Anyone out there experience in Camshaft design?

[sirhrmechanic]

Not for a bike... but looking to create a one-off cam for a 1925 Silver Ghost. I have a standard profile and think that some additional lift and duration would dramatically improve power. But just because I 'think' this doesn't mean it's a great way to go.

So anyone out there ever done a cam design or know a good resource? Retro Track and Air in the UK can grind me a new cam from scratch... but they need a profile blank (not a drawing) to go from. If I can design something, they can make it. But I'm not about to just take a SWAG at it.

Look forward to any input!

Cheers,

Sirhr

[fillibuster]

Not for a bike... but looking to create a one-off cam for a 1925 Silver Ghost. I have a standard profile and think that some additional lift and duration would dramatically improve power. But just because I 'think' this doesn't mean it's a great way to go.

So anyone out there ever done a cam design or know a good resource? Retro Track and Air in the UK can grind me a new cam from scratch... but they need a profile blank (not a drawing) to go from. If I can design something, they can make it. But I'm not about to just take a SWAG at it.

Look forward to any input!

Cheers,

Sirhr

Sihr, why? Is the rest of the engine built to spin 3000 rpm? Seems to me that "there's no substitute for cubic inches", other than considerable rpm increase, but again, why? Got "sleeper" designs, or something? somebody's pink slip? what? what?
btw, I'm glad you asked. I've been getting bored enough to poke a skunk.

[sirhrmechanic]

Car is going to set a new speed record for Silver Ghost in 2015. Because, well, I can! And, yes, 3K RPM is about what it's designed for. And torque enough to carry 2 tons of coachwork. But this one has a 300 LB Cunard body... so torque is not what is needed.

As for the speed goal... The current record held by a Ghost is 101.7. This is being set up to do 105 at the Loring AFB course (Loring Timing Assn.)

By way of background, two earlier Ghosts were set up for speed. 1701 "The Sluggard" set the current speed record in 1912 at Brooklands. That's the current record holder. Then 72MG was built and raced in the 1920's. 72MG is the twin to my car... both bodied by Cunard. 72MG ran 4 pages of modifications in its build sheets. 4.5:1 compression... all kinds of stuff. They did a special cam, but no one ever wrote down the design for it!

So as an exercise in seeing how far I can hotrod a Ghost while still maintaining durability and driveability, I am looking to make some mild modifications. Cam as 'standard' is so enemic that the joke is that the company used 20 HP to keep the other 30 HP quiet. With some attention to detail this engine should be capable of a lot more output. BTW, the company also built some '70 HP' cars such as the Dragonfly. But none of the records on how they did these chassis were kept. All destroyed intentionally after the Board forbid any racing efforts c. 1923. The company saved invoices for paperclip purchases in the 1930's... but anything done to improve output was destroyed. WTF...

BTW, we 'hotrodded' a Bentley S1 motor for a client a few years ago. It was a fun exercise, resulting in this: http://en.wikipedia.org/wiki/Black_Adder_6 BA6 will spin tires in every gear... It is utterly terrifying to drive. 60 MPH in second... at idle. With 2 gears to go.

And don't feel you are poking a skunk... this build and speed record is an exercise in silliness. But shouldn't we all be silly some times?

Cheers,

Sirhr

[exeric]

I've heard Crane Cams, here in Florida is very approachable and capable. Also, I would think they could advise about cam profiles based on engine data.

[sirhrmechanic]

Thanks, Eric. Thought about Crane or Isky... but not sure how far their 'vintage' experience extends. Or whether they will help with design if there is only, basically, a one-off in the offing. But you are probably right that I should head there.

I asked here, simply because there is so much talent among AMCA members... that perhaps someone out there is 'the' cam guy!!! Wouldn't surprise me one bit.

Cheers,

Sirhr

[Steve Slocombe]

Here in England I've used Joy Cams for my VL speed bike. Phil Joy mostly does speedway and race bike cams, but reprofiled a set of VL cams for me, with more lift and duration. You can feel the difference in the mid range, while the bike starts easily and idles well. I've also got Kent Cams here in town who specialise more in cars. They are a larger factory operation and make regular, prototype, and race car cams in low volumes. I can ask if they are interested. The Rolls Royce Car Club is of course also based in England and I can take messages if necessary. Are you wanting to reprofile an existing cam or have a new one made?

[fillibuster]

Thanks, Eric. Thought about Crane or Isky... but not sure how far their 'vintage' experience extends. Or whether they will help with design if there is only, basically, a one-off in the offing. But you are probably right that I should head there.

I asked here, simply because there is so much talent among AMCA members... that perhaps someone out there is 'the' cam guy!!! Wouldn't surprise me one bit.

Cheers,

Sirhr

It's been decades ago that I read some "breathing" literature, so I know it's out there.
Seems a list of particulars need to go with you to your interview. Optimum rpm would be one. You know what speed you want to peak at, and what gear ratios and tire sizes, so you can point to a target mph and figure rpm from there. They'll probably design a "load" cam that has the particulars you suggest, i.e.. a little more lift and duration, without chasing the r's too hard. ... and I think you will find torque is more in the mix of things.

[sirhrmechanic]

Fillibuster... that is all right on! And I have those numbers from working with Gearvendors on overdrive ratios.

The engine is designed all around torque. It's got 120lbs of crankshaft and flywheel. This is so the engine can haul around the chassis with 4,000 lbs of coachwork on it. Or, armor, in the case of some of them! This is at a sacrifice to top end power. They wanted cars to waft smoothly along, not to be able to get places quickly. That said, a 'stock' car would do 70+ with little difficulty. And that is with heavy coachwork.

So lots of things to consider. All the input here has been helpful, as always! Thanks!

Steve... thanks! PM Inbound.

Cheers,

Sirhr

[c.o.]

Ah... the pursuit of speed. Is there anything more noble? It would be interesting to see how you make out with this project.

[AFJ]

Not for a bike... but looking to create a one-off cam for a 1925 Silver Ghost. I have a standard profile and think that some additional lift and duration would dramatically improve power. But just because I 'think' this doesn't mean it's a great way to go.

So anyone out there ever done a cam design or know a good resource? Retro Track and Air in the UK can grind me a new cam from scratch... but they need a profile blank (not a drawing) to go from. If I can design something, they can make it. But I'm not about to just take a SWAG at it.

Look forward to any input!

Cheers,

Sirhr

If you have not already done so, it might be a good idea to look at a book called "The High-Speed Internal-Combustion Engine" by Harry Ricardo, the 1931 Edition, published by Blackie & Sons, London & Glasgow. It goes into great basic detail on cam requirements, gas flow, etc., on engines of that period. The book is available for free download on the Web.

AFJ

[sirhrmechanic]

AFJ: Not only is that a great idea, I think I have a copy of Ricardo's book at the shop in amongst dozens of old Mechanics annuals, engineers handbooks, etc.

Thanks for the lead!

Cheers,

Sirhr

[rwm]

it's easy simply grind 50,thou off the heels of each lobe. this will give you more lift.(good luck with the grinding) call crane.

ps. you doughnut vid is a fairy tail. no doughnut ever gets out of the parking lot intact.

[sirhrmechanic]

ps. you doughnut vid is a fairy tail. no doughnut ever gets out of the parking lot intact.

Ain't that the truth!!! Not to mention... no sprinkles!

Cheers,

Sirhr

[DanM]

I once had Jim Leineweber repair some 45 cams that had been damaged- he reground the profile.....He knows cams

http://www.leinewebercams.com/catalog.html

[MassHarley]

Try Joe at http://www.americancustomcam.com

He has a lot of experience with custom ground cams for Bonneville. He ground a cam for a Bonneville Ford Model A motor for me a few years back from a blank. He has a large selection of cam profiles. Might be able to hook you up.

Mike