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GMC V6 and V12 Engines Engine repair and rebuilding

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  #41  
Old April 23rd, 2023, 03:27 PM
jgpnashville jgpnashville is offline
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Default Re: 305e Holley 500 swap question

Good news all around. The PO of my 67 K15 did a true dual exhaust sometime before it was parked in the early 2000s, so I have plenty of exhaust flow. I made the newbie mistake of assuming the idle mixture screws on the Holley 500 were factory set, as it idled well when first installed, but they were darn near screwed shut. After screwing them in and backing out 1.5 turns for an initial set, the engine idles well. I adjusted with a vacuum gauge on the manifold vacuum line for maximum vacuum and although the gauge needle wiggles quite a bit at idle, the truck is running better than it ever has.
After taking it out for about a 10 mile drive yesterday, she died pulling into a parking lot and wouldn't restart until it cooled down. I believe I have a vapor lock issue, as I'm running the OE mechanical fuel pump with the section of steel line to the carb that runs under the water manifold inlet. I also have an inline clear filter right below the fuel pump inlet and I didn't see much fuel in the filter. Still has the gravity fed in-cab gas tank as well. At first I thought the fuel pump was to blame, but now I think I just had a vapor lock condition.
I was thinking about changing the steel line from the fuel pump to a section of flexible line and maybe routing it over the water manifold to see if this will fix the vapor lock issue. I have also consider going to a universal-style electric fuel pump, where its tied into the oil pressure switch to cutoff, but I'm trying to take baby steps and not re-work everything related to fuel all at once.
Thoughts?
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  #42  
Old April 23rd, 2023, 10:05 PM
jgpnashville jgpnashville is offline
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Default Re: 305e Holley 500 swap question

Well I went ahead with the 5/16" flexible fuel line from the OE mechanical fuel pump to the Holley's inlet and I was able to route the hose over the water manifold and away from the intake manifold altogether, so it should work. I also dropped the jets in the carb from the 74's that came in it to 69's and it no longer smells rich.
Thanks everyone for the ideas and help.
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  #43  
Old April 25th, 2023, 04:34 PM
jerrspud jerrspud is offline
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Default Re: 305e Holley 500 swap question

dying after a few minutes and starting after a rest is more than likely a plugged fuel filter. I had that issues on my original carb and it was just the sock in the fuel thank that was plugged.
Then I had a fuel issue again just this year and the inline filter was plugged.

I have a fuel pressure gauge and a fuel regulator on mine now and that has really helped with troubleshooting in both directions. I've had fuel pressure that was way to high and presser that was too low. The too high was a bad pump and the too low was plugged filter.
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  #44  
Old April 26th, 2023, 05:27 PM
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jbgroby jbgroby is offline
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Default Re: 305e Holley 500 swap question

Quote:
Originally Posted by jerrspud View Post
what's the number for that spring bracket? I don't know what it's called.
https://www.summitracing.com/parts/sum-g1327
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