Looking for some guidance here. I have a recently rebuilt 440 with a slightly improved cam and msd ignition with billet distributor. Exhaust is stock manifolds with TTi exhaust pipes.

The carburetors are the aftermarket version of the correct 6 pack carbs. They were recently rebuilt and tested on the bench. All in all the carbs work well with no stumble under hard acceleration but the carbs were running rich at idle.

The car starts well either cold or hot but always runs rich. I closed the idle air/fuel mixture screws on both sides of the center carb and expected the car to stumble so I could start to adjust but no stumble occured and most of the rich gas smell went away. I also had to lower the curb idle screw so that the idle was at 900 while in drive with foot on the brake.

A friend tells me that I am not running on the idle circuit and the carb must be giving the engine gas in some other way.

Why is the carb running and idling well with the air fuel idle mix screws entirely closed? This seems strange but in reality the car seems to run well.

Also, any opinions on whether center fuel bowl breather tube should be connected by a hose to the valve cover breather or left unconnected and no hose.

thanks for all the help.

Power valve is either ruptured, wrong PV gasket, and or wrong valve and gasket, there are 2 different PV/gaskets asseblies for the Holley

Run it to the valve cover if you wish?, using a 2 or 3 nipple breather, as far as leaving it open, an engine/carb fire is possible, not good...so I would put a vacuum cap on the fitting, won't effect anything

Mike

Thanks Mike. I will take a look at that.

Funny. I had a cap on it and someone told me that was wrong and must be left open or vented to breather cap on valve cover. Sounds like I will put the cap back on since my breather has only one port and that goes to my six pack air cleaner port. Thanks again. I think mancini's tilde me I could cap that port when I bought the single port breather.

Great advice.

100% with Dayclona. and until you fix the power valve issue you're pretty much chasing your tail. been there done that exactly with a leaky and wrong power valve.

You need to check your idle vacumn to determine which power valve you need, manifold vacumn holds the valve closed, not enough allows the valve to open and enrich the mixture. Usually a good rule of thumb is to check your idle vac and if it is, say 10", you would use a power valve marked 5 or 5.5. Since the carbs were rebuilt, I would also check the idle mixture screws on the end carbs, they could be open too much and be contributing to the overich idle. About 1/2 turn out from seated is a good start.

I have several sixpack cars all have the breather/vent on the center's bowl plugged with a vacuum cap, no issues, left open is what the factory did if the carb was vented and there where no provisions or requirements for evaporation control....left open you have a greater chance of a carb fire, and with the faster evporative rate of today gasoline, it's just drying up faster in the bowl if sitting for some time, which leaves you with crusty contaminates to foul the carb's passages...something you don't need esp on a multi carbed vehicle

Mike

Capping of the enclosed bowl vent valve hose fitting defeats the purpose external bowl vent valve.
The purpose of the vent valve is to provide an external path for the fuel bowl evaporation to improve hot starting. Without the idle bowl vent valve, all fuel vapors collect in the air cleaner through the main bowl vents, creates an over-rich hot start condition. Problem with six-packs, two other fuel bowls without external venting, still a beast to start hot with the air cleaner in place.

Agreed, but I'd rather deal with a hot start condition (never experienced that on a sixpack set up, don't jinx me...lol!) than the possibility the needle seat sticks and fuel leaks out the uncapped vent, sprays or puddles on the engine/manifold and the possibility of fire

Mike

As far as hot start,33 + years,no matter what temp,turn key,couple of rev's and drive it away !

can you up the initial so you can lower the idle speed? 900 just seems high for a mild cam. how many turns in is the idle speed screw? I would cover the basics, float levels/float saturation/float linkage hanging up/fuel psi at idle/power valve blown. all that is left is the idle circuit(s). 6pack newbie but iirc all (3) are contributing to the idle mixture provided to the eng & it's all gonna add up (1 eng but triple the carbs "amount" of idle fuel)

Robert,nothing wrong with the 900 idle speed,it is actually the factory recommended specs for 6 pk with idle solenoid engaged,evidently he has other issues.

Likely, not enough initial timing, factory specs are not good unless you have to smog test it. Throw the book numbers in the trash and tune it properly, it will run a bunch better.

They tend to like 16-20 initial using a stock camshaft. Cleans thing up a bunch! Tailor mechanical advance to hit your total number and run it.

He's at 900rpm in DRIVE!!!

OP, read this. There's some good info.

http://www.moparts.org/Tech/Archive/fuel/7.html

Not wanting to get into the middle of this "expertise / knowledge" contest but, HMMM???


https://board.moparts.org/ubbthreads/ubbt...umb.html#UNREAD

I was reading down this thread thinking someone must be gonna come up with this. I agree, first thing to check and adjust. Engine possibly not running on idle circuit causing idle mixture screws irrelevant.

Since you have to disassemble to replace the power valve it would be best if you base-lined your set up by using the guide to tuning six paks. A member here [sogtx] is the six pak guide testing dept. He just set up [base-lined] a set of carbs for an unknown 440 six pak. To the amazement of the shop experts where the car is living it started up,idled & ran beautiful the first time. Nice work Andy!

I don't think the bowl vent is the problem here, but as always you cannot troubleshoot a set up with out it being base-lined. Everyone who tries to help forgets this and tries to jump in in the middle of the problem. This is not criticism just an observation. I wish one of them would link every six pak inquiry to the guide so I would have more time to ride [mcycle]. As I work in Technical Support with very complicated technology we achieve proper results with the least amount of pain by starting at the beginning. Thanks to the Lift Off Hood Playground for posting the guide.

how to make the six pak work

Noted!

i think the issue is there are many variations or updates floating around on this site.

I did click on the link & had a copy sent to me. No plans for one but someone might ask me to look at there's. If I did run one I'd have the air cleaners poking thru the hood just for the cool factor.