396/425 Factory Cam Specs/Replacement P/N...Joe???

[James W.]

Joe,

Can you, Duke or Clem give me the correct GM factory cam specifications for a 1965 396/425 engine?

Is there a correct available GM replacement flat tappet, solid lifter cam that has the correct oiling groove that is present on an original cam?

Is there an aftermarket cam that would be a good replacement if a GM cam is not available?

The cam that was in the car when it was torn down is not the correct GM cam. I would like to put as close to the original cam as possible back into the car.

Thanks,

James West

[Joe L.]

Re: 396/425 Factory Cam Specs/Replacement P/N...Jo

James-----

Use a Crane #969961 with Crane #99250 lifters and I don't think that you or anyone else in the world will be able to tell the difference from original GM.

As far as the rear journal groove goes, I don't know if Crane still machines these cams for this feature, or not. It would be best to call them to check. However, you don't want to buy the cam directly from them unless they say the only way you can get it with the groove is to custom-order it. Buying direct from Crane will cost you full list price. Buying from a distributor like Summit will get you the cam at less than half of list price.

Also, if the current Crane unit does not have the groove, you can easily have a machine shop do that for you; no problem, at all, and likely not even very expensive.

[Clem Z.]

143 cam specs

all these specs are at .050 lift. 242/242 duration, intake 13/49, exhaust 61/1, lift .520/.520,lobe seperation 114 degrees

[Duke W.]

Re: 396/425 Factory Cam Specs/Replacement P/N...Jo

Federal Mogul Speed Pro also makes a replacement CS-165R, and you can cross this part on the NAPA web site for the Clevite (Dana Corp.) part.

I believe all these replacements do not have the rear groove, so they are really equivalent to the 3904362 that was used for '67-up SHP big blocks that have no groove, but the same lobe/indexing.

Be sure you have the groove machined if necessary and use the proper "three-hole" bearing, not the '67-up single hole bearing. Using the wrong cam and bearing in '65-'66 blocks has resulted in major engine damage due to lack of valve train oiling.

This subject was thoroughly discussed in a thread last year.

Duke

[James W.]

Re: 396/425 Factory Cam Specs/Replacement P/N...Jo

Joe, Clem and Duke,

Thanks so much for your input regarding the replacement cam and lifter recommendations. The machine shop was recommending a mechanical roller cam instead of the mechanical flat tappet cam. This was easily going to be another $300.00. I believe the roller would make more power, but since it is being built/restored to go through flight judging, I did not see that the extra expense was justified.

Best Regards,

James West

[Joe L.]

Re: 396/425 Factory Cam Specs/Replacement P/N...Jo

James-----

I agree with the machine shop on the benefits of the roller cam. However, the problem is that all of the available mechanical roller cams that I'm aware of are way too radical for a street engine. There is no off-the-shelf, roller equivalent of the 65-71 SHP big block camshaft.

[Duke W.]

Re: 396/425 Factory Cam Specs/Replacement P/N...Jo

The best way to restore a SHP big block is to follow the same basic pattern as with all other OE engines.

Pocket port and port match the heads and finish with multiangle valve seats and valves, and use the OE cam and '71-up dual valve springs. All this has been documented for over 30 years and extensively discussed on this Board.

The square port heads are very restrictive on the exhaust side (OE E/I ratio of about 0.60), and opening up the valve seat to accept a 1.88" valve will bring the E/I ratio to about 0.75 which is ideal for the single pattern OE cam.

It's often cheaper to replace the OE conn. rods with aftermarket replacements because they can often be had for the cost of Magnafluxing, replacing the bolts, and resizing the OE rods, which are "okay" but not bullet proof.

Spend the money on head work and quality OE replacement parts from Federal Mogul and Dana, not hot rod parts, and you will have the exact same broad torque bandwidth operational characteristics, driveability, and idle characteristics as OE, but more top end power and useable revs.

Typical replacement roller cams are hydraulic roller lifter type and usually have shorter duration than OE, but with more overlap. They may produce more peak torque, but will likely produce less low end torque and less top end power than the OE SHP cam, and they won't have the same idle characteristics. Mechanical roller lifter cams are strictly racing parts. Don't even think about going there!

These engines were very well engineered and produce excellent torque/power characteristics for a high performance road engine, and other than the head work to unlock more top end power, the later valvesprings, and maybe better rods they don't need any other "re-engineering". Don't let some local "engine builder" screw up a great engine. Unfortunately, may have.

Duke