Balance question

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Balance question

Post  glenevans on February 20th 2014, 7:25 pm

I am thinking of changing my setup from a Dove-c headed 545 ( scat cast crank kit ) external balance with -22 probe pistons, to P-51 heads and FLAT TOP probe pistons. The flat top pistons are 25g heavier than the dish pistons. So, can the pistons be lightened this amount, or what would the best method of maintaining the balance be. I also have a roller cam and 1150 dominator to go with the new setup. Cam is from Blake, originally for Mike Eagy "Dirtworker" for his old P-51 heads. Thanks.

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Re: Balance question

Post  c.evans on February 20th 2014, 7:55 pm

You can weigh your pins also, because it is the total reciprocating weight that counts.  Let's say your current pins weigh 155 gms.  Then when you order your new pistons and pins, you can upgrade to a thinner wall, but better quality H-13 tool steel pin that weighs maybe 142 gms.  That will save you 13 gms there.
 
Then on your new pistons you can do some under head lightening, pin boss lightening and etc. and save yourself the another 7 -10 gms.  But a knowledgeable engine builder can find several areas in the total reciprocating weight, in order to lighten things up that 25 gms.  Just don't try to get it all in one place, and in fact you don't have to get exactly 25 gms. Some people run under-balanced and over-balanced engines.
 
Charlie

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Re: Balance question

Post  glenevans on February 20th 2014, 8:20 pm

Thanks for the ideas. The current pin from probe is 2.930 long, 0.990 diam., 151g weight w/dbl spiral locks. Who or where can I get lighter pins from, or would it be better (overall) to get a new rotating assembly. Originally I figured by the time I sent my pistons out to be re-notched for the p-51 heads, paid shipping two ways, I could get new flat tops for not that much more money. ha ha

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Re: Balance question

Post  glenevans on February 20th 2014, 8:44 pm

I found some H-11 pins that come in .130 wall 130g, or .120 wall 123g sizes. Are these close to the H-13 steel in strength? They (competition products ) didn't give a rpm or usage guide with the ad I saw.

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Re: Balance question

Post  c.evans on February 20th 2014, 9:46 pm

The place to get your lighter pins is from Mark at Probe when you order the pistons. The major piston manuacturers always have optional pins available.

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Re: Balance question

Post  glenevans on February 21st 2014, 12:48 am

Yes I see on probe's website they have optional pins. Thanks again for the info!!! Much appreciated.

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