SDVette

Lots of history and cool photos! Even a JohnZ reference!

http://www.chevyhardcore.com/tech-st...lock-camshaft/

Bluestripe67

Good reading! Dennis

TCracingCA

I am known for upsetting people here, but I think Ed Winfield (famous engine man) should get more credit for the Duntov cam, than Duntov should get. As Duntov went to him, to get help!!!!!!!

65hihp

Duntov cam sounds better than Winfield cam.
I'll stick with Duntov.

MikeM

This isn't the first time I have heard this. There was a engine engineer that developed the camshaft, not Duntov. Can't recall his name. Duntov was a facilitator in the Corvette program, not an innovator.

SDVette

Steve Jobs didn't personally develop the iPhone either.. I think it's a little more complicated than that.

LouieM

Cool article indeed, thanks for posting

C5rider

I'm glad you like the story guys! It was a fun one to write up. As one reader mentioned, I failed to list the part number for the 30-30 cam, but he was gracious enough to include it in the comment below the story.

and TCracingCA, I did find references to Ed Winfield's input into the camshaft and I asked JohnZ if he knew anything about it. He said that he didn't have any knowledge of that occurring. That is one that we may never know the full story on how it really happened.

I've been doing some writing for the Power AutoMedia group for a while now, and just recently, I took on the role of Editor for CorvetteOnline.com. Dave K moved to another title and that opened a slot for me. Feels good to be focused on Corvette specifically again!

Again, thank you and I'm glad you enjoyed the story.

Andy B.
C5rider

LouieM

As someone who has written a lot in life, I enjoy your writing, so welcome back to full-time Corvette writing. I was unaware of corvetteonline.com, but I see it has a lot of interesting content, so thanks for mentioning it.

Lou

TCracingCA

MikeM

I've sometimes wondered how many million of the 097 or copies that have been sold OTC.

63 340HP

Thank you for the article. Revisiting history is a good thing as the knowledge base passes on.

I applaud the use of JohnZ as a reference. I also applaud you for not interjecting an inference that JohnZ has a published position that Duntov did, or did not, work alone on the 097 or 077 cam designs.

Zora would know. It might be wise to research if Zora published who should be credited for the cam. Zora may also have designed the 077 lobe profile, and a college graduate Engineer may have been tasked to tame the lobe dynamics with second and third order math analysis of lifter velocity and acceleration to result in the 097 lobe profile.

In the real world development laboratory of engine builders in the postwar proliferation of new high compression engine designs, most Los Angeles guys went to Isky or Howard or Herbert for advice on lobe profiles. The central California coast and San Fernando valley guys went to Engle. Did Zora have a trusted local cam grinder?

​​​​​​​
Zora had been a successful prewar Engineer and was well connected in the race components world, so he probably had one or more cam grinders to discuss lobe profiles and overlap ideas. Research and reporting on who Zora was documented to trust for advice would be an interesting topic for a future article. The technical history is as solid as the iron cam cores, but the history of the people of influence during the immediate postwar performance growth era is soft.

​​​​​

TCracingCA

SWCDuke

I tend to agree. Isky told me the same thing, too. Winfield was a big proponent of "soft action" cams. Valve spring materials and processes were not so good back then, so there were real limits on spring durability necessary to control aggressive dynamics.

I expect that, like Isky said, Winfield and Duntov were acquainted, and Duntov knew his cam design would have to work with the standard production valve springs, so he reduced acceleration with greater duration to achieve essentially the same lift with another 1000 revs added to valve train limiting speed without affecting spring durability.

I've always found it interesting that Chevrolet marketing literature and Duntov himself always referred to it as the "high lift cam" even though actual valve lift when you take into account clearance is a few thou LESS than the '57 regular production hydraulic cam, which was new for that year and the lobe design, same lobe on both sides, was actually asymmetric.

One story I read decades ago is that Duntov phoned in some basic specs while testing the Corvette speed car at the Mesa proving grounds that he hoped to set a class record at Daytona Beach. Duntov calculated that the engine needed about 30 more BHP for the Corvette to achieve 160 MPH on pavement and 150 MPH on the Daytona sand. A design engineer went to work on the details for a simple symmetric lobe, made a drawing, and the cam was ground and shipped to Mesa within a week or so.

Remember back then that the emphasis on engine "performance" was a smooth idle and lots of low end torque, so cams were generally short duration with low overlap. Some of the engineers thought Duntov's design wouldn't work, but he proved them wrong by making the target speed of 150 MPH on the Daytona sand.

Another note on both the base ('57-'66) and Duntov cams is that they have have harsh dynamics - particularly peak jerk, which occurs only a few thou above the base circle. Later designs, beginning with the L-79 cam have less peak jerk, and it occurs higher up the flank, which is probably something that fell out of Chevrolet's research with the Optron system in order to reduce false valve motion, increase valvetrain limiting speed, and reduce seat erosion.

One comment on the article is that the term "showroom stock" did not come into use until the 1970s when SCCA created the SS classes, and those cars were indeed showroom stock right down to the mufflers and emission control equipment.

Corvettes from the fifties were known in SCCA as "production cars". Some modifications were allowed such as removal of bumpers and trim and cut down windshields on roadsters and convertibles.

Mufflers could be removed, but no headers, and "no material could be removed from the head" other than an OE equivalent valve job. Camshafts had to be production, but could be "reground". Changes to the spark advance map and carb jetting were allowed, but that was about it. Anything more and they would be reclassified to a "modified" class.

I'll also add that the LT-1 cam consists of the L-72 lobe (same on both sides) on the inlet side on a smaller base circle indexed at 110 deg. ATDC POML. The exhaust lobe is identical to the 30-30 lobe (also the same on both sides) indexed at 122 deg. BTDC POML. The combination of shorter inlet duration and later indexing of the exhaust lobe yielded a wider LSA, which reduced effective overlap to about the same as the Duntov cam.

This is why it makes more low end torque than the 30-30, and in my experience about the same top end power as the 30-30, which is why I've always recommended the LT-1 to replace the 30-30 at rebuild time.

Duke

TCracingCA

SWCDuke

Isky was a real character and pack rat. (I don't know if he's still with us.) When I had lunch with him 15 or 20 years ago he was driving a seventies vintage Lincoln Continental Coupe, and it was PACKED with stuff - stacks of papers like magazines, etc.

This was before I got a hold of the lift data on the Chevrolet camshaft drawings, but I had a lift-crank angle diagram of the LT-1 cam I took back in the seventies. He was real interested in it and wanted a copy, which I made for him, and I recall him putting it into the Continental on one of the stacks. Who knows, maybe it's still there.

In the course of our conversation I told him I had a pretty good handle on what kind of acceleration could be designed into a lobe, but I didn't have a good feel for how much jerk could be tolerated.

He just gave me a wry grin.

Again, about 20 years ago I was reading something about Keith Duckworth, and he was quoted as saying something like (in the process designing one of this early engines, maybe the FVA) he "threw out the book on camshaft design", but I never had an opportunity to get an expansion on that statement with more detail.

Duke

65hihp

There is no note that I can see online that he has kicked the bucket.
He would be 97 years old now.

MikeM

Hey Andy! Remember this?

C5rider

LOL! THAT's goin' back a few years! Refresh my memory, was that a VetteHeads group?

Good stuff!

And, I'm glad this conversation is still going. They give me a word limit, but the info here just adds so much more to the story! Again, thanks.

Andy

MikeM

Yeah, VH group. Taken on Pine Island. I think you were doing an article on Jerry Clark's car. Spring Hill Jerry Clark, front row, far right. 2003-4?