Holley carb issue
- Thread starter bigfella
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If this is a "new" Holley carb and not a "new to you carb" I would also say the float level is probably too high, they come from the factory with a baseline setting and you adjust it from there, typically engines sit at an angle and you have to adjust the floats accordingly.
As far as flipping it over that affects nothing, when you rebuild a Holley you flip the float bowls upside down to do your initial float setting.
You do have a power valve(s) if this is a new factory Holley carb but as far as power valves blowing that would be highly unlikely since Holley's have come with built in power valve protection for the last 15+ years.
It is also possible depending on what mechanical fuel pump you are using it could be overpowering the needle and seat from too much fuel pressure, many performance mechanical fuel pumps require a regulator when using them.
As far as flipping it over that affects nothing, when you rebuild a Holley you flip the float bowls upside down to do your initial float setting.
You do have a power valve(s) if this is a new factory Holley carb but as far as power valves blowing that would be highly unlikely since Holley's have come with built in power valve protection for the last 15+ years.
It is also possible depending on what mechanical fuel pump you are using it could be overpowering the needle and seat from too much fuel pressure, many performance mechanical fuel pumps require a regulator when using them.
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Have you looked up that carb on the Holley site?
"WARNING: This carburetor is NOT designed for use with any automatic overdrive transmissions. If used on an automatic overdrive vehicle, severe transmission damage WILL result."
and it doesn't have any power valves...
"INSTALLATION INSTRUCTIONS Since this carburetor is intended for racing applications........."
https://www.holley.com/products/fue...le_pumper/classic_double_pumper/parts/0-4777C
http://documents.holley.com/199r7923-2rev2.pdf
"WARNING: This carburetor is NOT designed for use with any automatic overdrive transmissions. If used on an automatic overdrive vehicle, severe transmission damage WILL result."
and it doesn't have any power valves...
"INSTALLATION INSTRUCTIONS Since this carburetor is intended for racing applications........."
https://www.holley.com/products/fue...le_pumper/classic_double_pumper/parts/0-4777C
http://documents.holley.com/199r7923-2rev2.pdf
I would check a spark plug and see if they're black. That 750 you tried on it could have fouled the plugs causing it to run rough. An over rich bigger carb usually makes them seem to run like hell till the plugs get fouled. If you do not have a vacuum gauge, you cannot properly tune a Holley. Gauges are cheap. (around $15). You set the air bleeds to the highest reading on the gauge. After car is warmed up, put it in gear, gauge on manifold vacuum, whatever your reading is, split the number in half and that's the proper power valve size for your engine. To check primary jet size you must be driving normal above 35mph on a less populated side road and kill the engine, check the plug, and jet up or down depending on how they look. Only go 2 sizes at a time on jet size. You cannot just bolt on a new carb and expect it to perform at its best. Every engine is different and you have to tailor it. All the above tuning info depends on your timing being set correctly first. If the timings was incorrect, the carb tune will be too. To drain your carb float bowl on the car, I like to use a spray paint cap. Hold the cap under one of the bottom float bowl bolts and loosen the bolt and unthread it a bit. The gas runs into the cup and not all over the engine.
Not the float level , fired it up runs like a bag of crap pulled the plug out to set floats no fuel coming out of the hole but still over fueling the crap outta the engine ...
Needle and seat look good starting to lean towards power valve ?
When the engine is running if I pitch the fuel line off the engine ran well like it should
Needle and seat look good starting to lean towards power valve ?
When the engine is running if I pitch the fuel line off the engine ran well like it should
Since it ran well with the 750 and the only change was the to the 650 then I would personally just rebuild your rebuilt carb since it sounds like whoever you got it from could have possibly done something wrong and it could be anything from improper cleaning (clogged passageway) or the wrong metering block gaskets with improper hole placement or even gaskets that have shrunk or dried out from sitting on a shelf if the carb was ran and then stored.
Once you rebuild it properly all the replacement parts (power valve(s) , needle and seats, bowl and metering block gaskets etc. will be new which will eliminate all the variables and second guessing and since it will be apart you can set the jetting to factory specs if it has been changed.
Once you rebuild it properly all the replacement parts (power valve(s) , needle and seats, bowl and metering block gaskets etc. will be new which will eliminate all the variables and second guessing and since it will be apart you can set the jetting to factory specs if it has been changed.
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