350 SBC 300HP. Flat tappet , bone stock crate engine. 750 cfm edlebrock. Yes, I know I'm over carburated, but I'm saving my green stamps for a 650 cfm. The 750 came off the engine I thrashed. Starts with a tap of the key when cold, or within 5 minutes of shutdown. No gas pedal required. After sitting a bit, it wont fire without excessive cranking. So far it seems like just flooring the pedal works best, with it firing up after 3-5 seconds. Or wait an hour or so and boom, fires right up. I have a fuel pressure gauge and a mechanical fuel pump. I see 6-9 psi holding for hours after shutdown, so I know its not draining back away from the bowl. Ok...ready, set, go. Fix me up boys.
Likely just fuel boiling in the carb, flooding the engine....see about some insulation (carb spacer? heat shield?) between the intake and carb. Or get used to holding the throttle open for hot starts.
Odd...never had the issue with the old engine and I'm using the same intake and carb. I'll try a mycarta spacer and see what that yields
Fuel boiling ( corn fuel ? ) or the carb has a internal leak . Your pressure gauge wont show a spare 1/2 bowl of fuel . Did you have an electric fuel pump on your thrasher motor with this carb ?
You answered your own question ,,,,actually Squirrel did ,,,,,it’s a flooding situation . The symptoms you are experiencing,,,,,and the things you are doing to overcome it . If you have to floor the pedal to start it,,,,,,it’s flooded . 9 psi of pressure is at the top range,,,,,actually a little over the top in my book . And like someone else suggested,,,,a return line is not a bad idea . Tommy
Thanks. Pretty much says the same as Squirrel suggested, and I was thinking... hot fuel. Do you agree a micarta/ plastic spacer could remedy the issue?
Not sure how to go about plumbing in a return line on a mechanical fuel pump... Is the intent to bleed off pressure?
Try the carb spacer first,,,it’s a lot easier then plumbing a return line . However,,,,,your pressure is max,,,,,check it closely . You might could just lower the pressure and fix your problem ? Either way,,,,the pressure is too high in my opinion . Tommy
There are a couple ways to do the return line...one is to get a pump that was made to use a return line, they were pretty common on Chevys starting in the 70s. Or you could use a filter with a return line fitting built in, mount it near the carb, like a 33041 if you have 3/8" line, or 33040 if you have 5/16". either way you have to figure out how to connect a return line at the tank, such as by adding a 1/4 tube soldered into a hole in the sender unit, or something.
I’ll go with a spacer for now and see how that works. Oddly enough, I’ve been threatening to drop the gas tank and install a vent line from the top of the tank to the filler neck. I’m tired of getting a gas bath when standing too close to the fill door. It BURPS gas before the nozzle can react and shut off. If I do that mod, maybe I’ll plumb in a return line while I’m in there.
The 57 tank has a vent line for the filler, but the 55 neck needs to have the vent added to the top of it.
No, the spacer will not change the hard start hot issue, but it may (or may not) help with hot idle issues while running. The key in the link is to totally forget EVERYTHING you have been taught on pressing the footfeed to the floor to start a hot engine. The gas is so volatile the engine never (or takes a long time) catches up to the vapors. By NOT touching the footfeed, you shut off the supply of vapors to the intake, allowing the engine to pump out the overrich mixture. Try it, it won't cost you anything either in parts or labor; and it works! A return line will help, but may not completely solve the issue without changing your starting routine. Jon.
Appreciate the input...however...there's got to be a way to not crank for 5 seconds when hot. Whats the trick?
Run the non ethanol fuel. Hot engine with shit for fuel, a successful start after 5 seconds isn’t bad. As to your other remarks that this didn’t happen on your other engine last year,,, fuel out of the pump changes. Fuel evaporates, percolates, and goes stale faster than ever.
I’d have better luck finding Jimmy Hoffa buried in Amelia Earhart’s plane than finding non ethanol gas out here in the sticks...
wait until it cools off? I've had fewer problems with hot starts with 91 than with 87, on a couple cars. Might or might not help you,.
Your Edelbrock should see 4-5 pounds fuel pressure, maximum. You have a pressure gauge, do you have a pressure regulator? Anyway, with hot start, as @carbking said above, do not touch the gas pedal until the engine fires and you are ready to stop cranking. Touching it during cranking will cause flooding.
Several people have pointed to the high fuel pressure, yet this is ignored in responses. Why? It is easy to lower the pressure to a more acceptable (to the carb) level, so why not? If you don't have an adjustable fuel pressure regulator, you know what to do.
the fuel pumps with return lines were for emissions the vapours were routed into a charcoal canister back to the tank, i don't think that's the issue, i think when your intake was put on whomever didn't use those little square things to block off the heat risers under the intake so the carb is boiling , take your intake off an check , if they aren't there you have hot coolant heating your intake manifold an if you aren't living in the north pole you don't really want that
No trick. Just not HAMB friendly. DITCH THE CARBURATOR! I have done so and would not change back for anything. Ben