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73-87 Chevy _ GMC Trucks => 73-87 Chevy & GMC Trucks => Topic started by: C-TownC20Guy on September 27, 2017, 03:30:01 pm
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Hey guys I'm new to the group, so let me introduce myself. I'm Mike. I own a 1978 C20. Just had a 4 bolt main SBC 350 rebuilt and replaced the original with it. My truck is a running project, but we are slowly getting there. My problem is with the way it is driving. Like I said it's a project, but in my opinion it should drive like brand new since I did just drop $3k in to the engine bay. Over last couple of days the performance has been extremely sluggish. When cruising, the truck doesn't run bad, but when I try and accelerate out of a cruise into WOT, it immediately bogs down and then wants to kick and sputter and backfire. It continues to do this until I let off the gas. The truck does have significant exhaust leaks that I plan to fix. One such leak is at the manifold/downpipe, and then a few other small ones I have yet to locate. Will the leaks cause the truck to bog in WOT, or is it more of a fuel issue? Any help or advice would be much appreciated. Can also give more info on the truck of needed. TIA. (https://uploads.tapatalk-cdn.com/20170927/01b42aaeeca4b087ed0ddbd7a082748b.jpg)(https://uploads.tapatalk-cdn.com/20170927/5fa50ad8ddeb26de0aeeace8edfa86e0.jpg)
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Hello, welcome to the site. I don't know too much about working on trucks so I cant answer your question but that is a nice looking truck.
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What carburetor is on it? How is the ignition timing set? GM HEI? Vacuum advance connected to manifold vacuum source at carburetor? Are the fuel lines and hoses unobstructed and not kinked or collapsed? Fix your exhaust leaks or you will never get a good tune.
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is the fuel pump new?
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Hi C-town:
I dont think exhaust leaks at the exhaust ports is a cause of your cruise/WOT bogging...it sounds like a fuel system problem where the throttle plates are opening up with a lot of air but not enough fuel is coming in to keep the fuel/air ratio correct so it is stumbling. If you are also getting sluggish performance at other times it also could be fuel problem. There are at least 3 subsystems in the carb that could be causing these problems. What is the story on your carb? When you rebuild or put in a new longblock you need to at least give the old carb a tune-up if not a rebuild even if it was seeming to be OK before the engine replacement.
Regards,
Henry
PS: nice, clean looking longbed!...what is it?...Custom Deluxe?