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Cam design basics ?

General engine tech -- Drag Racing to Circle Track

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CamKing
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Re: Cam design basics ?

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hoffman900 wrote: Fri Jan 14, 2022 1:52 pm No, the 1994 engine when Rahal had to buy a Ilmor-Chevy Penske car to qualify for the Indy 500.
You're not going to believe it, but that 1994 engine that Honda developed, used a cast iron block. That added weight made those chassis that were designed around the all aluminum Cosworth, impossible to setup.
That was the problem with the Buicks too, but they had a big HP advantage to make up for their slower corner speeds.
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Re: Cam design basics ?

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CamKing wrote: Fri Jan 14, 2022 2:39 pm
hoffman900 wrote: Fri Jan 14, 2022 1:52 pm No, the 1994 engine when Rahal had to buy a Ilmor-Chevy Penske car to qualify for the Indy 500.
You're not going to believe it, but that 1994 engine that Honda developed, used a cast iron block. That added weight made those chassis that were designed around the all aluminum Cosworth, impossible to setup.
That was the problem with the Buicks too, but they had a big HP advantage to make up for their slower corner speeds.
Yikes! I guess with the Buick, if you made an aluminum block it wouldn’t be production anymore, and at that point, go full Ilmor 265E.

Who was designing Cosworth’s cams back then? I know Judd was doing some for the Williams F1 team in the 1980s, but into the 1990s. Jeff Williams (no relation) helped Ilmor out, A LOT (at least that I have read).
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Re: Cam design basics ?

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hoffman900 wrote: Fri Jan 14, 2022 3:07 pm Who was designing Cosworth’s cams back then?
We made cams for Vince Granatelli Racing and Penske, in the late 80's. By mid 90's teams couldn't even look inside the engines.
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Re: Cam design basics ?

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hoffman900 wrote: Fri Jan 14, 2022 3:07 pm Yikes! I guess with the Buick, if you made an aluminum block it wouldn’t be production anymore,
Actually, there was nothing in the rules about the block material having to be stock.
When my dad build the 209ci turbo Chevy V8's for indy, in the early 80's, he had Chevy cast the blocks out of Aluminum.
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Re: Cam design basics ?

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CamKing wrote: Fri Jan 14, 2022 4:50 pm
hoffman900 wrote: Fri Jan 14, 2022 3:07 pm Yikes! I guess with the Buick, if you made an aluminum block it wouldn’t be production anymore,
Actually, there was nothing in the rules about the block material having to be stock.
When my dad build the 209ci turbo Chevy V8's for indy, in the early 80's, he had Chevy cast the blocks out of Aluminum.
Was it a cost reason? It just seems crazy to me to use an iron block in a Formula / Indy Car.

Did you ever get a chance to look at the 265E cam / valvetrain up close? It seems that engine was held back by Mario Illen’s promise to be the same dimensions of the 265D, but I do get they were trying to keep the pushrods out of the ports. Do you know the events on those cams?

It would be cool if someone invited you on a podcast. Would be cool to hear more on your thoughts on cam design and Indy Car / Cart racing of the 1980s and 1990s.

Going back to valve events, I asked Billy in the EPE today about opening the valve too fast on a 2 valve engine (ignoring dynamics). He said the “Low Shock” stuff is about dynamics (and really just sound like an improved UDHarold lobe backwards, which he pretty much said it came from grinding one like that accidentally some years ago), but he believes the slower opening intake also allows for more overlap area for a given piston-to-valve clearance, where a fast opening means you have to wait before you can fire off the valve due to space constraints (again, ignoring dynamics).
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Re: Cam design basics ?

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I've only looked at pictures of the 209 Ilmor valvetrain. it was defiantly a compromise to keep the engine the same size as the 4 valve Ilmor.

It's funny what lengths Comp will go to, to not call their "Low Shock" designs, what they really are.
They're just mild I.R. lobe designs that can be ground with the normal large diameter grinding wheels.
Just like all out I.R. cams, they have a slow initial opening, then a high acceleration rate to max velocity, then slow down to max lift, then accelerate to max velocity on the closing side, then a high negative acceleration to a slow seating velocity.
I've measured a few, and they're nothing different from what we were doing in the 70's.
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Re: Cam design basics ?

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Stage II Buick V6, my 2 cents. Indy development was likely too rushed to have a proven alum. block in time. These came later for IMSA GTP.
I have heard, the iron blocks were acid dipped, for Indy. For a while, those heads reined as the best inline 2 valve,( even put on the sbc.)
Who knows, they might make a cool 3 cyl. ? You're results may vary.
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Re: Cam design basics ?

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agertz1 wrote: Fri Jan 14, 2022 6:32 pm Stage II Buick V6, my 2 cents. Indy development was likely too rushed to have a proven alum. block in time. These came later for IMSA GTP.
I have heard, the iron blocks were acid dipped, for Indy. For a while, those heads reined as the best inline 2 valve,( even put on the sbc.)
Who knows, they might make a cool 3 cyl. ? You're results may vary.
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I mean they were used up until / including 1996, well beyond the IMSA March-Buick.

A bunch of Buick Indy engines here: http://indycompetition.com/engines--engine-parts.html

Mike,

Hadn’t thought about them as IR designs, but I can see that now. Thoughts on that type of valve lift curve shape for flat tappet / OHC bucket type systems?
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Re: Cam design basics ?

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CamKing wrote: Fri Jan 14, 2022 2:39 pm You're not going to believe it, but that 1994 engine that Honda developed, used a cast iron block.
Yep, I worked on that engine.
It was a real drain to moral for the project.
One of my tasks there was fitting plated aluminum sleeves to those blocks, (nicest turning equipment I ever used, you could dial off a cut and the Voest Lathe would cut within 0.00005 reliably.)

They were desperate to solve a crankshaft bearing problem, they thought maybe if the block was more rigid, the problem would be mitigated (it wasn't).

It was a counterweight, materials, surface hardening and surface roughness problem.

They had aluminum blocks too.
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Re: Cam design basics ?

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SchmidtMotorWorks wrote: Fri Jan 14, 2022 9:51 pm
CamKing wrote: Fri Jan 14, 2022 2:39 pm You're not going to believe it, but that 1994 engine that Honda developed, used a cast iron block.
Yep, I worked on that engine.
It was a real drain to moral for the project.
One of my tasks there was fitting plated aluminum sleeves to those blocks, (nicest turning equipment I ever used, you could dial off a cut and the Voest Lathe would cut within 0.00005 reliably.)

They were desperate to solve a crankshaft bearing problem, they thought maybe if the block was more rigid, the problem would be mitigated (it wasn't).

It was a counterweight, materials, surface hardening and surface roughness problem.

They had aluminum blocks too.
Jon was that all HPD design or were you guys being fed stuff from Japan? Obviously it was fixed for ‘95.
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Re: Cam design basics ?

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hoffman900 wrote: Fri Jan 14, 2022 6:59 pm Mike,

Hadn’t thought about them as IR designs, but I can see that now. Thoughts on that type of valve lift curve shape for flat tappet / OHC bucket type systems?
All my cam designs(roller, flat tappet, bucket follower, finger follower) are designed the same way. If you took any of my non-roller profiles, and converted the valve lift curve into a roller, it would be an inverse radius.
The way we convert the valve lift curve into the lobe shape for a flat follower, you don't have an inverse on the lobe, but the lift curve is the same as an I.R. roller.
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Re: Cam design basics ?

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CamKing wrote: Fri Jan 14, 2022 12:51 pm That's exactly what we did with the classes that were restricted to 9-9.5:1 compression.
there were a lot of restricted compression classes in the late 80's, Modifieds, Asphalt Latemodels, Winston West stock cars, and others.
Besides the compression limit, these were engines that had been well developed (358ci SBC, 23degree aluminum heads, single plane manifold, headers, etc). Everyone in the industry had a lot of experience with every aspect of these engines, except the compression limit.
We started with what worked in a 13:1 version of the same engine. We kept shortening up the duration, and getting the area back by increasing the lift, and closing the intake valve earlier and earlier.
this increased the velocity of the intake charge, increasing the ram-air effect, which increased the mass trapped in the cylinder, and that increased the compression pressure and heat. On average, we were reducing the duration by about 8 degrees, and advancing the intake centerline by about 4 degrees, so we would have about the same intake opening point, but be closing the intake about 8 degrees sooner.
What we found when we kept going farther in this direction, you reach a point where you are no longer increasing the amount of mass being trapped in the cylinder, yet the temp keeps climbing. The higher heat required us to adjust the fuel and spark, and those adjustments would hurt the power.
Thanks Mike. As a follow up to this post I have another question. The last few years, I’ve had stuff come through the shop that in m opinion had ports with too much cross section. It’s easy to do today, especially since everyone buys heads base on flow. The question is I think the same thing can be done for these engines. Which is add lift and decrease duration to “help” the big, lazy ports. Am I close, or am I nuts??

I realize the correct fix is a properly sized port, but a cam change is cheaper than a head change. And God forbid, you suggest a head with a smaller port that flows better.

TIA.
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Re: Cam design basics ?

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ClassAct wrote: Sat Jan 15, 2022 12:13 pm
Thanks Mike. As a follow up to this post I have another question. The last few years, I’ve had stuff come through the shop that in m opinion had ports with too much cross section. It’s easy to do today, especially since everyone buys heads base on flow. The question is I think the same thing can be done for these engines. Which is add lift and decrease duration to “help” the big, lazy ports. Am I close, or am I nuts??
Yes, that's what we used to have to do when the 410 Sprints were running the huge -12 Brodix heads.
Shortened duration, and increased lift to get the area back.
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Re: Cam design basics ?

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CamKing wrote: Sat Jan 15, 2022 12:17 pm
ClassAct wrote: Sat Jan 15, 2022 12:13 pm
Thanks Mike. As a follow up to this post I have another question. The last few years, I’ve had stuff come through the shop that in m opinion had ports with too much cross section. It’s easy to do today, especially since everyone buys heads base on flow. The question is I think the same thing can be done for these engines. Which is add lift and decrease duration to “help” the big, lazy ports. Am I close, or am I nuts??
Yes, that's what we used to have to do when the 410 Sprints were running the huge -12 Brodix heads.
Shortened duration, and increased lift to get the area back.
I mean this is pretty much the current OEM recipe. Fuel injection and DI mean you can disconnect port velocity in relation to having to think in terms of carb jet signal. Of course they're worried about pumping losses at cruise as well.

I forgot you had mentioned the rollers are really just LARGE diameter flat tappets design wise.
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Re: Cam design basics ?

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hoffman900 wrote: Sat Jan 15, 2022 12:31 pm I forgot you had mentioned the rollers are really just LARGE diameter flat tappets design wise.
Other way around.
From the design standpoint
A flat tappet profile is just a roller profile with a 56" radius roller.
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