Hydraulic replacemennt 4 Duntov cam?

[studiog]

Hi,
I am building a 270 HP dual quad motor-1961. Does anyone know if there is a modern hydraulic cam that would have the same characteristics as the old Duntov mechanical lifter cam? Thanks for any help. You guys are the best!
Gary S

 

[jerrybramlett]

GM cam grinds

I have found the "097" Duntov cam to have a lope at idle in a 283. This cam even has a ragged 750 rpm idle in a 327. You can match this idle by using a 327/350 "151" hydraulic cam. It has much more lift but about as much duration.

I wouldn't use the "30-30" solid cam in a 283. This cam has a very rough 900 rpm idle in a small displacement engine like the 283. The low end torque is weak in 283 and 327 applications.

I stay away from mystery aftermarket grinds. I haven't found them to be significant improvements over the old factory grinds for street use. I call them a mystery because you never really know how they're going to perform in your application. The cam grinder's description usually overemphasizes the high rpm horsepower gains and ignores the low speed sacrifices.

 

[bossvette]

GM cam grinds

I agree with the previous post back when I was younger I got tired of adjusting the solids on a bored 283/270 and switched to the 327/350 hydraulic with excellent results.
As far as aftermarket I have had good luck with Isky, Crane, Erson and Edelbrock
speed pro/sealed power makes good quality replacement parts and should have the 327/350 cam in its inventory

 

[396 RAT]

As much as most of us drive these cars, I would stick to a solid cam. I drive about 1000-2000 miles per year max. How many yrs
per adj? So to me its not that big a deal. Not like in the 60's when they were daily drivers.
Just another option.........
Rhoads lifters and a serious hyd cam would sound about the same.
But I am not sure its worth the hassle. I love factory solid lifter V8's. Have had 3. 65 365HP Coupe, 65 K code fastback, and my current 65 425 vert. Its the only way to fly!

 

[JohnZ]

There are "blueprint" versions of both the original "097" Duntov and the later LT-1 cams available (forget the "30-30" cam); I'd stick with a solid cam and choose the LT-1 - it's the best street solid-lifter cam Chevy ever made, and works just fine with all GM stock valvetrain pieces. Solids aren't a big deal - adjust them once a season and forget them.

If you absolutely have to have a hydraulic cam, I'd choose the "151" 327/350 cam; it also uses all stock GM valvetrain pieces and is maintenance-free.

 

[Tom Bryant]

Personally I think that the clatter of solid lifters is part of the image of a 270. I can't imagine doing away with that.

Tom

 

[TWINRAY]

I agree with Tom. Nothing beats the sound of "solids":dance

 

[iron cross]

The GM 151 cam would be the best replacement for the solid lifter cam. But don`t change the solid cam.

 

[Dave65]

Jerry,

I have found the "097" Duntov cam to have a lope at idle in a 283. This cam even has a ragged 750 rpm idle in a 327. You can match this idle by using a 327/350 "151" hydraulic cam. It has much more lift but about as much duration.

This may answer a question I have. I have a 65 with a numbers matching L79 engine that a prior owner says currently has a Duntov 30-30 cam. I have not disassembled the engine yet.

I liked the lope in the idle before I started the body off (a young engineer who drives BMW's said it had a miss). I do not know what a L79 cam sounds like but you seem to be saying it will be similar? I like what I hear about the L79 torque curve and would prefer to go with hydraulic lifters to match the engine code.

Are they similar?

Thanks.

Dave

 

[jerrybramlett]

I wasn't very clear about the differences in the idle and low speed characteristics of these cams in my earlier post, so I'll give it another shot.

The 151 cam idle sounds kinda wicked in a little engine like a 283. In a 327 the 151 cam has a slightly rough idle at 750 rpm. I wouldn't call it a lope in a 327. It pulls a vacuum of maybe 15 inches at that speed. It will idle as low as 650 rpm in a 327. The off-idle torque is fine. You don't have to rev the engine much to pull away from a stop smoothly.

The Duntov cam in a 327 has almost as much low end torque as the 151, but the idle is a little rougher. It has a mild lope at 750 rpm, and pulls about 14 inches vacuum. It doesn't like to idle lower than that.

The 30-30 cam in a 327 has a definite lope and won't idle consistantly much below 800 rpm. The off-idle torque is relatively weak. You've got to rev the engine while slipping the clutch to leave smoothly. The idle vacuum of this cam is about 12 inches.

TO THOSE WHO WILL NOW POST THAT I'M FULL OF CRAP: Maybe so. Yes, the above info is based on my own driving experiences with these cams, not controlled lab experiments. Every now and then someone claims the Duntov won't idle as low as 750, the 30-30 has to idle around 1,000, or that the 151 makes only 10 inches of vacuum at idle. I don't respond to these people, but I think there's something wrong with their engines. I've had these cams in my cars (and now my towing truck) since 1969. Even though I am a simple person, given enough time I can make valid observations. Here's another one. My small block 400 truck engine has a smooth 700 rpm idle with the 151 cam and strong low speed torque.

 

[Dave65]

Jerry,

Thank you for the great answer. It definitely gets printed off and goes in the folder.

I did a lot of work on cars in the late sixties and early seventies but got away from it to raise a family and make money. Guys like me, who are doing their one and only vette, really appreciate the comments and observations made you, Duke, JohnZ, J Lucia (none for sale) and others. The Internet is amazing.

Thanks.

Dave

 

[JohnZ]

The 30-30 cam in a 327 has a definite lope and won't idle consistantly much below 800 rpm. The off-idle torque is relatively weak. You've got to rev the engine while slipping the clutch to leave smoothly. The idle vacuum of this cam is about 12 inches.

Jerry's right on the mark, as usual - I have the (original) "30-30" cam in my stock '69 Z/28 (one of the few left that haven't been tubbed and slammed with a blown big-block sticking through the hood ), and the off-idle torque is very weak - just one of the things you learn to live with when you have a '67-'69 Z/28 or a '64-'65 L-76/L-84 Corvette. If the time ever comes for a rebuild (only has 34K miles on it), I'll replace the "30-30" with the LT-1 cam.