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Old 12-13-2008, 07:40 PM
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Home-made cam doctor...

The builder of my short block didn't provide me a cam card (I should've withheld payment 'til I got it ). I have a cam degreeing kit from Comp. I assume there is a way to work up the typical cam card data with a degree wheel, a dial indicator and some technique... what is the technique?

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Old 12-14-2008, 02:33 PM
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http://www.compcams.com/Technical/In.../Files/145.pdf
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Old 12-14-2008, 05:06 PM
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Some Wooden V blocks and a dal indicator will get it done. Put the degree wheel on it of you wanna get IOEC.

There should be No. on the cam itself on the same end the Dist. gear is and a search or email to them Should get ya what you need.
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Old 12-14-2008, 08:00 PM
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that CC link is for degreeing the cam in the engine. anyone have info on how to degree on the bench?

thnx, jack vines
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Old 12-15-2008, 03:13 AM
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You're mixing terminologies. You degree a cam when it's in the block. You can't degree a cam on the bench. You're asking how to find the cam data concerning the particular lobe design. That is, to reverse engineer a cam.

It would be easier to read the model number on the cam, and call the manufacturer.

If it's some junky cam with no model number stamped in the distributor end, then just chuck it, and get a replacement with the specs you want.
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Old 12-15-2008, 05:20 AM
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Well yes, I am being a little loose with my terminology. I know the real Cam Doctor is a benchtop tool. What I meant was how would I go about working up the equivelant of a cam card with the cam in the block. The cam is a custom grind from Comp, according to the race motor shop that built my short block. The guy said he would send the cam card with the block, but he didn't. I had already paid him, so bugging him by phone to get the card didn't work.

This is more of a curiosity thing than anything else. I can degree the cam without the cam card info. I don't want to disassemble the motor just to get the cam number.
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Old 12-15-2008, 05:33 AM
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I'll try to find my post here on HR on how to do it.

I read up on it quite a bit. V-blocks, a dial indicator, degree wheel and some sort of homemade jig to be able to use a lifter on the lobe. The lifter is needed if you can visualize how the lobe makes contact on the lifter at changing points on the lifter face as the lobe turns. That can't be checked accurately without a lifter
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Old 12-15-2008, 05:43 AM
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Also, bear in mind that duration is a iffy term. Some cam companies measure duration at different "start-end" points...meaning "duration @ .030" lift or some other measurement.

Note in my pic that I used a flathead ford lifter. I did not have a early Olds lifter handy, and my readings were off a little, because the Ford lifter is a lot bigger diameter....and that really does affect the readings! All I was trying to do is find out if it was a solid or hyd, plus a rough idea on duration.

Lift can be checked without a lifter, but not duration or determining the size & duration of the "lash ramp" built into the cam lobe. That lift ramp determines hyd or solid, plus it tells what lash setting to use.
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Old 12-15-2008, 06:33 AM
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Some basic info on the reading:

Measuring lift at lobe gives a certain figure that you then multiply X the ratio of your given rocker. Example: .300 at lifter X 1.5 ratio rockers figures out to be .450 lift at valve.

Lash ramp: That is the area on the cam where the lifter begins to lift at a very slow rate of climb, to where it abrubtly changes to a much higher rate of climb.

A lash ramp for Hyd is a very "short" ramp...maybe 3-6 thou; were a solid cam would be say 6-15 thou. The lash ramp on a hyd is there to close the bleed valve, so it does not need to be very "high". The lash ramp on a solid is there to keep the lobe from "smacking" the lifter at the beginning of the lift.

When you get your doctor set up, all this can be seen quite easy.

Checking duration: You set the indicator to zero at the heel of the cam, then rotate the cam. When you see the indicator go to 30 thou lift, mark the degree wheel where your pointer is. Then rotate the cam all the way through the lobe until you get to 30 thou on the back side of the lobe and read the degrees. Now multiply the total degrees between the two 30 thou readings by 2. (cam travels at 1/2 that of the crank).


EDIT: The one question that was never answered on the race tech sites was "do you measure that 30 thou lift point at the valve, or the cam". I have no clue. You may want to get on a race site to ask that one question, because it would change the actual duration reading.

Last edited by F&J; 12-15-2008 at 06:54 AM.
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Old 12-15-2008, 09:16 AM
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To digger64 as to your assertion
Quote:
You're mixing terminologies. You degree a cam when it's in the block. You can't degree a cam on the bench.
Of course, one can "degree" (admittedly a loose term for determining the specifications) a cam on the bench. It is done every day in the cam R&D shops, however, they use several thousand dollars of equipment from Cam Doctor (now obsolete), Audie or Andrews to do it easily and quickly. To amplify, I was asking if anyone had come up with a shadetree method of using the standard degree wheel, a lathe or Vee-blocks and a dial indicator to get a reliable reading. So far, it seems the answer is no.

To F&J - EDIT:
Quote:
The one question that was never answered on the race tech sites was "do you measure that 30 thou lift point at the valve, or the cam". I have no clue. You may want to get on a race site to ask that one question, because it would change the actual duration reading.
Most cam specifications are given at .050" of lifter rise off the base circle of the cam. Ed Iskenderian told me he was the first to standardize this measurement back in the '60s.

thnx, jack
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Old 12-30-2008, 03:57 AM
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Hi

We're a small boutique cam company in Ann Arbor, MI.

We do prototype cams for OEM's and we did some race cams for some major pro teams in NHRA and NASCAR.

**************

Last edited by engineczar; 12-30-2008 at 05:34 AM. Reason: Advertising. Please see: commercial posting guidelines.
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Old 12-30-2008, 05:39 AM
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Hi NC cams and welcome to Hotrodders.com

Sorry about having to edit out your post but commercial advertising regardless of who, what, and where is not allowed. Your input from a technical perspective will be greatly appreciated.

Thanks for your expected cooperation.
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Old 12-30-2008, 06:56 AM
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Send the cam into one of several dozen camshaft grinders/manufacturers to get your cam measured, specs determined, and printed for you. Last time I had one done is was 20-25 bucks.
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Old 12-30-2008, 09:39 AM
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pursuant to comments made in prior posts, we among others would be happy to read the cam. I hope this offer does not violate the anti ad rules of the M/B.

BTW, there is a lot more to "reading a cam" than just checking lift and duration. Three are a lot of lobe issues that NONE Of the hot rod magazines mention when they discuss cams. THings such as base circle runout, bent, twist, wheel chatter, out of balance can show up in lobes - these are typically grinding problems.

IT takes a keen, trained eye to find and properly identify such cam lobe issues. LIke engineczar says, call a cam company and solicit proper/trained reading services.

WOuld you do a do it yourself removal of your apendix? Why do cam inspections with do it yourself hardware?
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Old 12-30-2008, 09:52 AM
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Great post NC

Home made setups might get you some rough numbers. ie cam lift and duration@.006 or .050 but both will probably be off by a few thou or a couple of degrees. Which may be fine if all you're looking for is a reference point but to get the super accurate numbers you have to go to a cam company.
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