Question for those that have installed a Paxton on their 289..

[robert_t_wallace]

ok.. narrowing down on my problem with the car flooding and shutting down. This is hard to do when 3 or 4 people have worked on the car over the years....

Just to recap.. My car is a Hipo 289 with a SN93 Paxton and Mighty Demon 650BC (Blower Carb). The car runs fine for 30 minutes and then shuts down...let it sit for 20 minutes, it starts back up.. Strong smell of fuel..

I have ordered a wideband, so this should help isolate the problem...

Now, the question....

--->>>>>Based on the below Paxton install guide, it looks like my carb needs modification, but was not... Since My carb is a Demon Blower Carb, do I still need to do that modification?? or... Did my uncle forget to do it and it needs to be done




I actually found the Paxton install guide...

Appendix A (For the Bonnet Kit)

A.1 Carburetor Modifications

a..It says to use a Holley 650, 4776 or 4777 (I have the Demon 650BC)
b..Remove the float bowls
c..Remove the floads and exchange them with the solid floats p/n 1163000.. (I assume the Demon BC has this, right??)
d..Drill a 7/16" Hole, Tap 1/4-18 NPT Thread size per enclosed diagram in each Float bowl.. (This was not done...)
e..Install the elbows and their supplied inlet fittings (This was not done)
f..Use the supplied gasket as a teplate and drill 4 1/16 Holes through the carburetor baseplate to throttle shafts..(this was not done)

Jetting
g. USe the following as a guide depending on the type of exhaue system your vehicle has:
-Headers and Dual Exhause - 0.67 primaries and .089 secondaries (No clue what I have as it is the stock Demon 650BC)..

[shaneh]

That Demon may be set up for draw through, not blow through. You're probably going to need to call them to discuss the mods they make on them.

[robert_t_wallace]

Originally Posted by shaneh

That Demon may be set up for draw through, not blow through. You're probably going to need to call them to discuss the mods they make on them.

ok..thanks!

[TJH]

I would use the Holley as recommended (it will most likely solve your problem). I have not had good experience with Demon. Good luck.

[MT]

Those are all pretty simple mods. Why don't you just do them? I have a Demon GSS with a paxton blown 340. They are very sensitive to the hollow floats. They would tend to crush them when you floored it then lifted off the throttle.

[robert_t_wallace]

The Demon GSS's are way cool...

I am pretty sure (although not 100%) that the mighty Demon 650BC (BC was the "Blower Carb") had the solid floats..

I am actually trying to go through the mods to make sure I am comfortable with them. I hate to ruin a perfectly good carb...

[rooeng]

I agree with shaneh. Those blower carbs do not need solid floats. The carb on top of a roots blower isn't pressurized, so it's not needed. You need to find whether or not you have hollow or solid floats.

Is the entire carb in an enclosure or do have a carb hat that just covers the four barrels?

Is the power valve working? Doesn't the Demon BC need an external power valve source? How did you address that?

Is the fuel pump boost referenced?

Have you tried running it without the bonnet to determine if its blower/fuel related and not something else like electrical or ignition or something else?

When it shuts down pull a plug and see if it's wet with gas.

[robert_t_wallace]

I agree with shaneh. Those blower carbs do not need solid floats. The carb on top of a roots blower isn't pressurized, so it's not needed. You need to find whether or not you have hollow or solid floats.

TW-----> I pulled the bowls and they are hollow black (appear to be plastic) floats. They were not collapsed... I think the paxton only runs about 5 lbs of boost..

Is the entire carb in an enclosure or do have a carb hat that just covers the four barrels?

TW-----> The entire carb is in the bonnet so it is enclosed..

Is the power valve working? Doesn't the Demon BC need an external power valve source? How did you address that?

TW---> No clue.. Don't see anywhere for an external power and don't think I need it..

Is the fuel pump boost referenced?

TW---->Yes.. There is a hose that goes from the fuel pump to the supercharger

Have you tried running it without the bonnet to determine if its blower/fuel related and not something else like electrical or ignition or something else?

TW----> Definitely not a spark problem.. Confirmed that.. I have run it without the bonnet and seems to have a similar problem with to much fuel..

When it shuts down pull a plug and see if it's wet with gas.

TW---> I will do that..