Topic: flathead piston


F100    -- 05-14-2018 @ 8:33 AM
  h*llo .. new here and have a question for you wise sage's.
I have a 53 F100 with a 51 Merc flathead in it. obviously when the builder put in the engine it was stuck and I found the number 8 piston dome had a hole in it from an obviously big screwdriver being hammered into it. my question is can I just replace the 1 piston and what if any are the concerns with doing so.

thanks in advance


carcrazy    -- 05-14-2018 @ 12:59 PM
  What is your goal for this engine? Is the engine free in that it turns over by hand when you rotate the crankshaft? If you just want to get the engine running and don't intend to have it be a reliable engine in a vehicle that you can take long road trips with, you can just replace the one piston. Several things to be aware of if you are just replacing the one piston are: be sure you get a piston with the correct piston pin to crown dimension for the stroke of the engine, be sure the piston has the correct external dimensions for the bore in which it will be installed, and be sure the weight of the piston matches that of the other pistons in the engine.
Of course the best thing to do, if your budget will allow it, is to rebuild the engine with all new pistons and freshly bored and honed cylinders.



cliftford    -- 05-14-2018 @ 8:20 PM
  Since you have to pull the pan to replace the piston anyway, I would take the engine apart and rebuild it. I wouldn't trust a mechanic who would punch a hole in a piston like this.


F100    -- 05-15-2018 @ 8:03 AM
  thank you for your input and you guys are right.... believe it or not.. this engine (6 volt) starts runs well at idle and drives around my neighborhood really well on the 7 working cylinders, albeit smokey from the cylinder not being sealed and probably some from worn rings on other cylinders) I do have a bunch of flathead pistons on hand I've collected with some other engines. I'm handy and I'd really like to try it but it seems like if I'm going to get into it might be best to do it right (my father's voice is in my head telling me to do it right the first time)
God bless


42wagon    -- 05-15-2018 @ 12:53 PM
  Be careful driving around with a hole in a piston. Why? Well with each revolution of the engine you are introducing a gasoline and air mixture to the crankcase. You are also getting a spark with each revolution. Charge the crankcase enough and it becomes a great big bomb. I know because when we were kids a friend of mine did it and ended up with pieces of cast iron everywhere and the hood out in a field.


shogun1940    -- 05-15-2018 @ 2:53 PM
  I would do a cylinder leak down test to see what all the cylinders are doing. If they are good then i would take the pan off and plastigage all of bearings if they pass i would go for the one piston. When you take the head off check the cylinders to see if it has a large ridge. If you try it it is a set of head gaskets and oil pan set.
GOODLUCK


TomO    -- 05-16-2018 @ 7:24 AM
  42wagon is correct and another reason to stop driving it is that you can dmage the block beyond repair.

Tom


village grande    -- 05-17-2018 @ 5:33 PM
  While doing a valve job on my 8ba I found a piston with a small hole in the top, after removing the piston I found the top ring was gone and must have exited through the hole in the piston got chewed up and exited out the exhaust valve. To make a long story short there was no damage to the cylinder wall. After measuring cylinder walls I determined there was very little wear on the engine ( practically no ridge). I purchased a new matching 8ba piston and installed it after honing cylinder and installing new rings and a new rod bearing (I had to by a whole set of rings). 2,500 miles later no problems with excellent compression. I guess it depends on engine wear and condition, a complete engine rebuild would be out of reach for many of us.


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