Technical Cam Regrinding: Why the Pointy Lobes?

How is it that you would know that?

 

Never mind how I know- a Better question is how do you know

 

That just put a whole new visual to how many licks until satisfaction is met.

 

I just want to know what all this has to do with regrinding camshafts.

Daddy
Yes son
What's a "bumpstick".

 

I was going to reply to this earlier but I didn't make it to the shop until today to get a few pictures of these flathead cams. Someone needed to put some pictures up, so I figured, what the heck. The one cam you can easily see, is a re-grind and, from what Dad told me, it came out of an old hopped up flathead that was in a hotrod he rebuilt for a friend. It also had a 3x2 setup and a mag. The story goes that it was a really strong runner back in the day but the guy didn't want to spend the money to go through it. He wanted a modern engine and trans in it instead. He ended up just giving the engine to Dad.
The stock cams both have rather pointy lobes. They are for comparison.
I'm guessing that the regrind didn't get any spray welding from the looks of it. Someone ground the holy crap out of it. Lots more duration!

 

Well, now I know what a regrind cam looks like. Thanks.

 

Maybe that explains the designation of 3/4 cam mystery
You get 3/4 back and 25% of its gone in a regrind

 

Is it just me ? Mind you I have no idea which end I'm looking at on these cam's. Does the cam on the left (rusty one) have a milder ramp (left side of lobe) as compared to the other side.

 

Hi , what the name and grind of the regrind cam in the pics?
You can read in on nose of the cam

 

Have ya' all found yourselves in the Rhealm of Clothoids and Snap, Crackle, and Pop? It never occurred to me that when railroad track transitioning from a straight to a curve must employ high derivatives too! Consider that Jerk is the force that moves the lifter and Snap is the rate at which that force is applied. Obviously, you need to apply the force as "uniformly" as possible to minimize wear and vibratory excitation of the valve train and to keep trains from derailing (!) No intuitive handle on Crackle and Pop yet,

RE: those flat head cams: I really couldn't tell which was the regrind from the pics mainly because they didn't drop the heel/baseline/base circle to the min diameter of the casting.

I'm also wondering about he spray welding process: is this good for flat tappet or roller? From what I understand FT is chilled cast iron and R is steel.

I almost shed tears when I learned that Pittsburgh Crankshaft went out of business and the dozen Stude 332 steel cams he had stacked above the cam grinder, along with all the other rare cores had been scrapped.

 

We always used the stock flat tappet cam to start with. By spray welding it up you gain in every respect. I makes room for the lobe profile you need as well as giving it a harder surface so it doesn't wear as fast. It was also much cheaper than making a billet blank. The best of both worlds!

I'd do some looking around, there might be someone that already has a cam available for your application.

 

When I was a kid, a long time ago, a friend's Dad had a lathe & tool post grinder in his garage. My friend Walter (RIP) took a Model A camshaft, and used the grinder to reduce/remove most of the base circle on all of the lobes. This was very precise work (?)
Anyway, he put the cam in and the thing made LOTS of noise. Ran like a rocket (Model A rocket). Engine didn't last too long tho.
I thought it was sooo cool

 

We used to do that on our Briggs go-kart motors (yard karts) only we did it by hand on a belt sander and knocked the heel off several thousandths. They would really run then!

We had to (lap) grind the valves in an equal amount though to maintain some sort of reasonable clearance. We really thought we were doin' something!

 

I knew a screw machine wizard that fabbed some low speed machine cams with get this: a bandsaw blade that had loose riveted files on it - you used it like a continuous file. Using magnification, you could file to the center or a scribe line.

Knocking the heel off with a belt sander might work pretty good - would be difficult to produce kinks, steps, etc!

But actually, that is exactly what I was getting at: keep the lobe nose and remove the heel. I'm still thinking you could lower the heel 0.100 inches and still end up with reasonable Snap, Crackle, and Pop and still preserve most of the OE lobe.

 

FWIW, Stock 324 olds cam with an old timey Isky E-3 lobe ground on it. Relatively low lobe lift, by HAMB standards pretty big duration.

 

No offense, but I'm not sure you're getting what we're talking about here. First of all, .100" more lift at the cam is a ton of lift! If you have a 1.5 rocker arm ratio, that's .150" more lift at the valve! Serious consequences will follow.

Second of all, it will surely coil bind the stock springs and make interference between the rocker arm and the spring collar and bend all the pushrods at start up.

Third of all, it will most likely give you valve to piston interference at or near TDC. Maybe even valve to valve interference depending on the valve placement in the head.

Fourth of all, if it doesn't do any of the previously mentioned, it will surely loft the valve at the higher RPM .100" more lift at the cam will give you, plus it will bounce the valve at closing because the ramp angle has been radically changed.

What I'm saying is that you can't just radically change one thing and not look at the rest of the picture. My advice to you is to talk to a cam grinder that will work with you and offer some good advice as to how much and where.

If you just want a little more pep, try some more rocker arm ratio? For instance, 1.5 increased to 1.6 will safely increase both lift and duration at the valve and give a noticeable increase in power. As far as Snap, Crackle, and Pop, you're asking a lot from a reworked stock cam.

Plus, I think .100" off the cam is way too much to do by hand! This ain't just a kid playin' with his flathead Briggs anymore!

 

Are you sure you saw the last four pictures I posted. The first two pictures were used stock cams for reference. the last four were of the regrind.

 

zombiecar: I looked at those pics and thought they were side by side comparisons. Unless same cam and side by side, it's hard to assess what was ground off.

montanal: All those issues go without saying in my world. Just to get an idea where my attention is, I'm having trouble finding lifter resurfacers that will put a proper spherical profile on lifters - they all do conical and make a point of not mentioning it. I suppose they figure the vertex will wear down ???? Unacceptable.

If I could get one lobe profile w/ramps, I could prove or disprove what I think is possible. Unfortunately, I don't have a full lobe profile - the one I have does not have the ramps. And it is a pain to measure one in he car or to rearrange my 1-car garage to put a block on a stand an measure a cam.

 

He can't be seeing the pics.

 

Stock cams in pic top - reground cam in lower pic.
They took all they could and then some

 

Please don't be offended, but I think you're in way over your head.

 

I never looked for it when I took the pictures. The next time I go over to the shop I will check that and let you know what I find.

It could just be wear. Both of these are stock cams as far as I could tell. There are a couple more that looked very similar to these. I just grabbed a couple for pictures

 

Ok, How's this?

 

"GRIND the base circle, leave the lobe alone...
This old man went..."

Do you think I could resist?
BTW, those Weber flatmotor cams with the 'F' designation... (I had a 296" with an F1 cam, hairy...High RPM.
274" with Weber F2, lopey...Good street cam in my channeled 'A' roadster, 1800 lb. car.
Sent a Weber F4 to Delta Cams for analysis: within 2 degrees (!) duration of a Winfield SU-1A!
Funny, those guys copied Winfield a lot! ...And Delta was able to 'copy' the SU-1A on a new cam core! CHEAP, too...They're in Spokane, Wash. Look up their site, and go on their online tour. Recommended.

 

Mike, I thought Delta was in Tacoma? Opposite side of the state, Spokane is in east WA.
I read the 404 was a loose copy of an offy cam that Winfield designed.

 

I don't get it-
Obviously there's something funny in that but I don't get it

 

Thanks !
Looks good!

 

Montana, do you work for a cam grinder that does spray welding? Maybe Cam Research?

 

Hey George....Those pointed lobes are for pointed head racers....LOL

 

Yea, I like mine with a little more area under the curve! I won't even talk cam specs on here anymore, it's just not worth the rumpus it causes...