The Ford Barn

larry harding · 05-04-2024, 02:43 PM

i acquired an engine in a trade. it was "supposedly" rebuilt. i did a test run on a stand and the rear main leaks. i reshimed after using a plastigage... still leaks.
i pulled the oil pan today and looking around i noticed each piston had a slot hacksawed in the skirt almost up to where ring groove would be. also looking down in the pistons (engine is upside down on stand) there looks like a 10/32 threaded hole in the bottom of the wrist pin area of the pistons. i have no idea what the guy was doing, any ideas? it would be nice to have this for a spare engine, but it looks like a complete tare down and rebuild.

jg61hawk · 05-04-2024, 03:01 PM

https://forums.aaca.org/topic/303369...ts-of-pistons/

Try this link...I don't know if it's good advice but it's an answer!

ursus · 05-04-2024, 04:09 PM

The older pistons were often made with a split skirt, sometimes with a hole at one end of the split in order prevent cracking. I think this started when pistons were round and needed the split for expansion. Later, when cam-ground pistons were made, the split disappeared. Many of the replacement pistons made for the Model A still retained the split skirt well into the 1970s.

nkaminar · 05-05-2024, 07:13 AM

The piston design was changed several times during the production of the Model A. The Service Bulletins talk about this at pages 312 and 339. As Ursus said, the round pistons had the slots and the cam ground pistons did not. All modern engine use the cam ground pistons.

larry harding · 05-05-2024, 08:20 AM

the sawed slots ran from he bottom of the to just below the ring area. they were not very straight, hand hacksaw work i guess. still wondering about the threaded holes into the wrist pin area... you can see the wrist pin in the holes.
the work was likely done in the last 10 years using modern pistons i think, but who knows. any suggestions on the rear main leak of redoing the main bearings?

Flathead · 05-05-2024, 10:45 AM

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Just out of curiosity, are the pistons slotted on both sides or just one side?

larry harding · 05-06-2024, 12:49 PM

they are slotted oposite the cam side only.

05-04-2024, 02:43 PM	#1
larry harding Senior Member Join Date: Sep 2015 Location: western n.c. Posts: 398	weird stuff i acquired an engine in a trade. it was "supposedly" rebuilt. i did a test run on a stand and the rear main leaks. i reshimed after using a plastigage... still leaks. i pulled the oil pan today and looking around i noticed each piston had a slot hacksawed in the skirt almost up to where ring groove would be. also looking down in the pistons (engine is upside down on stand) there looks like a 10/32 threaded hole in the bottom of the wrist pin area of the pistons. i have no idea what the guy was doing, any ideas? it would be nice to have this for a spare engine, but it looks like a complete tare down and rebuild.

05-04-2024, 03:01 PM	#2
jg61hawk Senior Member Join Date: Oct 2014 Location: Central New Jersey Posts: 418	Re: weird stuff https://forums.aaca.org/topic/303369...ts-of-pistons/ Try this link...I don't know if it's good advice but it's an answer!

05-04-2024, 04:09 PM	#3
ursus Senior Member Join Date: May 2010 Location: Oregon Posts: 1,378	Re: weird stuff The older pistons were often made with a split skirt, sometimes with a hole at one end of the split in order prevent cracking. I think this started when pistons were round and needed the split for expansion. Later, when cam-ground pistons were made, the split disappeared. Many of the replacement pistons made for the Model A still retained the split skirt well into the 1970s.

05-05-2024, 07:13 AM	#4
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 4,002	Re: weird stuff The piston design was changed several times during the production of the Model A. The Service Bulletins talk about this at pages 312 and 339. As Ursus said, the round pistons had the slots and the cam ground pistons did not. All modern engine use the cam ground pistons. __________________ A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past.

05-05-2024, 08:20 AM	#5
larry harding Senior Member Join Date: Sep 2015 Location: western n.c. Posts: 398	Re: weird stuff the sawed slots ran from he bottom of the to just below the ring area. they were not very straight, hand hacksaw work i guess. still wondering about the threaded holes into the wrist pin area... you can see the wrist pin in the holes. the work was likely done in the last 10 years using modern pistons i think, but who knows. any suggestions on the rear main leak of redoing the main bearings?

05-05-2024, 10:45 AM	#6
Flathead Senior Member Join Date: May 2010 Location: Southern Maine Posts: 1,502	Re: weird stuff Sponsored Links (Register now to hide all advertisements) Just out of curiosity, are the pistons slotted on both sides or just one side?

05-06-2024, 12:49 PM	#7
larry harding Senior Member Join Date: Sep 2015 Location: western n.c. Posts: 398	Re: weird stuff they are slotted oposite the cam side only.