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I got my rebuilt 650 running good but the only thing is after you shut it off it is hard to re-start...I could turn the key off and right back on and I would have to crank it over while feathering the gas on and off for atleast a minute..I thought maybe it was vapor lock as I re-plumbed the fuel line with a fuel filter when I swapped carbs ... The fuel line looked ok except a small portion of it is near the lower radiator hose... I checked the timing and it was a little retarded so I bumped it up to 12 initial and re-adjusted the mixture...That helped a little but still isn't quite right...when I move the throttle I can see fuel coming out the squrters but when I crank it I can see a little bit of vapor rising from the carb... Im wondering what inside the carb might cause hard starting, could it be the float level? What else might I try aside from just tuning the mixture and timing?
I had just a regular hose running from my fuel filter to my fuel line then one day it wouldn't start as the carb wasn't getting any fuel...The rubber hose was kinked so I replaced it with a steel braded line...The fuel line hose isn't near my header and I loosely zip tied the filter to the brake line. The steel braded part is near my lower radiator hose though, I might insulate the fuel line just as insurance...
I would say it definitely sounds like it's flooding after you shut it off.
A high float level (and/or bad needle and seat) will allow fuel to drip from the boosters once the engine is shut off. (It will typically cause a rich idle as well)..
This will make it seem like it's flooded when you try to restart it.....IE have to put it to the floor for it to crank.
That's where I would start.
Vapor lock won't cause your issue.....Trouble restarting.
Just because the fuel boils in the fuel line once it's shut off doesn't mean there still isn't fuel in the bowls.
The fuel in the bowls alone is enough to start it and run it for a few seconds.
The next thing I would check for is a bad power valve of metering block gasket.
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I set the float level at about half and than tweaked it after I got it started a couple of weeks ago....I don't have a vacuum gauge or a fuel pressure gauge... Right now the timing is at 12 and 36 I adjusted the mixture by turning the mixture screw in till the engine started to die and backed it off about a 1/4 to 1/2 a turn and set the idle at about 800 rpm...The Jets are 67 in the front and 76 in the rear...
The rest of the set up is a basic 350 with 882 heads and a mild mystery cam installed by the previous owner(wish I knew the specs)... a basic performer intake and 1'spacer... Newer MSD HEI dist with new plugs and wires, 3000 stall and 411 gears in the rear...
You mentioned vapor in the carb with the engine shut down. Sometimes that is a good indicator that fuel is leaking into the intake and the heat is vaporizing it. I had that problem with my Edelbrock and it was driving me crazy. It died when I stoped and was hard to restart. I had pulled the carb off and noticed the thick fog in the intake. It was soaked with gas. My floats were way off from the factory. I fixed that problem but the carb still doesn't run right. I have a Holley for it but it's just too hot to fool with it now. Good luck.
What distributor are you running? I had the exact problem with my BB Nova and my son's race car started acting up too. Neither car wouldn't start after driving them or racing, ended up to be the pickup coil in the HEI distributors. Both of them were aftermarket distributors, as soon as I changed them they're running great with no starting issues now. I thought it was the carb too, adjusted then again and again, and each time it seemed better until the pickup finally burt out at 2 cylinders. I diagnosed the second one much sooner, because it was the same as the other.
__________________ 3 69's, 2 L78's, 51 Fathom & 71 Lemans #'s match both w/4spds & 69, 53 glacier blue 4 door
I tried adjusting the floats but its still not right. Maybe one of the needle and seats are bad ??? While tuning it, it developed an off idle stumble which may be caused by one of the accelerator pumps...This was a carb that was rebuilt and then put on the shelf. When I took it apart it was clean and it doesn't leak fuel anywhere...
The carb may not need to be completely rebuilt but I decided to buy "Quick Kit" for $50 as I'm tired of farting around with it. All the Holley carb websites say its better just to buy a kit than throw individual parts at it...
When the kit arrives next week I will replace both the needle and seats, both accelerator pumps, and the power valve...
Most gm starter motors have an extra terminal marked igntion this is to supply full 12v power to your ignition system when cranking your motor i know it makes a huge difference with a points ignition i always hook this wire up. Without it my motor always used to fire just as i stopped cranking.
hard starting could be your ignition not your carb maybe?
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