Grooved Cam for 65-66 425hp Big Block

[Patrick B.]

Re: Grooved Cam for 65-66 425hp Big Block

I will check the box again when I go to my garage (17 miles from home) next. I noticed it said "printed in USA", but the only American thing about it might have been the box.

[Duke W.]

Re: Grooved Cam for 65-66 425hp Big Block

Maybe some of the engine design specialists on our panel can explain the effect of cam lobe width. My point was that the CS-165R cam was changed from the GM spec in the direction of higher lifter contact pressure, adding to concerns about break-in and oil additives that are much discussed here.

...not an easy calculation to make. It is assumed that hydrodynamic lubrication occurs between the lobe and lifter, which means there is no metal to metal contact, but from a practical standpoint there are periods of boundary lubrication such as cranking and too low idle speed, which is where engine oil anti-wear additives come into play. The higher the relative velocity, the more likely lubrication is hydrodynamic, so cranking and excess idling represent the worst potential conditions.

Overall friction loss in the valve train is not as high as some may think because most of the energy that goes into compressing the springs is returned on the downside - at least at low speed, but there is some loss (called hysterisis), and it grows exponentially with engine speed.

That's why at sustained high revs valve springs can generate a lot of heat and good oil flow to the valve springs is important for cooling.

Duke

[Clem Z.]

Re: Grooved Cam for 65-66 425hp Big Block

when we ran mushroom tappet camshafts in NASCAR SBC engines the lobes were only .375 wide and we ran springs a lot stiffer than stock SBC and we never has a wear problem in 500 mile races at 7000+ RPMs

[Christopher A.]

Re: Grooved Cam for 65-66 425hp Big Block

If i remember correctly, the oil stopped at the cam and did not proceed to the cam journals/bearings or to the valvetrain. I had plenty of assembly lubricant on the lobes and cam journals, so everything was ok, but I only ran it for under a minute or right around a minute max. Any more and i am sure i would have experienced major issues.

[Richard F.]

Re: Grooved Cam for 65-66 425hp Big Block

I just miked the lobes on a 3928911 L-88 cam and a Crane version of the same I bought when Crane was apparently leaving us forever, and both of them have lobes about .595-.600. The 911 is still in its tube and the Crane is still in its box.

[Joe R.]

Re: Grooved Cam for 65-66 425hp Big Block

I'm starting to finally get serious about putting my engine together. I bought the TRW TP-165 cam from Pat. Pat, I hope I don't hurt your feelings by making sure this is the real McCoy. I thought I would compare the specs posted on the box to the original. Here's what Clem said they were in another thread:

GM 3863143: lobe separation 114 degrees, all following specs are in degrees at .050 " lift, duration 242 intake / 242 exhaust, Intake Opens 13, Intake Closes 49, Exhaust Opens 61, Exhaust Closes 1, lift .520 " intake / .520 " exhaust

The photo shows what's on the box. Do you all think it's the right cam for a L72? These cam specs are always confusing to me! If it's the right one, can I assume that I can buy lifters from Sealed Power and that will work just fine with it?

Joe

[Duke W.]

Re: Grooved Cam for 65-66 425hp Big Block

If you add 180 to the .050" timing points you get 242 on both sides, which is the correct answer as is the 108 IPOML and 114 LSA.

You can also measured the heel to toe dimension. which is the sum of base circle diamter and gross lobe height. Both sides use the same lobe.

1.27914 + 0.30572 = 1.58486" nominal, and figure up to about two thou tolerance on a new lobe.

I believe the F-M lifter is AT840R, but verify on the NAPA online catalog. This is the big block OE type "piddle valve" lifter. It also has to be used in small blocks because I don't know of any sources for the OE SB "edge orifice" type lifters.

Duke

[Bill W.]

Re: Grooved Cam for 65-66 425hp Big Block

Ok Joe we know what cams were service replacements and for what engines. we also know the specs. for these replacement cams. My question is , Do we know the part or cast number that the original "396" was built with??? Also the 425/450 hp 427 66 ?? If so how would we find the original specs. for these two overlooked monsters. I was always told that the 396 had more HP and was faster than the 427 . Clem can maybe answer this he has owned both ..
I have what I think is the original cam from 396 #16120 . The only stamps is an X on the rear It has a "GM3" cast in the lobes and "3144" cast between the lobes. Any help???? Bill

[Joe L.]

Re: Grooved Cam for 65-66 425hp Big Block

Ok Joe we know what cams were service replacements and for what engines. we also know the specs. for these replacement cams. My question is , Do we know the part or cast number that the original "396" was built with??? Also the 425/450 hp 427 66 ?? If so how would we find the original specs. for these two overlooked monsters. I was always told that the 396 had more HP and was faster than the 427 . Clem can maybe answer this he has owned both ..
I have what I think is the original cam from 396 #16120 . The only stamps is an X on the rear It has a "GM3" cast in the lobes and "3144" cast between the lobes. Any help???? Bill

Bill-----

1965 L-78 and 1966 L-72 used exactly the same camshaft assembly (cam + dowel pin), the GM #3863143. This camshaft assembly was identified by casting number 3863144 or, just, 3144, as in your case. They usually also have casting symbol "OMO" between the lobes.

[Clem Z.]

Re: Grooved Cam for 65-66 425hp Big Block

Ok Joe we know what cams were service replacements and for what engines. we also know the specs. for these replacement cams. My question is , Do we know the part or cast number that the original "396" was built with??? Also the 425/450 hp 427 66 ?? If so how would we find the original specs. for these two overlooked monsters. I was always told that the 396 had more HP and was faster than the 427 . Clem can maybe answer this he has owned both ..
I have what I think is the original cam from 396 #16120 . The only stamps is an X on the rear It has a "GM3" cast in the lobes and "3144" cast between the lobes. Any help???? Bill

the 65 396 corvette was quicker because it had a 15# flywheel vs a 30# one in the 427. the flywheel is still in the performance parts book but i would not use it unless you have a 3.70 or deeper rear gear.