Franklin Pistons

D

davism

New member
My 150 hp Franklin had the top ring groove worn in my #1 piston. A replacement piston I received is lighter than the rest and has no letter designation for weight stamped in it, A-F. I have 2 questions;
Does anyone know what the equivalent weights are to the letter designations? And, why is it important to ballance the weights of pistons directly across from each other when on either side of the firing order might be more important?
 
I do not know what the weights are supposed to be, I my experience a C weight piston may weigh several ounces more than another. I balance all of the pistons in my engines to weigh the same. It is important to balance the pistons and rods to make the engine run smoother (less vibration). I have seen engines with different weight pistons run smoothly but the same weight pistons always opposed . If you have all of the pistons out just have them balanced. There is an area just above the skirt that is perfect for removing material to balance. If you can't find someone to balance them contact me and I will balance them for you.
Greg
 
davism said:
My 150 hp Franklin had the top ring groove worn in my #1 piston. A replacement piston I received is lighter -- why is it important to ballance the weights of pistons directly across from each other when on either side of the firing order might be more important?
Click to expand...
By running the same weight piston directly opposite each other - you have equal weight 180 degrees apart . If you move the same weight to the next firing point you have the weight at 60 degree intervals possibly creating an even worse balance problem than you had. In the perfect world - all your pistons and rods need to weigh the same to protect the engine from any balance induced stress. Eddie Franklin Cylinder Service
 
Thanks Eddie and Greg for your responses. The weight question is almost cured for me. I will be weighing all pistons and then looking for a piston to replace the lightest so I don't have to grind all the same-weight pistons down to the weight of the lightest. I will be contacting Greg when that is done, in hopes that he has what I need.
 
[quote I will be contacting Greg when that is done, in hopes that he has what I need.[/quote] Will be easier to match a piston if you have the other 5 there to compare. I would recommend boxing them up and sending them to Greg or I so they can all be matched up. You will be surprised at the differences in weight you will see.
The pistons also need to be checked for the same deck height. We have found pistons with as much as 30 thousandths difference in deck height. That is enough to vary the compression ratio by 1 to 1 1/2 points. Typically shop time takes about an hour to clean, check and balance a set of pistons. Greg and I are headed to Sun and Fun in a couple of weeks. Will not be back till the 23rd.
 
I found a good scale and weighed all pistons and c-rods and all weighed within 5 grams except for one that was 20 grams lighter. I would like to buy a piston that weighs 834 grams to match the others. Do you know of any?
 
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