641 workmaster piston install

[Steve255]

Each piston has a green dot, I think this means that the dot goes towards the front. Is this right? Also, one of the pistons has the dot on the opposite side of the piston based on the part number and "STD" stamp on the top of the piston. Do I Go by the dot or the imprint??

 

[Ultradog MN]

I might have guessed the dot meant up.
You would stagger your end gaps. 120° 240° 360° etc.

 

[john in la]

The STD stamped on the top of the piston tells us it is a Standard size piston as apposed to a Oversized piston.

Installing pistons has been standardized in all engines for years. The mark on the piston top always goes to the front unless it is a 1 cylinder engine where there is no front. Then the mark points to the exhaust valve.

The rod has to be installed the correct way in relation to the piston for it to work right.
The piston should be installed in a bore with proper clearance; and the rings spaced evenly around the piston.
The rings should be fitted to the engine bore(end gap) before installing on the pistons. Rings should also be checked for side clearance in the piston grove.
Rod bearings should be checked with plastigage to make sure everything is fitting right.
Cylinder walls should be lightly honed to take off any polish. This will help the rings to seat.

Most likely more info than you wanted but miss any of the above and the rebuild may not last.

 

[john in la]

OH forgot...........
The rod cap must be installed on the rod facing the correct way.

Most likely other things I forgot to add but you get the idea.

 

[Wayne IA]

The proper procedure is as stated by others but the real issue is to make sure the little squirter hole on the top side of the bottom half of the rod is aimed at the camshaft side of the engine.

 

[RBnSC]

I was wondering if end gap theory had changed. I have taken 2 diesel fords apart in the last 6 months and all but 1 piston had the gaps perfectly aligned. I guess that may have been what caused their demise.
Ron

 

[Steve255]

Very helpful photo, but, my cylinder does not have that mark on the top of it. Is there another mark to look for??

 

[Brian Allen]

Steve
All your information is there.
Put the rod hole shown in the picture toward the camshaft, and stagger the rings as these posters suggested and all will be well(provided you have done everything else correctly)
Brian

 

[Steve255]

What direction does the piston go?? It has no
directional mark