The Ford Barn

bobbycoke · 05-05-2011, 03:53 PM

This may seem silly but when changing my leaky head gasket I cleaned up the carbon on the piston heads... I could move the pistons noticeably left and right with my finger pressure [ not so much forward and back]. I did not think much of it as compression on all were good 55-60 lbs and it runs good! I did not measure the wiggle and buttoned it up thinking it was normal and at least the rings were working. I purchased a pick up in pieces and it,s engine was apart in the chassis, the head was off and it looks like they did rings etc and were up to the valves.... no play to speak of on the pistons.... nice and tight and they turn over fine, do not have the head on so I haven't measured compression.. My question is this wooble acceptable and/or an indication of future engine block work with oversized pistons in my future??

Special Coupe Frank · 05-05-2011, 04:05 PM

"My question is this wooble acceptable and/or an indication of future engine block work with oversized pistons in my future?? "

"No, and yes."

Did you notice whether those pistons had "Ford" script stamped in the top, and any numeric markings to indicate an over-size part ?

I had the head off my tired 82,000 mile (then ) '28 Coupe last April, and when I cleaned the carbon off the deck and piston crowns, I noticed the same "slop" between the piston and the cylinder walls, and was a little surprised to discover that my engine has its original stock-bore "Ford" pistons and valves... apparently my engine has never been rebuilt.

I put my engine back together with a new head gasket and am still running it.

It knocks, raps, rattles, smokes, but keeps going.

I knew last year that this engine is on borrowed-time, but I figured I'd see how much more I can wring out of it.

If your engine isn't making ugly knocking noises, and consuming massive quantities of oil, you can probably keep driving it moderately...

Might not be a good candidate for a cross-country tour though....

Just my 2-cents worth....

J and M Machine · 05-05-2011, 07:40 PM

Chances are you may need to have the engine rebuilt sooner than later.

As Frank says don't take it cross country.
Depending on the amount of free play of piston to wall clearance you have. If you have more on one plane than another, that would be the indication of the cylinder and piston wear.

We recently did an engine for a customer which claimed the same thing other than a leaky rear main,his ran fine. After disassembly the snap ring which retains the wrist pin was on the verge of coming out. You never know until it happens.

dave in australia · 05-05-2011, 09:02 PM

Piston clearance is different accross the engine compared to along the engine. Also, pistons pivot accross the engine and the conrod holds the piston in the alignment along the engine. I hope I'm explaining myself well here. Pistons are also cam ground, ie, they have more clearance when measured in one direction compared to the other way, up to .020". Using compression as well as a leak down test and just listening when the engine is running are better ways of getting an indication of wear.

Tom Wesenberg · 05-05-2011, 09:23 PM

Did you have any cylinder wall wear? Did the cylinder have a ridge at the top?

If not, and if the pistons don't slap, then I'd keep running it and wait until it needed new rings or babbit work, then rebore it for the next oversize.

pat in Santa Cruz · 05-05-2011, 11:51 PM

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in addition to being cam ground, as Dave said, and checking for cylinder wear as Tom says, the clearance at the top of the piston is greater than at the bottom of the skirt. If you really want to know the clearance, you will have to pull the pan and run a feeler up the skirt 90 degrees from the pin ends. That should be .002-.003 on new pistons. At .004-.005 they start to get noisy. On racing pistons, the clearance can be .006 intentionally. On a fuel dragster, it could be .025. I recently tore down an engine that sounded like a diesel from the piston noise. It was bored .125 over, but someone put .100 over pistons in it. I agree with Tom, if its not slapping, don't worry about it.

05-05-2011, 03:53 PM	#1
bobbycoke Senior Member Join Date: May 2010 Location: pawlet vt/ port jefferson sta. ny Posts: 183	loose pistons anyone? This may seem silly but when changing my leaky head gasket I cleaned up the carbon on the piston heads... I could move the pistons noticeably left and right with my finger pressure [ not so much forward and back]. I did not think much of it as compression on all were good 55-60 lbs and it runs good! I did not measure the wiggle and buttoned it up thinking it was normal and at least the rings were working. I purchased a pick up in pieces and it,s engine was apart in the chassis, the head was off and it looks like they did rings etc and were up to the valves.... no play to speak of on the pistons.... nice and tight and they turn over fine, do not have the head on so I haven't measured compression.. My question is this wooble acceptable and/or an indication of future engine block work with oversized pistons in my future??

05-05-2011, 04:05 PM	#2
Special Coupe Frank Senior Member Join Date: May 2010 Location: Northeast Penna Posts: 2,108	Re: loose pistons anyone? "My question is this wooble acceptable and/or an indication of future engine block work with oversized pistons in my future?? " "No, and yes." Did you notice whether those pistons had "Ford" script stamped in the top, and any numeric markings to indicate an over-size part ? I had the head off my tired 82,000 mile (then ) '28 Coupe last April, and when I cleaned the carbon off the deck and piston crowns, I noticed the same "slop" between the piston and the cylinder walls, and was a little surprised to discover that my engine has its original stock-bore "Ford" pistons and valves... apparently my engine has never been rebuilt. I put my engine back together with a new head gasket and am still running it. It knocks, raps, rattles, smokes, but keeps going. I knew last year that this engine is on borrowed-time, but I figured I'd see how much more I can wring out of it. If your engine isn't making ugly knocking noises, and consuming massive quantities of oil, you can probably keep driving it moderately... Might not be a good candidate for a cross-country tour though.... Just my 2-cents worth....

05-05-2011, 07:40 PM	#3
J and M Machine Senior Member Join Date: Oct 2010 Location: 40 Mt.Vickery Rd. Southborough,MA 508-460-0733 Posts: 352	Re: loose pistons anyone? Chances are you may need to have the engine rebuilt sooner than later. As Frank says don't take it cross country. Depending on the amount of free play of piston to wall clearance you have. If you have more on one plane than another, that would be the indication of the cylinder and piston wear. We recently did an engine for a customer which claimed the same thing other than a leaky rear main,his ran fine. After disassembly the snap ring which retains the wrist pin was on the verge of coming out. You never know until it happens.

05-05-2011, 09:02 PM	#4
dave in australia Senior Member Join Date: May 2010 Location: Victoria, Australia Posts: 1,177	Re: loose pistons anyone? Piston clearance is different accross the engine compared to along the engine. Also, pistons pivot accross the engine and the conrod holds the piston in the alignment along the engine. I hope I'm explaining myself well here. Pistons are also cam ground, ie, they have more clearance when measured in one direction compared to the other way, up to .020". Using compression as well as a leak down test and just listening when the engine is running are better ways of getting an indication of wear.

05-05-2011, 09:23 PM	#5
Tom Wesenberg Senior Member Join Date: May 2010 Location: Mpls, MN Posts: 27,582	Re: loose pistons anyone? Did you have any cylinder wall wear? Did the cylinder have a ridge at the top? If not, and if the pistons don't slap, then I'd keep running it and wait until it needed new rings or babbit work, then rebore it for the next oversize.

05-05-2011, 11:51 PM	#6
pat in Santa Cruz Senior Member Join Date: May 2010 Location: santa cruz, calif Posts: 2,011	Re: loose pistons anyone? Sponsored Links (Register now to hide all advertisements) in addition to being cam ground, as Dave said, and checking for cylinder wear as Tom says, the clearance at the top of the piston is greater than at the bottom of the skirt. If you really want to know the clearance, you will have to pull the pan and run a feeler up the skirt 90 degrees from the pin ends. That should be .002-.003 on new pistons. At .004-.005 they start to get noisy. On racing pistons, the clearance can be .006 intentionally. On a fuel dragster, it could be .025. I recently tore down an engine that sounded like a diesel from the piston noise. It was bored .125 over, but someone put .100 over pistons in it. I agree with Tom, if its not slapping, don't worry about it.