Sorry for the repost, I accidently posted in the fordson forum. I have a 1966 Ford 4000 that has a 192 gas in that I'm overhauling because of blowby. #3 piston has two rings broke and top one partially missing. At what point is it still permissible to use std pistons. The bores aren't torn up too bad that honing may clean up the cylinder. If I have to have it bored, is there any cylinder issues that typically result afterward? I'm just worried about the life of the block being bored. Is cracking or porous holes leading into the cylinder prevalent to these engines? I haven't measured the bore yet to see what size it is. What are the specs for bore size and recommendations to install oversized pistons. Most engines I work with you can hone about .008 over before boring. Any help or recommendations would be appreciated. I don't want to do this job twice. Thanks in advance.
- Thread starter mkuhns
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Ultradog MN
Well-known Member
- Location
- Twin Cities
There is just no way to help you much without knowing something about your bores. We need some accurate numbers - how much over standard, taper, out of round, etc.
The diesels were prone to cavitation and porosity in the bores. On those it is recommended that you sleeve back to standard size.
On a gasser I don't think cavitation is an issue. Or at least I have asked here before and never got examples of gassers having the same porosity problems.
The diesels were prone to cavitation and porosity in the bores. On those it is recommended that you sleeve back to standard size.
On a gasser I don't think cavitation is an issue. Or at least I have asked here before and never got examples of gassers having the same porosity problems.
Standard bore size is what I'm looking for right now. At how much over standard bore spec is it required to go to the next size piston is what I'm looking for. Maybe I didn't make state question correctly. I will get my measuring tools from work on Monday and get some true measurements. If I don't have any #s to go by, I'm wasting my time trying to hone a cylinder that is too big to begin with.
Fordfarmer
Well-known Member
I can't remember off hand, but it's either a 4.2" bore or a 4.4". I'm thinking it's a 4.4" bore and 4.2" stroke. Would be obvious when you measure which it should be.
Ultradog MN
Well-known Member
- Location
- Twin Cities
Yes 4.4 bore X 4.2 stroke.
So if his bores read more than say 4.406 or so it's time for a bore and sleeve job.
So if his bores read more than say 4.406 or so it's time for a bore and sleeve job.
Ultradog MN
Well-known Member
- Location
- Twin Cities
Thanks.
Thanks for your help. I went through the archives, and thought I read .007-.009 piston clearance was recommended in these engines. Is that correct? Sometimes a little looser is better because of heat and piston expansion. All the piston skirts that were removed were scuffed. It probably got hot at some point in its life, or the pistons were too tight to begin with.
Ultradog MN
Well-known Member
- Location
- Twin Cities
Looking at my FO-31 here for gas engines proper piston clearance on a 4.4 bore is .0032 - .0042
Diesel is significantly greater .0080 - .0090
Diesel is significantly greater .0080 - .0090
The diesel pistons get much hotter, so they need more room to expand.
My rule of thumb is for used parts to have about 3 times the tolerance of new parts.
Thus, using your numbers, I would think an addition of .003 would be okay.
People used to knurl pistons to enlarge them, and they used to put spacers in
the ring grooves to take up slack.
My rule of thumb is for used parts to have about 3 times the tolerance of new parts.
Thus, using your numbers, I would think an addition of .003 would be okay.
People used to knurl pistons to enlarge them, and they used to put spacers in
the ring grooves to take up slack.
Ultradog MN
Well-known Member
- Location
- Twin Cities
I put new rings and rod bearings in a 3000 about 10 years ago. Bores were worn past spec but I just wanted to tighten it back up a little - stop the smoke, etc.
There is a big engine rebuilder here in the Cities (Wagamon Bros) that knurled my pistons for me. They let me watch them do it. It was a special machine that just knurled the sides of the piston - not all the way around. The machine was dusty from sitting for a long time. I mentioned the dust and the fellow doing the work said yeah, we don't do this very often any more.
I ran that engine for about 4 years and then found a new engine from a school tractor that I put in. Then I sold the old short block to a guy as a rebuilder. Kept the relatively fresh head for another project. It cost me about $200 for 4 years of decent power so was worth the half fast rebuild.
There is a big engine rebuilder here in the Cities (Wagamon Bros) that knurled my pistons for me. They let me watch them do it. It was a special machine that just knurled the sides of the piston - not all the way around. The machine was dusty from sitting for a long time. I mentioned the dust and the fellow doing the work said yeah, we don't do this very often any more.
I ran that engine for about 4 years and then found a new engine from a school tractor that I put in. Then I sold the old short block to a guy as a rebuilder. Kept the relatively fresh head for another project. It cost me about $200 for 4 years of decent power so was worth the half fast rebuild.
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