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Old 04-14-2005, 07:07 PM
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Small base circle cams???

I was wondering, is it always mandatory to run a small base circle cam in a 383? Because every time i call Comp cams they tell me i have to get a custom grind with a small base circle.... Can i not just buy the right rods and do some clearancing? Its just that ive heard that the small base circles can make the cam alot weaker. Thanks for your thoughts.

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Old 04-14-2005, 08:29 PM
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Quote:
Originally Posted by Lthompson
I was wondering, is it always mandatory to run a small base circle cam in a 383? Because every time i call Comp cams they tell me i have to get a custom grind with a small base circle.... Can i not just buy the right rods and do some clearancing? Its just that ive heard that the small base circles can make the cam alot weaker. Thanks for your thoughts.

I'm building the same engine myself and was told that since I'm using 6.000 H-beam rods that I MUST use the small base circle. However, I have also been told by my cam builders that if I were using the 5.700 rods I MAY not have to use the smaller cam. They tell me that with the cam being a billet steel cam that it will be strong enough. I, like you, believe that it'd be weaker but if I'm not mistaken, the small base circle just makes the lobes closer to the spaces in the camshaft.
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Old 04-14-2005, 08:36 PM
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if you use a capscrew rod, like a crower you can order a stroker rod for your application that comes clearanced. also a sportsman rod is small enough you only have to remove half the top of the rod bolt on the cam side.
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Old 04-14-2005, 10:01 PM
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im using eagle 5.7's with cap screws i had to grind down the top part of the top half of the rod... only the part that goes inside closest to the cam.. i do not have a small base cam.. i have a crane with around .516 lift i belive.. also.. do NOT get your assembly balanced until AFTER you grind the rods down.. i made this mistake..
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Old 04-15-2005, 12:24 AM
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That is news to me, that you "must" run a small base circle cam with 6" H-beam rods. My cam is not a small base circle and I have 6" H-beam rods. Ran these same rods in two different strokers, one with a solid roller and this one with a solid flat tappet, never had rod to cam clearance issues.

It depends on the rods you use. The only way to know for sure is to measure and grind as needed.

Royce
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Old 04-15-2005, 02:59 AM
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Camaromans right it does depend on the rods you use. Since strokers have become so common most of the cap screw rods are designed to require little to no clearancing, but its always good to check. Even with the old eagle SIR rods I've used in countless engines I barely have issues. Eagle has just released a new h-beam rod that has been specifically CNC machined to clear big cam strokers. As far as balancing after you clearance, Its not really that critical as you are only removing a few grams and it doesnt alter the ballance enough to be concerned with. You can balance before or after it's fine either way.

Doc
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Old 04-15-2005, 08:00 AM
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I was planning on running the XE288HR cam with a 520/540 lift (which translates to a 347/360 at the lobe) and either scat or eagle H-beam rods, whichever one can give me the lightest H-beam. scat has a lighter weight H-beam with the same strength as regular ones. Ill be sure and get a clearanced version if i can. THanks for info.
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