i have a holley 750dp that im putting on and taking off an edelbrock 650. I am confused about some vacuum lines. there are 3 on the edel but i could only see 2 on the holley. one of the 3 is blocked off. what goes where?

also how do i tell if its vacuum secondaries b/c if i twist the throttle the primaries open but not the secondaries and i dont know if i just didnt put a rod on...

 

It can't be both a DP and have vacuum secondaries.

 

ok so then i am missing some linkage if the secondaries dont open with the throttle right?

 

The secondaries won't open if the choke is closed.

 

Sounds like you have a vacuum secondary carb. The link is on the passenger side of the carb, goes up to a diaphragm. There is a link on the driver's side to keep the secondaries closed until the primaries are open.

Check out the sticky in the top section of this forum (Welcome to the Carburetor Forum, etc.). There's a link there to the Holley website that explains the operation.

 

ok so i realized that the secondaries will open if i twist them, but only when the primaries are open, and i think it is vacuum secondaries because it has a diaphram.

so is Apeiron wrong b/c it is both dp and vacuum as far as i know...

there are also little pieces like a small spring and a black clip that i dont know where they go... and on the diaphram there is another screw and clip for something but i dont know what.............

any help?

 

No, it can not be both. Either the secondaries are vacuum operated, or they're mechanically operated and a secondary accelerator pump is required, which makes the carb a "double pumper". The diaphragm you're looking at on the secondary side is probably the secondary accelerator pump.

Can you get the list number of the carb stamped into the choke horn, and/or post a picture of the carb?

 

i'm guessing that the choke horn is the flap that the choke opens because the only number stamped that i could see is on that, the number is 388.

do only dp's have dual fuel inlets?

 

no all 4150s have dual fuel inlets my vs carb has two...l
does your carb more closely resemble this one

http://www.holley.com/data/products/...gerNewShot.jpg
or does it more closely resemble this one
http://www.holley.com/data/products/...rge0-4779S.jpg

ignore the finish of them. on the first pic that black plastic piece on the side is the vacuum diaphram. it could be plastic or metal but will be generally the same shape and size in that spot. if you have that diaphram then your carb is a vacuum secondary carb.

 

ok then it is a vacuum secondary carb b/c it has that diaphram which would make it a non dp, ok so now that i know that, the secondaries arent opening and i dont think there is a vacuum source to that diaphram, where would it connect to? would the secondaries open if i rev it by hand at WOT?

 

no u wont see the secondaries open reving the motor, there has to be load for them to open and u dont hook up any vacuum for it, its self containded in the carb...

 

oj, also there is a vacuum line rinning to the electric choke, but the edelbrock was blocked off, should i do the same with this one?

what should i be adjusting with this to get it tuned? i already adjusted the float bowls, i think they are good. what else?

 

Idle mixture screws should be next after setting the floats, adjust for the best vacuum at idle, then set idle speed

if its electric choke i dont know what vac line your referring to but there should just be a ground and a hot wire to your ignition, and you adjust it by turning it and usually you can use a pencil to set the gap or is that for an eldebrock i cant remember.

theres gonna be a vac line for your pvc or brake booster and maybe a full manifold and a ported one for your distributor.

 

i dont have a vacuum dial but i am getting it dyno yuned tuesday, should i have him do it there if he can or is it not that important?

maybe its not vacuum but there is a metal nipple going into the choke assembly and a line came with the carb.

 

yeah its pretty important you can go by sound too (engine rpm) and tune for highest rpm

 

ok how to do it sounds pretty simple. at what idle rpm should i adjust it at?

 

http://www.youtube.com/watch?v=RUrCP_KPLYY

idle screws




http://www.youtube.com/watch?v=_QM0L...eature=related

idle speed




http://www.youtube.com/watch?v=2YCbk...eature=related

choke

 

ok cool, hopefully i will get it tuned right, thanks for the help.