Whats the biggest cam grind you ever heard of?
And what was it used in?

Pro stocks are using over 1 inch of lift now.

I designed a .600" lobe lift intake and a .530" lobe lift exhaust for someone with an 815-cid Ford engine in IHRA. He was using 2.00:1 on the intake(1.200" gross lift) and 1.90:1 on the exhaust(1.007" gross lift). I haven't heard how it's done yet.
The .556" intake/.530" exhaust I did for 1.8:1/1.7:1 rockers goes well over 9000.
I'll have to check on durations tomorrow.....

UDHarold

Harold, a simple rocker change can give you those kind of lifts?
Interesting, guess its true you learn something new every day.
I would assume there is some extreme piston notching going on with that kind of lift. Does that change the power band also?
Say in my case i have the UD .586/.586 Solid for the 427 using standard rockers and it is good from 2,000 to 7,400. If i used 1.9 rockers would my power band move to say 4,000 to 9,400 for example? (Not saying those numbers are acurate)
And what advantage would i gain by doing so?
Also i realize this would also hinge on the flow of my heads.

Thanks Harold, I was hoping you would respond, have been trying to figure out how to make this cam a little bigger without removing it because its just so dam bad ass!!!
Everywhere i go people take note of the awsome ground pounding idle this thing gives out! :eek:

Truely out did yourself with this one! graemlins/thumbsup.gif

A few degrees of valve timing won't affect your powerband much, like changing from 1.7 to 1.8 rockers. It will give you a slight change it total lift but won't drastically move where that power is made. Your only looking at .030 lift or so. It will take a whole different cam to move the RPM up by a lot at which time many other factors must be taken into account, like how strong are the rest of the parts in my engine. The cam in my son's 540 powered Chevelle is 285/298 @ .050 and .801/.785 lift, and makes power from 3000 RPM to about 7200 RPM but requires real good valve springs, valves and big valve reliefs in the pistons. If you threw this a street motor it wouldn't perform well at all. Any cam lift above .550-.560 lift will require much caution to keep from running into the pistons. Also as the motor size increases the same cam will have a lower powerband.

what about 1.9 rockers? where would that take me too?
from .586 int and ex.
Trying to stay under .640 which is where we pre notch the pistons to clear too.(.640 roller that is, right now its a solid tappet non roller)

Engine was built to spin to 8900, knowing that there would be serious upgrades in the near future, so the reliability isn't an issue just the piston, valve clearance.
and is it worth it money to power gain by changing from 1.7 to 1.9?

If you wanted to make a 1.9 rocker work you would have .655 gross lift with your cam.

But,,, Changing the rockers to anything over 1.8 in a rat is not as easy as bolting on rockers,, unless you are using shaft rockers.
You will have some serious geometry problems as you are moving the pushrod point closer to the pivot & or making the tip further away from the pivot.
As Harold Sutton said, you are not going to change the RPM where the cam operates much if at all as you are not changing the seat timing assuming you are compensating for the different ratio with a lash adjustment.
The engine is going to see a more aggressive cam profile at the valve but not a larger cam.
One of the main reasons to go to a larger ratio is to get the valve open further for a head that likes lift.
It also give you a fatter lift curve overall as you will gain timing in relation to lift everywhere except at the seat

Also I think you may have misread UD Harold's post a little.
The reason for the huge lift numbers at the valve was not just a rocker change it was also because of a huge cam lobe,, .600".

Gross valve lift is simply cam lift times rocker ratio.
In your case with .586 with a 1.7 rocker you divide the .586 by your rocker ratio of 1.7 which is .345 & then multiply by your new ratio of say 1.8 & you would have .620 gross lift.

One thing ya have to be aware of with respect to rocker changes is that when you increase the rocker ratio you also increase the rubbing forces on all points of contact. Especially with flat tappets if you increase these forces to the point where the oil can no longer do it's job.... then the lobe and lifter tend to grind each other into metal dust.There are limits that one can go.Putting a 1.9 ratio on an already aggressive flat tappet could be exceding those limits.... By all means talk with your cam grinder before hand.

Originally posted by 69LS1:
...you also increase the rubbing forces on all points of contact... Big block Dave, come in - Big block Dave. Psst. He said "increase the rubbing forces..."

I hope something bad hasn't happened to BBD! :confused:

I have posted before about talking with Harold once about making a solid lifter cam that acts just about like CC's 288AR street solid roller cam because it's such a good one for that application. BUT I don't want the worry of when I will lose a lifter axle and needle bearings.

His response was that it can be done up to almost getting the same performance out of a solid cam by using 1.8 ratio rockers and making sure you match up the duration at .050", .100" and .200" as close as you can AND still not exceed good lobe/lifter life!!! I do figure the solid lifters with the little-bitty hole in the foot would help here too......

Think about this for a minute..

That's why I wish somebody would chime in and tell us any stories about the Schubeck lifters and cams for street hy-po motor use!!

pdq67

Originally posted by UDHarold:
I designed a .600" lobe lift intake and a .530" lobe lift exhaust for someone with an 815-cid Ford engine in IHRA. He was using 2.00:1 on the intake(1.200" gross lift) and 1.90:1 on the exhaust(1.007" gross lift). I haven't heard how it's done yet.
The .556" intake/.530" exhaust I did for 1.8:1/1.7:1 rockers goes well over 9000.
I'll have to check on durations tomorrow.....

UDHarold what would a cam like that do in something like my 355? :D :eek:

Put a hole in your pistons on the first revolution. :D

The Ultra-Lobe cams have to be made on BIG cores. The .556" lobe is for a 60mm core and the .600" lobe is for a 65mm core. These core sizes are necessary because of the tremendous valve spring pressures and very high rocker ratios. On regular cores, which would be extremely small(the lobes have to fit though the journals), the forces would cause the cores to bend downward between each cam journal. Breakage would follow shortly thereafter.
Regular SBCs are limited to around .480 or less lobe lift before the core gets too weak and flexible.
I have always gotten my 'specialty' cores from Cam-Motion, although I have gotten a few from Steve at LSM.

UDHarold

Harold,

Just out of curosity even with these huge cores do they require non relived grinding or would that even help or can even be done on these Ultra Lobes ?

69LS1,

Since cores of this sort are not "stocking" items, they are basically made to order. So that if you wanted a 65mm core with a .600" lobe lift, this is what would be machined out, then heat-treated. Very little metal would have to be removed during the grinding process, most of it caused by the difference between the roughing profile and the finishing profile.
As an aside, a 65mm core with a .600" lobe lift is 116% stiffer than a normal BBC core with a .500" lobe lift cam. When a core is 10% stiffer, it is a worthwhile gain.......

UDHarold

BTW, don't let this turn into a UDHarold-only thread. I am interested in what you guys have heard or seen from other companies. Back in the old 'cam wars' days of the 1960s, there were a number of 380° to 400° cams from companies such as Chet Herbert and Howards. I'm sure that Comp Cams, Crane, and Crower(Wow! All 'C's...) have a number of 'big' cams. What have you heard or seen?

I was going to mention Herberts " 400 400 " cam. I had a cam ( got in a trade ) that was approx. .860in .840ex Duration was 330'in 360'ex adv. on a 119 L.S.A. Cam Dynamics grind for SLRE

Speaking of old cams back in 1975 Dick Landy was building some large displacement engines ( Large for back in those days as 600 CID engines were not common place back then )
anyhoo he built what they called the 575 Milodon Mastodon Hemi ( See HotRod Sept 1975 ).

They used a Crane core that had it's base circle cut from .975 down to .900 that according to the article was .800 lift at the valve and 300 deg @.050.

As I look through my Crane 1978 lobe spec sheet there are several with dur @ .050 over 300 deg.The longest they show is:

R 308/4458 lobe...346 @ .020

R 300/5098 lobe...332 @.0225

Perhaps the most intense was thier SSR series of Super Stock rollers...

R 286/517 lobe .... 323 @ .020

In their origional Hi Low No Pop lobes they had an

R 296/500 lobe ... 336 @ .0162

Even back nearly 30 years ago there were alot of .800 valve lift cams available witch in them days were gargantuan.... not so today.

EDIT : all of these above were on normal sized cores.