Last year I installed a Holley 350cmf carb on my Bronco w/351m, and I never can get is set right...... A bud (Chebby guy) was helping me with plug wires cause a thunderstorm was rolling in and by mistake ran the plug wires clockwise on the dizzy and when I fired up the truck the first time with the new carb on BOOM a big fire ball out of the brand new carb.......

Well thies carbs have that backfire protection on the power valve so I just figured that it was still ok, but now that I have tried everything to get the truck to run leaner but nothing. I can turn in the jetting till the truck almost dies and it still is smelling like it runs rich............

If there is anything else I might be missing plz fill me in........

 

Yes, you have a blown power valve. I assume you have a 2bbl as you say it is 350cfm. Chebbie guys don't understand Fords, the cylinder numbering will confuse them if nothing else.

 

If the float isn't too high, then the power valve is probably shot.

 

Float is ok I have checked it many times so I guess I am off to get a new power valve..............

Are they hard to change????

 

Well now that I have thought about it all day and have done some more reasearch on the net here is some more info because I am still undecided on the power valve.


this is how the truck is acting right now...........

I have a gas smell all the time and more so when I am at a idle, but when I floor it to pass someone it runs great but when I let off on the gas I get a really strong gas smell.

In the colder weather it will start but I have to feather the gas even with the choke on almost like it is flooding.

When I first start it it will bog and I have to feather the gas to keep it running but this only lasts for about 15 seconds or so than it will be fine.


Here is where I am relly getting stumped......I really have no black smoke from the pipes and when I turn in my one of my idle mixture screws the truck will try to die.........And thies are the 2 biggest things that I have heard that show you that you have a bad valve.............

I am probibally going to change the valve anyway just to be safe (only $12.00 from the shop that I got the carb from) but I have to pull it apart before I go to get it so I know what size to get and if there is other things that I can try first I would rather not pull my 5 month old carb apart and risk messing something else up.........


Sorry fot dwelling on one topic for so long but I really want to get this done right and I am new to carbs.......

 

Take a vacuum reading at idle in gear. Divide that by 2 to get the needed size. 6.5 is pretty standard on most Holleys. If you can turn in the mixture screws and the engine dies, then it's probably not the power valve, you may just need to drop 2 jet sizes.

 

You might have had a hard time tuning that in because 350cfm is a little on the small size for that truck. Plus, Holleys run rich. You might be better off getting a 1.23 Autolite or Motorcraft carb for it.

 

The 350 should be fine for that engine with the 2bl manifold. first we need to determin if your running rich or lean. pull one of the spark plugs, look at the base, that's the part of the plug the ground strap is attached to , it should have a nice equal layer of gray soot all the way around. The insulator ( that white part in the middle ) should be a light tan to light brown in color ( this takes a while so the base is the more inportant color ) now if your plugs are dark or sooty and the base has clumps of carbon on it. you are to rich. if the base only has partial color around it you are to lean. the thing about holleys is the float level has to be correct ( easy to do with the site window ) the power valve has to be good ( replace it if you think it's bad ) and the jet size needs to be right ( this may take some expermation on your part. That carb should run great if the above conditions are met. also did you check your timeing with a timeing light ? you might be off one sparkplug at the dizzy, this would make everything off.