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how much vacuum at idle?

2K views 10 replies 8 participants last post by  Slant3 
#1 ·
i just got a vacuum gauge today, and i was wondering how much vacuum do u think i should have at idle with valve lift .443/465, .050 dur. 214/224 and adv dur. 280/290.

thanks
 
#3 ·
well the engine isnt running yet, its just sitting in the chassis.
 
#4 ·
Vacuum

Hi!

Doc here:pimp:

18 to 20 hg is proper for your engine.

I'm not sure on a Cam of that lift / Duration about the pulse...

However on a Stock Setup, they say (Whoever "They" really are...) If the needle bounces on Idle look at valves, Valve train...This, again may go out the window with a non~stock cam.

My Vette pulls 20 at Idle, drops to about 16 on throttle, Then returns to 20...and all is Happy and well in "General Mystery" land...

Sooo I'd say if your in the ballpark , and it runs good ... It should be All Good!

Doc:pimp:

=============
Flying is not dangerous;
crashing is dangerous.

You can only tie the record
for flying low.
 
#5 ·
thanks, i didnt know if id loose a little with the lopeyier cam.
 
#7 ·
I ran a very similar cam in a 351W, initial vacuum upon installation was 10-12. After serious carb tuning and timing adjustment/tweaking I managed to get 16-18 running a 750 Holley DP on an open plenum manifold. Since this engine was equipped with an automatic the extra vacuum I got from tuning made a big difference in driveability and mileage. This engine actually got 16mpg in city driving with a 3.25 axle in a 3200 pd car afterward.
 
#8 ·
4 Jaw Chuck said:
I ran a very similar cam in a 351W, initial vacuum upon installation was 10-12. After serious carb tuning and timing adjustment/tweaking I managed to get 16-18 running a 750 Holley DP on an open plenum manifold. Since this engine was equipped with an automatic the extra vacuum I got from tuning made a big difference in driveability and mileage. This engine actually got 16mpg in city driving with a 3.25 axle in a 3200 pd car afterward.

Same here. Before, 15 hg in park, now, 17-18 hg in park.
If I give it gas it goes down to 10 hg.
 
#10 ·
16-18, ok cool, thats what ill try and shoot for. you got some pretty good gas mileage, im going to be running a 3.36 gear, through a 4 speed manual. hopefully ill get desent gas mileage.


thanks for your replys
 
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