same oil filter on the fender well. Its a toilet paper filter. They change it when they change the canister filter. Its a partial (low volume) flow filter. In theory it will clean the oil better the the canister oil filter, but it return back to the oil pan and not to the engine. I had removed mine. It had made a very big mess on the frame below it.
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