Conference vmsnet::car$note:carbuffs

    I'm removing the power valve in my Holley, and the book says, 
    "If you do this, you must go up 6 to 8 sizes on the main jets".
    
    OK, do I need to go up 6 to 8 jet sizes on the secondary side too,
    or do I just do this on the primary side?
    
    MadMike

It all depends on what you want to do with the thing.

The power valve is designed to open when the manifold vacuum drops below a
specific level.  10.5" of mercury for a 105, 8.5" of mercury for an 85, etc.

At normal cruising speed, the power valve should be closed.  When you open 
the throttle, the power valve opens as well and dumps about 6 or 8 jet 
sizes worth of extra fuel into the throat.

Do you want to drive this car on the street?  If so, leave the power valves 
alone or drop the rating down to 25 or so.  That way they'll only open at 
WOT

    My M151 Jeep has a Power Valve carb and when the engine shuts down, as
    the makes it last couple of turns, it give a squirt into the engine
    doing wonders for restarting in the summer. Another 'your tax $$ at
    work' design. 
    
    Steve

    The application is race only.  Drive on/off the trailer, idle through
    the staging lanes or it's floored.
    
    So the baseline goes up 7 jet sizes on the primary.  What about
    secondary, I'd assume so.  The current jetting is 70/80.  It doesn't
    make sense to wind up with 77/80 when I'm done.
    
    MadMike

If you pull the power valve out of either jet plate and replace it with a 
plug you will have to compensate for the reduced fuel flow elsewhere, i.e.
by enlarging the jet sizes.

    Just for clarification, the carb is a 750 double pumper.
    The primary block has a power valve.  Current main jets are 70.
    The secondary block has no valve, current jets are 80.
    
    When I get done I'll plug the primary and jet it at 77.  I'll jet
    the secondary 87.  Fortunantly I have quick change bowls on both
    ends.
    
    The problem I'm trying to solve is blowing the thing out all the time,
    AND having one other variable in the tuning equation.
    
    Thanks
    MadMike  

>    Just for clarification, the carb is a 750 double pumper.
>    The primary block has a power valve.  Current main jets are 70.
>    The secondary block has no valve, current jets are 80.

>    When I get done I'll plug the primary and jet it at 77.  I'll jet
>    the secondary 87.  Fortunantly I have quick change bowls on both
>    ends.
    
If the secondary doesn't use a power valve, don't re-jet the secondaries
    

    THAT'S WHAT I NEEDED.  :^)
    
    Only raise the jets where the powervalve is present, i.e. primary in 
    this case.  So to baseline, it'll be 77/80.
    
    MadMike

Oh, you sent me some mail, didn't you.  I musta accidentally deleted it 
cleaning up the nearly 400 mail messages I got while I was in Australia.

Send it again.  Something about a button on the shifter???????

    
    
    	I'm considering popping a new 4 barrel carb and intake manifold on
    my '78 305. I'm not looking for a hotrod here...just a little extra
    oomph. What kind of problems can I expect to run into? Different
    linkages, etc? The local shop has some edlebrock (sp?) carbs and
    manifolds.
    
    	thanks,
    
    	jim

    Get the Edlebrock Performer manifold.  Skip the Edlebrock carb,
    I'd get a holley... 600-650 cfm.  
    
    Simple bolt on.  If the linkages aren't positioned properly, you can
    get a simple adjustable throttle bracket for cheap.
    
    MadMike

    
    	thanks. that's the info I was looking for.
    
    	jim