Grinding a new profile onto the stock cams?

[G-Forces]

Aww that soooo sweet....glad to see you guy could come to a truse.

OK I'll change my original comment. I'll never put a set of regrinds in an SR20DE...and I'll give VERY careful thought to putting a set in any other engine.

[808Infiniti]

New cams, ground on new billets are better, and more expensive.

But regrinds are ok, hard welding the lobes with stellite on original cams is perfectly acceptable. By building the material up on the lobes first and then re-grinding them creates a newly profiled (ramp, duration) cam with the orginal geometry (base circle). A lot of motorsports divisions utilize this method of regrinding cams. I believe that stellite welding a cam actually is more durable than the stock billet, the stellite material is supposedly a harder, denser surface. This is the method that any reputable cam re-grinder utilizes to create new profiles on usable older cams.

Any accomplished engine builder's want to chime in?


-808Infiniti

[G-Forces]

Problem is most garage monkeys you go to will just do it the old barber shop method..."a little off the top" and that's it. If say Sunbelt was to try and sell me regrinds and they said they used all the methods you mentioned I'd be inclined to try them out. However there are too many garages/companies that will just whip something off and take your money than put some thought or science into it.

[T4 Primera]

Originally posted by 808Infiniti
But regrinds are ok, hard welding the lobes with stellite on original cams is perfectly acceptable. By building the material up on the lobes first and then re-grinding them creates a newly profiled (ramp, duration) cam with the orginal geometry (base circle). A lot of motorsports divisions utilize this method of regrinding cams. I believe that stellite welding a cam actually is more durable than the stock billet, the stellite material is supposedly a harder, denser surface. This is the method that any reputable cam re-grinder utilizes to create new profiles on usable older cams.

Any accomplished engine builder's want to chime in?


-808Infiniti

Hey, I had forgotten all about that. Back when I worked in a machine shop, we used to use a eutectic, spray-on, welding method for building up components that were undersized like shaft bearing journals etc.. It consisted of pre-heating the component (often while rotating in a lathe) and then a combination gas torch/spraygun was used to weld more material on. You could then machine and grind the components to the right size.

[Neil82]

I am having my SRi (130 Hp) SR20DE engine upgraded to GT Primera spec on Tuesday. The parts consist of a new intake cam, exhaust manifold, down pipe, back box and a GT mid section. I will be getting the car dyno tested after I have the bits fitted so I wil let you know what gains i make and if it feels any faster.

[T4 Primera]

Originally posted by Neil82
I am having my SRi (130 Hp) SR20DE engine upgraded to GT Primera spec on Tuesday. The parts consist of a new intake cam, exhaust manifold, down pipe, back box and a GT mid section. I will be getting the car dyno tested after I have the bits fitted so I wil let you know what gains i make and if it feels any faster.

Excellent, that's exactly what we need to find out. If you have part numbers for the bits would you please post them? - so we can price them here in NZ.

[pche059]

Hey guys

Yes we are awear of this.We have found that around .040" is an exceptable amount to grind these cams without unduely loading the valve train.This amount to grind these cams without unduely loading the valve train.This the skid type rocker.

so .....

[Moppie]

It means Kelford came through!!!

They are clearly aware of the problems that P10DET mentioned, (also showing that hes right ) and that they have worked out how much you can grind off the base circle with out causing problems.
And when they created the profile they made sure the amount that needs to be ground off is below the problem causing amount, as only a small change in the base circle is needed to achieve noticable gains, (also showing that im right )

What a great debate, leading to us all learning something. Im rather impressed, and P10DET thanks for getting me into it.

(I did notice at the end they mention the skidtype Rocker, did they say anything about the roller rocker? (which they use on the race car,))

[G-Forces]

He's probably relying on the hydrolic lifters to take up the slack there.

Welp, if anyone decides to get them make sure you get before and after dyno plots. It should be interesting.

[808Infiniti]

I still think the cams should be hard welded first for the following reasons:

1) keep valve train geometry in stock form

2) durability is better for the cam and valvetrain

3) you can grind a more aggressive cam with better ramping

4) cost shouldn't be prohibitive

5) Kelford cams should know better........ If they are aware of the limitations of altering the base circle, they should hard weld the cams first to avoid this situation.

Just my opinion......

808Infiniti

[Moppie]

Originally posted by 808Infiniti

5) Kelford cams should know better........ If they are aware of the limitations of altering the base circle, they should hard weld the cams first to avoid this situation.

Kelford cams do know better.
Thats why in thier reply they mention the limited grinding of the base circle.
I believe there have been problems with Hard welding the lobes, namely if the welding isnt done to a high standard it can fail.
I think there's also a cost issue, which is one reason people choose a regrind over a billit, if the hard welding push's the cost up, and billits are avliable then the point of getting a regrind is lost.