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: L pistons and rings and other parts


claudia
01-22-2011, 12:00 PM
I am not sure this is true or not but some years ago A retired Gravely dealer told me that the gravely pistons are the same as was used on the old model
T fords.also many of the components (bearings,bushings,seals etc) are off the shelf parts that are easy to get in places other than a dealer. I never checked on the piston claim but I do Know he was correct on the other parts. Any model T fans who can verify this. I think this practice of using off the shelf parts was a common cost saving practice and still is today.

gm1276
01-22-2011, 12:36 PM
Can't confirm or deny the Model T story, but I do know there is some sort of automotive piston out there that exactly matches the Model L piston and can be used to replace it. People have used Willys Jeep pistons in Gravelys before -- I have seen .040 oversize and .060 in _way_ oversize (.060 and .080, respectively) Model L cylinders. My 1937 Model L (now Shoman666's) has an .080 over cylinder with a Willys Jeep piston.

There is some sort of uncommon American car out there with pistons that can be used in a Model L. One member of the yahoo group acknowledged knowing the model, but did not disclose -- I believe he was working on setting up some kind of arrangement to have new pistons made available for sale. Anyone know more on this?

beaner2u
01-22-2011, 03:56 PM
gm1276,

Does your '37 model L 'thump' a little bit? It would seem as though the weight of a very oversized piston would throw off the balance of the flywheels. I suppose you could shave off some of weight on the skirt in a lathe, just so that piston pin to top of piston dimensons are the same.

Wow, .080" over?, and the tractor has not blown out a cylinder? There must be a lot more meat to those cylinders than I thought.

Roger,

arcam8123
01-22-2011, 04:16 PM
There are lots of pistons that will fit the bore, but that number drops when you take the piston pin dia into account. Also,the closest to the true gravely dimensions and weight is about .06" too short. The result is 60 psi of compression, which is a usable machine, but not the HP rating. Compression should be just over 70psi.

gravely-power
01-22-2011, 04:27 PM
gm1276,

Does your '37 model L 'thump' a little bit? It would seem as though the weight of a very oversized piston would throw off the balance of the flywheels. I suppose you could shave off some of weight on the skirt in a lathe, just so that piston pin to top of piston dimensons are the same.

Wow, .080" over?, and the tractor has not blown out a cylinder? There must be a lot more meat to those cylinders than I thought.

Roger,

Depending on the piston being used it could actually be lighter. Besides an .080 over piston wouldn't much heavier than a std. one.

beaner2u
01-22-2011, 05:13 PM
OK Ron,

Now put your math hat on, if someone tried your 'closest' piston, adjusted said piston to weigh in the same as a standard Gravely; then shaved .060" off the top of a cylinder, re-did valve seats, added 1/16" spacers to valve springs, and re-adjusted valve settings? I believe you can adjust valve tappets for a .060" difference.

I also believe the top of a cylinder could afford to loose .060"

Roger,

gm1276
01-22-2011, 05:35 PM
gm1276,

Does your '37 model L 'thump' a little bit? It would seem as though the weight of a very oversized piston would throw off the balance of the flywheels. I suppose you could shave off some of weight on the skirt in a lathe, just so that piston pin to top of piston dimensons are the same.

Wow, .080" over?, and the tractor has not blown out a cylinder? There must be a lot more meat to those cylinders than I thought.

Roger,

Roger,

Shoman666 (the one who pulled apart and reassembled the machine after purchasing it from me) will probably be along with more details eventually, but the machine does not thump. The cams were also redone by P/O -- the carburetor is a Zenith from a larger tractor of some kind. The machine runs at around 1600 RPM at wide open throttle and idles down to somewhere south of 100 (!) RPM. It is truly unbelievable and one of the most interesting tractors I've ever seen. The compression is enormous (though I'm not sure he's measured it) and the timing is also different (obviously) but I don't remember where it is set to fire offhand.

arcam8123
01-22-2011, 08:27 PM
OK Ron,

Now put your math hat on, if someone tried your 'closest' piston, adjusted said piston to weigh in the same as a standard Gravely; then shaved .060" off the top of a cylinder, re-did valve seats, added 1/16" spacers to valve springs, and re-adjusted valve settings? I believe you can adjust valve tappets for a .060" difference.

I also believe the top of a cylinder could afford to loose .060"

Roger,

Let's see. Hey, it just might work!

Todd W. White
02-08-2012, 12:31 PM
It's not a Model T piston.

New pistons for the L-series pistons are now available here:

http://gtgravelyparts.com/newproducts.html

Richard-tx
02-08-2012, 01:12 PM
gm1276,

Does your '37 model L 'thump' a little bit? It would seem as though the weight of a very oversized piston would throw off the balance of the flywheels.


As far as I know, the L engine was never balanced to begin with. I dont' recall ever seeing any balancing holes drilled in the flywheels. I might be wrong as it has been a while since I took a Gravely engine apart.

Gravely Model L Guy
02-08-2012, 02:03 PM
I own a model T and have over-hauled the engine and I know for sure that Gravely pistons and model T have absolutely nothing in common.

Richard-tx
02-08-2012, 02:28 PM
My father claimed that the L pistons were from a car or truck. I think he said it was from a Studebaker It was not from a Ford or GM product.

gm1276
02-08-2012, 02:53 PM
No, they are definitely their own piston. There have been a few made to work, including, as I mentioned, Willys Jeep pistons. Here's a link to the story of that tractor -- seeing the revival of this thread reminded me.
http://www.mytractorforum.com/showthread.php?t=124881

Todd W. White
02-08-2012, 07:23 PM
Old man Gravely did, in fact, use a piston that was in production at the time. The problem is he picked an engine that wasn't made for very long before the company got bought and the new owners merged that engine into their line of engines, changing the compression height at the same time.

For a while, aftermarket piston companies made these pistons and they were purchased by people who owned the original engines. With the advent of the 1950's, though, the number of people buying the pistons dwindled, and Gravely ended up being the only ones buying them. At some point, therefore, they changed the ring setup from 4 to the now familiar 3.

The ones being sold at gtgravelyparts.com match the Gravely piston in all critical dimensions, including the size and depth of the ring grooves, compression height, and diameter. There are only two differences - the location of the oil ring, which was the result of the casting used but doesn't affect performance, and the thickness of the skirt, which actually adds strength to the piston where they have a tendency to crack.

rscurtis
02-08-2012, 10:01 PM
I had a discussion with one of the Schmoll brothers, I believe it was at Somerset. They had a 4-ring piston that I believe was originally a flathead Plymouth application. Its deck height was a little short as Ron mentioned. What would be really interesting would be to take an old L crankshaft and re-locate the crankpin to increase the stroke. Problem solved and more HP.

Todd W. White
02-08-2012, 11:01 PM
The 4-ring piston they have is a Plymouth piston - it's 1/8" too short.

The ones at gtgravelyparts.com are identical in height to the original, factory piston.

Problem solved.

rscurtis
02-09-2012, 12:28 PM
You're correct, the problem is solved. But the opportunity to experiment is lost. Since there are plenty of old L crankshafts around, it would be an interesting experiment for someone with the machining capabilities.