The Ford Barn

1955cj5 · 09-09-2015, 09:50 AM

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...

Y-Blockhead · 09-09-2015, 09:56 AM

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.

Patrick L. · 09-09-2015, 10:11 AM

Piston to wall clearance is measured from the piston skirt [90º to the pin] and the bore. The ring land area is smaller.

1955cj5 · 09-09-2015, 10:22 AM

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

Tom Wesenberg · 09-09-2015, 11:05 AM

If you are doing an engine rebuild, then I'd buy the next oversize and have the cylinders bored to fit.

George Miller · 09-09-2015, 11:08 AM

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Quote:

Originally Posted by Tom Wesenberg

If you are doing an engine rebuild, then I'd buy the next oversize and have the cylinders bored to fit.

Plus 1

J Franklin · 09-09-2015, 11:59 AM

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

1955cj5 · 09-09-2015, 01:01 PM

Quote:

Originally Posted by Tom Wesenberg

If you are doing an engine rebuild, then I'd buy the next oversize and have the cylinders bored to fit.

Well that was one of my questions...would you buy pistons first and then bore to fit, or see how far it needs to be bored and then buy pistons? Or is the .010 size increase generally enough to take care of out of roundness or other issues? There are a few small corrosion pits in the walls of #3..

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....

J Franklin · 09-09-2015, 01:33 PM

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.

hardtimes · 09-09-2015, 02:18 PM

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.

DJ S · 09-09-2015, 02:21 PM

Quote:

Originally Posted by 1955cj5

Well that was one of my questions...would you buy pistons first and then bore to fit, or see how far it needs to be bored and then buy pistons? Or is the .010 size increase generally enough to take care of out of roundness or other issues? There are a few small corrosion pits in the walls of #3..

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....

You would have to purchase the pistons after the machine work because it may take more than .010 to get the cylinders cleaned up.

Tom Wesenberg · 09-09-2015, 02:26 PM

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.

Tom Wesenberg · 09-09-2015, 02:30 PM

Quote:

Originally Posted by DJ S

You would have to purchase the pistons after the machine work because it may take more than .010 to get the cylinders cleaned up.

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.

George Miller · 09-09-2015, 02:48 PM

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.

DJ S · 09-09-2015, 02:59 PM

Quote:

Originally Posted by Tom Wesenberg

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.

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.

Mark in MT · 09-09-2015, 03:33 PM

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. $$$$$

1955cj5 · 09-09-2015, 07:57 PM

I'd say #2 had some "issues"..

DJ S · 09-09-2015, 08:01 PM

Quote:

Originally Posted by 1955cj5

I'd say #2 had some "issues"..

Just a few

Farrell In Vancouver · 09-10-2015, 12:42 PM

Cj5 do you have a photo of the entire top of the block where you posted the top of the piston? Just curious.

1955cj5 · 09-10-2015, 02:16 PM

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...

09-09-2015, 11:05 AM	#5
Tom Wesenberg Senior Member Join Date: May 2010 Location: Mpls, MN Posts: 27,582	Re: Piston movement... If you are doing an engine rebuild, then I'd buy the next oversize and have the cylinders bored to fit.

09-09-2015, 11:59 AM	#7
J Franklin Senior Member Join Date: May 2010 Location: Oregon Posts: 5,959	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

09-09-2015, 01:33 PM	#9
J Franklin Senior Member Join Date: May 2010 Location: Oregon Posts: 5,959	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.

09-09-2015, 02:18 PM	#10
hardtimes Senior Member Join Date: May 2010 Location: South California Posts: 6,188	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, 02:26 PM	#12
Tom Wesenberg Senior Member Join Date: May 2010 Location: Mpls, MN Posts: 27,582	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.

09-09-2015, 09:56 AM	#2
Y-Blockhead Senior Member Join Date: Jul 2011 Location: Redondo Beach, CA Posts: 5,848	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.

09-09-2015, 10:11 AM	#3
Patrick L. Senior Member Join Date: May 2010 Location: Largo Florida Posts: 7,225	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.

09-09-2015, 02:48 PM	#14
George Miller Senior Member Join Date: May 2010 Location: NC Posts: 2,975	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.

09-09-2015, 03:33 PM	#16
Mark in MT Senior Member Join Date: May 2010 Location: Western MT Posts: 218	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. $$$$$ __________________ Mark in MT Always looking for another opportunity to be wrong.

09-10-2015, 12:42 PM	#19
Farrell In Vancouver Senior Member Join Date: May 2010 Location: Pitt Meadows BC Posts: 1,003	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.