flat top pistons with craters in them

SDE · Jan 24, 2015

I cleaned the crud out of the cylinders on a dead 44 MH engine. I found that all 4 pistons had irregular shaped holes in them. A couple were off center and a couple looked to be near the center. They were all at least 1/4" deep or more. If I can get them freed up, are they useable, repairable or just junk? And is this damage from someone running with too hot of a spark plug in the engine?
Thank you
SDE

David G · Jan 24, 2015

Post a picture

Steve@Advance · Jan 24, 2015

My guess would be they were caused from extreme over heating.

As low compression those engines are, I doubt wrong plugs or way too much timing advance would cause that, but I could be wrong.

Several factors would determine if they are usable. Once they are out look at the skirt. If it's been really hot, they are probably scuffed and seized. That may be why they won't come out... If they are, likely not usable.

Another thing to check, how thick is the top? If they are burned 1/4" deep, probably not much left. Can that be repaired? Yes, it could be ground out and welded up, but unless you have the equipment or connections, probably cost as much as replacing them.

And, what is this going to be? A working tractor or show? Do you feel lucky? LOL

dr sportster · Jan 24, 2015

THat is bad , that is very bad.
Wrong reat range plugs will hole a piston Half melted spots mean throw them away or make cool auto show trophys with pinstripes all over them .

pete 23 · Jan 24, 2015

Timing an engine by ear. These old tractors are low compression but they have a very long spark advance along with that. Probably as much as 40 degrees. So, you can see if you time it where it sounds best you may well be up to 50 degrees. Detonation is real.

Geo-TH,In · Jan 25, 2015

Get new pistons.

From what I've read, too hot of plugs can cause that. Low octane causing pinging, pre-ignition, can cause that. Some say running too lean causes pinging. I'm sure timing plays a part too. High compresssion pistons cause it too. Pinging blows holes in piston. New cars use ultra sonic mics to alter timing, EGR, perhaps fuel to cool thing off a littlt to prevent pinging on low octane fuels.

I had a 62 Jag, 9.5:1 compression,that needed high octane leaded gas or it would ping. I had to retard the spark to lessen the pinging. I let the car sit. Sold it 11 years ago for 5 times what I paid for it.

SDE · Jan 25, 2015

I tried to take two pictures this morning. The quality of the pictures is poor at best. #4 piston looks to have a pin hole all the way thru. #2 and 3 have two craters in each that are bigger in diameter and also deeper. At least the size of a quarter. They are not in the center and there must be more material there. I did not have a light with me yesterday and so I did not know that the two pistons that were in the down stroke position were so bad. They are junk. Sorry to have wasted your time.
STEVE

dr sportster · Jan 25, 2015

Not a waste of time at all. The holes probably sit right under the spark plug locations.Too hot of a plug.

flat top pistons with craters in them

SDE

Well-known Member

David G

Well-known Member

Steve@Advance

Well-known Member

dr sportster

Well-known Member

pete 23

Well-known Member

Geo-TH,In

Well-known Member

SDE

Well-known Member

dr sportster

Well-known Member

Similar threads