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GMC V6 and V12 Engines Engine repair and rebuilding

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  #21  
Old May 17th, 2019, 10:42 PM
jerrspud jerrspud is offline
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Default Re: 305e Holley 500 swap question

wow.. thanks guys... I appreciate the info!

I got my 56 with a 4 barrel holley running again and once I get that one tuned, I'll have a better idea how to tune the truck and get the carb dialed in. I'm trying to get as much info as I can to help others as well because there isn't much info on the swap besides some the one page on this site.
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  #22  
Old May 22nd, 2019, 09:07 PM
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Default Re: 305e Holley 500 swap question

so I'm making progress. I discovered a new problem. I have bubbles in my fuel line. I noticed that when I pulled the sight plug and there was no fuel coming out no matter how much I turned it out.

So my guess is the line to the sending unit is not sealed,but I'll check the whole system. Besides that major issue... she idles great.
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  #23  
Old May 22nd, 2019, 11:24 PM
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Default Re: 305e Holley 500 swap question

I had a similar problem with air getting in the line. When it happen I could not get the fuel pump to prime, once I did it would run. What I had found is the new fuel sending unit has a fitting solder to the line. Well it didn't look right but I thought it was just me. I turn out the fitting had back off of the line just enough during manufacturing it had allow air between the fitting and the line. I solder it back on in it proper position and the rest is history.

Here is the thread from FetchMeAPepsi
https://6066gmcclub.com/showthread.php?t=47321&page=58
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  #24  
Old May 22nd, 2019, 11:25 PM
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Default Re: 305e Holley 500 swap question

If you have air in the line, you might have to prime it to the pump to get it flowing again. I tied a tube to my fuel funnel and then tied that into my steel line coming up from my undercarriage to my fuel filter. So it went funnel, tube, steel line under the truck, under cab fuel filter (pass side), fuel tank. Hold the funnel up high and fill it about 5 or six times so it fills the entire line, then take it loose and hook it back up to the pump. Prime the carb and boom, off you go.

If it's sat without gas for awhile the seals dry out and leak air. If you get them wet with gas again they usually seal right back up.


Edit: Haha, James beat me to it! He's a quick one!
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  #25  
Old May 23rd, 2019, 09:32 PM
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Default Re: 305e Holley 500 swap question

On all my vehicles I usually start a folder with information I gather over time from forums or experience. Since we are talking about the Holley 2300 series of carburetor here is the number for the fitting that adapts the original fitting from the stock carb fuel line to the Holley. Fitting to fit Holley 2300 series carburetor for fuel, inverted flare to pipe, BQ248.

One other thing, on my hard to start Willys car after sitting for a long time, starting became really easy after I installed a check valve from Summit racing in the fuel line close to the carb, from then on it always started right away as the gas never had a chance to escape from the line. When the pump started it was always primed.
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  #26  
Old May 26th, 2019, 07:53 PM
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Default Re: 305e Holley 500 swap question

I thought about it for a couple of days and my theory was the sock was plugged. The pump is pulling so hard that air is getting in past the rubber lines. I pulled the sender and sure enough it was plugged up. I have it back in the tank and everything seems to be running well now. I can dive the truck again and it doesn't stall anymore. Much more junk came out then what is in this picture.


So next I'll pull the tank and flush it. The prior owner said he "drained the tank", but I think I just pulled the gas out and never flushed the tank.
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  #27  
Old May 27th, 2019, 01:09 AM
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Default Re: 305e Holley 500 swap question

I believed that what is left of the fuel that had dried up in the tank. Hopefully it won't make your intake valves stick.
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  #28  
Old June 26th, 2019, 06:39 PM
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Default Re: 305e Holley 500 swap question

so some updates.

Truck as been running well, but lot's of black soot out of the exhaust on driveway.

I pulled the 73 jets and installed 72. I also put in some clean plugs to keep track of how they look. I can't imagine one size down is enough... but I'll just drive it an see. Long term plan is to install an O2 gauge, but this will tell me something for now at least.


Anyone running a 2" tach? they are either cheap garbage or really expensive... nothing in between.

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Last edited by jerrspud; June 26th, 2019 at 06:49 PM.
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  #29  
Old June 27th, 2019, 01:03 AM
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Default Re: 305e Holley 500 swap question

Quote:
Originally Posted by jerrspud View Post
so some updates.

Truck as been running well, but lot's of black soot out of the exhaust on driveway.
Just a thought, the black soot could also be from the oil.
Put some miles on it and see if the black soot in the tailpipe goes away.
Have you been tracking your gas mileage? This will also show an improvement if it was too much fuel. Should also perform better to.
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  #30  
Old July 16th, 2019, 05:25 AM
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Default Re: 305e Holley 500 swap question

Put an HEI in as well if you don't already have one to help burn the fuel. I'm running a 500 cfm eddy 4 barrel on my 305E. Opened up a magnum intake. It's way more than the engine needs, but ready for the future 401 or 478 I may find.
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