First off, let me say I have never liked to mess with carbs. Why? I am scared of them because I have no experience with the modifying, maintaining or tuning of carbs. I am upon the mercy of the Chevelle forum carb guys for tips and assistance making this carb right again.
So, in order to face my fears, I have decided to rebuild my aging and incredibly neglected carb. It is a Holley 750dp mechanical secondaries stamping 4779-7.
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Ages ago I shoved an extra spark plug boot in the manual choke actuator to prop it open... worked great! Now I am embarassed by how it looks and came across an unused HP main body for cheap (70$) to completely do away with the choke tower. Yeah, it doesn't match the finish on the carb (shiny carb, dichromate body) but I'll get over it. :yes:
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So, the specifics are, in no specific order:
71 primary jets, 80 secondary. Power valve in the primary metering block had 3 numbers on it, 656 H, secondary metering valve had a block off plug. Pink primary and brown secondary throttle shaft cams. 30cc accelerator pumps. Main body has changeable main and idle air bleeds, #s 75 and 36.
The HP main body comes with 72 and 84 jets, in their paperwork, they say is recommended as a baseline for the conversion.
Here are some pictures of the tear-down. Please note if anything looks out of the ordinary.
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I cleaned up the throttle plate and put on the new Main body. The pumps had a wierd crunched side, both primary and secondary.
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So, my main questions are which rebuild kit should I get for this, and where should I jet this for safe operation. I just need to have recommendations for jetting, power valve replacement, the stupid umbrella deals at the top of the acc pumps just about disentegrated so they will need to be replaced, ect. The HP body also has changeable air bleeds, so I'll need to know if the ones from the factory are good or need tuning, also.
I am not real familiar with tuning a carb, to be honest, so any walkthroughs or links to tunes with a similar carb would be very helpful. I am not looking to tune this thing for maximum output, just safe operation after the rebuild, really (this is to tide over a couple years so I can replace the drivetrain in one shot). This carb had some issue like only one side of the discharge nozzle would push fuel... which might explain my hesitation off idle. :sad: secondarys were leaking fuel into the intake while off.
Oh. I'm sure folks will ask specifics... so I'll fill in what I can. (I lost the cam card...) BB 396 (moderate lift cam), intake #3963569, rect port iron heads, 1-7/8 primary headers, 2.5" exhaust, TH400 2800 stall, 12-bolt 3:73 open rear gears.
Advice is welcome, as well as critics. My skin is thick.
Thanks in advance...
So, in order to face my fears, I have decided to rebuild my aging and incredibly neglected carb. It is a Holley 750dp mechanical secondaries stamping 4779-7.
Ages ago I shoved an extra spark plug boot in the manual choke actuator to prop it open... worked great! Now I am embarassed by how it looks and came across an unused HP main body for cheap (70$) to completely do away with the choke tower. Yeah, it doesn't match the finish on the carb (shiny carb, dichromate body) but I'll get over it. :yes:
So, the specifics are, in no specific order:
71 primary jets, 80 secondary. Power valve in the primary metering block had 3 numbers on it, 656 H, secondary metering valve had a block off plug. Pink primary and brown secondary throttle shaft cams. 30cc accelerator pumps. Main body has changeable main and idle air bleeds, #s 75 and 36.
The HP main body comes with 72 and 84 jets, in their paperwork, they say is recommended as a baseline for the conversion.
Here are some pictures of the tear-down. Please note if anything looks out of the ordinary.
I cleaned up the throttle plate and put on the new Main body. The pumps had a wierd crunched side, both primary and secondary.
So, my main questions are which rebuild kit should I get for this, and where should I jet this for safe operation. I just need to have recommendations for jetting, power valve replacement, the stupid umbrella deals at the top of the acc pumps just about disentegrated so they will need to be replaced, ect. The HP body also has changeable air bleeds, so I'll need to know if the ones from the factory are good or need tuning, also.
I am not real familiar with tuning a carb, to be honest, so any walkthroughs or links to tunes with a similar carb would be very helpful. I am not looking to tune this thing for maximum output, just safe operation after the rebuild, really (this is to tide over a couple years so I can replace the drivetrain in one shot). This carb had some issue like only one side of the discharge nozzle would push fuel... which might explain my hesitation off idle. :sad: secondarys were leaking fuel into the intake while off.
Oh. I'm sure folks will ask specifics... so I'll fill in what I can. (I lost the cam card...) BB 396 (moderate lift cam), intake #3963569, rect port iron heads, 1-7/8 primary headers, 2.5" exhaust, TH400 2800 stall, 12-bolt 3:73 open rear gears.
Advice is welcome, as well as critics. My skin is thick.
Thanks in advance...
