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sellecting the correct cam for YOUR APPLICATION

PostPosted: November 13th, 2008, 11:01 pm
by grumpyvette
sellecting the correct cam for YOUR combo

look you may not want too hear this but...IF YOU FOLLOW the advice BELOW EXACTLY, youll have a decent cam, ignore it and your very likely to find youve sellected a cam that won,t run correctly in YOUR APPLICATION

heres a semi-fool proof method

write a list of all factors that will influence the choice DON,T LIE tell them EXACTLY what you expect and what you have currently ,installed that the cam must work with NOW, NOT what you intend to install later
YES you NEED too KNOW your COMPRESSION RATIO, and all the other answers to the questions below BEFORE calling....
car weigh?
rear gear ratio?
tire dia.
trans and gear ratios?
stall speed if its an auto?
HEADS (flow numbers)(lift restrictions)
intake type
tire size
intended use
max rpms
launch rpms
fuel octane
carbs,mpfi? CFM

call a minimum of 5 major cam companys, (6-8 is better)
write down thier recommended cam type,its lift, and duration at .050 and LCA.

read off the list to each manufactures tech guys, but DON,T DISCUSS IN ANY WAY WHAT OTHER MANUFACTURERS SUGGESTED

AVERAGE THE RESULTING LIFT DURRATION and LCA info from each cam, and buy the cam thats CLOSEST TOO THAT AVERAGE, (ALL the MAJOR MANUFACTURERS HAVE DECENT CAMS) this tends to give consistantly good results
keep in mind solid lifters generally have an rpm advantage and roller cams generally out perform flat tappet designs but cost more ... parent=327


its MORE critical that the converter stall speed and rear gear ratio match the cam timing and compression ratio if its an AUTO TRANS,......
than if you have a manual trans, which is far more flexiable as to what it will function with.
but having the rear gear ratio and compression ratio match the cam is mandatory for good results
and the larger the displacement and the better the heads flow the more likely it is that youll find both good low rpm tq and mid to upper rpm hp youll want in a street/strip combo, Ive seen many bad combos put together due to sellecting a cam based on, the flawed logic
(well my buddies running cam (X) his car runs good...and I want to beat him so ILL buy the NEXT more aggessive cam with just a bit more durration and outrun him)
in most cases youll be far better off, researching and sellecting a combo with better cylinder heads, intake flow rates and larger displacement, rather than trying to go with a wilder cam.
remember your rarely going to make a huge improvement in hp per cubic inch with cam upgrades once youve reached about 1.25 hp per cubic inch displacement, but increasing the displacement, compression ratio and DISPLACEMENT tends to give a good boost over similar combos with lower displacement/cpr and head flow rates
if a 350 with 9.5:1 cpr that makes 1.25 hp per cubic inch thats 437 hp
build a similar stroker combo that has 401 cubic inchs and 10.5:1 cpr and your far more likely to have about 520hp based on similar components
(the same 1.25 hp per cubic inch plus .04 increased tq due to the higher cpr and increased stroke ) plus all that at a slightly LOWER rpm thats easier on the valve train stress.
you might want to remember that a restrictive exhaust will kill much of the power potential, so decent TUNNED headers and a low restiction exhaust is a necessary part of any build, and unless you can maintain the correct fuel/air ratio you can,t make good hp, so matching the fuel delivery and injector size to the applications mandatory