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Discussion Starter · #1 ·
hey, i was recomended due to my severe stumble on my cleveland to convert to ported vaccuum.
im not reall sure how to do this.
as of right now, there is a fitting on the intake manifold with a vacuum hose going to a plastic "F" and there is another hose that goes to the vaccuum advance. finally there is a 3rd hose from the carb metering block to the vaccuum advance. what do i have to plug off or switch to goto ported vaccuum?>????
thanks in advance
dan
totally stock 351 4v cleveland with 600cfm holley and autolite dizzy
 

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The metering block connection IS a ported connection.

The manifold connection is full time (or manifold) vacuum.

The "F" is a temperature operated vacuum switch that gives the dizzy different vacuum during warm up.

I'd check to see if the dizzy gets vacuum at idle when the motor is fully warmed up or not.
 

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Discussion Starter · #3 ·
so your saying i shouldnt have to change anything? i sent you a PM, but i hooked up a vacuum gage to the metering block at idle and i get ZERO vaccuum at idle, and when i rev the motor the gage goes to the Normal range on the dial
 

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Thats ported. Now you just need to get it to your dizzy to carry out your plan (IIRC, it alsready should be that way).


Why does your friend think it's the advance causing the hesitation anyway?
 

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I'll assume you have a 4V intake on those 4V heads.


Thats A LOT of intake volume.....


Personally, I would start with the orange holley pump cam (screw in the #2 position), and a .028 accelerator pump shooter (MAYBE a .031 nozzle).


I would place the idle mixture screws about 1.5 turns out from gently seated.
 

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Discussion Starter · #7 ·
yea its a 4v intake with 4v heads. its a stock M code 351

how would i do the orange holley pump cam (scre in the #2 position)....i know about increasing the nozzle sizes, but the cam thing is new to me
 

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The pump cam is on theback side of the throttle arm (where the throttle cable ataches to the carb).

It is attached via a screw that you can see from the front of the throttle arm...there are two holes, labeled "1" and "2". #2 usually delivers pump shot where many cars need it but it's a tuning thing.


The cams are color coded, and have a number on their back side. I have the orange #466 cam on my Cleveland.



The idle mixture and speed, as well as the jetting, need to be close before the pump can be final tuned.....


But I'd probably try an #466 pump cam (#2 position) and a .031 pump nozzle if I had a 4V Cleveland with a 600VS.



Incidentally, in your shoes, the 600 holley is probably exactly what I'd use on that stock 4V.
 

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Discussion Starter · #9 ·
so all i have to do is put the screw in the #2 position, increase the nozzle size, and fix the idle screws? i left the idle screw the way holley set them
 

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... and don't see how the ignition timing advance would be the cause of a "severe stumble", or even a stumble at all. I'm in the process of tweaking both an Edelbrock 600 and a Holley 670 Street Avenger - both of which had some light acceleration / cruise stumble. The Edelbrock (not nearly as bad) was due to a lean cruise condition that was solved by going 1 step rich on cruise/power modes with a rod change.

The last time I had the Holley on, I would describe it like your "severe stumble" on light accel/cruise. The guy who had the carb before had jetted it way back due to another problem he was having with his motor - so I'm fairly sure that the carb is running much too lean. Going to test that soon with some more stock-like (larger) jets.

Just some FYI, and that IMO it sounds like your stumble is due to a lean condition - which may be helped by sharkmouth's suggestion of tweaking the cam - but *may* require a jet change as well... Good luck!
 
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