V3307 piston to bore clearance

[Bgblock427]

I have looked in the manual and measured everything and don't like that I am only getting .001 piston to wall clearance. being a avid automotive engine builder this seems very tight for a diesel engine.
I don't see in the manual what the clearance should be only see allowable limits for bore wear? The sleeves and pistons that we installed were a kit. What's every set the clearance to?

 

[North Idaho Wolfman]

Did you have the sleeves bored to size?
They do not come pre sized.
They are only semi finished.

 

[Bgblock427]

Did you have the sleeves bored to size?
They do not come pre sized.
They are only semi finished.

Yes the cylinders were honed, but being someone that checks all clearances when I assemble, I want to know what the minimum piston to bore is for this engine. I just looked at the manual again and I don't see a piston OD measurement stated. The bore is specified just not the piston. they are measuring in at .001

 

[North Idaho Wolfman]

Yes the cylinders were honed, but being someone that checks all clearances when I assemble, I want to know what the minimum piston to bore is for this engine. I just looked at the manual again and I don't see a piston OD measurement stated. The bore is specified just not the piston. they are measuring in at .001

I've never heard anyone honing those liners to size???
What size did you hone them to?
What size do the piston you have spec out at?

Yes I'm looking into the specs on piston size.

It would also help to know Exactly which V3307 your working on as there are several.

One note: This is a Ultra High compression engine @ 569psi every spec is super tight.

 

[Bgblock427]

I should have said the machine shop that installed them finish honed them. I was reading 3.700
engine is a 2006 v3307 from a M7040 tractor. 6S0389

 

[North Idaho Wolfman]

So your getting 3.700 on both the cylinder bore and the piston, give or take .001.

Take a ring and check the gap on the bore.

I have looked at 10 different WSM's for that engine class and oddly none spec out the cylinder size.

That engine is odd in that it has moly skirts so it is a very tight tolerance piston to begin with.

Looking at every other engine spec I have for Kubota engines the pistons spec at .003 under the cylinder.

I'll keep looking at different specs.

 

[Bgblock427]

So your getting 3.700 on both the cylinder bore and the piston, give or take .001.

Take a ring and check the gap on the bore.

I have looked at 10 different WSM's for that engine class and oddly none spec out the cylinder size.

That engine is odd in that it has moly skirts so it is a very tight tolerance piston to begin with.

Looking at every other engine spec I have for Kubota engines the pistons spec at .003 under the cylinder.

I'll keep looking at different specs.

Thanks for looking, I posted the question on a machinist site asking also. The Cylinder bore size is in the wsm for the tractor.

 

[North Idaho Wolfman]

Thanks for looking, I posted the question on a machinist site asking also. The Cylinder bore size is in the wsm for the tractor.

Is the piston measuring 94mm exactly?

 

[Bgblock427]

Got my answer, the machine shop I use that does allot of Kubota engines said it needed to be .003-.004 piston to bore. after measuring and measuring i discovered that the piston skirts were tapered on these new pistons almost .004. we honed the bores to correct the tightness. after checking what was done the first time it was discovered that the clearance was only .0008 because no one thought to check the end of the skirt, this engine would have seized up after a few min if I had just assembled it and not checked the work that was done. Not the fault of the Machine shop. they measured where they should have on the skirt and would have had the required clearance. No one anticipated a taper on the skirt so extreme. Lesson learned, the piston sleeve, piston kits need to be checked very well! Nothing worst that putting a engine back in a machine and having it have to come back out that was avoidable. BTW this will be my last diesel engine I will build for a friend, I'll do automotive engines all day lol.

 

[dragfan66]

OP and NIW both did a good job solving this problem before it became a costly mistake.

I wish Joe would read threads like this between tokes.

 

[lugbolt]

Got my answer, the machine shop I use that does allot of Kubota engines said it needed to be .003-.004 piston to bore. after measuring and measuring i discovered that the piston skirts were tapered on these new pistons almost .004. we honed the bores to correct the tightness. after checking what was done the first time it was discovered that the clearance was only .0008 because no one thought to check the end of the skirt, this engine would have seized up after a few min if I had just assembled it and not checked the work that was done. Not the fault of the Machine shop. they measured where they should have on the skirt and would have had the required clearance. No one anticipated a taper on the skirt so extreme. Lesson learned, the piston sleeve, piston kits need to be checked very well! Nothing worst that putting a engine back in a machine and having it have to come back out that was avoidable. BTW this will be my last diesel engine I will build for a friend, I'll do automotive engines all day lol.

I've been doing engines for my entire life (pushing 50 years) and every single piston I've measured, is not "square", IOW the bottom of the skirt is usually a little bit bigger than the top (directly under the oil ring). I can't say I have ever seen one (that I remember) that wasn't.