1965 6.6HP Engine Teardown - MyTractorForum.com - The Friendliest Tractor Forum and Best Place for Tractor Information
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post #1 of 24 Old 10-01-2019, 08:07 PM Thread Starter
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1965 6.6HP Engine Teardown

Due to the flywheels not aligned I started tearing down an L8 engine today. The engine had been rebuilt before I purchased the tractor and the out of alignment issue was caused when I was removing the starter clutch for repair. I felt the flywheel move as I was applying torque to the clutch.

Should be easy, the engine was rebuilt....not many hours on it. Sounded great, like a gravely should.

Teardown was going fine, then...

Let the fun begin!
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post #2 of 24 Old 10-01-2019, 08:34 PM
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Re: 1965 6.6HP Engine Teardown

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Originally Posted by RI-GravelyMod View Post
Due to the flywheels not aligned I started tearing down an L8 engine today. The engine had been rebuilt before I purchased the tractor and the out of alignment issue was caused when I was removing the starter clutch for repair. I felt the flywheel move as I was applying torque to the clutch.

Should be easy, the engine was rebuilt....not many hours on it. Sounded great, like a gravely should.

Teardown was going fine, then...

Let the fun begin!
I couldnt fix that, at least not in this decade. If something like that happens to mine its gonna be my other parts tractor.
Sorry and good luck.
P.S...Is that a piece or two of a bolt that broke?
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post #3 of 24 Old 10-02-2019, 08:09 AM Thread Starter
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Re: 1965 6.6HP Engine Teardown

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P.S...Is that a piece or two of a bolt that broke?
Gerrard, that is a set screw that holds the drive pinion bearing in place in the engine casing. They can occasionally work loose, most of the time they are staked in place.
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post #4 of 24 Old 10-02-2019, 08:30 AM Thread Starter
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Re: 1965 6.6HP Engine Teardown

The parts I was removing were in good shape and the workmanship showed a skilled level. Jug was a 7.6, lifters had been replaced, good interference with piston & wrist pin with light evidence of old oily residue.

I had performed the usual initial removal of the L/H axle housing and cleaned the sump of sludge when I purchased the tractor a few years ago. Got it running, no spark, and parked it due to the projects ahead.....

Removed the spreader bolt and found the second surprise inside the crankpin. Sludge, new sludge. Just some but enough. Took some of it and dissolved it in gas. Inserted a magnet in the mix and it looked like a porcupine. Something steel is wearing!

This prompted the disassembly of the crankshaft. Found the crankpin and rod in good shape. Minor trace of sludge behind the drive pinion allen head screw.

Time to located where the metal is coming from. In addition to the engine teardown have to look into the tranny.
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post #5 of 24 Old 10-02-2019, 11:58 AM
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Re: 1965 6.6HP Engine Teardown

A cpl things you mentioned are a lot like mine. I have a 1966 6.6 L but had to put a late 50's 7.6 L I jug on it.

God willing and the crick dont rise it might work.
Having a mechanic around wouldnt hurt either lol.

Of course I have limited time to work on it but Ive been 3 to 4 days just trying to get a belt on it. Meaning drive belt @ top & bottom pulleys.
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post #6 of 24 Old 10-02-2019, 01:41 PM
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Re: 1965 6.6HP Engine Teardown

Quote:
Originally Posted by RI-GravelyMod View Post
Gerrard, that is a set screw that holds the drive pinion bearing in place in the engine casing. They can occasionally work loose, most of the time they are staked in place.
Right. It's not a big deal.

If this engine was rebuilt, it seems highly likely that whoever did the rebuild either didn't stake the setscrew, or didn't do it hard enough.

RI, if that's the biggest problem you have, you're in good shape. It does sound like something else in there is making metal, so you likely need to keep looking into it. If the the flywheels have been out of line, there are several candidates, for instance the ball bearing on the other end of the crank, or the gear drive to the oil pump.

The good news is that it's a simple robust engine. If you get it cleaned out and the flywheels aligned, I expect you'll be fine.

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post #7 of 24 Old 10-02-2019, 06:54 PM Thread Starter
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Re: 1965 6.6HP Engine Teardown

Cleaned up the crank parts and took measurements. Parts look great, the best I have seen. The lower end most definitely had been worked.

All are within tolerance except for the pin interference. Will need both dry ice and a press for this assembly. Pin interference are .019 and .013". Oddly the pin or the flywheel show no signs of forced interference. Disassembly was not difficult. With replacement pins, does one have to have the ends machined for the interference?

Time to place a parts order and clean up the rest of the engine.

RB
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post #8 of 24 Old 10-03-2019, 02:22 AM
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Re: 1965 6.6HP Engine Teardown

OMG Sounds like surgery or something.
Are you a machinist or something like that?
I'll just read this thread and keep my opinions to myself because I know nothing that can help you thats for sure lol!
I cant even seem to manage to get the belt on LOL!!
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post #9 of 24 Old 10-03-2019, 06:59 AM
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Re: 1965 6.6HP Engine Teardown

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Originally Posted by RI-GravelyMod View Post
Parts look great, the best I have seen.
+1. From that pic, those parts look real nice.

How's the clearance on the bushed ends of the rod? If you need to replace bushings, this is the time to do it
Quote:
All are within tolerance except for the pin interference. Will need both dry ice and a press for this assembly. Pin interference are .019 and .013".
That sounds pretty high.

I could swear I saw a manual saying what the interference fit is supposed to be, but I can't find it now. Beaner, are you listening?

But it was together before, it'll go back. I'd recommend heating the flywheels in an oil bath, in addition to dry ice on the pin. I've used that technique to avoid having to press at all, though in this case, I expect you'll still need it.

I love the pix

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post #10 of 24 Old 10-03-2019, 10:13 AM
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Re: 1965 6.6HP Engine Teardown

Its hard to tell size from pix but that connecting/piston rod looks like it came from a dang 440 big block or something! Sheesh... I didnt have to take mine out when replacing jug because I was just working from the top end and never even saw the rest of it.

Not to complicate things or muddy the water but does anyone know the dia. of a 6.6 or 7.6 piston?
I would like to try to confirm what an old man told me who used to work at the Gravely plant.
At anyones leisure of course
Later and thanks
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post #11 of 24 Old 10-03-2019, 11:02 AM
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Re: 1965 6.6HP Engine Teardown

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does anyone know the dia. of a 6.6 or 7.6 piston?
Stock piston diameter for all L model pistons is 3.250".

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post #12 of 24 Old 10-03-2019, 10:15 PM
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Re: 1965 6.6HP Engine Teardown

If you are talking about installing the crank pin, all you need is some large washers and some all thread and two pieces of channel iron with a hole drilled in the center. Give your wife some money to go away for awhile, Then put the crank-pin in her freezer and the flywheels in her oven at about 250-300 degrees use the all thead/washer/nuts to press the flywheels together and the channel iron and all thread to align the the flywheels That should get you real close. Then you can use the straight edge method or center with a truing stand, lathe or drill press. Always use oil when pressing bearings, pins ect together. And make sure the kitchen is spotless when she gets home.
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post #13 of 24 Old 10-04-2019, 02:23 AM
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Re: 1965 6.6HP Engine Teardown

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Stock piston diameter for all L model pistons is 3.250".
I'll get back w/you on this, dont wanna jump an important thread or anyones thread for that matter.

Thanks
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post #14 of 24 Old 10-04-2019, 06:09 AM
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Re: 1965 6.6HP Engine Teardown

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Originally Posted by Toddnails View Post
If you are talking about installing the crank pin, all you need is some large washers and some all thread and two pieces of channel iron with a hole drilled in the center. Give your wife some money to go away for awhile, Then put the crank-pin in her freezer and the flywheels in her oven at about 250-300 degrees use the all thead/washer/nuts to press the flywheels together and the channel iron and all thread to align the the flywheels That should get you real close. Then you can use the straight edge method or center with a truing stand, lathe or drill press. Always use oil when pressing bearings, pins ect together. And make sure the kitchen is spotless when she gets home.
Wow. Will that really work for that kind of an interference fit? .019"?

I guess I'll have to go brush up on my coefficients of expansion of steel.

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post #15 of 24 Old 10-04-2019, 01:33 PM
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Re: 1965 6.6HP Engine Teardown

Isn't the rod on the 7.6 different than earlier engines? It was made stronger and is heavier for the application? I was told that piston is same as 6.6 though.
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