Visit The Dirt Forum for More Information

Author Topic:   Vacume help by 6/11/05???
Stevei2i0
Dirt Full Roller

Total posts: 54
posted June 08, 2005 07:20 PM  
Rules say "Must pull 18" vacume. I can only get 16". 350 Jasper, standard bore flat tops, 488 lift cam, holley 4412, timing set on 36'.Carb adjusted with vacume guage.Must fix by 6/11/05. HELP???

iowatoolman
Dirt Freak

Total posts: 369
posted June 08, 2005 09:54 PM  
is it a solid or hyd cam?

maybestroked
Dirt Newbie

Total posts: 1
posted June 08, 2005 11:05 PM  
quote:
Originally posted by Stevei2i0:
Rules say "Must pull 18" vacume. I can only get 16". 350 Jasper, standard bore flat tops, 488 lift cam, holley 4412, timing set on 36'.Carb adjusted with vacume guage.Must fix by 6/11/05. HELP???

what are valves set at

97dirt
Dirt Forum Racer

Total posts: 94
posted June 09, 2005 06:42 AM  
You need around a 114 centerline to pull 18 in.

iowatoolman
Dirt Freak

Total posts: 369
posted June 09, 2005 01:05 PM  
if it is solid advance the cam 4* and open the lash up by .004 that should get you there if not advance the timing you can go up to 44*

drive hard or drive home

iowatoolman
Dirt Freak

Total posts: 369
posted June 09, 2005 01:06 PM  
i do that with a cam that is 111 CL
quote:
Originally posted by 97dirt:
You need around a 114 centerline to pull 18 in.


Stevei2i0
Dirt Full Roller

Total posts: 54
posted June 09, 2005 03:22 PM  
Valves are set at .003. Cam is hydrolic, with Rhoads lifters.May try bumpin the timing and the valves. What about the power valve???

97dirt
Dirt Forum Racer

Total posts: 94
posted June 09, 2005 07:07 PM  
iowatoolman how high do you have to set your idle?

Stevei2i0
Dirt Full Roller

Total posts: 54
posted June 09, 2005 07:10 PM  
Rules say must pull 18" at 1000 rpms.

iowatoolman
Dirt Freak

Total posts: 369
posted June 09, 2005 08:05 PM  
set at 1000 rpm with a solid cam

sorry i don't give away my cam numbers

drive hard or drive home

97dirt
Dirt Forum Racer

Total posts: 94
posted June 10, 2005 07:20 AM  
At our track you must pull 18in at 600 rpm, cam must be hyd, thats hard to get under a 114CL, we tried several 112CL an one 113CL, Its much easier at 1000 rpms

sc1 racing
Dirt Freak

Total posts: 419
posted June 10, 2005 11:46 AM  
i run a solid cam .518/.530 on a 110 lobe seperation and pull 19-21 on the gauge..

iowatoolman
Dirt Freak

Total posts: 369
posted June 10, 2005 05:06 PM  
i run a .547 lift and pull almost 19" @1000rpm
with a 725 2bbl carb

i have pulled 16 with a cam as big as .567 on a 110 CL

sorry i don't share secrets
and don't play well with others

drive hard or drive home

Footlead
Dirt Roller

Total posts: 24
posted June 10, 2005 07:12 PM  
Lift doesn't have much to do with vacuum. It is the lobe center and duration @.050 lift that matters

racer17j
Dirt Forum Champ
Total posts: 5390
posted June 10, 2005 08:14 PM  
Hey just drill and tap a small hole in the back side of your exhaust manifold angled down toward the ground, screw a pipe nipple in it and hook a vacuum line to it. that will create vacuum. but you can route the vacuum line so they wont think to follow it, and be sure you cant see the nipple. DISCLAIMER...
check your local rules, I am not responsible for you getting called a cheater if you do this and get caught.

------------------
Hey, check out my new site www.freewebs.com/0sixracing

nine finger
Dirt Forum Racer

Total posts: 76
posted June 11, 2005 04:25 AM  
steve the only posts that make any since are by iowatoolman. i cant believe some of the **** people are trying to post.you need to learn not to listen to half of this stuff.Call a cam manufacturer!!! I prefer comp cams but most can make good cams, find a salesman write down his extension and talk.find a good salesman and you will find that you will no longer have to look through catalogs to pick cams. i have been building motors for a long time and i still rely on my cam man to provide me with the very best grinds available for what i am doing. now to your question, compression helps.assuming you are running a chevy fel pro makes a still shim rubber coated gasket .015 thick this will help if your static compression is low.valve job must be correct and fresh for maximum vaccum.intake must sill tight same for carb. check throttle shaft for vaccum leaks. if you run a pvc must function properly for max vaccum. hint i run two and very low oil ring tension. carb must be set properly for the range it will be tested. if your throttle blades are past the transfer slots to get it to idel you can forget any vaccum. while the cam does affect vaccum there are a lot of other things you need to look at. it sounds like iowatoolman has already figured this out. also run as much timing you can at the rpm range you will be tested. your timing needs to be locked down. then you can run a vaccum advance of of manifold vaccum only, not from ported carb vaccum. lets say your locked timing is set to 40 degrees, then you add 10 to 15 vaccum advance it wont hurt your motor at idle and your vaccum will be a point or two higher.

sc1 racing
Dirt Freak

Total posts: 419
posted June 11, 2005 06:14 AM  
cam does not effect vacum?

i dont get that cam controls vacum and compression

nine finger
Dirt Forum Racer

Total posts: 76
posted June 11, 2005 07:41 AM  
yes a cam does affect vaccum read it again. you can take a stock cam and have evarything else messed up and it might only make 15 in. of vaccum. what i am saying is if you dont pay attention to all the details you will never know the vaccum potential of any cam.

iowatoolman
Dirt Freak

Total posts: 369
posted June 11, 2005 10:05 AM  
a cam does control vacuum and compression

advancing the cam will pick up more compression not so much static as dynamic

yes nine fingers has it right that everything works together and relies on each other to get the highest vacuum

and yes timing has alot to do with vacuum

but enough of the schooling for today IT'S RACEDAY

drive hard or drive home

97dirt
Dirt Forum Racer

Total posts: 94
posted June 11, 2005 03:45 PM  
quote:
Originally posted by iowatoolman:
set at 1000 rpm with a solid cam

sorry i don't give away my cam numbers

drive hard or drive home


Hey Iowatoolboy,either I'm blind or you can't read,no one is asking you for your top secret, special agent, Barney Fifthe, security clearance, black magic, witches brew, NASA spaced aged cam secrets!!!!!!

iowatoolman
Dirt Freak

Total posts: 369
posted June 12, 2005 07:50 PM  
i was just stating it up front but thanks for the notice


LOL :-)

drive hard or drive home

Stevei2i0
Dirt Full Roller

Total posts: 54
posted June 16, 2005 08:50 PM  
OK... this was fun, but it over... Thank ALL for Your OPINIONS!!! I just backed off on the valves a lil, and last time I checked, at 160', the vacume was 18.5. Again...Thanks! (whew)('.')

petordragon
Dirt Maniac

Total posts: 167
posted June 17, 2005 11:26 AM  
good luck running lash on a hydraulic cam.

Stevei2i0
Dirt Full Roller

Total posts: 54
posted July 10, 2005 09:55 AM  
OK! Its now the 10th of July. The cam held out just fine with the "lash". Cant say the same for the #5 piston, when the water pump belt jumped off and blew the head gasket. Thanks again for all the thoughts!

Back to the Archives