A bit of surging at idle, and hot start delays

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   Several weeks ago I installed a Speed Demon carb with a plastic body. The car runs great with it, except that it now takes several seconds for it to fire up, when it has been sitting for more than a few minutes. I'm assuming that despite the plastic body, fuel is still evaporating. It also surges a bit at idle, and rpm is down some. I only have to drive for less than a minute, and it idles just fine. The car still runs as it should, cruise, wot, no issues. But the surging is new. It has an electric choke and even in freezing temps it fires immediately, as long as I push the throttle down once before turning the key. I'll check vacuum at idle to make sure it's not too lean, and I'll see if I can install a spacer and not mess up the linkage. Anything else I should do?

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Dino Members Profile Send Private Message Find Members Posts Add to Buddy List Member Joined: 08-September-2023 Location: Jackson Mi Status: Offline Points: 150	Post Options Post Reply Quote Dino Report Post Thanks(0) Quote Reply Topic: A bit of surging at idle, and hot start delays Posted: 16-November-2023 at 5:24AM
	Several weeks ago I installed a Speed Demon carb with a plastic body. The car runs great with it, except that it now takes several seconds for it to fire up, when it has been sitting for more than a few minutes. I'm assuming that despite the plastic body, fuel is still evaporating. It also surges a bit at idle, and rpm is down some. I only have to drive for less than a minute, and it idles just fine. The car still runs as it should, cruise, wot, no issues. But the surging is new. It has an electric choke and even in freezing temps it fires immediately, as long as I push the throttle down once before turning the key. I'll check vacuum at idle to make sure it's not too lean, and I'll see if I can install a spacer and not mess up the linkage. Anything else I should do?

78FordLtd2 Members Profile Send Private Message Find Members Posts Add to Buddy List Member Joined: 19-April-2021 Location: Canada Status: Offline Points: 184	Post Options Post Reply Quote 78FordLtd2 Report Post Thanks(0) Quote Reply Posted: 17-November-2023 at 4:34PM
	Either the fuel is evaporating or the float bowl is draining out back to the pump or tank. Sounds like initially the pump is not providing the carb with enough fuel to light it off and idle right away. Have you tested your fuel pressure? Having low fuel pressure might be what is causing some of your surging issues along with possible vacuum leaks. I'd check for those too. Start with the basics and check your fuel pressure, float level, mixture settings and your choke settings. Also spray some brake cleaner around the base of the carb. You may have a vacuum leak. Try that and hope that helps.

aquartlow Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 19-December-2011 Location: Summerfield, Fl Status: Offline Points: 2341	Post Options Post Reply Quote aquartlow Report Post Thanks(0) Quote Reply Posted: 17-November-2023 at 10:44PM
	If you have tried different spacers to isolate the carb from manifold heat and still have issues, this may be the remedy. I've tried a version of this on a Holley and had great results, but it involved drilling the umbrella seal mounting pad with a pin drill (.015") for bypass. This condition is relatively inherit with Holley's when they went from the ball/catch for the accelerator seal to the umbrella type of seal. Hope this information is helpful. holley with fuel coming out of squirters after shut down - CorvetteForum - Chevrolet Corvette Forum Discussion
	www.supermotors.net/22468 Yeah, It's a Hybrid...It burns gas and tires. No matter how good she looks, somebody, somewhere, is tired of her sh*t. Beauty is skin deep, ugliness goes clear to the bone.

Rockatansky Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 30-July-2010 Location: On The Road Status: Offline Points: 6398	Post Options Post Reply Quote Rockatansky Report Post Thanks(0) Quote Reply Posted: 18-November-2023 at 7:08AM
	my 1st thought. is it a lean surge or a rich surge? i'd give the carb opening a shot of something to determine if it's rich or lean, if it runs smooth on a spray shot then it's lean, if it stumbles worse it's rich and you can use that info to go from there
	72 GT Ute

Dino Members Profile Send Private Message Find Members Posts Add to Buddy List Member Joined: 08-September-2023 Location: Jackson Mi Status: Offline Points: 150	Post Options Post Reply Quote Dino Report Post Thanks(0) Quote Reply Posted: 20-November-2023 at 7:09AM
	Thanks guys, I'll run those tests and see what's what.