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Hello all and thank you in advance for any help!!

First off let me say I don't know a lot about carbs so if you tell me something in general terms I will have to research the hell out of it. I don't mind doing that but I just want you to know the type of person you're helping. For instance it took me an hour to figure out which Holley I had and how to adjust the floats (which I havent yet) Just want you to know where I'm coming from.

I just bought a 1968 396 350HP with a Holley 4165. It has full disk brake conversion and M20 transmission rebuilt to M22. The previous owner rarely ran it (likely very old fuel if that matters). I towed it home and have only driven it on short trips (2 to 5 miles)

Day 1. I test drove it about 2 miles with no issues.

Day 2: When I got it home it was fine for about 2 miles then it started idling rough like it was going to stall at the light. When I was driving it fast it was fine. I got home and took the air filter off and notice it was shooting fuel out the front vent tupe while idling. Did some research and it said the float needed to be adjusted. I waited before I was going to attempt this.

Day 3: Started it up and no fuel coming from the vent tube. Was fine at first. After about 1.5 miles the RMPs climbed from 1100 at idle to about 2500. When driving at about 40mph it would maintain speed without pushing down on acceleration pedal. I drove it to gas station and added about 15 gallons of 89 fuel. Still ran at high RMPS.

Drove it home from gas station and let it sit while I did some research. I was thinking that I needed to adjust the low idle but research said I shouldn't have to mess with this. I let the car sit for about 3 hours. It cooled down. Started it up and it was idling at about 1100 rpms. It ran for about 10 minutes in the garage total time. At about 3 minutes in I revved it up with no issues. About 5 minutes in I revved it up again but this time the RMPS stayed at about 1500. I let it sit like this for about 3 minutes then shut if off.

So if I had to make some general observations:

Runs fine when cold. The warmer and harder I drive it the higher the RMPs and possibly the fuel float gets stuck???

Was considering putting Seafoam down the gas tank in case carb was "gummed" up.

Thank you for any help.
 

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Best thing I can suggest is to buy a Holley carb rebuild/tuners guide. I have a very old copy (bought it for a dollar at a garage sale). The book is still available, and is an EXCELLENT book for a novice. It explains how the carb works, how to troubleshoot, repair, and tune a Holley carb.

Here's a link to the book I'm refering to (even though it states 4150/4160, it applies to all their carbs). Other Holley books are available, and are an excellent choice for those that want to learn through easy reading: https://www.thriftbooks.com/w/holly...YBSABEgJW6PD_BwE#isbn=0895860473&idiq=7082214
 
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