cam "blue printing"

[dickita15]

I had a hard time following Dick Patullos first rule of screw ups, to wit: "Assume stupidity before malice"......

Jake if you are going to quote me get it right, “Never attribute to Evil what can easily be explained by stupidity”.
It is a good rule to live by, it helps be resist the urge to kill people.

[lateapex911]

Yes, good point Dick. I bow to your correct wordsmithing...

[Andy Bettencourt]

Tons can be learned from the history on cams in SM. From the dowel pin issue to what we have today, published specs for every lobe and tolerences.

Using a 'new' cam that is manufactured to those exacting tolerences is nothing more than blueprinting IMHO. IIRC, a set like that for my car is around $700. A huge chunk of change as compared to just buying a nice new set from Mazda...but we know we can't legislate spending.

Dan - if I was you, I would sure as heck keep the stock cams around. You pay to have teh cams pulled on a protested car, have them measured against what you 'know' to be stock, and then you decide if you want the protest to head to Topeka.

[lateapex911]

Dan - if I was you, I would sure as heck keep the stock cams around. You pay to have teh cams pulled on a protested car, have them measured against what you 'know' to be stock, and then you decide if you want the protest to head to Topeka.

Then rent.... errrr...sell the stockers to the guy who just watched his (obviously suspect) cams head off into the sunset. Profit!

[dj10]

Dan - if I was you, I would sure as heck keep the stock cams around. You pay to have teh cams pulled on a protested car, have them measured against what you 'know' to be stock, and then you decide if you want the protest to head to Topeka.

I've contacted SCCA Tech to see if they have E36 cam profiles or cam's. I'm planning to keep the cam's with me.......just in case.

[Jeremy Billiel]

To answer your hidden question, yes Ed the cams that you happen to have in that certain motor in the garage *may* be legal to the book/ maximum allowable specs, but clearly not within the intent of the rules.

Has anyone ever officially tested one of "these" cams?

[Ed Funk]

No "hidden" questions. I'm confidant that the motor in the garage is a well built, legal, Serra motor. And i'm confidant that it'll idle like a Honda. It's other "lumpiness" I'm asking about.

[MMiskoe]

Ahhh, the beauty of running a Miata. All the cam specs are on file in Topeka.

Yes, but! Once they are out of the car you have no way of measuring the relative difference between intake & exhaust timing...... Ahh the beauty of dual cam designs.

[quadzjr]

Couldn't you say that about all cams? In the case of the DOHC motor required to us e an offset key. the only timing changes available are +/- a tooth.

-Which I have seen some motors benefit from moving the a cam a tooth relative to the other.. (motorcross Yamaha 450 engines produce significant gains from doing this, and my street MR2 turned was a gas saver! I fixed the cam timing on teh MR2 and now it is faster, but gas mileage went to crap)

[Greg Amy]

Once they are out of the car you have no way of measuring the relative difference between intake & exhaust timing...

If that's important to you, specify measuring relative cam timing in your protest. But, if all you protest is the cam itself, you never asked for that to be looked at anyway...

Don't forget to spec checking the gear(s) for altered keyways (compare it to known stock example), and/or widening of the keyways (allows you to move the cam timing, and it don't take much), and/or modified timing chain (though that's REALLY taking it to an extreme level of cheating...) - GA

[quadzjr]

Don't forget to spec checking the gear(s) for altered keyways (compare it to known stock example), and/or widening of the keyways (allows you to move the cam timing, and it don't take much), and/or modified timing chain (though that's REALLY taking it to an extreme level of cheating...) - GA

How would you alter a timing chain to get a +/- degrees? Either case.. that is a bit extreme but isn't the use of offset bushings (SOHC) and keys (DOHC) legal? I would think your best bet is to just put a degree wheel on the thing and dail gauge.

However does the Tech shed have the proper tools to do such a job.. I.e. piston stop, degree wheel, dial gauge, etc? I guess that is the point of the adance warning.

[Greg Amy]

How would you alter a timing chain to get a +/- degrees?

Use/make one with different-length links.

isn't the use of offset bushings (SOHC) and keys (DOHC) legal?

Only on the crankshaft pulley.

However does the Tech shed have the proper tools to do such a job

Not likely.

GA

[Ron Earp]

Don't forget to spec checking the gear(s) for altered keyways (compare it to known stock example), and/or widening of the keyways (allows you to move the cam timing, and it don't take much), and/or modified timing chain (though that's REALLY taking it to an extreme level of cheating...) - GA

And cam gears that have the drive pin and mark re-indexed, another extreme example.

[GKR_17]

isn't the use of offset bushings (SOHC) and keys (DOHC) legal?

Only on the crankshaft pulley.

And only to bring the timing back to factory specs.

[Andy Bettencourt]

...*may* be legal to the book/ maximum allowable specs, but clearly not within the intent of the rules.

I disagree. It's all part of blue printing - very much allowed by the rules in black and white. No doubt that some cars may benefit more than others...

Tolerances seem to be tighter on Japanese cars but sooo many teeeny-tiny little changes occur every year with these companies. I would guess that the Miata is one of the ONLY cars in the ITCS where the full cam specs, for every lobe - with tolerences, is documented.

[Ed Funk]

you can't use SM cam specs for IT, at least not universally.

Why not?
Aren't both classes supposed to be using stock cams?

[Andy Bettencourt]

Why not?
Aren't both classes supposed to be using stock cams?

Beat me to it Ed. Why do you say this Travis? Both classes are required to use stock cams.

[tnord]

Beat me to it Ed. Why do you say this Travis? Both classes are required to use stock cams.

since when do rules from one class apply to another?

[Greg Amy]

since when do rules from one class apply to another?

When both classes are required to use stock parts? Plus, we're not talking about rules applying from one class to another, we're talking about the sanctioning body's consistent application of identical rules between classes.

I suspect Travis is referring to the fact that SM engine builders were cherry-picking various iterations of cams that Mazda supplied with their Miata engines over the years. Additionally, many of them were "Spec Miata Cheating" their cams, optimizing profiles within the easily-available lift and duration specs, and/or moving the timing pins to optimal locations.

To address this cheating - and it WAS cheating, at least in terms of the optimization - Topeka procured a Cam Doctor and a specific example of a specific camshaft that it deemed "the legal camshaft" in SM. Everyone has to run THAT cam to be legal, REGARDLESS of what may have come in their "stock" engine.

So, what I think he's saying is that there may be instances out there where someone is truly using the stock cam that came from Mazda - fully legal in IT - but it's not legal in Spec Miata. - GA

[Andy Bettencourt]

The specs were defined by Topeka to keep the 'cheater' cams out. If they did there job correctly, I see no way a stock cam could fall outside the specs/tolerences.