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Old 06-14-2010, 10:08 PM
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650 Holley Questions

Hey guys, I have a few questions about a carb that I'm trying to get running.....and I'm not sure how much info is needed to answer but I'll throw it out there.

I have the following motor in a '70 GMC:

350 4 bolt that was line bored and paralleled (355 cu in), Fm Pistons @ 11.25: 1, forged crank .010/.010 with hd forged rods with ARP connecting rods/bolts, Cloyes tru roller chain, CompCam 284/484, Speed Pro lifters and push rods.1998 vortec heads with dual springs pocket ported and Bowl Hawged. Edelbrock "Performer" intake, Hedman headers, Accel wires , GM stinger HEI, 85 GPH Fuel Pump, etc.

Originally I had a 600cfm Edelbrock performer on top but wanted something a little more potent so I went ahead and got a remanufactured 650 Holley double pumper. I'm having some trouble getting it to run and would love any suggestions!!!!

Some of the things I've tried are:
1.) Adjusting the float levels but I'm assuming in order to use the sight plug..........for which I'm assuming it has to be running in order to keep the level because when it's off you can't see any fuel in the bowl through the hole........and I can't keep it running on it's own to check!

2.) Adjusting my idle mixture screws

-------- With all the messing around the best I've gotten from playing with both the float levels and mixture screws is that it starts and seems to run a little rough (definitly smokier than normal = Rich) but even after that I have fuel puking out the top and sitting around on my intake = worried about a fire!!!! Even then it still eventually dies from what I assume is flooding based on the exhaust in the garage!

I'm not real familiar with using Holleys or double pumpers so is a good part of my problem that I need to use a pressure regulator? I also didn't have a gauge on the fuel line so I don't know if it's in the 7psi range or not. I also do not have the choke connected either but didn't think I'd need it.

Any suggestions on where to start before I have to tuck in my tail and drag it down to a mechanic shop would be appreciated!!!!!

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Old 06-14-2010, 11:10 PM
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I'm no expert as I am still learning myself, but I would say you need to hook that choke up first things first...
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Old 06-14-2010, 11:15 PM
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Sorry I didn't catch everything you said the first time.....did I read that right you have fuel pouring out the top of the carb?
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Old 06-14-2010, 11:30 PM
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Edelbrock 5 psi max at the inlet.
Holley 6 psi max at the inlet.
With 11.25:1 SCR, this must be a drag truck, so run minimum 1/2" line from the cell to the filter, to the pump, then to a regulator (that will return excess fuel to the cell through another 1/2" line), then to the carb. Mount the pump as close to the cell as possible. Filter/pump/regulator all right there together at the rear.
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Old 06-15-2010, 07:54 AM
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Carb Continued

Hey again guys,

In response to the last thread I didn't mean to put my compression ratio at 11.25:1!!! It would be more in the area of 9.5 or 10. Definitely not a drag truck!

As for the choke.......the assembly itself and components are all in place, I just have not put a cable on it as I generally won't be using it in a condition where a choke application on start-up would be required. So, that shouldn't really affect the running of carb would it?

Also in regards to where my fuel is flowing........I was flying solo during the test starts so when I did get it to run (with the floats raised higher) for about 30 seconds, there was fuel running down the sides and onto the intake and some collected on the top of the carb.

First things first I'm pretty sure I'm going to have to install a regulator and gauge on the line to see where my pressure is at as I might be just trying to force as much fuel in as my pump will push right now! If you leave it for a few minutes and try it, the engine will start then quickly fail which may be because it's overwhelmed with fuel.
- Going to go with a deadhead regulator first since I don't want to run additional lines back to the tank just yet! I know they aren't the best way to go but if it'll get it running for now thats a start.
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Old 06-15-2010, 09:00 AM
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a cam that big needs lot of ignition timing. I would say about 25 degrees at idle and about 38 to 40 max.

get the timing setup first then mess with the carb.

read this.

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Old 06-15-2010, 11:30 AM
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There is a good chance the power valve could be damaged and leaking fuel.
I would try that first.
I would check for base plate to see if not warped. Sometime the gasket between the base plate and carb body may not seal properly.
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