SalikDDD

well, i figured i'd post in here instead of in the Classic part since i own a 67..

anyway here goes with what my car has...


289 Bored 30 over
flat tops with valve reliefs
GT40P heads
comp cams springs, roller tip rockers 1.6 ratio, hardened push rods etc.
comp cams xe268H cam .509/.512
edelbrock performer rpm port matched
tri y headers
25-2800 stall
C4 with valve body work etc
8.8" Rear with 3.08 (soon to be 3.73)
etc etc

right now i have a Holley 4160 - 600cfm universal carb with a single inlet, 64 primary with a .39 plate (70 jet)

the secondaries never, ever open. i've tried swapping springs, it never needs the air or fuel or whatever. they just don't open. i've checked the ball, the diaphragm, everything. i swapped pump cams around etc but now everything is back to stock on the carb with the exception of we put 62's in the front.

the car runs really rich, i mean blacked plugs - sooty exhaust, gas smell

it doesn't really load up per say when u get on it, it moves but definitely not the way it should if all 4 open...

so what's going on here? do i have TOO large of a carb? ? - we tried rejetting to a 52.. then a 56.. - you'd gas it and it'd wanna konk out then it'd move. .. still no secondary movement..

what's going on ? should i just dump it and get a 570 street avenger? smaller? something?

someone help before i light this on fire and collect insurance.

67mustang302

Have you actually pulled the diaphragm out and looked at it? And will the secondaries open if you operate them by hand? Open the primaries so the secondary lock disengages and try to open the secondaries by hand. What spring is in the diaphragm housing?

mjr46

are the secondaries vaccum operated??? also a 600 should be fine...what is the float level set at?? and what is the fuel pressure set too?? what type of fuel pump??

SalikDDD

hey guys, yeah i checked the diaphragm it's not ripped or anything, and it works manually i didn't think it'd be that pressurized or whatever you wanna call it to push it open but they open by hand. springs? right now i have the original silver spring back in it. i went all the way down to lightest one and nothing :|

yes vacuum secondaries and.. no idea what the fuel pressure is, it's a mechanical summit 110gph pump so it's free flowing i believe. just goes from tank to pump to a filter to carb.

can't adjust the floats or anything, they're non adjustable. :|

67mustang302

When you open the secondaries by hand, if the vacuum diaphragm housing is sealed up you should hear air rushing from the carb barrels. Did you?

SalikDDD

sure did.

tyler72

You should be fine with that carb, but it sounds like there may be a problem with it. I would get a Holley or Demon with the center hung floats. In my opinion they are way better. For a 289 though I wouldnt think you would need bigger than a 575 unless you were going to turn it 7000 RPM. If you go to holleys website you can go to the Carb recommender link at the top and it asks you questions and then will suggest a carb to use.

67mustang302

How do you know the secondaries aren't opening? Your tune could just suck so bad that it's falling flat and feels like it's running on 2bbls.

SalikDDD

easy, paperclip, tape, paint. etc. tried it all, they never open.

tinman

What is the indicated vacumn from the engine?
Is there a low vacumn condition?