Having trouble getting the fuel level to stabilize on my Holley 390 carb.I have set it dry 3 times and lowered it so its a little lower than specs.Still getting too high fuel level when checking by using the site plugs.Thinking now I may have a bad float.Had a real good backfire through the carb when I set the timing 180 off.I dont see any damage to the float but how can I check without buying a new float?

  

Take it out and shake it - if you hear something it leaks. Also immerse it in water. If you get bubbles out, it leaks

54 Victoria 312;  48 Ford Conv 302, 56 Bird 312
Forever Ford
Midland Park, NJ

You didn't mention if the problem occurs at both primary and secondary. I assume this is an early Holley without externally adjustable floats. If only one end has the problem that helps narrow it down. A needle/seat with slight leak could also cause the problem.

If you find no other problems you might check fuel pressure.

http://ford-y-block.com 

20 miles east of San Diego, 20 miles north of Mexico

Hi John.Its a late one with external adjustment.I have tried lowering the float level a little at a time with no success.Set dry it shouldnt be out by any more than 1/4 turn.Thats why I am thinking the float may have gotten't damaged when it backfired through carb.I changed the needle and seat to the steel ones but even with the original "soft tip" ones it still is too high.I am going to try Pauls suggestion tommorrow.

  

Mark

   I am getting a disconnect from your post. If you check it with the sight plugs then why not set it with the sight plugs? Are you saying it will not stay set or something else. Every time I had a bacfire with an early Holley it blew the powervalve not the float.

   More info might help. Pete

Pete! I set it dry initially so I was sure I was starting with a very close to correct setting.Run it for a few minutes so fuel level is stabilized.Check the level via the site plug.Turn the level down gradually.Doesnt have any effect.Shouldnt take more than 1/4 turn at most to set it properly.Another party suggested  maybe the float got damaged when it backfired although visually I see none.Its  brass float by the way.

  

Mark, a backfire cannot damage a float. Since yours are brass you would here and feel fuel sloshing around in it if it was leaking. On a Holley each flat on the inlet adjusting nut ( 1/6 turn ) changes the fuel level approximately 1/32" so your 1/4 turn would only change the level 3/64" barely perceptible by eye. Hope this helps. Mike

1956 Fairlane Victoria (ORREO)

 

Overlooking Beautiful Rimrock AZ

Stuff like this is so valuable, just wish I could remember it!

Mike, located in the Siskiyou mountains, Southern, OR 292 powered 1946 Ford 1/2 ton, '62 Mercury Meteor, '55 Country Squire (parting out), '64 Falcon, '54 Ford 600 tractor.

I can't remember it either. Has gotten worse since I turned fifty. Wife always says, did you google it. Has bailed me out numerous times mike

1956 Fairlane Victoria (ORREO)

 

Overlooking Beautiful Rimrock AZ

Mark - At the inlet to the bowl on a 4160 type carb, there is a filter element captured under the inlet fitting. Be sure its clear. Wash with rubbing alcohol and a (very) fine brush.

Just one more thing to look at...

 
 Steve Metzger       Tucson, Arizona