Joe Lucia& Duke Williams Re 340 HP Cam

[Len Rayca]

Hi Guys: I am having my '63 340 HP SB rebuilt to original specs. and would like your help in recommending what camshaft I should have installed. Is the original GM cam still available? If not what cam is suitable for replacing the original solid lifter cam? Any sdvice from you valued experts will be greatly
appreciated. Len #39247

[Duke W.]

Re: Joe Lucia& Duke Williams Re 340 HP Cam

The "Duntov" cam (3736097)that was OE on the 340 HP engine is still available in reproduction from the aftermarket, but I highly recommend the LT-1 cam to replace ALL OE mechanical lifter SB cams, including both the Duntov and 30-30.

The LT-1 cam (3972178) is the result of over 15 years or research by Chevrolet on high performance camshafts. It has some very unique features including a long duration early phased exhaust event and very soft action on closing that produces better torque bandwidth than any other mechanical lifter cam while being very easy on the valve train. It's idle characteristics will be very similar to the Duntov. This cam will work fine with pressed in studs and the standard small block valvesprings that were used in all other small blocks along with generic OEM type pushrods and rocker arms. Pushrod guide plates and hardened rockers are not necessary.

A LT-1 cam and lifter kit is available from GMPP and it is also available from Federal Mogul Speed pro - CS1145R. Use with the AT840R lifter, which is the edge orifice type used OE with the Duntov and LT-1 cam. I don't have a part number for the GMPP kit and don't know the type of lifter supplied - edge orifice or piddle valve.

E-mail me if you want the document on how to properly set the lash on this cam.

Duke

[Joe L.]

Re: Joe Lucia& Duke Williams Re 340 HP Cam

Len-----

I agree with Duke; the GM #3972178 is absolutely the best way to go if you're going to use a mechanical lifter camshaft.

Both the 3972178 and the 3736097 ("Duntov") are GM-discontinued. Both are available in reproduction from several aftermarket manufacturing sources, including Crane, Federal Mogul/Speed-Pro, Comp Cams, Wolverine, and others.

The Crane-manufactured reproduction of the 3972178 is available as a kit under GM #12364054. I believe that the Crane mechanical lifters supplied with this kit are either a piddle valve type or a "hybrid" type of their own design.

[Len Rayca]

Re: Joe Lucia& Duke Williams Re 340 HP Cam

Duke & Joe: Thanks for your speedy and informative replies. I value your opinions and expertise very much,and appreciate your willingness to share it with anyone for the asking. Thanks again Len 39247

[Joe C.]

With All Due Respect To Joe And Duke..............

What do you want to do with your car? Is it going to be an NCRS trailer queen/museum piece? Do you wanna enjoy it, and drive it? Ya gotta go with your gut.
I concede that the LT1 camshaft will guarantee better driveability than the "Duntov" or the "30-30", but if you are willing to change the heart of your powerplant, then why not opt for a ZZ4 crate engine.

[Len Rayca]

Re: With All Due Respect To Joe And Duke..........

Joe: I want to stay as close to the original specs and configuration as I can given some of the original GM components are no longer available.I may have it judged someday, but for the most part it is a hobby car and nice day driver, but it is not/will not be a trailer queen or musuem piece. Thx Len

[Dave Suesz]

It's not ALL about max power...

I have the Duntov in my car, because it always had it, and I want the car to perform, for all its peculiarities, like it did back in the day.

[Clem Z.]

when these cars were sold new

with the 097 cam they were sold with 4:11 gears which made all the difference in the world. we never complained about turning 3500/4000 rpm while crusing down the road. every corvette i ordered even the big blocks had 4:11 gears and we drove them everywhere including vacation trips of 1000+ miles. it depends how you want to drive the car,just putting along or running it to the redline every chance you get. the newer cams have are better but back then the 097 was the only choise.

[Duke W.]

Re: It's not ALL about max power...

Yes, one of the most attractive attributes of a vintage SHP engine is their unique visceral character, and I prefer my L-76 to sound and feel like a real L-76.

The LT-1 cam will provide better torque bandwidth than the Duntov or 30-30, but will be indistinguishable from either except for a VERY experienced and savvy expert. The LT-1 would likely be indistiguishable from the Duntov or 30-30 by all but the most experienced PV judges, and even then it is a subjective call because there is no visible evidence to distinguish one from another.

It's tough to get good comparable dyno numbers or event SOTP comparisons between cams on an otherwise identical engine, but I have done extensive research on engine simulation programs and the LT-1 not only outperforms the other OE mechanical lifter cams, it also outperforms all the popular high performance hydraulic aftermarket cams, and my accurate lift-crank angle diagram shows that it has some very unique design features that have never been duplicated by any other cam that I am aware of.

Duke

[Duke W.]

Re: when these cars were sold new

I never had an issue with the Duntov cam pulling through my CR four-speed and 3.08 axle. Of course I wasn't a drag racer and the first 40 MPH never counted, but from a rolling start there was nothing that could keep up with me if I had enough open road ahead. One 440 Charger driver once learned that when he ran out of revs at 130 MPH, and I shifted into fourth and walked away!

On top of that I could cruise at 80 MPH at a lazy 3100 revs and got 20+ MPG to boot.

Duke

[Joe C.]

Re: With All Due Respect To Joe And Duke..........

Len:

It absolutely sounds that you intend to use your car for Sunday drives, when the weather is nice.....probably show it off at some Corvette shows, parades, etc, etc. That is EXACTLY what I do with my ,65, which I restored "by the book", including bicycle tires, and pesky tar top battery. I wanted to have this car exactly as it came from the factory, with all its quirks. Will I have it NCRS judged.......never. Why? Because I don't need any "so called" experts to tell me what I already know. Because I don't use my car to buy groceries, but only occasionally, it is A VERY SPECIAL TREAT every time I get behind the wheel, fire up that lopey, smelly, loud L76, let out the clutch and TAKE OFF. I really think that you intend to enjoy your car, as I do.

All that being said, let me give you a piece of advice. Absolutely do not rebuild your engine using flattop pistons, use the original type 11.25:1 popups. If you intend to use it as above, then why switch to a different cam? If you aren't going to race the car, and you aren't going to use it to buy eggs and milk, then what's the difference. I'll repeat the word "visceral" that Duke used before. I think that if you put in the more docile LT1 (or should I say, refined), your car will lose some of its personality and appeal. This is just one man's opinion, I am sure that many will disagree with me on this.

Before I understood how these old engines worked, I was advised to use flattop pistons in my 1965 L76, because "the gas doesn't have enough octane". Well, I went with the domed buckets, and I also used a "30-30" blueprinted clone from Sealed Power, as original. Boy, am I glad I did, because the engine runs flawlessly, with no detonation, with timing ADVANCED slightly above recommendation.( I wouldn't try this with the mild cammed versions, however, because they have much less overlap)

Whenever I think of what a very respected contributor to this Forum once wrote, that "the '64-'65 L76/L84 were probably the most high strung smallblocks ever produced by Chevrolet, with the exception of the '69-'70 302 Z28" , I usually find myself grinning. Why? Because I know that I've got a REAL L76 sittin' under my hood.

Joe

[Dave Suesz]

Exactly! ...

Every time I have changed my engine to get closer to original (original coil, original type wires, original type resistor plugs, original type inline static supressor in the distributor lead) the car ran better! More to the point, it runs with the same sound & feel it had when I was a kid. In the 60's the engine blew, and we put in a 283 with the original 265 carb, intake, and exhaust. Later we had the 265 reconstructed exactly as original (including an argument with the builder as to the originality of the dual valve springs). The reconstructed 265 ran noticably different than the 283, with a very different feel, sound, and acceleration curve.