If this is your first visit, be sure to
check out the FAQ by clicking the
link above. You must be an NCRS member
before you can post: click the Join NCRS link above to join. To start viewing messages,
select the forum that you want to visit from the selection below.
Is there a rhyme or reason to the numbering on distributor cams? I have several different distributors which have differnt cams. For example 732 CCW or 528 CCW, is the number descriptive? I assume CCW means counter clock wise.
The numbers indicate a diferent slot length in the slot where the advance pin fits, may also reflect positioning of the pivot pins for the advance weights. I know of no correlation, but I have slot measurements vs stamp numbers for some configurations if you need the info, post your number, and I'ss see ifit is one I have..
There were different distributor cam assemblies (consisting of the cam and weight plate) to provide different total centrifugal advance values, which is determined by the length of the curved slot. There may be some other slight differences, too, like weight retaining pin location or actual lobe geometry, but I'm not sure. If you measure the length of the slot on the two different part numbers you have, they are probably different. Corvette distributors in the sixties had total centrifugal advance of 24, 26, 28, and 30, and this list expanded in the emission era. The old GMPD P&A catalogs reference some distributor part numbers to cam part numbers. Also, Delco has (or HAD) master catalogs with parts breakdowns for major assemblies like distributors, starters, and alternators.
The geometry of the cam brazed to the top of the shaft also varies, and it has an impact on advance rate including non-linearity in the advance curve.
...not sure what CCW means. Distributors rotate clockwise on vintage Chevrolet V-8s unless they have gear drive camshafts, but the cam assembly moves CCW to advance the spark.
My hunch is that the digits are the last three numbers of the GM long part number, but for sixties and seventies vintage Corvette single point distributors the last three digits of the cam part number are 002, 686, 632, 492, 644, and 057
actually the clockwise or counter clockwise rotation of a mechanical device is determined from the drive end---thats why you see the ccw on the dist. parts---chevy dist. turns ccw from an engineering stand point---just my 2 cents,phil
Thanks for the info guys. The vacuum controls seem to have a number that designates how much advance the unit provides and I was hoping there was something on the cams. I've been learning alot about timing, vacuum levels, and carbs lately. I pulled the Duke no no and put in a cam that was a different spec than factory. So now I'm trying to work through the issues of not having enough vacuum to properly work the VC on the distributor. Given that there are not alot of parts readily available I'm trying to piece it together from what I have or what's available.
With that said I figured I'd tap into the experts and see if there was something to the number on the dist cams. Hopefully it would be benefical to others on the board. Thanks again.
Original and NOS Delco replacement VACs have the last three digits of the long GM part number and the maximum crankshaft advance stamped on the mounting bracket, but this doesn't tell you the vacuum level required to achieve maximum advance.
All replacement VACs including those sold under the "Delco" brand are made by Standard Motor Products, and they have a three character alphanumeric code stamped on the mounting bracket to identify their advance-vacuum characteristics.
There are a total of THREE that meet the needs of all pre-emission control OE Corvette engines, and if the installed camshaft has signficantly different idle vacuum than OE you use the "Two Inch Rule" to select a suitable VAC.
Searching the last 12 months archives should reveal everthing you need to know about this subject.
Duke ETAL, CCW is a distributor cam used in boats. Engine that run backward from our Corvettes so to speak. CCW is counter clock wise.
I just happen to have gotten stuck with a nice ebay NOS CCW cam. Been staring at the d thing for a number of year now. Here's some worthless trivia on that CCW. If I was in dire need of a cam I would have to disassemble that cam and flip the "plate" upside down-then flip the posts right side up-then reassemble the thing and then I would end up with a CW cam. Whew! JD
We use cookies to deliver our services, and to analyze site activity. We do not share or sell any personal information about our users. For additional details, refer to our Privacy Policy.
By clicking "I AGREE" below, you agree to our Privacy Policy and our personal data processing and cookie practices as described therein. You also acknowledge that this forum may be hosted outside your country and you consent to the collection, storage, and processing of your data in the country where this forum is hosted.
Tweet
Comment