My LS5 is making 16 lbs of vacuum at idle...The initial timing is at 18* @ total @ 38* see my sig for eng combo. Does 16 sound like too much? I was expexting around 12. Does the high # indicate anything good or bad?

Not a damn thing wrong with that much vacuum...actually it's a good thing. Typical of Harold's Voodoo cam line... I had a 60101 cam in a stock 350 pulling nearly 19 inches at idle. :thumbsup:

I don't think there is any such thing as too much vacuum. Consider what vacuum means: your engine wants to run and you hold it back by closing the throttle. A higher vacuum indicates you are able to close the throttle more, so less air and fuel are required to keep your engine running.

If I were to hazard a guess though, you are probably running more initial timing than is typical for that amount of cam. My impression is that 270 is about the break point, above that is where the initial really needs to be bumped up. Below that you can often get away with stock settings. You seem to be running the big cam initial timing setup on a smaller cam. It seems to like it. I would not change nor worry about it.

Not trying to hijack the thread, but have a similar issue 16 in. of vacuum. Running that much vacuum would require what power valve. I am running 6.5 now but holley math says vacuum divided by 2. Is there an issue using 6.5 instead of 8 ?

NO It only means the valve is opening a little later with the 6.5. Unless you motor is leaning out, I'd leave it alone.

Does the high vacuum give an indication of engine condition?

Hi Dan,yes,good vacuum with a cam like yours does indicate a good solid engine.

From what i remember your cam some where about 227-232 deg int dur @.05 on a 110 or 112 deg L/S?

If so with 454 cubes i would est approx 15-16 iches at idle and your right on that .

My 396 with 50 cubes less used to idle with appox 12-13 inches of vacuum with a cam that had 228 deg int dur @ .05 on a 112 deg L/S close to your cam specs . A motor with 50 cubes more like yours will have more idle vacuum with same approx cam and you motor's idle vacuum is just where i think it should be.

If it's still running as good as you said it did right after the cam change i would not worry about it and have fun driving it with whats left of this summer which is quickly going by the wayside.

But i did get to the Danbury Sat night Cruise 2x this summer,was real nice cruising to CT. from Pok NY. & back listening to the nice (suttle but not too loud) 396 exhaust note the entire time,it's music to the ears.

Have you had a chance to test out the motor going through 1st/2nd/3rd gears winding it up tight since you broke in the new cam and dialed in the timing & carb for new cam?

I ask this because i am curious how much better you think the perf is and at what rpm you feel the motors power drop off at with your new cam vs the stock cam that was in it?

Scott

I have & let me tell you............what a difference!
Power seems to drop around 5800-6000.(the old cam would drop HARD around 5000-5200) But I need to put in a lighter spring in the secondaries since I feel a rush of power @ 2800 from the seconaries opening.
I feel that the car is now a solid low 13 sec car based on how my low 10 sec Nova felt. (maybe even high 12's with traction & a good driver on the stick)

(btw the Voodoo 268 is 227/233 @ .050 & .542/.554 Lift on a 110* lc)

ttt so scott can see it

Hi Dan,thanks for the ttt,great to hear that cam change was worth all the effort and really woke the motor up alot when compaired to the stock cam.

I was really bumbed out when the that Voodoo cam you have came out a couple yrs after i rblt my motor,i would have used it in a heatbeat.

I went a little too conservative on the cam when i rblt the motor(DANG !!!) it specs out to 222/226 deg due @.05,.525/.525 lift,112 deg L/S angle and is a flat tappet hyd cam.

But my 396(now 402) motor is 50 cubes less then your motor so the Voodoo cam your running would have a more choppy idle and be somewhat hotter in my motor . I think the Voodoo would have a nice fairly hot sounding choppy idle but still be a very streetable cam in a 396/402.

If my comp cam ever goes south i will upgrade to a hotter cam then.

But i cant complain,it does run strong up to 5,000-5,200 rpms where it just plain runs out of steam partially due to stock highrise cast intake,stock ex manifolds,and then the cam.

My friend drove my car and loved the way the motor ran so he put same cam in his car that has same exact motor setup,gear,and 4spd as mine. But his motor pulls a little stonger on top end and doesnt fall off untill approx 5,600 rpms because he is running headers and you can really feel what just the headers do for the power.

His motor is .030 over like mine,same heads,some pistons,same comp,stock gm cast intake,q-jet setup the same,same 3:31 gear,same muncie,same timing curve,etc . But his headers really wake up the mid range and top end of the motor power range when compaired to my motor with stock ex manifolds.

Scott