[sLOW63]

been trying to tune my carb in and thought i had it all dialed in, but recently when im idling while in drive the car sorta lunges, not enough to move the car when my foots on the brake, but definatly something is wrong
almost at the point where im going to put a whole new carb on it(even went to the speed shop to price it out)
i
f i hold the brake and hold the gas pedal a bit it goes away, so maybe i can just up my idle speed a bit, but thats where i had problems w the carb before. idle speed was way too high and tranny would shift real hard into gear bc rpms were so high, after going through everything that time the only thing i could amount that problem to was some dirt stuck in the idle circuit of the carb

a little background info
194 six, holley 390 4 barrel carb, vacume advance

when i was messing w it last week,
-i put new plugs in (the burn on the plugs looked better than they ever have, but hey had a lot of miles on them)

-cleaned the dist cap and rotor (cap inside terminals always are covered in a white chalky residue that i scrape off, not sure whats causing this)

-set the timing, tuned the carb w a vacume gauge (got its highest at about 14 inches, may be higher think my gauge may be broken, needle starts a below the 0)

-HEI timing set at 8 degrees advanced, i know the advance is fucntioning bc if i unhook it, the car runs like poo on the freeway (higher up in rpms) but not sure what how many degrees the advance is

im pretty sure its running real rich, getting a strong smell of gas out the back

-also swaped out the carb to manifold gaskets and put in a new spacer(old one was cracked) this made it run a lot better got rid of probally a huge vaccume leak, it ran good for a few days and now its running as ive described above

help! going to mess w it sat morn, but not real sure where to start.....

(i know its a long post, hope i got it all in there)

 

[bowtie0069]

holley 390 4 barrel carb

I ran one of those carbs on my 230" 6 cylinder; they tend to be very rich on the idle circuit(typical of Holley stuff) I had to put restrictors in the idle feed circuit-some people add lead shot in the hole, then drill it to size. I put a piece of copper tubing in the hole and it got better, then I stuck a smaller piece into the first piece and it got better again, so.........It all depends on your combo, but with some time and effort you can make them better. They also sell metering blocks with changeable jets to do this, but for the price, it may not be worth the trouble.
In my opinion it's just not a good street carb. for that small an engine, and the gas mileage is not so hot either.

 

[Keith64]

Sounds like your plugs are loading up at idle. As suggested above, the idle circuit may well be the culprit. It would be nice to tune it using an air/fuel ratio meter. That would really tell you wether it is running rich or not and at what RPM. If you don't mind the expense, you could buy one but it's several hundred dollars for one that's suitable for tuning. You also would have to weld a threaded fitting onto the exhaust near the engine so that you could install an oxygen sensor. If you don't want to do that, you might be able to find a shop that can test your air/fuel ratio for you.

Keith
64v8ss4spd
:chev:

 

[Twisted6]

Was this a NEW or used carb?? What happens when you turn the screws all the way in? Will the Motor die Or stay running with No change at all. If nothing changes Then the is a Issue with the metering block it self.

 

[sLOW63]

im not going to drop a couple hundred on a meter, but i may know a guy that has one, so hopefully i can try that

as for the air screws when i turn them all the way in the motor dies

the carb was used, but hasnt had this problem the whole time ive had it, i rebuild it when i first got it, and put about 20,000+ since then, also swapped over to a manual choke, put on a quick change spring kit (now it has the lightest spring in it), and also put a new diaphram for the secondaries in it

i didnt get a chance to mess w it this weekend, the weather wasnt so hot (more rain)

i dont know where to insert the copper tubing? could someone please explain this a little better,

the problem is also intermintent, cant put any rhyme or reason as to what sets it off

(also going to hook my tranny cooler back up, i dont think the problem is in the tranny but it couldnt hurt to put it back on)

thanks guys, keep the suggestions coming!