Holley street avenger running too rich.
Asked by Qc_pepsi May 17, 2021 at 08:06 PM about the 1973 Mercury Marquis
Question type: Maintenance & Repair
Hey guys! I installed a Holley street avenger 770 on my 460. The car runs but
I have black smoke coming out of the exhaust and I keep fouling my spark
plugs. The carburetor came with .70 main jets that I replaced with .64. It also
came with a .31 squirter which I replaced by .25. turning the idle mixture
screws doesn't affect anything even up to 5 turns counterclockwise. I can't
find any squirters or jets smaller than this so what do I do next. The timing is
set at 12° with the timing advance disconnected and plugged. the rpm is
around 700. the engine has an Edelbrock 2167 camshaft with Edelbrock
5767 springs and a set of Speed Pro H535CP flat top piston. other than that
it's basically stock. Thanks for reading!
15 Answers
Sounds like the float is stuck.
My carburetor has 2 sight glass on the side of the bowls and the fuel level goes to the middle of the sight glass which is what you want, I don't think the float is sticking or I would be able to notice it through the glass.
I am pretty sure turning the idle mixture screws counter clockwise 5 turns is the wrong thing to do. Turn them in and bottom them out lightly and back them out about one turn for starters.
Why eliminate the vacuum advance? Unless you recurve the distributor you won't get the proper advance when cruising. It won't make it run rich and foul plugs but it will hurt your fuel economy.
What I mean is I bottomed the idle mixture screws then slowly turned them counterclockwise. Nothing happened, even with 5 full turns. they are currently at 1 1/2 turn. I am using the vacuum advance. I only plugged it while adjusting the timing.
https://www.holley.com/blog/post/here_is_the_correct_procedure_for_setting_an_optimized_i dle_mixture_and_speed/
Is it rich all the time or just at idle?
I didn't drove around with it since the carb change, but I revved it up to 2000 rpm for a couple a minutes and it still smoked.
Yes, I followed a couple of guides from Holley and others but none of what I did fix my issue
Is this a new or used carb? I might take it back if it is new.
Is the choke stuck closed?
the choke is closed on startup and slowly opens up afterward. keeping the butterflies open doesn't seem to do anything. this is a brand new carburetor from summit racing. at this point, I think I either have to try and get a new one or try to find a shop that can take a look at it.
if I do end up getting another one do you think a 670 cfm would be better suited for my purpose?
I would think that 670 CFM would be plenty for a mild engine. You should see better low end throttle response with a smaller carb. I would fully warm it up and take it for a drive before doing anything. A few full throttle runs would be a good idea. Check the plugs then and see how they look.
