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Well... I guess it isn't the choke. Sorry for buttin' in.
 

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If adjusting the idle mixture screws had no effect, then the carb probably has a blown out power valve. (In the primary metering block)

Also, if a Holley carb has center hung float bowls AND a secondary metering block, it IS a 4150. Maybe it didn’t start life that way but it is now.
And it’s perfectly ok.
The secondary metering block is better than a metering plate.
 

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Discussion Starter #24
If adjusting the idle mixture screws had no effect, then the carb probably has a blown out power valve. (In the primary metering block)

Also, if a Holley carb has center hung float bowls AND a secondary metering block, it IS a 4150. Maybe it didn’t start life that way but it is now.
And it’s perfectly ok.
The secondary metering block is better than a metering plate.
Thank you for the info! The secondary metering block has no idle mix screws. Does that matter?

And interesting about the power valves, because it seems the throttle plates are adjusted properly. Maybe that's the source of my problems because the carb looks pretty clean inside. Is it possible internal passages are clogged as well? Should I dunk it in break cleaner or just scrub it?
 

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A vacuum secondary carb doesn’t have mixture screws in the secondary metering block.
A mechanical secondary with 4-corner-idle would.
Not all mechanical secondary (a.k.a. Double pumper) carbs have 4-corner-idle.

Clean everything with your solvent of choice. Blow out with compressed air.
 

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Where you located? Probably better to find a reputable carb shop and have them rebuild it. I paid $225 for a full rebuild of a Holley HP double pumper that sat for two years with ethanol fuel gunking up all the insides. Car ran perfect after the rebuild.
 

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Discussion Starter #27
Where you located? Probably better to find a reputable carb shop and have them rebuild it. I paid $225 for a full rebuild of a Holley HP double pumper that sat for two years with ethanol fuel gunking up all the insides. Car ran perfect after the rebuild.
Maybe...but at that cost arnt I better off buying a new carb? I mean after being rebuild is this thing even worth $300?

And yep, I relate to years of sitting with old ethanol fuel.

I'm located at the bottom right of NH USA. 40 mins north of Boston, MA
 

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To me it was worth more then an off the shelf carb. For $225 they took my engines build sheet and dyno graph and tuned the carb based on my cam, displacement.. etc. Car went from a light switch type gas pedal to smooth acceleration from idle to wot. I'm not sure I could have gotten that from just doing a home rebuild. As it turned out, my carb had a bunch of parts switched out by the previous owner who probably was trying to get it just right. Unfortunately, he went the wrong direction. I used a place called Performance Carb in CA and was impressed with the level of service. Good luck...
 

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Discussion Starter #29
To me it was worth more then an off the shelf carb. For $225 they took my engines build sheet and dyno graph and tuned the carb based on my cam, displacement.. etc. Car went from a light switch type gas pedal to smooth acceleration from idle to wot. I'm not sure I could have gotten that from just doing a home rebuild. As it turned out, my carb had a bunch of parts switched out by the previous owner who probably was trying to get it just right. Unfortunately, he went the wrong direction. I used a place called Performance Carb in CA and was impressed with the level of service. Good luck...
Thank you, this is an awesome idea. I'll research some places nearby. Maybe they'll even suggest a whole new carb and possibly buy this one off me. Appreciate you sharing your experience.
 
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