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707 Problems


ahrensfx
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Looking for some help with a stuck 707

Last year I drove my 1963 Mack C-95 into the pole barn. I was having clutch issues at the time. I had a lot of slipping so I knew it was time for a clutch this year.

Went to start the motor this year and it wouldn't start. Batteries were low so I charged them up. As I turned the motor over I heard what sounded like maybe a rubbing sound? Anyways decided to wait for a buddy that is a mechaninc to stop by. About a week later he stopped over. Went to roll the motor over and it rolled a quarter turn and it stopped, HARD. Motor will now roll back and forth about a quarter turn but will not budge past that point.

So here is what I have done so far. Dropped the pan down. Oil is fresh and looks good, no metal shavings anywhere, and no coolant in the oil either. Pulled the valve covers and took off the rocker arms. All valves appear to be moving freely. Start is out and it moving freely also. Took the clutch assembly down last week and the motor is still stuck( Clutch definitely needs rebuilding though). Pulled the the plugs to check for Hydraulic lock. Every one is clean at this point.

I know this motor has a aux shaft that spins the distributor, govenor and the Air Compressor. It all runs the Power steering pump off the air compressor but I have removed the belt and that spins free also. Shaft appears to have play in it when the motor is hand turned to the lock point.

That is as far as we have gotten at this point. We have been doing a piece by piece disassembly to see at what point the motor breaks free.

Any help would be greatly appreciated.

Dave

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Too strange and interesting.

Haven't you seen valves moving during 1/4 cranking?

The only idea is a problem of timing.

It looks like piston moves until meets a valve. That could be result of a gear key break.

Definetly it's not a piston-cylinder stuck.

Or, maybe - haven't you provide any repairs of screwing in any new bolts? In the timing cover area.

I had a chance to lock the engine during assembling by the bolt of unnormal length.

Vlad.

Никогда не бывает слишком много грузовиков! leversole 11.2012

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Before you pull any thing else off with some one on the crank with a wrench trying to turn it and with it in the locked position flee of each rod and see if it has any side play. If its a cyl locked then when its at the lock postion the cyl at fault will be locked enough to were no slack in the rod brg.If its a cyl locked then pull the rockers off and see if all valve come up to close postion.

glenn akers

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  • 2 months later...

Hey Guys,

It has been a while since I posted last because I haven't had a chance to do much. I just wansted to thank you for your suggestions.

I think in the spring I am going to pull the motor and completely go through it. It has never been overhauled so it's probably a good idea anyways.

Thanks

Dave

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Hey Guys,

It has been a while since I posted last because I haven't had a chance to do much. I just wansted to thank you for your suggestions.

I think in the spring I am going to pull the motor and completely go through it. It has never been overhauled so it's probably a good idea anyways.

Thanks

Dave

dave this might sound stupid but it happened to me once on a 260 brockway. the mice had gotten into the bell housing and had built so much of a nest it would only let that continental gasser turn about a quarter of a turn. after i had pulled the heads i found the nest and thats all that was stopping the motor from spinning. like i said there was so much stuff wadded up in there it got bound up between the flywheel and starter. might be worth a quick look.

and remember

"PREFORMANCE COUNTS"

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The 707A I'm working on had a stuck rocker that caused symptoms like you descirbe. It also had a ton of broken rings and scored cylinder walls. I wound up sleeving the motor. I have a bunch of 707C parts if you need anything. I also know a guy who has a complete 707C who would likely part with it for a fair price. The good news is that the gaskety sets available are geared more for the C than the A. I've had to hand make almost all of mine. As a thought, you could get a scope and pull the oil filler neck off and look at the gears on the front of the motor. You've got to jack her off the motor mounts to pull that front cover all the way off. It's a pain.

Good luck.

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