"S" cam part numbers

[Mark McClure]

Hi,

What is the part number for the "S" cams for a 3.0lt SC. Also what are the specs for this?

Cheers

Mark.....

[jluetjen]

The "S" cams that everyone always talks about were manufactured between 1967 when the early S was introduced and 1973 when the 2.4 liter S was discontinued. There was also an S cam which was not discussed a whole lot that was used on the CIS 2.7 liter motors. That cam was slightly less "mild" then the normal 2.7 CIS cam, but a mere shadow of the earlier S cam when it comes to performance. I don't think that this cam will give you any benefits over the normal SC cam.

In order to use the "Early S" cam in an SC, you'll need to rebuild the motor with new pistons (to prevent a spatial event between the valves and the pistons), carbs or MFI as well as potentially some porting work.

Here is what I have for part number for the '69, 70 and 71 S cams:

Left: 901-105-16700
Right: 901-105-16800


Here are the spec's that I have available for the "Early S" cams.

Intake: 267 deg of duration (@ 1mm of lift), .459 inches of lift
Exhaust: 235 deg of duration (@ 1mm of lift), .450 inches of lift.

When set to the factory specs, the valves had the following events:

I opens: 38 degrees BTC
I closes: 50 degrees ABC
E opens: 40 degrees BBC
E closes: 20 degrees ATC

[Mark McClure]

John,

Thanks for the detailed information. So to avoid major work the S cam is not the thing to do! In the engine now the cam is stamped as 930-105-148-08 and 930-105-148-08. Are these the standard SC cams? and do you have the specs. How do these compare with the likes of Crane cames

Thanks for your help and advice.

Cheers

Mark.....

[Early_S_Man]

Actually, there aren't any true factory 'S' cams that would fit the SC engine with the larger 49 mm journals for the 4-bearing cam towers! All 'true' high-revving 'S' cams used the smaller 46 mm journals. Web-Cam, Elgin, and others can provide 'S' cam grinds on the larger blanks, or regrind your cores to 'S' specs.

[Mark McClure]

Thanks,

A regrind has me wondering......if the lift is higher then the lobe has to be raised/hightened......how is this achieved. If an addition is made to the lobe then what material do they use and how reliable is it.

Also if they do regrind do they restamp the cams?

Cheers

Mark.......

[CamB]

I don't know the answer to your questions - sorry - but I was wondering if you had made any progress getting the engine to run right?

Warren - I didn't know that was the case - now some of the stuff the guy who sold/installed my cams told me makes sense (about them being "new" when they were first installed a few years ago).

Cam

[Mark McClure]

Cam,

The things runs great......but is still down on power and runs slightly hot. Since the compression test is 145/150 on all six it looks like it is running 8.5:1 compression, with standard cams and pistons. This is from a claimed 240hp engine.

I now have the dilema of ;

1. leaving it alone and being happy wit it as is
2. Putting together some internals (cams, maybe 3.2 P&C'S)
3. Selling the lump and putting a 3.6 in it.

Since it is my daily driver then option 2 means time of the road. Option 3 will cost even more and time of the road. Option 3 is the best in the long run but also the most costly. To be honest I would be better of selling the whole thing. Maybe that is option 4.

Ah well at least I have these options......some people only dream of owning one of these things!

Cheers

Mark......

[HawgRyder]

Mark:
When your cam is reground....the grinder has to reduce the lobe circle (round - back side of the lobe) to gain some room for the regrind.
If you look at a lobe from the side it looks like an egg (sort of)...now imagine the bottom (large end) of the egg bring a smaller radius...this means the top of the egg (lobe) suddenly gets a lot more lift.
Now...if you shave the top to get back to roughly the same lift....you have an egg (lobe) with a big flat top (duration)...now shape the sides to blend into the top...and there you have it....more lift (maybe)...more duration...and if you ground it slightly off-centre....the start and finish of the lobe are different (intake and exhaust - overlap).
Now students....don't try this at home....rely on your good friend the machinist!! LOL
Bob

[TimT]

If an addition is made to the lobe then what material do they use and how reliable is it.

Some of the less reputable cam grinders will just grind a new profile onto your cam.. this leaves a smaller lobe center, and plays havoc with your rocker ratio...

The people that do cams right will weld the lobes of your cams then grind them to your specs (or mimic proven specs) while maintaining the proper lobe centers.... The alloys used to weld the cams are similar to those used to hard face cutting equipment. They are more than up to the task of cam reprofiling

Also if they do regrind do they restamp the cams?


Yes the cams are marked ( Ill qualify this by saying the reputable cam grinders mark there product)