Rich rich rich just to idle in gear

[69sport]

Hey all,

I got a 318 with 340 heads, a Holley 1850 600cfm and hemi street performance cam and I’ve never been able to lean it out. The car runs super rich with the idle mixture screws out a turn and a half. The driver side screw is a bit wobbly and doesn’t respond like the passenger side screw which is suspicious. I drilled 1/8 holes in the throttle plates thinking that would help but I think it made it worse, it’s like it’s not getting enough fuel without the idle mixture screws turn out so far otherwise my vacuum drops from 15 to 5 going into gear and i stall. I got the secondaries open up about two turns, I can’t get it to idle without them open so far.

Is this a sign of a bad electric fuel pump or just poorly tuned carb/wrong carb for the car???

 

[hunt2elk]

Did you get your timing dialed in before messing with the carb? Kind of sounds like you need some more initial timing?

 

[snakeoil24]

Use a vacume gauge to set idle ratio seek the highest you can if this does not solve problem then something in idle circuit is needing attention

 

[69sport]

Use a vacume gauge to set idle ratio seek the highest you can if this does not solve problem then something in idle circuit is needing attention

I hate to say it but my highest vacuum is about two turns out I’m worried about fouling my spark plugs or is it okay to run like that??

 

[69sport]

Did you get your timing dialed in before messing with the carb? Kind of sounds like you need some more initial timing?

No I haven’t yet and I was trying to play around with it but I need someone to hold the break in gear to check the vacuum while I adjust, that’ll be the next thing I try

 

[snakeoil24]

When you turn screws in what happens to vacum on gauge

 

[hunt2elk]

No I haven’t yet and I was trying to play around with it but I need someone to hold the break in gear to check the vacuum while I adjust, that’ll be the next thing I try

You have to get your timing dialed in before working on the carb. In park with the vacuum advance unhooked, where are you at?

 

[69sport]

You have to get your timing dialed in before working on the carb. In park with the vacuum advance unhooked, where are you at?

15in of hg but idle is at 12-1300 rpm from the open secondaries, once I go in gear I drop to 800 rpm and 5in of hg

I tried screwing in the curb idle and closing the secondaries some but it stalls immediately with curb idle screwed in a small amount (about 1-1.5 turns)

 

[69sport]

When you turn screws in what happens to vacum on gauge

Vacuum drops from 15in in park to about 8in until it eventually cuts out completely

 

[4vnut]

How's your exhaust system? kinked? plugged? ???

 

[69sport]

Passenger side is good, driver side has a hole in the headers that I patched other than that it’s all good

 

[snakeoil24]

Did you look at the idle circuit slots under butterflies to see if butterflies are closed only letting slots being visible? Yes timing is critical but if idle circuit is off you need to check

 

[69sport]

Did you look at the idle circuit slots under butterflies to see if butterflies are closed only letting slots being visible? Yes timing is critical but if idle circuit is off you need to check

The slots aren’t visible under the butterfly’s when closed, I haven’t had luck keeping the car running with them just visible from the underside of the carb however this might just be an insane balancing act I have to perform

 

[Paul_G]

Everything above is spot on. What are your cam specs? A cam with lots if overlap will sound cool but be sending unburnt fuel out the tail pipes. Are you using an air fuel ratio gauge? That is very helpful.

 

[multimopes]

What is your fuel pressure? Do you have a regulator? Have you ever measured it? Sounds like it might be too high to me. I had an electric fuel pump way back when on my old 383 Challenger. I did, however use a pressure gauge and a regulator. It was noisy and the car never ran reliably with it. I went back to a factory mechanical pump & it was much better! I assume that your exhaust pipes are black or very dark inside which indicates a rich mixture. Good luck!

 

[snakeoil24]

The slots aren’t visible under the butterfly’s when closed, I haven’t had luck keeping the car running with them just visible from the underside of the carb however this might just be an insane balancing act I have to perform

You should be able too see the slots when butterflies are closed. Also you mentioned secondaries being open. What’s with that?

 

[4vnut]

Your transfer slots should make a square when viewed from the bottom of the carb. Start with the timing first as suggested in post #7 THEN move to the carb.

 

[R413]

Carb history? Have you rebuilt this carb or is it an unknown used? What power valve is in there? Has it ever backfired through the carb?

 

[69sport]

Everything above is spot on. What are your cam specs? A cam with lots if overlap will sound cool but be sending unburnt fuel out the tail pipes. Are you using an air fuel ratio gauge? That is very helpful.

Idk what the specs are on the cam all I know is my dad installed it in the 80s, I’ll have to dig through all the documentation to find out all I know is that it was called a hemi street performance cam? And no I haven’t used that gauge, I should make that investment. What ratio am I looking for if I get that?

 

[69sport]

Carb history? Have you rebuilt this carb or is it an unknown used? What power valve is in there? Has it ever backfired through the carb?

I did rebuild the carb in April and it was a rebuilt kit for the Holley 1850 vacuum secondaries so the power valve is just whatever comes stock which I’m not sure but I have backfired out of the carb since then but I had the carb off last week and the power valve looked okay