C1 1958 base cam spec

[Al C.]

Does anyone have specifications for the cam (Lobe Profile, Intake Center Line, Lobe Separation Angle, ???) for the base cam used in the 1958 245hp engine?
What are the best current sources for a stock-type cam?

thanks, ... Al '58 245hp

[Clem Z.]

Re: C1 1958 base cam spec

the listed GM specs cam # 3733431 hyd,IO 12.30 BTC,IC 57.30 ABC, EO 54.30 BBC, EC 15.30 ATC,.398 lift both in and ex. speed pro lists several cams that are close

[Al C.]

Re: C1 1958 base cam spec - Thanks Clem *NM*

[Duke W.]

Re: C1 1958 base cam spec - Thanks Clem

Chevrolet cam specs are quoted in a unique context that are not comparable to most current aftermarket cam specs. Specs without context are worse that no specs at all because you could end up with something completely different.

The 3733431 was used in base and optional medium performance SBs up through 1966. The base engine cam was changed for 1967 and this 3896929 cam also became the service replacement for the 3733431. The 929 cam is generally referred to as the "300 HP cam", and it continued as the base 350 CID cam up to 1980.

Basic specs for the 929 are 196*/202* duration at .050" lifter rise, 108/116 centerlines, .390/.410" gross lift.

It will provide the same idle and torque characteristics as the 431.

Duke

[Al C.]

Re: C1 1958 base cam spec

Duke - I appreciate the further info.
Is the 108 the "intake center line"? Is the 116 the lobe separation angle? From Clem's numbers I calculate the older cam at 112.5 and 111 (x2?). I assume that the extra 11 mils of valve lift is OK with the standard springs?
If you were buying such a cam, where and under what part number would you go for a high quality replica? Same question for lifters (hydraulic) and pushrods - or do you advise a matched valvetrain set from one source?
Regards, ... Al '58 245hp

[Duke W.]

Re: C1 1958 base cam spec

The "lobe center angle", assuming the lobes are symmetrical, is the arithmetic average of the inlet and exhaust "centerlines", so (116+108)2 = 112. Some cams, particularly the later SHP cams like the 30-30, L-72, and LT-1 cams have asymmmetrical lobes, so the actual centerlines are offset from the points of maxiumum lift by two to six degrees. The 929 cam lobes are very close to symmmetrical with less than two degrees of asymmetry.

On the surface this seems like a fairly narrow lobe separation angle, lower than some SHP cams, but since the durations are fairly short, actual effective valve overlap is very low, which is why this cam will pull 18" manifold vacuum at 5-600 RPM and idle butter smooth.

Chevrolet also changed the valve spring circa 1967, and the "newer" spring has just a bit more rate, so I would suggest you use the later SB valve springs, though the early type are still available. The later spring OE part number ends with "068", and they should be widely available in the aftermarket. Just specify a 1967 or later SB.

Since the 929 cam was installed in literally millions of SBCs, it is available from most quality aftermarket manufacturers, like Federal Mogul. I don't have a part number, but check with a FM dealer and ask him to look up the cam for your engine, a '67 300 HP, and a seventies L-48. They should all be the same part number - a 929 clone.

Duke

[Clem Z.]

Re: C1 1958 base cam spec - Thanks Clem

speed pro # CS1103R,194/202 DUR @.050,.398/.420 lift,112 lobe CL

[Al C.]

Re: C1 1958 base cam spec - Thanks both *NM*