Demon carb tuning...help

[TCullen]

i've got a road demon carb on a 302. its running terribly rich, leaving black clouds here and there.

the floats are set under 1/2 way, and appear to close properly.

when the idle screws are turned in, it stalls.

however, the squirters are constantly squirting when the idle is off and the engine is warm.

also, the vacuume secondaries don't open when it is floored. looking down the carb when the car is parked and the air cleaner cover is removed.

and gas mileage is terrible, around 10-12 per gallon.

any idea what all of these symptoms add up to and how to fix it?

 

[enferno]

the squirters leaking at idle could be a vacuum problem inside the carb. i know on some carbs if you block the overflow tube it will dump fuel out the squirters.

the secondaries won't open unless the engine is running and at a high rpm/load.

sounds like you just need to rebuild the thing and start fresh

 

[TCullen]

in response to your answer, the secondaries don't open when the engine is running and redlined. the squirters don't leak at idle, they do however, let off a shot of gas when the accelerator is pressed and the choke is off

 

[rbohm]

a couple of things to check;

1: the power valve. even though barry grant has improved the power valves, they can still blow due to back fire.

2: make sure there is a check valve in the accelerator pump circuit. sometimes there are two of them. if left out vacuum will draw fuel through the pump circuit.

as the others have stated the secondaries dont open until the engine is under load. when they do start to open you should hear a hissing sound.

 

[fvike]

I'd reset the butterfiles, if they are open on idle, you may get a flooded carb. Also, I'd check the accelerator pump linkage. It could be keeping the butterflies open.

 

[Max Power]

OK, you will never see the vacuum secondaries open at idle. You need a load to get them to open, and it won't happen at idle. Many people are convinced that their secondaries aren't opening, they are wrong 99.9% of the time. What primary jets are you running? Was the carb working fine before and this represents a change in behavior? What cam are you running? What is your vacuum reading at idle? Did you start wiith fresh plugs and have you taken a reading off them?

Here are some pics on how to check secondary operation, although they are not related to your problem:

Set a paper clip here.,,,

View attachment 383976

Like this....

View attachment 383977

When the car is WOT under load, the vacuum secondary link will move up, as shown, when the secondaries open...

View attachment 383978

After your test drive, the paper clip should have moved down the linkage as shown. If it did, your secondaries are opening.

View attachment 383979

Your secondaries have nothing to do with your rich problem though. Get a rebuild kit, go through it, get some smaller jets just in case. Make sure to replace the power valve. And consider buying this book:

http://www.cartechbooks.com/vstore/...st2=-76261&st3=-91594&Product_ID=1657&CATID=3

 

[bnickel]

in response to your answer, the squirters don't leak at idle, they do however, let off a shot of gas when the accelerator is pressed and the choke is off

ummm, they are supposed to do that. they are to give the engine a shot of fuel from off idle so it will have enough fuel until the part throttle enrichment circuit comes on line.