Camshaft "Renewing"?

[PSherm]

The cam in my old engine, as well as the couple of spares I have, is worn and not up to spec (read: not making enuff p0warz...). The cam is NLA from Chrysler as well as aftermarket oem replacements. Has anybody gone thru a process to build up the cam then grind it back to spec? If so, what process? The only ones I'm familiar with are welding, flame spraying or plating.

Also, if anyone has been thru this, did you contact aftermarket mfgr to have a cam made? I know Crane, Comp, Crower can make cams to your specs, but is it prohibitively expensive?

TIA,

[JeffYoung]

Couple of folks have had blanks cut to stock specs (Tom H? I think Ron has made some calls).

I don't think it was really that expensive.

Given the producation variances in cams, it may be an advantage as well. Get ALL of the spec lift and duration afforded you by the shop manual.

The cam in my old engine, as well as the couple of spares I have, is worn and not up to spec (read: not making enuff p0warz...). The cam is NLA from Chrysler as well as aftermarket oem replacements. Has anybody gone thru a process to build up the cam then grind it back to spec? If so, what process? The only ones I'm familiar with are welding, flame spraying or plating.

Also, if anyone has been thru this, did you contact aftermarket mfgr to have a cam made? I know Crane, Comp, Crower can make cams to your specs, but is it prohibitively expensive?

TIA,

[chuck baader]

Contact Delta Camshaft, Washington state. They had the blueprint specs for my cam, which is also NLA. Chuck

[ShelbyRacer]

Is it compliant to use a reduced-base-circle cam, ground to the correct lift/duration/overlap/etc. if the stock cam is not available?

[bamfp]

Is it compliant to use a reduced-base-circle cam, ground to the correct lift/duration/overlap/etc. if the stock cam is not available?

Don't do this. You will loose rpm. The ramp speed on the cam will increase and it will require more spring rate to control the valve. I know this first hand.

[MMiskoe]

Get ALL of the spec lift and duration afforded you by the shop manual.

Not to be pessmistic, but I doubt the FSM has all the information needed. I have not seen much detail in those that I have looked at. (hence all the compliance methods employed in Spec Miata)

[Ron Earp]

Get ALL of the spec lift and duration afforded you by the shop manual.

And don't forget that rocker/follower ratio, it might not actually be what is specified....

If it says you get 0.446" valve lift then you damn sure can make sure you get 0.446" valve lift.

[chuck baader]

And if there is no factory shop manual? Chuck

[Andy Bettencourt]

And if there is no factory shop manual? Chuck

If no shop manual, and by that we know you mean 'no spec', you should really try and find as new a part as you can, used. Fudging the parts that have no spec is a slippery slope. You then make it a judgement call by the PC and the Appeals committee when I pay to have them procure 10 used ones, have all 10 within a certain 'range' and the renewed one is obviously out of that statistical range, IMHO it wouldn't be a long shot for them to throw your stuff out.

That is the one nice thing about the Miata's, the cam specs are spelled out to the Nth degree in the SM section so messing with that stuff is stupid. Buy a new one and go. A luxury not everyone has.

[chuck baader]

Have been going through that for 4 years. Delta cam had the stock specs from way back with the old style follower cam grinding tool so I have had my cams reground as needed there. This year I finally found a NOS cam on ebay in the original packaging, wrapped in a newspaper from 1998 and that is what I have run this year. The trick now would be to find 10 examples of stock cams as most shops just throw away "e" heads and cams because everyone wants the "i" parts. Guess that is another "warts and all". Chuck