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Discussion Starter · #1 ·
hey tex.... i am planning on racing in one of my first mud races this weekend, but i am concerned that i won't be able to run in a street class.. i think i am ok except i am unsure if i am going to pull enough vacume..where does it usually get measured? there is a new track here i like.. an actual mud bog with deep holes where my lockers might be usefull and i don't think anyone will run with me in street class..

~~Elusive~~
it's sort of still a cj thingy....
 
G

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They generally check it off the manifold or carb - wherever a line is handy. Most places will require 15" at 800 RPM's if they're checking vacuum, & you have to have a relatively hot cam to not pull that. Most places that do deep pits don't bother with the vacuum since tires play a more important part than engine the deeper it gets. But, some places do check it & I check it in my very lowest "Pit" street class at my G.U.M.B.O. events.

TEX

/wwwthreads_images/icons/wink.gif Got Mud?
G.U.M.B.O. Mud Racing
 

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Discussion Starter · #3 ·
thanks.. i think i have a 292 lift with 508/510 duration.. is there a trick to getting it to pull a bit more?? maybe with timing..just for the check?
i am running in the street class with my prodject tj-7...it's a jeep frame and original engine.. i think i'm ok...
thanks

~~Elusive~~
it's sort of still a cj thingy....
 
G

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Yeah, you're going to be really borderline at best. Timing can help, and I've heard that having the engine fully warmed up is the way to go, but some of these vacuum guys can either verify that or not. I've even heard of guys with roller rockers loosening up the valvetrain for tech & fixing it afterwards. 'Course if you have to pass a post-race tech, you're gonna be SOL with that method. Oddly enough, in my 13 years of mud racing - all in street stock & super stock, I've never had a vacuum test. The only events that I've attended that had a vacuum check had me bumped up out of the vacuum class due to some other mod - like an engine swap.

TEX

/wwwthreads_images/icons/wink.gif Got Mud?
G.U.M.B.O. Mud Racing
 
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