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jgs240 08-15-2009 07:18 AM

Poor performance, gas smell, black smoke...
and hard starting (i have to keep it floored to get it to start up).

I have a 305 w/holly two barrel (unsure of anything more than that). This is the first time the car has ran in over 5 years. My father in law helped me go through the carb and remove all the old gas/varnish. I replaced all the fuel line heading up to the carb due to dry rotting, and i replaced the fuel line that runs across the back of the carb. I re-assembled it, and put it back on the car to get things it runs pretty rough.

It idle's high, you have to floor it to get it started, i smell like i have been riding a two-stroke dirtbike after i drive it around awhile, it is really down on power, and throttle response is horrible.

Is this a simple jetting issue? My in-law suggested that the carb on their is a bit larger than what he would like to see for a stock 305, and this would be a good time to move down to a smaller carb.

How do id my current carb? I know their are stamped numbers on it, but i dont know which ones are used for ID.


jgs240 08-15-2009 07:53 AM

I just went out, got a few pics to help with an id and also wrote down all the numbers i could see besides the patent #'s.

Near the top, front side of the carb on the drivers side were these numbers:


Where else should i look for numbers? Also i noticed that my choke is safety wired open....which would explain the full throttle starting? I dont know how the slipped by me before now, ill chalk that one up to not knowing better lol.


And this has me a little concerned, another thing i skipped over until now.

Thats the throttle linkage, does this pose a safety risk? The spring rubs on the intake....?

BugRod 08-15-2009 11:12 AM

First of all, thats not a two barrel but a four barrel. And yes having the choke open will make cold starting harder. I think you have a leak somewhere in the carb or the float level is set too high

saitek5678 08-15-2009 11:23 AM

Ya, count, its 4 $barrel. Carb floats are not floating , stuck or not adjusted right. I would guess you need to go through the carb again. No adjustment would make it flood that radical.

saitek5678 08-15-2009 11:25 AM

Nice pictures by the way!

carsavvycook 08-15-2009 11:36 AM


Originally Posted by BugRod
First of all, thats not a two barrel but a four barrel. And yes having the choke open will make cold starting harder. I think you have a leak somewhere in the carb or the float level is set too high

I agree that the float levels may be set too high, or there is some 'junk' keeping the needle and seat open.

Take the float adjustment screws off, and lift up the adjustment nut. Then count the threads showing above the float bowls, with the lower gasket removed. Somewhere close to 3 1/4 threads showing is very close to the correct float level.

Make these adjustments, and road test it, being sure the secondaries open. This will lower the fuel level in the float bowls. Then when you get back, leave it idling, and remove the float level sight plugs. The fuel level should be at the bottom edge of the threads. If a lot of fuel runs out, the needle and seat is most likely bad.

To raise the float level turn the adjustment nut counter clockwise, to lower it turn it clockwise.

saitek5678 08-15-2009 11:47 AM

Nice thing about holly four barrel of this type YOU CAN adjust float level external. maybe go full low adjustment, if it still floods there is a poblem with the float or needle and seat. Also if you did a carb kit and there were many gaskets to chose from make sure you used the right ones.

wildthing 08-15-2009 12:09 PM

yep i had this with my rebuilt holley. i just bought a new carb and cured the problem. also check your plugs they are probley black from flooding with fuel.

jgs240 08-15-2009 01:06 PM

Thanks guys!

Plugs were just put in during the time i went over the carb. Should i pull them again and clean them up before trying to do any more adjustments?

'carsavvycook', or anyone else for that matter...are their any online diagrams showing what is what on these? Im very inexperienced with larger carbs like this (2 stroke carbs im ok with lol), but i am assuming the floats in inside of the large rectangle boxes on the fore and aft of the carb right?

saitek, you say you can adjust the floats externally....can you direct me to the screw?

jgs240 08-15-2009 01:07 PM

Here's one for those interested:

Its been sitting for awhile...i was busy in college and finally have time for something like this :)

jgs240 08-15-2009 01:10 PM


Originally Posted by saitek5678
Nice pictures by the way!

Thanks, these didnt come out all that great...ive been working on it though:

carsavvycook 08-15-2009 01:14 PM

It is on the top of each float bowl, it is the flat blade screw, and the IIRC 5/8" nut. I can see them clearly in your pictures.

I do not have a Holley float bowl to take a picture of, maybe somebody else does.

saitek5678 08-15-2009 01:21 PM

LOL that frog makes me laugh! that is neat as hell! ya turn the one screw out and lock it into place with the nut. Looks like they are wrong in the pic

saitek5678 08-15-2009 01:25 PM

I mean both screws, I am still laughing, you should submit that pic of the frog to smisthonian or somthing! Its sick!!

saitek5678 08-15-2009 01:30 PM

Refer back to carsavveycook and it will make more scince now

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