hi to all, hope sombody can help. I am building a ford 755a turbo diesel backhoe. my customer started this project 10 years ago and now he is able to finish. the pistons with the kit are to high of a deck hgt. by about 1/8th. inch, will depth mike later. Do you think it is ok to machine the deck hgt. of minus .014" off the top. 2nd. how do you set the fuel pump inj. timing mark when the timing cover is in place as it would be if the engine was in the tractor. thank you. :?:
- Thread starter 70monte72
- Start date
Dontcha just love these jobs....?
I guess the first question that comes to mind regarding the pistons... is are they actually the correct pistons? Are you absolutely sure? It's not uncommon for the Ford's to clear the deck by a little bit but 1/8" seems like a bit much. I'm also thinking that a 256T should have a bit less protrusion that a N/A engine so mabey they should be flush...
I think the best suggestion I can make is that you check through the service manual for those specs. A Ford tractor manual for a 7700 will suffice if you don't have the 755's manual.
I wouldn't be too comfortable with the idea of cutting the pistons down tho.
Is there a chance that the block was decked by a large amount? That might be a problem too...
I forget the timing procedure on that thing now. I know there's a timing window in front of the flywheel on the right side, below the starter. Not knowing what was done previously though... I think I'd want to check the timing marks on the gears and make sure it's right.
Rod
I guess the first question that comes to mind regarding the pistons... is are they actually the correct pistons? Are you absolutely sure? It's not uncommon for the Ford's to clear the deck by a little bit but 1/8" seems like a bit much. I'm also thinking that a 256T should have a bit less protrusion that a N/A engine so mabey they should be flush...
I think the best suggestion I can make is that you check through the service manual for those specs. A Ford tractor manual for a 7700 will suffice if you don't have the 755's manual.
I wouldn't be too comfortable with the idea of cutting the pistons down tho.
Is there a chance that the block was decked by a large amount? That might be a problem too...
I forget the timing procedure on that thing now. I know there's a timing window in front of the flywheel on the right side, below the starter. Not knowing what was done previously though... I think I'd want to check the timing marks on the gears and make sure it's right.
Rod
shaun wallace
Well-known Member
Piston protrusion on 7700 turbo is .004 below to .013 above.
thank you both, after 10 years it is hard to remember anything. i used to have a full time auto machine shop and did a few tractor engines where we modified the parts like pistons. i checked head thickness and found over .500" of mtl. i checked with a tractor service co. they said there should be enough piston left to remove the .139" actual amt. thanks again, Dick
I'd err on removing as little as possible from those pistons. It may not be such an issue in a backhoe, but a large number of those engines fitted to tractors were turned up, and turned up a LOOONNNGG way.
Pistons and rings are usually the first victim...
I'd not want to mill them down too much as the compression was none too high to start with either.
Rod
Pistons and rings are usually the first victim...
I'd not want to mill them down too much as the compression was none too high to start with either.
Rod
RBnSC
Well-known Member
We have a 755A and ours has a 268 Which has the same bore size as a 256. What you have got is 256 pistons with a 268 crank. I am not sure that they made a 256 turbo. We had a couple of 5550's that had 256 engines that were non turboed. I am thinking that a non turbo piston and then cut it down you would end up with a lot more compression than it was designed for.
Ron
Ron
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