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Old 03-26-2012, 01:53 PM   #16
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Default Re: Big base circle vs small base circle cams

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Old 03-26-2012, 05:21 PM   #17
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Default Re: Big base circle vs small base circle cams

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If done right, the lifter motion per degree will be identical.

Side loading will increase.
Wheel RPM will decrease.
If you had to go to a smaller barrel diameter on the cam core, cam flex will increase.

Thanks guys, pretty much what the cam grinder said just clearance issues with the alum rods forced this situation.
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Old 03-26-2012, 07:14 PM   #18
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Default Re: Big base circle vs small base circle cams

When we use a .900 or smaller base circle we add 2-3degrees at 050 and .030-040 lift at valve.Bill C.
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Old 03-27-2012, 02:43 AM   #19
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Default Re: Big base circle vs small base circle cams

agree with post # 18.....also to help minimise twist and flex use a legitimate 8620 ot 9310 core....!!!!!!!!

not some cheap flame hardened pos....
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Old 03-27-2012, 09:18 AM   #20
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Default Re: Big base circle vs small base circle cams

I will go to a .904 lifter with small base circle cams. Just about everything I build now uses a .904 lifter.
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Old 03-27-2012, 02:50 PM   #21
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Default Re: Big base circle vs small base circle cams

Thanks for the core mat'l info.
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Old 03-27-2012, 02:56 PM   #22
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Default Re: Big base circle vs small base circle cams

Would there be any advantage to running a 55mm cam core, with a small base circle other than for cam to rod clearance?
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Old 03-27-2012, 03:50 PM   #23
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Default Re: Big base circle vs small base circle cams

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agree with post # 18.....also to help minimise twist and flex use a legitimate 8620 ot 9310 core....!!!!!!!!

not some cheap flame hardened pos....
The 8660 Quench and Tempered cores have a much deeper heat treat then the 8620 or 9310 cores.

The ones you want to stay away from are the 1050 steel cores.
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Old 03-27-2012, 07:35 PM   #24
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Default Re: Big base circle vs small base circle cams

We often use #5160 material for small base circle cams ,believe it is a little brittle but less likely to twist and bend,maybe Mike Jones has info on 5160./Bill C.
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Old 03-27-2012, 08:57 PM   #25
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Default Re: Big base circle vs small base circle cams

How do you identify these different cam cores?? Or do you just ask at time of manufacture,and hope that cam grinder gives you the good stuff....
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Old 03-27-2012, 09:12 PM   #26
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Default Re: Big base circle vs small base circle cams

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We often use #5160 material for small base circle cams ,believe it is a little brittle but less likely to twist and bend,maybe Mike Jones has info on 5160./Bill C.
Too brittle and they break... I've had small base break on the rear lobe.... never caused damage due to it being the rear lobe thankfully, but isn't there a maximum you want to see in the core, which will be different than the maximum hardness you see on the lobes?
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Old 03-27-2012, 09:21 PM   #27
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Default Re: Big base circle vs small base circle cams

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How do you identify these different cam cores?? Or do you just ask at time of manufacture,and hope that cam grinder gives you the good stuff....
X2. Also is Cryo treating a cam a good idea?
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Old 03-28-2012, 03:32 AM   #28
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Default Re: Big base circle vs small base circle cams

flame hardened stuff usually is NFG.... for this application / lobe / base circle...

it does not help very much to have the larger 55 mm bearing if the base circle is still .900"

this was done back in the 1970's...and there needs to be space or undercut in between the lobes to clear lifter on other side/ bank of block....

HUMM...
.........afterall,
......................this is why there are raised cam blocks to begin with.....!!!!!
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Old 03-28-2012, 11:01 AM   #29
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Default Re: Big base circle vs small base circle cams

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maybe Mike Jones has info on 5160.
Haven't used it in years. They had a bad habit of breaking. Back in the 90's, Scott Bloomquist was running away with a $50K to win Dirt Late Model race, when my cam broke right before the dist gear. That's when I stopped using those cores.
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Old 03-28-2012, 11:02 AM   #30
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Default Re: Big base circle vs small base circle cams

When we use a smaller base circle lobe...we wish we had a bigger one the whole time we run it ;(
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