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Discussion Starter · #1 ·
I have a 427 425hp engine all stock I am running a Comp Cam factory Muscle 520 lift 242 duration 107 intake center the most Idle vac I can get is 13 to 14 we played with timing no luck I had to add a vac pump to insure my power brakes does this sound normal?
 

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Yes
 

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I'm running a
• Adv. 288/300 .050" 229/241
• LIft 600/570 with 1.7
109 Lobe Sep
And I have great power brakes. Where are you drawing vacuum from? Mine is direct in to the intake behind the carb and not the baseplate of the carb.
 

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I'm running a
• Adv. 288/300 .050" 229/241
• LIft 600/570 with 1.7
109 Lobe Sep
And I have great power brakes. Where are you drawing vacuum from? Mine is direct in to the intake behind the carb and not the baseplate of the carb.
Yours is a roller. Not sure what the OP has. Also 107 “could” make less.
 

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Vacuum is developed when valves are closed. The narrower the LSA, the less time the valves are closed.
However, when decelerating, you have a closed throttle and vacuum should increase enough to the needed requirement for power brakes, i.e., 16-20 in/HG
You might check booster vacuum line/route is good and no kinks.
Also, you might run a vacuum gauge inside just to see how much vacuum there is in a driving condition.
 

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Well, as far as the cam goes when you say "all stock", the cam can't be included, which is a critical part of how it will perform on the street. A 107 overlap is ridiculously too radical. Most of the 60's 427's were around 112-114. L88's were solid lifter. I'm not sure what the COPO's came with but my guesss was it fell in line with the L88's and L78's.
 

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Discussion Starter · #10 ·
Well, as far as the cam goes when you say "all stock", the cam can't be included, which is a critical part of how it will perform on the street. A 107 overlap is ridiculously too radical. Most of the 60's 427's were around 112-114. L88's were solid lifter. I'm not sure what the COPO's came with but my guesss was it fell in line with the L88's and L78's.
Thank You for your input When I say stock 11 to 1 compression not modified heads that profile is the closest to stock and listed as stock replacement I am considering a change I am not Drag Racing mostly street I am open to suggestions.
 
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