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Shaving pistons

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fattyboy

Active Member
Hi everybody,Merry Christmas. Back to the 113,got pistons the ones that replace the old ones are screamin eagel pop ups,I have to shave them down to make them flat tops,Does anybody no if iam going to have problums or should it be ok? Thanks.
 
I would think that is a highly engineered area of the piston to gain maximum power from combustion chamber. Are you saying you are just going to shave piston top or are you doing some type of measured machining process? Why not just get the proper pistons for your application....
 
This should be done only when you do not have piston to valve clearance, have you done a clay build up to check clearances? This can also weaken the piston, you may want to order the correct pistons or rethink your build for thicker gaskets or another way around compromising the pistons JMO
 
I have to shave the pistons for valve clearance, and i already have them and their new dont have the money to buy another set,and these are for the bigger bore cyls. that i had to take 10 over.
 
fattyboy said:
I have to shave the pistons for valve clearance, and i already have them and their new dont have the money to buy another set,and these are for the bigger bore cyls. that i had to take 10 over.
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Depending on how much clearance you will need, you may try thicker base and head gaskets then do a clay mock up to check your clearances you may need to get a longer intake manifold to make up the difference,. this will also change your compression ratio
 
fattyboy said:
I have to shave the pistons for valve clearance, and i already have them and their new dont have the money to buy another set,and these are for the bigger bore cyls. that i had to take 10 over.
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I am by no means a expert but should there not be a concern about just shaving piston. Like Jack suggested, what are you compromising by doing this when you have expensive in performing upgrade in the first place. Is a speed shop going to shave and balance pistons so not to create a soft spot in piston head and vibration do to unbalanced. And how mush is the cost if pistons are not shaved properly and causes engine failure or some other damage. It might be best to figure out a way to get the proper pistons for your upgrade so that you can have a solid and reliable build....
Best of luck.....
 
fattyboy said:
I have to shave the pistons for valve clearance, and i already have them and their new dont have the money to buy another set,and these are for the bigger bore cyls. that i had to take 10 over.
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dangerdan said:
Check out this site. It might help.

NRHS - High Performance for your Harley Twin Cam, Evolution, Sportster or Buell!
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Boy that's an excellent article Dangerdan, and explains what Jack was saying. Fattyboy who was it that told you that you had to shave the pistons ? I would think "they" would be the ones to ask the question of how much to shave.

Back many many years ago when us teenage guys used to rebuild car engines in sheds out back, we always bought pistons of a desired compression ratio from manufacturers that specified what engines they would work in. Even the cams (if they were high enough lift) were specified what OEM scenarios they would (or would not) work in. So I remember if you bought higher compression pistons and a cam both, you had to either order them both from the same manufacture OR do as Jack said and "carefully" check the clearance.

Remember if you are going in blind, you need to turn it by hand "slow" or you could still damage your valve train even with the clay if you turn it too fast or hard and you haven't shaved enough. Probably you would just bend the pushrod a little. Leave the spark plugs out, that way you can turn it easy with a normal socket.
 
You need to check with the manufactor of piston. Yes you can clearance the valve notches some. But...only so much or will create a weak spot in piston.
wilks3
:USA
 
wilks3 said:
You need to check with the manufactor of piston. Yes you can clearance the valve notches some. But...only so much or will create a weak spot in piston.
wilks3
:USA
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Yes you can if you know the material and have a good milling machine, guess that is why most good pistons are already fly cut for valve relief JMO Pistons must match combustion chambers for correct squish and compression ratio
 
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