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Poor performance, gas smell, black smoke...

6K views 71 replies 8 participants last post by  jgs240 
#1 ·
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 running...now 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.

Thanks!
 
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#2 ·
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:

1850-4
2496

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.

Pics:












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....?
 
#6 ·
BugRod said:
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.
 
#7 ·
saitek5678

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.
 
#9 ·
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?
 
#18 ·
thanks cook, im looking into it now.

Also i just went out and found two loose plug wire boots, they clicked when i pushed them down. Its smoothed out a lot, but i am still getting noticeable black smoke. Which way should i be turning the float screws/nuts? 3 1/2 threads showing right?
 
#19 ·
jgs240 said:
thanks cook, im looking into it now.

Also i just went out and found two loose plug wire boots, they clicked when i pushed them down. Its smoothed out a lot, but i am still getting noticeable black smoke. Which way should i be turning the float screws/nuts? 3 1/2 threads showing right?
After lifting the nut off, count the threads showing, then just set the nut back on it, and turn it until you see 3 1/4 to 3 1/2 threads showing. Place the nut back on, and while holding it with a wrench, reinstall the screw and tighten it.
 
#21 ·
saitek5678

jgs240 said:
Followed your directions to a T, but there was no difference. For reference, they were around 2.5-2.75 threads before i adjusted it.

Should i leave them where they were, or leave them where you instructed me?
I think you have a stuck float or the needle and seat are not closing in one of the float chambers, the float actuates the needle and seat, an old fashion way to check this is to blow into the gas port and turn th carb upside down and see if it seals.
 
#22 ·
jgs240 said:
Followed your directions to a T, but there was no difference. For reference, they were around 2.5-2.75 threads before i adjusted it.

Should i leave them where they were, or leave them where you instructed me?
You can pull the needle and seat assembly out, by turning the nut counter clockwise. Use a magnifying glass to look for any debree between the needle and it's seat. Also make sure the o'rings are in good shape.

If you do not find anything wrong, you may have a sunk float. This would require the removal of the float bowl in question.

Did you test drive it?
 
#23 ·
carsavvycook said:
You can pull the needle and seat assembly out, by turning the nut counter clockwise. Use a magnifying glass to look for any debree between the needle and it's seat. Also make sure the o'rings are in good shape.

If you do not find anything wrong, you may have a sunk float. This would require the removal of the float bowl in question.

Did you test drive it?
Thanks, ill try that out.

No we did not test drive it, i thought that if goosing the throttle did not result in what we wanted then its not fixed....is this wrong?
 
#25 ·
Bingo

Even though i didnt follow your directions exactly the first time around, i lucked out and found this when i pulled the needles:



Both have severe o-rings deterioration and both had little bits clogging the seats. But now my question is this....if this is how these look...what else should i be concerned with?
 
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