secondary butterflys

Anonymous · Post by **Anonymous** » Sat Aug 13, 05 11:03 am

you can yes, but drilling of butterflies is a bandaid for a mismatched combination somewhere along the way.

The demons now have an idle eze grub screw under the filter stud that does the same thing, bleed air instead of opening up the butterflies or drilling them BUT it's only ever needed if somethings not matched right

It will take a while to do correctly as you need to start very small and increase in size till it's running right

Dave-R · Post by **Dave-R** » Sat Aug 13, 05 11:13 am

It is perfecty fine to drill a couple of holes in the throttle blades. But doing it on the primary side is better unless you already have good sized holes there.

Sure as Will says it is better to start with a carb built exactly for the engine combo but that is not always possible.

You did the right thing in opening the secondary blades with that litle screw to start with.

BUT!

Why would the engine then start to run on the main jets????

Adjust the throttle closed enough so that you loose vacuum on the dizzy vacuum port. Once there it cannot run on the main jets.

If the idle speed is too low for you (under 850rpm I would guess would be rough) then open the secondaries a bit more.

Anonymous · Post by **Anonymous** » Sat Aug 13, 05 11:42 am

if the butterflies are open too far to get it to idle then yes it will start to run on the main jets

no difference to opening the throttle, there comes a point where it's in transition from the idle curcuits to the mains.

Demons have idle air slots in the body and on a street car on the primaries there should only be 0.020 of the slot showing and the secondaries should be shut.

The slots are an indicator only and at 0.020 the primaries are open a little,
they are 0.020 wide so viewed from the bottom they look square, when they do then the primaries are right IF the carb is matched to the motor if it's not then out with the screw driver and find the idle eze, this is only relative to a street car

Anonymous · Post by **Anonymous** » Sat Aug 13, 05 12:12 pm

We cant all go the way of the Demon though, money and originality are issues aswel!
Im having same problem, and theres no way them Holley six paks are going in the bin!

Anonymous · Post by **Anonymous** » Sat Aug 13, 05 12:20 pm

James I was just saying how it's done on a demon is all, pretty much the same as a Holley but there's an indicator to how far the butterflies ought to be open and if the slots are much more than 0.020 and square on the primaries then it's going to want to pull fuel from the main jets

Dave-R · Post by **Dave-R** » Sat Aug 13, 05 2:55 pm

It is easier just to put a vac gauge on the spark port than to measure how much transfer slot you can see.

Dave-R · Post by **Dave-R** » Sat Aug 13, 05 5:10 pm

When you say it is drawing out of the secondary main jets...

How do you know?

I am sorry I don't know your level of knowlege in this area so i may be talking down to you but is there a chance you are looking at the pump shot squirters??

They sometimes dribble fuel in if not adjusted correctly. If the adjustment is a fraction too tight the vibration of the engine causes fuel to pump out of the pump shot. The cure is to back off the adjustment.

Dave-R · Post by **Dave-R** » Sat Aug 13, 05 7:27 pm

In that case close the secondaries until the flow stops and drill holes instead. When you get up to about 1.5mm in the primaries start drilling the secondaries. Spread the air flow around like that and it should not have any effect on the main jets.

Dave-R · Post by **Dave-R** » Sun Aug 14, 05 8:52 am

Wait wait wait!

Are you sure the fuel bowl is not filling too much?

Take the sight plug out of the side and check that the float level is set right and that the valve is working. Check fuel pressure too. Keep it under 7psi.