.904 Flat Tappet Lobes

[hoffman900]

Hey guys,

Looking for anyone with experience with these lobes, in an circle track / road race application. Rev ceiling around 7500rpm.

Comp Camps MM lobe series:
Duration @ .020 305*
Duration @ .050 279"
Duration @ .200 197*
Lobe Lift: .433"
Lash: .018"

UltraDyne NF69

Duration @ .020 304
Duration @ .050 277
Duration @ .200 193
Lobe Lift .4265
Lash: .016"

Bullet FC304/425

Duration @ .020 304
Duration @ .050 274
Duration @ .200 190
Lobe Lift .425"
Lash: .012"

Bullet FC306/435

Duration @ .020 306
Duration @ .050 279
Duration @ .200 197
Lobe Lift .435"
Lash .011"

[mag2555]

For what cid motor my friend with what heads , as my crystal ball is in the shop getting recalibrated, lol!

[hoffman900]

For what cid motor my friend with what heads , as my crystal ball is in the shop getting recalibrated, lol!

34ci / cyl. Limited to 1.5 rocker ratio per rules. Flow is inconsequential

[hoffman900]

Also, does anyone have any information on some of the lobes designed for the 1" diameter mushroom tappets (NASCAR, circa 80s early 90s?).

I know Crane, Comp, et-al had designs for these, but for obvious reasons, don't advertise these in their catalogs. Mike?

[DaveMcLain]

Also, does anyone have any information on some of the lobes designed for the 1" diameter mushroom tappets (NASCAR, circa 80s early 90s?).

I know Crane, Comp, et-al had designs for these, but for obvious reasons, don't advertise these in their catalogs. Mike?

The designs that Reed Cams used for their mushroom cams were actually an older series of roller lobes that had new masters made so that they could be ground as a flat tappet. They worked on about a 1 inch diameter lifter.

[hoffman900]

Also, does anyone have any information on some of the lobes designed for the 1" diameter mushroom tappets (NASCAR, circa 80s early 90s?).

I know Crane, Comp, et-al had designs for these, but for obvious reasons, don't advertise these in their catalogs. Mike?

The designs that Reed Cams used for their mushroom cams were actually an older series of roller lobes that had new masters made so that they could be ground as a flat tappet. They worked on about a 1 inch diameter lifter.

I forgot about Reed. Mike Ingram on here would know a lot about those as he worked there, and might have been involved in the design of them.

Mike Jones has also shared on here that he designs his flat tappers as rollers, but uses a very large roller diameter value to get it there.

[statsystems]

Also, does anyone have any information on some of the lobes designed for the 1" diameter mushroom tappets (NASCAR, circa 80s early 90s?).

I know Crane, Comp, et-al had designs for these, but for obvious reasons, don't advertise these in their catalogs. Mike?

Check with Jim at Racer Brown for the mushroom tappet lobes.

[CamKing]

274-279 @.050"
That's a ton of duration for a 7,500rpm rev-limit.

[hoffman900]

274-279 @.050"
That's a ton of duration for a 7,500rpm rev-limit.

Mike,

How would you go about designing a cam for an application like this?

How would you maintain your velocity constraint, while keeping acceleration in check, and get as much lift as you can. Engine has zero included valve angle and a small bore, so it’s very under valved and needs to make it up with lift. Rules mandate a 1.5 rocker ratio.

In similar engine without the rocker rules, we’re running 270* @ .050” and it peaks at 6700rpm. Nice fat power band too. For this engine, LSM, Crower (Bruce spec’ed), and Crane (Chase Knight spec’ed), given information blindly, all spec’ed cams with 2* @ .050”, and .005” lobe lift. Your brother’s program, when tweaked a little, spat out exactly what one of the three recommended . The Crane is the “chosen” one, however.

Stats, looked up their catalog. I’ll post some of what they have when I get back to my desktop.

[CamKing]

it’s very under valved and needs to make it up with lift.

No, it needs to make it up in area.
Email me all the specs on the engine, and I'll tell you what it needs.

[hoffman900]

Stats,

Here is a comparable Racer Brown, 1.00" lifter (mushroom) lobe:

STX-60

Adv. Duration (.020?) 310
Duration @ .050 271
Lift .632" w/ 1.5 rocker arm.

In similar engine without the rocker rules, we’re running 270* @ .050” and it peaks at 6700rpm. Nice fat power band too. For this engine, LSM, Crower (Bruce spec’ed), and Crane (Chase Knight spec’ed), given information blindly, all spec’ed cams with 2* @ .050”, and .005” lobe lift. Your brother’s program, when tweaked a little, spat out exactly what one of the three recommended . The Crane is the “chosen” one, however.

To add to this, Steve Gruenwald (Integral Camshaft era, former Elgin) designed a 324* @ seat, 273* @ .050, .385" lobe lift. Granted, he was hindered by the cam core at the time in regards to lobe lift. This is what was used before the above mentioned cams. However, this engine isn't hindered by a rocker ratio rule. Also, the engine peaked around 6700rpm.

No, it needs to make it up in area.
Email me all the specs on the engine, and I'll tell you what it needs.

Mike, out of curiosity, why would I be looking at .050"? If seat to seat is the same, but the lobe is designed for a larger tappet diameter, then of course .050" is going to be fatter since we'll be above the lash ramp by then. The engine 'sees' all of it, but the valve is cracked open at the seat number. And will do.

[hoffman900]

Also, does anyone have any information on some of the lobes designed for the 1" diameter mushroom tappets (NASCAR, circa 80s early 90s?).

I know Crane, Comp, et-al had designs for these, but for obvious reasons, don't advertise these in their catalogs. Mike?

The designs that Reed Cams used for their mushroom cams were actually an older series of roller lobes that had new masters made so that they could be ground as a flat tappet. They worked on about a 1 inch diameter lifter.

Dave,

I found this and thought you might find it interesting:

Harold Brookshire:

I designed the Reed PR-R lobes in 1976, finishing up a long-term agreement I had with John. Cams such as their famous R296-02ULX family, the TRs, the SRs(Not the SRAs--John did those with a program I sold him), a lot of solids, Reed was my 1st major customer for cam design, starting in Dec 1972......
I'm happy to see some of them being sold for Pro-Stock/Pro-Mod engines. The only problem with Jason using ANY cam of .480 lobe lift is that he is going to need about a .850 BCD with his stroke. There are no cores made that will put a .480 core on a .850 BCD. He needs a Rocket Block or a 50mm with raised cam location, so he can get away from the small base circle, IF he wants to run very high lobe lifts. That is why I mentioned the 1.6 rockers.
The 312 shares the identical positive acceleration curve of the 302, which on another thread I mentioned going 8 hours, 15 minutes, turning up to 8500, behind a 5-speed. The 321 turns 9400 with ease, and is much easier on the valve train than the 312.
One set of springs should last all year or so, unless he is prone to 11,000-RPM mistakes.....