360/390 perkolate problem
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Cross-Country
Joined: Oct 2007
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360/390 perkolate problem
Hi Gents, Has anyone ever over come the after run hot soak percolation problems with the sister engines. both my 360 and 390 run with new alum. radiators and both perk the carbs and cause miserable hot starts unless let cool for 20-30 mins.
The 360 is stock 2300 carb and cast manifold. The 390 has an edelbrock 4 bbl, and an alum performer manifold. I mean less than 20-30 min possibly more cool off and it's foot to the floor and a long grind to finally get them to kick. Some times I even get a pop out the carbs on start up then usually a die-off cause no fuel till it pumps enough into the carb then normal run. I have started em on idle circuits as no foot feed and many times I get a start then the die after a short run requiring another long turn over to put fuel it the carb then we run normal. Get this one, once I got a back fire and blew off the welsh plug on top of the left booster venturi which happened 15 miles from home so the idle was shot and could hardly run.
got home and put in a new plug and cured that problem, now to see about the hot starts.......some times I retard the timing to get a faster spin once running I put it back to normal I dont get a back fire n it turns over faster.
The 360 is stock 2300 carb and cast manifold. The 390 has an edelbrock 4 bbl, and an alum performer manifold. I mean less than 20-30 min possibly more cool off and it's foot to the floor and a long grind to finally get them to kick. Some times I even get a pop out the carbs on start up then usually a die-off cause no fuel till it pumps enough into the carb then normal run. I have started em on idle circuits as no foot feed and many times I get a start then the die after a short run requiring another long turn over to put fuel it the carb then we run normal. Get this one, once I got a back fire and blew off the welsh plug on top of the left booster venturi which happened 15 miles from home so the idle was shot and could hardly run.
got home and put in a new plug and cured that problem, now to see about the hot starts.......some times I retard the timing to get a faster spin once running I put it back to normal I dont get a back fire n it turns over faster.
Posting Guru
Joined: Mar 2016
Posts: 1,412
Likes: 1
From: Barre Mass
Sounds like the gas is boiling in the carb. Common problem. You may need a phenolic carb spacer.
This is just an image off google. you should order one for specific carb model. Good luck hope you get it resolved.
Tuned
Joined: Jun 2018
Posts: 334
Likes: 9
Those help alot I have one but I'm afraid today's gas boils at a lower temp than gas 40/50 years ago especially if running a mechanical fuel pump losing it prime , you can keep the mechanical fuel pump if you want and run a low pressure 2-3 psi elec fuel pump with it so it will never lose its prime again Holly has one several psi levels actually called a mighty mite . Run it from your tank line into pump then it will pump it into your mechanical fuel pump run a toggle switch if you only want to use it on hot soaks ...I run a 5-7 psi mighty mite from my aux tank needs no regulator blocked off the mech fuel pump section never had a problem again ...
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