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abides.
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Camshaft Base Circle - how low can you go?
Is there a suggested lower limit for camshaft base circle diameter?
I have read about the problems with valve adjusters when the base circle becomes too small, but when does that actually come into play? The reason I ask is because there is a local (and reputable) shop that can regrind cams for a whole lot less than I would spend at webcam for a new or hardwelded set.
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Graham 1984 Carrera Targa |
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10-14-2011, 04:01 PM
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Chain fence eating turbo
Join Date: Dec 2008
Location: Austin, TX
Posts: 9,141
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Contact "camgrinder"
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Cory - turbo'd '87 C3.2 Guards/Blk, 3.4, 7.5:1 CR, 993SS cams, Borg-Warner S366 turbo @ 1.2-1.5 bar, Treadstone full bay IC, 70mm TB, TiAL F46 WG, HKS 1 1/2" BOV, twin 044 pumps, MicroSquirt AMP'd w/GM smart coilpack, Bilstein coilovers, Tramont replica Speedlines (285's rr, 225's frt), Big Reds frt, 993 rr., tower brace, MOMO wheel |
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10-14-2011, 08:32 PM
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Platinum Member
Join Date: Jul 2001
Location: Leave the gun. Take the cannoli.
Posts: 21,097
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I've been burned a few times with the 'local shops' with simple stuff like wheel alignments & mounting tires..... just saying.....
It's alot easier to ship the cams to the expert than fix any problems later. |
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10-15-2011, 04:21 AM
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abides.
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Bump
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Graham 1984 Carrera Targa |
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10-18-2011, 08:02 AM
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Registered
Join Date: Oct 2003
Location: Central Fla
Posts: 1,864
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base circle
A rule of thumb when I set up custom valve lengths, adjust the valve lash and remove the rocker without changing the adjuster and look to see what you have for threads exposed, I shoot for 1/2 to 1 thread exposed on the backside of the rocker and that will apply to base circle size as well
Mike Bruns
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The two most useless things to a driver are the braking distance behind you and nine-tenths of a second ago. |
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10-18-2011, 02:48 PM
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Registered
Join Date: Jul 2000
Location: So. Calif.
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Don't fall for MM's contention they can grind an S cam profile on a T camshaft - there's not enough meat. The base circle will be too small and the valve/rocker geometry will be incorrect.
(in case you're conversing with them) Sherwood |
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10-18-2011, 05:41 PM
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PFM
Join Date: Dec 2009
Location: Southern California
Posts: 290
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GTC,
Not knowing the "local shop" I will share this from Speed Talk: Re: cam lobe design for radius pad rockers New postby CamKing » Fri Oct 21, 2011 11:50 am We've done plenty of these, and you can't use any lobe that was designed for a lifter the rides in a bore. When you have a rocker riding directly on the cam, you have to design the valve lift curve, and then work back thru the geometry of the rocker follower, to generate the lobe profile. With a cam that has a lifter riding in a bore, the lifter moves in a straight line, and you just need to design for the radius of the tappet face(or roller). With your type, you not only have the radius of the follower pad, but the arc of the centerline of that radius also.  Mike Jones Jones Cam Designs The cams in a lifter type motor is nothing like the Porsche OHC. Denver, NC jonescams@bellsouth.net camwave
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Stay Tuned, PFM |
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10-21-2011, 07:53 PM
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1984 Porsche Carrera Targa
