cam ID

[Adam H.]

I just found a lobe rounded off in my 69. I'm going to get a new one, but I wonder if the cam I have is original. The only numbers I can find are 6964, which is between #7 exhaust lobe and the third bearing, gm 24 on the opposite sid of the bearing, 24 on the bottom of that and J22 (casting date?) between #3 intake and the second bearing. Any ideas if this is the original cam? My car is a 350/350. Thanks for your help.

[Duke W.]

Re: cam ID

That's a GM 3996964 finished camshaft, which was sold over the counter as an "assembly" of camshaft and indexing pin, part no. 3996962.

It is the OE camshaft assembly for the L-46/82 engine options.

I'm surprised that a vintage cam would wipe a lobe, but verify that you have the correct 3911068 or equivalent (like Sealed Power VS677) valve springs.

Also, you should be using CJ-4 or CI-4 oil.

I have a Speed Pro cross reference for this camshaft - CS-1045R - but it may be discontinued. I believe the Clevite 229-1615 is also manufactured to the ...964 GM print. GMPP might also still sell a ...962 cam/lifter kit, but with the demise of Crane, who was the supplier... Sourcing OE vintage camshafts is becoming a problem!

Do your due diligence and verify that the basic specs are equivalent to OE: .050" lifter rise duration 224/224, IPOML 114 ATDC, EPOML 114 BTDC, LSA 114, I/E lobe lift .30000/.30667". (Despite the same .050" duration the inlet and exhaust lobes are different as evidenced by the different max lobe lift.)

If you can't verify the valve springs, just buy a new set of VS677. They only cost about a buck apiece. These same valvesprings were used on most small blocks from '67 to well into the seventies including your grandmother's 2-bbl. 283 and LT-1s.

With careful spring height setup the ...946 cam/OE valvetrain will go to 6500, but without some head work a L-46 will be wheezing before it gets there.

"GM24" is likely the tooling set number. "J22" could be a date code, but it doesn't seem to jibe with the '69 model year. The camshaft was OE from 1969 to 1970 (L-46) and '73-'79 (L-82).

It's an excellent cam for a high compression 3.48-3.75" stroke SB, but not so good for the low compression L-82. Though the lobes are different in detail from the L-79 lobe, it is essentially a L-79 cam retarded four degrees, or if the ...962 is advanced four degrees from OE indexing, it's essentially a L-79 cam.

Some specs might list the .050" lifter rise duration as 222 (same as the L-79), but my analysis of the lobe data from the GM drawing, rounded to the nearest degree, is 224 deg. @ .050" lifter rise.

Duke

[Adam H.]

Re: cam ID

So it is the original grind cam? If I'm not mistaken, the L-46 is the 350/350. would the date code read J(october) 22(twenty-second) or J(october) 2 (second) 2 (1972)? my car is a december 68 car, so if it is october 22, would that work? I have a GM replacement cam from my local Chevy dealer I just picked up. I got new lifters with it, but I want to know more about the oil you mentioned. I've talked to a few people about it and they say most oils no longer have zinc in them to protect the cam, and that a lot of people are having this problem. Should I return the cam and get a roller cam that has close to the same grind?

I verified the lift, but I do not have the tools to verify the duration. I have right at about .300 lift on the lobes that are not rounded.

[Duke W.]

Re: cam ID

Yes, it appears to be the correct OE type cam for you engine. Date codes usually include the month, day, and year, so my best guess is that it means September 2, 1972 or 1982 or possibly even 1992. ("I" is usually skipped in the month code.) So it is likely a replacement part, but the same as installed when the engine was built at Flint.

Unless someone knows specfically how cam date codes are organized... There is some variation in date code algorithms depending on the part.

You should have the Summer 2008 Corvette Restorer. There is a feature article on oil for vintage Corvettes that should answer all your oil questions, and there are many threads in the archives.

If you provide the part number for what you bought from the dealer, I or others can verify if it's the correct OE replacement cam.

Duke