I mud race in stock class and new regulations in my race club requires 15 inches of vacuum at idle in stock class trucks.
I have steered away from caming my truck as it is cheating in stock class,
but everyone was doing it and thats why the new regulation.
I was wondering if which comp cam will help or if i should stick with the stocker?
Have a 390, with msd ignition, holley street dominator( will soon change to dual plane wieland or edelbrock) and flowtech headers.
would prefer to get 16 or 17 inches for some breathing room.
any ideas?

 

I'd cheat. Bump the ignition timing up and you'll likely get the vacuum you want (unless it is very radical). Use a vacuum advance, and adjust it so it drops back to where it should be when you put the engine under load.

By increasing the ignition timing on my FE, I can get 18 inHg with my Crane 290deg solid lifter cam, but that's not a good place for it to run. And I suppose my cam isn't all that radical, but it might be worth a try to see if can get over 15 inHg.

 

I would call the cam mfg. of your choice and talk to their tech dept.

 

Get a roller cam

 

A comp 268 cam would be pretty close, but I know a 265 would do it.

Just get the newest mostradical of the cam like the ones above and you should be good to go.

 

Get a cam that has less than 270° of duration but has over .5" of lift I always liked .515 to .525" of lift. Recurve the dist. so you can run 15° of initial but no more than 38° of total mechanical advance. Do NOT use the vacuum advance. It is a gas mileage enhancer and never helps performance. If the rules require it to be connected, just plug the vacuum line between the carb and the advance can and leave it connected.

 

I would definitely call a cam mfg.....Crower Cams & Rhodes use to make bleed down lifters that would allow the cam with a lot higher druation/lift while maintaining good idel & vacume.