cam change 1962 C-1

[Hank Rossi]

I am in the process of doing a body off restoration or rebuild whichever term is correct on my 1962 340hp. Vette.. I have owned this car since 1968 and for many years it was my only car. I put over 150,000 on the Vette over the years, and like many others paid little attention to retaining wear items like generators ect. The last time I rebuilt the engine I replaced the mechanical cam with a 350hp or a 365hp hydraulic cam from a C-2. The car runs great on the current cam. My question is this do I replace the current cam with the original? The body is off the car with the engine installed. I seem to recall that you can replace the cam without removing the engine. Is This so? What is the point deduction for the hydraulic cam? The car has all the original parts motor, intake, trans, ect. My initial focus was to replace all the worn parts with new, and now am thinking I might want to have the car judged. I just rejoined NCRS, I was a member thru 1977, got my old number back 1175.

Thanks for any help,

Hank

[Mike M.]

Re: cam change 1962 C-1

hank: welcome back. yes, you can R&R a small block cam without removing the engine. judges may or may not pickup fact the engine is hydraulic cam'd but i wouldn't take the chance if its to be judged. buy a new solid lifter cam and lifters and gear/chain set.good luck, mike

[Duke W.]

Re: cam change 1962 C-1

I recommend replacing Duntov cams with the LT-1 cam. It has about the same overlap as the Duntov, but an earlier opening exhaust valve and later closing inlet valve. It will have the same idle characteristics and vacuum and about the same low end torque, but more top end power, and I would defy a PV judge to be able to tell the difference during a PV drive.

You can still buy both from Federal Mogul Speed Pro.

Duke

[Hank Rossi]

Re: cam change 1962 C-1

Duke, The current cam is a LT-1, so you doubt anyone could tell it is not a Duntov. That is good because I agree it runs stronger and is hassle free.

Hank

[Jim Callan]

Re: cam change 1962 C-1

Hank,

Is that LT-1 cam hydralic ? I'm looking for a replacement cam for my '71 350/270hp.

Jim

[Duke W.]

Re: cam change 1962 C-1

No, the LT-1 cam is mechanical lifter.

There was a thread last week with a detailed discussion on '71 base engine cam and other rebuild options.

Duke

[Duke W.]

Re: cam change 1962 C-1

In your original post you indicated it had either a 350 HP or 365 HP cam. The 350 HP cam is hydraulic. The 365 HP cam is the "30-30" mechanical lifter cam.

The LT-1 cam is yet a third design circa 1969. It was the last SHP mechanical lifter cam ever designed by Chevrolet for the SB engine.

So it's not at all clear to me what cam you have!

Duke

[Hank Rossi]

Re: cam change 1962 C-1

Duke,

Sorry for my confusion. when you said LT-1, I remembered incorrectly. The cam is hydraulic and is a Corvette cam, so it must be the 350hp. So I'm still left wondering if I should change it, and how many points are deducted for the wrong cam. all of this happened a long time ago.

Hank

[Duke W.]

Re: cam change 1962 C-1

During ops check or PV a good judge should be able to tell the difference between a hydraulic lifter cam and a mechanical lifter cam.

So whatever you do I would recommend that you reinstall a mechanical lifter cam, and like I said, I don't think a judge could discern between a LT-1 cam and Duntov cam in either ops check or PV, Both will have similar idle characteristics and idle vacuum, and both will make about the same low end torque, but the LT-1 will yield more peak torque and power, so it will be stronger in the upper third of the rev range.

The L-79 (327/350HP) cam has less overlap that the Duntov and LT-1 cams, so it has better idle quality and more manifold vacuum, and there should be no discernable lifter ticking if it's properly adjusted. It's an excellent cam, it just doesn't give the engine the same visceral quality as the mechanical lifter cams.

Duke

[Michael H.]

Re: cam change 1962 C-1

But if the LT1 cam and the correct cam sound about the same, (which they don't) and perform about the same, why use a non original LT1 cam?

[Duke W.]

Re: cam change 1962 C-1

They don't perform the same as I stated previously in this thread, and they DO sound close enough, depending on total idle timing, that it's impossible to tell them apart with any surity. I've already been around the horn with you on this issue at least once, so I'm not going to address it again.

You have your opinion, and I have mine.

Duke

[Michael H.]

Re: cam change 1962 C-1

I think this would be the third or fourth time actually.

[Clem Z.]

i would try to adjust the hyd lifters

at .002 to .004 lash and see what it idles and sound like and you may be able to get passed the judges.

[Duke W.]

Re: cam change 1962 C-1

I actually do have a comment on sound. For example a '62 340 HP engine sounds quite different than a '63 340 HP engine because of both the difference in exhaust system configuration and the vacuum advance on '63 engines. The greater idle timing provided by the vacuum advance means that the cylinder pressure is lower at exhaust blowdown, so the '63 version has a less sharp exhaust note (and pulse you can feel at the exhaust pipe), and the overall spectrum is lower frequency - more guteral - because of the larger exhaust pipes.

By the same token, a '63 FI has a noticeably different exhaust note than a '63 340 because there is no heat riser on FI, which functions as a crossover, so the '63 FI has an even more gutteral sound and sharper exhaust pulses than a '63 340 HP.

For two cams that are close in overlap (exhaust closing and inlet opening), the sound of the engine will be more a function of total idle timing and exhaust system configuration than differences in the exhaust opening and inlet closing points.

Duke

[Duke W.]

Re: i would try to adjust the hyd lifters

Yeah, that might fool 'em.

Duke