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09-09-2015, 09:50 AM | #1 |
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Piston movement...
I bought a core engine and am getting it ready to send to the machinist...
Happened to notice that there is quite a bit of side-to-side movement in the pistons.. I'm able to get an .030 feeler gauge in the gap no problem.. I don't have any way to measure the bore except at the top rim..it's about 3.909 to 3.914.. I'm thinking those .030 over pistons have been in there a very long time...there are piston expanders in the skirts...
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Early '29 CCPU that had a 4-speed, but not any more.......in the family since '62 |
09-09-2015, 09:56 AM | #2 |
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Re: Piston movement...
Depends on where you are measuring. The top of the piston is normally a smaller diameter at the top by the ring lands than the diameter of the skirt. Sticking a feeler gauge in at the top will not tell you what the piston clearance is.
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09-09-2015, 10:11 AM | #3 |
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Re: Piston movement...
Piston to wall clearance is measured from the piston skirt [90º to the pin] and the bore. The ring land area is smaller.
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09-09-2015, 10:22 AM | #4 |
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Re: Piston movement...
OK I can measure that at the skirt....I'll let you know...Will the expanders need to come off? I'm not sure how they attach...there is an angled slit in the skirt and the expanders are in that slit
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Early '29 CCPU that had a 4-speed, but not any more.......in the family since '62 Last edited by 1955cj5; 09-09-2015 at 10:31 AM. |
09-09-2015, 11:05 AM | #5 |
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Re: Piston movement...
If you are doing an engine rebuild, then I'd buy the next oversize and have the cylinders bored to fit.
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09-09-2015, 11:08 AM | #6 |
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Re: Piston movement...
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09-09-2015, 11:59 AM | #7 |
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Re: Piston movement...
There was a shop in L. A. Cal. Lou's Garage advertised overhauls with new rings and expanded pistons, adjust valves, new gaskets & Etc. A real bare bones job done very cheap. I went there with a friend to pick up his car and noticed the dirt parking area was well oiled! I thought of this when I saw your expanders
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09-09-2015, 01:01 PM | #8 | |
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Re: Piston movement...
Quote:
I'm sure I'm dreaming but I was sort of thinking I could buy .010 over babbitt rods(the rod journals measure .009 under...all within .0005) from Bert's, and a set of .040 pistons and rings and after it's bored I could do the assembly myself....
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Early '29 CCPU that had a 4-speed, but not any more.......in the family since '62 Last edited by 1955cj5; 09-09-2015 at 01:11 PM. |
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09-09-2015, 01:33 PM | #9 |
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Re: Piston movement...
Have the machinist mike everything, then you can buy what is recommended and assemble it yourself. If the shop assembles it you may benefit from any implied warrantee.
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09-09-2015, 02:18 PM | #10 |
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Re: Piston movement...
Interesting. I don't see any ridge, or did you remove such ?
I would have machinist / engine builder measure engine and IF it is in good sound basic condition...bore/fit pistons to his recommendations. |
09-09-2015, 02:21 PM | #11 | |
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Re: Piston movement...
Quote:
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09-09-2015, 02:26 PM | #12 |
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Re: Piston movement...
A well oiled parking area is fine, as long as the dirt stays outside. I know a tractor mechanic that works with his hands full of dirt and grease, even while installing valves and pistons. He won't be doing any engine work for me. I also stopped at Harkin in Watertown, S.D. to see his babbit operation. He wouldn't let me see it buy pointed to the building it was in. It appeared to be an old chicken coup. My friend had his engine babbit done by him, and the block was full of dirt and sludge when he got it back. We had to take it apart and clean it up. Another guy had the same complaint from work done by him. I think he's no longer in business.
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09-09-2015, 02:30 PM | #13 |
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Re: Piston movement...
Actually the norm is to measure and inspect, then buy the pistons and bore and hone to fit the new pistons. A lot of shops will jump the bore by .030" just to be sure, but I'd rather go just enough to get past any out of round or taper.
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09-09-2015, 02:48 PM | #14 |
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Re: Piston movement...
Cylinders wear more on one side than the other. Most of the time you need to double what the wear is. If it checks .010 over size at the top of cylinder, it probably is going to take .020 to clean up.
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09-09-2015, 02:59 PM | #15 |
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Re: Piston movement...
You learn something new everyday! I thought it made sense to bore .010 over and see if that cleaned it up enough and if not then machine another .010 off and if that did the trick, then purchase pistons based on how much the machinist had to go over stock measurements. Then when pistons came in, hone the cylinders so the pistons had an adequate amount of clearance.
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09-09-2015, 03:33 PM | #16 |
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Re: Piston movement...
I measure the bores with a bore gage to find the maximum taper and out of round. Take that measurement and divide it by .7, that usually gives you an approximation of the minimum oversize that you need. Example, .023 difference from top to bottom divided by .7= .0329, so you would need at least .040 larger than it is now. You will have to go to the next largest piston available, unless you want to spring for some custom made ones. $$$$$
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09-09-2015, 07:57 PM | #17 |
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Re: Piston movement...
I'd say #2 had some "issues"..
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Early '29 CCPU that had a 4-speed, but not any more.......in the family since '62 |
09-09-2015, 08:01 PM | #18 |
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Re: Piston movement...
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09-10-2015, 12:42 PM | #19 |
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Re: Piston movement...
Cj5 do you have a photo of the entire top of the block where you posted the top of the piston? Just curious.
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09-10-2015, 02:16 PM | #20 |
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Re: Piston movement...
I can sure take a picture...the pistons are all out but the valves are still there....are you looking for something specific?
Here's one...
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Early '29 CCPU that had a 4-speed, but not any more.......in the family since '62 Last edited by 1955cj5; 09-10-2015 at 02:28 PM. |
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