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Author Topic:   Need help with cam rule.
ars
Dirt Full Roller

Total posts: 34
posted December 09, 2002 03:17 PM
Our track is starting a new class in 2003...Pure Stock. Rules allow double hump heads, flat top pistons, holley # 7448 or # 89787-1. My question is on the cam rule. " any hydraulic cam and lifters may be used.....Maximum allowed lift is .280 inch measured directly on the lobe by installing a dial indicator into the center of the lifter.... minimum vacuum of 17 inches at 800 rpm ". Ok What lift of a cam can i run ? Any recommendations would be helpful.

cmiller51
Dirt Full Roller

Total posts: 68
posted December 09, 2002 03:23 PM
Well, with that kind of vacuum rule, not much at all! Probably your best bet would be to call a cam company, tell them your engine rules and let them decide which cam is for you. I have a friend that had these same rules a few seasons back and he may have a cam number. If so, I'll post it.

outlawstock17
Dirt Forum Champ
Total posts: 620
posted December 09, 2002 04:41 PM
reed "sodbuster" series.

ars
Dirt Full Roller

Total posts: 34
posted December 09, 2002 04:47 PM
quote:
Originally posted by ars:
Our track is starting a new class in 2003...Pure Stock. Rules allow double hump heads, flat top pistons, holley # 7448 or # 89787-1. My question is on the cam rule. " any hydraulic cam and lifters may be used.....Maximum allowed lift is .280 inch measured directly on the lobe by installing a dial indicator into the center of the lifter.... minimum vacuum of 17 inches at 800 rpm ". Ok What lift of a cam can i run ? Any recommendations would be helpful.

How do you figure the maximum lift of cam that can be used? I'm guessing but .280x1.5 [rocker arm ratio]= .420. Is this correct ?

outlawstock17
Dirt Forum Champ
Total posts: 620
posted December 09, 2002 05:44 PM
that's correct ars. lobe lift X the rocker ratio = valve lift.

why have a vacuum rule in addition to a maximum lift rule? some of the guys that write these rules need a little help. keep it simple........

makes me wonder if they throw rules like that in there so they can have a reason to tear a guy down and make his life miserable if they want. i just don't get it.

Scoot
Dirt Freak

Total posts: 330
posted December 09, 2002 06:16 PM
Talk to Charles with Camcraft, He helps sponsor the Forum and can get you what you want, custom grind etc. I got mine from him and it was great.

------------------
Scoot
Smith Racing Team
870-365-5989

PEDDLER
Dirt Freak

Total posts: 298
posted December 09, 2002 07:30 PM
My Question also.......Why have a lift and vacuum rule?.

redneck bubbas racing
Dirt Freak

Total posts: 213
posted December 09, 2002 10:12 PM
Fairly simple answer Peddler. When we ran pure at HOT we had the 450 lift rule to contend with. I have an Iskedarian catalog that lists cams for lift rule class's. Some of them have outragous duration. That would have been fine if we only raced at HOT. I know you have seen and heard some of the cars with those cams-rumpity rumpity rump rump We also raced at Thunder Mountain in Rusk which had no lift rule but did have a a vaccum rule. No big cams there, too noticable by idle sound. By having a lift and a vaccum rule they are basicly elimanating any cam much more than stock. Just the way I see things.

tilley88
Dirt Freak

Total posts: 353
posted December 10, 2002 12:41 AM
Ditto.....

75xracer
Dirt Full Roller

Total posts: 40
posted December 11, 2002 09:34 AM
My engine builder has a trick to get around that vaccum rule, but can't help with the lift rule. Basically, if you restrict the oil pressure to the lifter bores with a valve, your hyd. lifters compress, lowering the lift, and raising vaccum. Of coarse, you have to have a hidden valve, and oil lines to do it, and would be hard to hide, but then again, most people wouldn't know what it was anyway. I've never tried it, but it's been done. They say you have to give the lifters a minute or two with it running to compress after you shut the valve off, but the vaccum will go way up. So, I guess that's one reason why they have a vaccum AND a lift rule.

[This message has been edited by 75xracer (edited December 11, 2002).]

DMS CEO
Dirt Freak

Total posts: 212
posted December 11, 2002 11:32 AM
Howards makes a cheater cam we used to run that you had special lifters with. It was hellacious and pulled 18 all day long.

Z28SpeedKing
Dirt Newbie

Total posts: 1
posted December 11, 2002 05:24 PM
That trick wouldent work with Solid lifters would it ??????

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