Piston question

D

DWester

Member
Well, I'm finally getting back to this rebuild and have a question on the pistons. This motor is a 1948, 59a with a 8ba rotating system in it. The cylinders are stock/standard 3 3/16th as are the pistons. When I disassembled it, I did notice that there were two pistons unlike the others. They are like the one on the right in the photo. The rest are like the left one. I noticed the difference in thickness between the compression ring groves and the thinner lower ring grove on the one to the right. The right one also measures to be a slightly taller piston from the pin to the top. A couple of the other six say Mercury inside.

My problem now is trying to find two standard pistons to match the six I have so I can order the right set of rings. Anyone have a couple of these laying around? Haven't found anything in my search so far.
 
Opp! Here they are.
 

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DWester said:
The right one also measures to be a slightly taller piston from the pin to the top. A couple of the other six say Mercury inside. QUOTE]

You say "slightly taller"......Does it measure 1/8" taller? If so, they ARE Mercury pistons for a 4" stroke crankshaft. DD
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I think I would go and carefully re-measure the stroke on your crankshaft to verify what it actually is. 3.75" would be Ford, and 4.00" stroke is the Merc. DD
 
Perhaps pre '48 Mercury pistons? Back in the 50's and 60's, we would mix and match junkyard pistons as long as they weren't cracked and were nominally to size with very few problems (flatheads can be very forgiving). That being said, I think in this day and age, a new set of pistons is in order, since some of these have probably been in and out of an engine(s) more than once.
 
I think you will find if you stick one wrist pin into each piston you'll find both pistons the same height, if there both the same height you still have to measure the stroke to get the right piston. You might have a hard time matching a piston, there usually a lot different in weight. If there difference weight they usually cause a vibration. Walt
 
I have a set of 8 standard pistons with pins that I removed from a running engine. 4 pistons are marked on the inside "Ford made in Canada" and 4 pistons are marked 2F9. If interested send me a PM. (3 3/16")
 
Thanks for all the replies. To be honest, this motor will be going in an old farm truck that will get maybe 200 miles on it a year. It's not mine, it's something I'm trying to help out for a friend of mine who feeds hay with. There's nothing more I'd like more than to be doing a build with all the new parts and end up with a really nice flatty. That's just not the case this time. I'm just trying to get him up and running with a decent running motor without spending too much $, yet something that will keep him feeding cows for a few years more.

I've done a stroke test and it's definitely 3 3/4, not 4. I'll just have to find two standard pistons or a set, whatever comes first.

Thanks so much for your response,

Darol
 
DWester said:
Opp! Here they are.
Click to expand...

Darol, I might have a couple of good used std. full skirts pistons, the rings are usually 3/32-3/32-3/16-3/16 you can have them just for shipping, I won't have a chance to go to my storage barn today but maybe tomorrow. The barn is 500 feet from my house and the snow is getting deeper. walt
 
Walt Dupont--Me. said:
Darol, I might have a couple of good used std. full skirts pistons, the rings are usually 3/32-3/32-3/16-3/16 you can have them just for shipping, I won't have a chance to go to my storage barn today but maybe tomorrow. The barn is 500 feet from my house and the snow is getting deeper. walt
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That sounds great Walt! So, if I ordered a set of rings for the pistons I have six of, will the rings also fit the pistons from you?
 
DWester said:
Thanks for all the replies. To be honest, this motor will be going in an old farm truck that will get maybe 200 miles on it a year. It's not mine, it's something I'm trying to help out for a friend of mine who feeds hay with. There's nothing more I'd like more than to be doing a build with all the new parts and end up with a really nice flatty. That's just not the case this time. I'm just trying to get him up and running with a decent running motor without spending too much $, yet something that will keep him feeding cows for a few years more.

I've done a stroke test and it's definitely 3 3/4, not 4. I'll just have to find two standard pistons or a set, whatever comes first.

Thanks so much for your response,

Darol
Click to expand...

You might try what Walt suggested, put one wrist pin to two pistons, if they're the same height, weigh them... If they are close- run them as is...

Karl
 
I wanted to do that, but the two pistons that are different require a different set of rings. In my picture above, you can see that the one on the right uses slightly smaller oil rings than the others. I figured it would be a PITA if even possible to get rings for just two pistons that were different from the others. Maybe I'm wrong???
 
Measure the groove widths and report back to us.They should all be the same.

If not the 2 pistons appear to be from a 46 to 49 59a. (5/32 oil rings).

R
 
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OK. On a dial caliper, the two different pistons (on right) measures .256. The left one is .285. This is the oil ring groves only. The compressions are the same. So the six I would like to use have a slightly larger oil ring grove. Which of these are odd ball?
 
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Those measurements don't seem to match what 8ba and 59a engines have for oil ring widths. They should measure either .1875" for 3/16" or .156" for 3/32 have you measured accurately?? Your measurements are over 1/4" How about .
.156" and .185" looks like a typo (confirm)

R.
 
Sorry Ronnie. I tried to get back to correct that, but you beat me to it. Yes, the correct #'s would be .185 and .156
 
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