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Diesel Piston questions

Ultradog MN

Ultradog MN

Well-known Member
Location
Twin Cities
I'm about to put some new pistons in a 3 cyl Ford 4000.
Interference, valves and head on these engines.
Test fit of the pistons shows them to raise a little higher above the block than I feel comfortable with. Machine shop can shorten my rods about 10 thou for about $65 apiece. I could cut 10 thou off the tops of my pistons in a lathe for free. Adviseable? Or not?
I know racing engines have pretty close tolerance on piston and rod weights. How close are run of the mill, out of the box tactor pistons weightwise to one another? How about rods?
Normally I would throw these in and not give weight a second thought. But cutting them makes me wonder. Could I make a difference in balance?
3 cyl engine aint the smoothest to begin with.
Maybe go locate my local drug dealer and ask to borrow his gram scale to weigh my pistons?
I could do a little fileing and weighing if it would do me any good. Make it smoother.
Maybe this is rediculous stuff to even think about on a 2200 rpm tractor.
But I want to know just the same. And this is a good place to ask.
Thanks to any and all.
 
I think it makes a difference, take your pistons to a NAPA store that mixes paint, it"s mixed by grams. ask them if you can use there machine. I think its called a shadowgraph and weight them up. I had a Continental engine balanced with cast iron pistons and they took a quarter inch off the bottom of the heavy one to match the rest. If I remember right a gram weights about the same as three quarters. I once had NAPA order me ten aluminum pistons to get four that weighted about the same. It will make that tractor engine vibrate less. Mike
 
You need to find out what the factory spec is. If you machine off the top, you will lose compression rapidly.
Did you compare with the original pistons?
 
Please check the decking height. I don't have that spec for that particular engine handy and I don't want to give you a 10 series spec in case it's different.... but the numbers you had don't sound bad to me. If you go lowering the piston height you'll be lowering compression on what is already a low compression engine....

Rod
 
For what it's worth, last time I looked at a 30 series 201 engine the pistons almost came through the gasket, well above the block...
 
UD,

I don't know what the spec is, but I do know that if you lower the compression of a diesel (and especially one without glow plugs!) you will greatly affect the cold weather starting. You do not want to reduce the compression at all. The Ford diesels have been well engineered.

As to balancing the pistons, I think that is a great idea. Now, I am NOT your local drug dealer, but I do have a gram scale which you can borrow. It is a good scale with a shady past, but was donated to my scientific endeavors by some fellow in blue. Maybe that was Ford Blue??

Paul in MN
 
Thanks fellows.
I did some more measuring today and decieded to leave them alone. I thought they were too far above the deck (I'm used to gassers) but then measured the head gasket and found I have about .015 to spare.
So I got one of them installed today. Didn't mess with the weights or anything, just threw it in after work today.
We're losing light fast this time of year. Thought i'd get a couple in at least but was running out of light fast.
Thanks Paul for the offer. I may take you up on it next time around.
 
(quoted from post at 22:36:19 10/14/10) I'm about to put some new pistons in a 3 cyl Ford 4000.
Interference, valves and head on these engines.
Test fit of the pistons shows them to raise a little higher above the block than I feel comfortable with. Machine shop can shorten my rods about 10 thou for about $65 apiece. I could cut 10 thou off the tops of my pistons in a lathe for free. Adviseable? Or not?
I know racing engines have pretty close tolerance on piston and rod weights. How close are run of the mill, out of the box tactor pistons weightwise to one another? How about rods?
Normally I would throw these in and not give weight a second thought. But cutting them makes me wonder. Could I make a difference in balance?
3 cyl engine aint the smoothest to begin with.
Maybe go locate my local drug dealer and ask to borrow his gram scale to weigh my pistons?
I could do a little fileing and weighing if it would do me any good. Make it smoother.
Maybe this is rediculous stuff to even think about on a 2200 rpm tractor.
But I want to know just the same. And this is a good place to ask.
Thanks to any and all.
Click to expand...

AS long as the head gasket is thick enough to keep the pistons from whacking the cylinder head. Keep the piston height.
Even 10 thou off a piston will drop diesel engine compression. All the compression possible is required for cold starts.
A diesel that starts worse instead of better after a rebuild is common. Some bargain minded rebuilder grinds and valves and seats which sinks them. Which increases combustion chamber volume.
 
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