Chevy 383 needs a small base circle? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 08-05-2005, 12:45 PM
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Chevy 383 needs a small base circle?

Hi all I am new to the forum and I need some advice. I am buiding a 383 stroker and have been told that it will need a small base circle cam. How small should it be? Most cam specs dont show the base circle size on the description from the mailorder companies. I am using eagle h-beam 5.7 rods that are supposed to have added stroker clearance. Someone please put this to rest for me so I can buy a cam!

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Old 08-05-2005, 01:40 PM
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If you use a regular cam you will need to mock up the assmebly and grind away some rod material if need be. Crane/comp cams sell all there cams in small base circle you just need to call them and ask for it. I doubt you will find them advertised in Jegs or Summit
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Old 08-05-2005, 03:56 PM
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A small base circle cam will cost more. Your valve train geometry will be wrong and you will have to get matching pushrods for your cam. And of course they cost more. For the small aggravation of grinding a rod bolt here and there. I would save my money. Take the bolts out to grind them or you will get filings in your motor.
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Old 08-05-2005, 08:06 PM
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I used a Lunati stock base circle for my 383 with the Eagle rods and crank. Didn't have any issues with the cam clearance but did have to grind some relief in a few areas around the block and cylinders, no big deal. Didn't have to grind any bolt heads either.
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Old 08-05-2005, 08:53 PM
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breall, depending on what combination I am putting together for a customer, I prefer to use a small base circle cam when necessary. I know this will stir controversy, but I'm not big on grinding on fasteners, especially one's that hold part of the rotating assembly. I'm well aware that many people have ground on their rod bolts and have had no problems. It's just a personal preference. If I am building something more than a stocker or very mild street engine, I use all new pushrods and always make sure the valve train geometry is correct. Since you are using con rods with cap screws instead of bolts, you should be fine. It will depend on the lift, duration and lobe sep. of the cam you are planning on using. I realize this is kind of vague, but the only way to be sure is to check.
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Old 08-06-2005, 12:14 AM
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Quote:
Originally Posted by topfuel
breall, depending on what combination I am putting together for a customer, I prefer to use a small base circle cam when necessary. I know this will stir controversy, but I'm not big on grinding on fasteners, especially one's that hold part of the rotating assembly. I'm well aware that many people have ground on their rod bolts and have had no problems. It's just a personal preference.
i'm like you, i don't see putting in high dollar rod bolts just to grind them off. we put a 406 together once & the machinist ground on two of the rod bolt heads, when we started torquing them down, we made it to 35 foot pounds on one of the rods that had the bolt ground when the top pulled off the bolt! their wasn't much removed from the bolt neither. i will always use a small base circle cam after seeing that.

you will just have to put your bottom end together to see if you have any clearance problems. as the push rods go, i've ran small base circle cams with .100" longer push rods. their not a high dollar item, & new push rods never hurt.
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Old 08-06-2005, 09:50 AM
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I don't really have an opinion either way here. A lot depends on the specific parts involved.

Here is what Comp Cams has to say about small base circle cams:

"We do not recommend using a small base circle cam with a cast flat tappet cam , as the casting is prone to breakage and catastrophic engine falilure is almost certain to occur."

tom
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Old 08-06-2005, 03:04 PM
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Thanks to all who replied. This place rules! I will be using a solid roller cam with about .555 in lift. I am going to try a normal base circle and see what happens. The rods are capscrews so I dont forsee any problems with grinding a little at the top of the radius. Ill let you guys know what happens. Thanks again!
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