Correct Cam

[Walter R.]

I am completing the rebuild on 427/425 and am replacing the mechanical cam with a hydraulic replacement. Any suggestions on a compatible cam that would serve the purpose. For drivability would the replacement of the mechanical with a hydraulic be recommended.

[Duke W.]

Re: Correct Cam

Why aren't you using an OE replacement for the original mechanical lifter cam?

Duke

[Walter R.]

Re: Correct Cam

Suggestions on where I would get an OE replacment? NAPA or a specialty supplier that carries OE parts. What are your thoughts of going to the hydraulic cam.

[Joe R.]

Re: Correct Cam

Walter,

I've heard that if you go to a different type cam, you'll lose that sound. Why would you consider going hydraulic? I've heard that the GM solid lifters are obsolete. I've also heard from Duke and others that Federal Mogul (Sealed Power) and Crane are the manufacturers to use due to the Parkerizing process they use. I've also heard you should get new lifters from the same manufacturer with a new cam. Here's the info on the F-M cam:

Camshaft and lifter kit, part number KC-165R (includes (1) CS-165R (camshaft), (16) AT-992 (lifters), (1) 55-403B (assembly lube) $219.99

It's available from Carquest or NAPA.

Joe

[Duke W.]

Re: Correct Cam

What are your thoughts of going to the hydraulic cam.

As far as restoring an L-72, NO WAY! I've tried many difference cams in the L-72 using the Engine Analzyer V3.0 simulator and I have never found one that equals the OE cam's combination of torque bandwidth, top end power, valvetrain limiting speed, and civilized albeit somewhat "cammy" idle.

GM really did their homework on the lobe design and it is so good they used the L-72 lobe on the inlet side of the LT-1 SB cam.

As machined by GM the early closed chamber rectangular port heads have a restrictive exhaust port and can use more exhaust than inlet duration, but typical head massaging brings the E/I flow ratio to about 0.75 which is ideal for equal duration on both sides, so the OE L-72 cam, which uses the same lobe on both sides ends up being the ideal camshaft for a high performance road engine.

The only thing I recommend is installing it with some retard on strokers - about 4 degrees with a 4" stroke and six with a 4.25" stroke.

Duke

[Ridge K.]

Re: Correct Cam

I am completing the rebuild on 427/425 and am replacing the mechanical cam with a hydraulic replacement. Any suggestions on a compatible cam that would serve the purpose. For drivability would the replacement of the mechanical with a hydraulic be recommended.

Walter, I can't speak directly as to the 427/425 camshaft, but can tell you Chevrolet still stocks a 427/400 (L68) camshaft and hydraulic lifter kit over the dealership parts counter. It's a duplication of the original 390 and 400hp camshaft, now manufactured by Crane Cams.
For the 390/400 hp, it is currently, GM parts number 12364055, and lists for around $185, complete with lifters. Pretty good price.
I would suggest you talk to your local Chevy dealership parts sales persons. Give them your application, and see what they come up with. A search of the archives will display many, many favorable comments about Crane camshafts. Hope this helps.
Ridge.

[Joe R.]

Re: Correct Cam

Walter,

I should have mentioned that the part numbers I listed are for the solid lifter cam (GM part number 3863143). Also, the cam for 65 - 66 only has to have the groove ground in it for proper oiling. And the rear cam bearing must be the three hole design for 65 - 66 as well for the same reason.

I think you will lose power if you swap in a hydraulic cam. If you do you may want the matching oval port heads.

Joe

[Michael H.]

Re: Correct Cam

One more thing that no one has mentioned is that... if you still have the factory pistons with advertised 11.0-1 CR, you WILL have a lot more issues with detonation/pinging if you install a shorter duration hydraulic lifter cam. A shorter duration cam raises the effective compression ratio quite a bit.

Personally, I would definitely go with the correct original 143 solid lifter cam. Adjusting valves is NOT much of an issue with a big block with good valve train components. I've gone many thousands of miles in mine without having to mess with adjusting valves. (unlike most small blocks of the same era)

[Duke W.]

Re: Correct Cam

I've always been amazed by the number of guys who refuse mechanical lifter cams because of the "hassle" of adjusting valves. The same applies to point ignitions.

Not counting the time to R&I the valve covers, I can adjust the valves on a Chevy V8 in less than ten minutes if someone is reading the sequence to me and recording the data, and nothing more than basic hand tools are required.

Compare that to the three vehicles I own with shim over bucket DOHC valve trains, each of which requires a unique special tool to swap shims and a good supply of shims if you want to get the job done in one shot.

GM recommends a check of mechanical lifter lash every 12K miles for engines of the era, and given the annual mileage accumulation of typical vintage Corvettes this could be several years.

If the cam/valvetrain is in good condition with all OE equivalent parts, little change in lash should occur in this interval unless the engine spends a lot of time at high revs.

Maximum rev and power potential is only available with mechanical lifter cams, and it's always been my position that real Corvette engines have mechanical lifters. Back in the early sixties mechanical lifter 327s were unique to the Corvette and not available in the regular passenger car line.

Duke

[Walter R.]

Re: Correct Cam

Duke,
I just got around to reading your response and have been undecided about the Hyd./Mech. cam decision until now. I am convinced that the right way to go is with the mechanical cam and lifters and will go that route. Thank you and everone for the advice.
Walter

[Joe R.]

Re: Correct Cam

Walter,

This is a little off topic, but when rebuilding the L-72, make sure you use the second design valve springs. The first design was very prone to breakage. I can provide part numbers if you need them.

Joe

[Walter R.]

Re: Correct Cam

Thanks for advice. What is the part number?

[Joe R.]

Re: Correct Cam

Walter,

The part number for an engine set of valve springs is GM #12371061. It includes the valve spring, retainer, and seal. I hear it is still available from GM today.

Also, on the cam groove, it is the rear journal that must be grooved for 65-66.

Joe

[Walter R.]

Re: Correct Cam

Local NAPA could not locate SP part number KC-165R. My block is a 1972 427 so it does not require a groove on the rear journal. This could further complicate the matter when getting a correct cam. What are the specifications ( lift, duration) on the 66 cam. I might have to go this route as a 1966 427/425 cam would give me a cam with a grooved rear journal.

[Joe R.]

Re: Correct Cam

Walter,

Your local NAPA man might have better luck looking for Federal-Mogul PN
KC165R. I got mine from a local NAPA store no problema. Here's the NAPA web site:

http://www.napaonline.com/NOLPPSE/(S(ant54g453ufjw145lf5pkmzh))/Detail.aspx?R=KITKC165R_0184231555

It's also available from Summit Racing:

http://www.summitracing.com/parts/FEM-KC-165R/

The cam is not available with the groove in the rear journal. Most of us mere mortals have to hire a machinist to cut the groove for us.

Joe