Mystery Camshaft

[Patrick C.]

Re: Mystery Camshaft

As for the 3896929 cam, I just built a 1968 Chevelle 250hp 327 EI engine suffix. That engine is .030 over with about 9-1 compression. The heads were 1.72/1.50 and we used 1.85 intake valves and an edelbrock performer intake. Using the dyno sim software it showed right at 250hp at 4000 rpm and 375 lbs torque at 2500 rpm. Pretty much right on the factory numbers.

[Duke W.]

Re: Mystery Camshaft

There's no way a 327 will make over 450 lb-ft of gross peak torque. Typical chassis dyno numbers are high 260s to low 280s, a fairly narrow range because peak torque is primarily a function of displacement and compression ratio and those chassis dyno values equate to approximately 350 to 375 SAE gross with STP correction.

SHP engines typically make less peak torque than base engines, but the peaks are at higher revs.

Also, these 327s gross power was overrated by 10-15 percent and peak torque overrated by up to 5 percent.

After using a couple of simulation programs early on including Desktop Dyno, I settled on Engine Analyzer because it allows the simulation of SAE net at the flywheel with the engine in the same configuration as installed in the vehicle including exhaust backpressure. SAE gross on a lab dyno is a fantasy!

Check out this recent test of a Special 300 HP engine (massaged heads and McCagh Special camshaft). Note that even with about 11 percent more top end power than a Flint-built 327/300 (essentially the same as a Flint-built L-79) it still only made an estimated 287 gross HP, but peak torque exceeded the advertised gross peak.

I recently came upon a GM dyno test (SAE net at the flywheel) of the new Z06 DOHC 4-cam engine. Interestingly the Special 300 HP configuration above makes slightly more torque and power up until about 3500 RPM. Between 3500 and 3800 LS6 (about the same displacement) torque and power increase by a whopping 50 percent! You'd think it was turbocharged with lots of lag, but it's naturally aspirated, and it's probably going to feel soggy below about 4000 compared to the base C8 engine, even with its shorter gearing.

https://www.forums.ncrs.org/showthread.php?130027-Chassis-dyno-test-results-Special-300-HP-configuration-w-McCagh-Special-camshaft

Remember the old adage: people buy horsepower, but what they really like is torque.

Duke

[Patrick C.]

[Joe L.]

Re: Mystery Camshaft

I contacted Joe Lucia and asked him to look into this. He's out of town at the present time and away from his voluminous information sources, but he should be chiming in within a couple of weeks.

Duke

Duke------

The camshaft with a abbreviated casting number of 2944 was, indeed, a small block camshaft of GM complete casting number 6262944. The part number for the finished camshaft, including dowel pin, was GM #340284 as has been reported. This camshaft was released in late 1971. It has specs very similar to the base 327/350 camshaft of abbreviated casting number 6930 and complete casting number of 3896930. The GM part number for the finished camshaft, including dowel pin, was GM #3896929.

I cannot find any information that the 340284 camshaft was ever used for any Corvette application although it's possible it was used for 1971 or 1972 L-48. I can say, for certain, that the 340284 was never catalogued by GM for SERVICE for ANY Corvette application. The GM #340284 and its predecessor part number 3998962 were used for many 1971 and later light truck and marine applications with 350 cid engines.

I believe that all 1967 through 1981 Corvettes (except 1980 with 305 CID engine) with base engine or L-48 were equipped with the GM #3896929 camshaft.

[Duke W.]

Re: Mystery Camshaft

Duke------

The camshaft with a abbreviated casting number of 2944 was, indeed, a small block camshaft of GM complete casting number 6262944. The part number for the finished camshaft, including dowel pin, was GM #340284 as has been reported. This camshaft was released in late 1971. It has specs very similar to the base 327/350 camshaft of abbreviated casting number 6930 and complete casting number of 3896930. The GM part number for the finished camshaft, including dowel pin, was GM #3896929.

I cannot find any information that the 340284 camshaft was ever used for any Corvette application although it's possible it was used for 1971 or 1972 L-48. I can say, for certain, that the 340284 was never catalogued by GM for SERVICE for ANY Corvette application. The GM #340284 and its predecessor part number 3998962 were used for many 1971 and later light truck and marine applications with 350 cid engines.

I believe that all 1967 through 1981 Corvettes (except 1980 with 305 CID engine) with base engine or L-48 were equipped with the GM #3896929 camshaft.

Don't you mean 327/300?

Duke

[Joe L.]

Re: Mystery Camshaft

Don't you mean 327/300?

Duke

Duke-------


Yes, the 3896929 was used for 1967-68 327/300 (base engine for Corvettes) as well as base 350 cid engine (or, L-48) for 1969-81 Corvettes.

[Joe L.]

Re: Mystery Camshaft

Don't you mean 327/300?

Duke

Duke------

I see what you mean now. By "327/350" I was not referring to 327 cubic inch, 350 horsepower. I just meant Corvette base engines of 327 or 350 cubic inches. While 1967-68 base 327 engines were 300 horsepower and 69-70 base 350 engines were also 300 horsepower, after 1970 the base 350 cid engines were of varying horsepower ratings.

[Scott R.]

Re: Mystery Camshaft

Patrick, I have a mystery one too, rear face has E095P stamped, front between distributor drive gear and first lobe raised cast EP2 and green paint dab,beween 12th and 13th lobes raised cast C1 and D1, aslo after fuel pump lobe , depression cast F5 and 8 with white paint dab. the cam has no signs of wear, lobes are black. Anyone know what this is ? Scott

[Duke W.]

Re: Mystery Camshaft

Patrick, I have a mystery one too, rear face has E095P stamped, front between distributor drive gear and first lobe raised cast EP2 and green paint dab,beween 12th and 13th lobes raised cast C1 and D1, aslo after fuel pump lobe , depression cast F5 and 8 with white paint dab. the cam has no signs of wear, lobes are black. Anyone know what this is ? Scott

It's probably an aftermarket cam. Does the casting have "CWC" embedded? A Parkerized cam has a dark gray mottled finish except the journals which are silver because the Parkerizing is polished off.

If the lobes are still the same color as none contact areas, then it's probably never been run in an engine.

Duke