I'm looking at some STOCK roller cams .....

Question #1

One is strange looking as the machine marks between the lobes are not smooth but cause those areas to be almost octagonal...almost crude looking.

Why??? was this an indication of ....what?? Or just the graveyard shift?

Question #2 (FOUND THE ANSWER JUST NOW BY MORE SEARCHING ON THIS ONE QUESTION)

Cam # 1 lift at the CAM is .275" / .284" and has the above tool marks. It has laser I.D. markings behind the front bearing journal of 773CPC.......any idea as to part number?? or whatzit?


Question #3

Cam # 2 looks like a roller cam should be machined .....lift at the CAM is .277"/ . 280" and has laser markings on the rear face of the back journal 1264

1 10

6330

POSSIBLY this is a Vortec cam from the mid 90's ???...any idea as to p/n or whazzit?? the lift figures dont exactly correspond to a stock Vortec cam that was discussed in the archives a few months ago.....but there might b more than one grind??

I'm trying to determine duration and l/c's without making a movie of this.

 

I can answer the first one. The cams blanks are index milled before they are ground to remove most of the material without eating OD grinding wheels like candy. The entire process is accomplished faster by machining first rather than grinding the entire way.

Each visible "step" is the machining that takes place on each pass. The mill machines a flat in the appropriate places and at the appropriate depth along the entire length of the cam blank. Then the blank is indexed (turned) a few degrees for another pass. The areas of the blank that will not become a lobe are not ground smooth, so that index-machined surface is the final finish.

As for you cam lift numbers, I can tell that they are NOT from any of the LT1 family. Could be a Vortec or later TPI.

 

you have confimed my thoughts re machining.......thanx.

I have found the answer to ?? #2.....its a L98 piece....1990-92

Still in the DARK re ? # 3...... anyone?????????

 

.412/.426 and .415/.420 net lifts could be a lot of possibilities, but it's low enough for the factory to use, and is a dual pattern as in the later factory grinds. Does there appear to be any wear at all?

The I.D. numbers don't help me a lot, since I don't have any kind of interchange/reference.

 

Possibility on Cam #1 if there is a little wear/production tolerance:


1990-92 TPI
305 G92 5spd / 350 AT 5000-5500 RPM Redline;
GM p/n 10111773;
.413" IN, .428" EX;
202°/207° Duration;
114.5 LSA (116/-116)

BTW - "CPC" is a GM designation for the "Chevrolet, Pontiac, Canada" production group, which would be consistent with a factory part (along with the indexed machining).

BTW - .275/.284 is a stock BBC grind. Is the cam a SBC piece? (22¼" long,