I think my demon is possessed.....

[beanhead]

Fired up the 440 today (I needed to hear that music) let it come up to temp, idled it for a bit while I checked things out and shut it down. It was about 65°-70° out, engine got up around its normal 180° or so. About 5 minutes after I shut it down, I heard this little hissing noise... I walked over and noticed that about every 30 seconds or minute, the primary squirter was squirting a few jets of gas into the carb... float levels were good, fuel wasn't boiling or percolating that I could tell, carb didn't seem too hot to the touch anywhere... This was so weird it went on for a good 10 minutes maybe- what the heck?!? It's a Speed Demon 850 by the way...

 

[oldbee]

Too high a float level setting,fuel boiling out, BAD FUEL(like all that's sold now!)My best guess is the 3rd one.

 

[beanhead]

Too high a float level setting,fuel boiling out, BAD FUEL(like all that's sold now!)My best guess is the 3rd one.

Yeah no kidding. Seems to be tricky to tune this carb, too...supposed to be easier than a holley (which if I remember is why I bought it back in '08) I can't seem to get it mixing good consistently...get the timing happy, get the mixture set with about a steady 14" of vacuum and then it will do something like not snap back to idle right away when I let off the throttle, or it will start idling faster, or rougher...seems to be pickier the warmer it gets so I'm sure the gas is a factor

 

[PurpleBeeper]

If fuel comes out of the squirters and you're not hitting the throttle (accelerator pump), then "something" is pushing the fuel out. I suspect that you ARE boiling fuel, but maybe a little upstream from the carburetor....maybe a fuel line close to a header? That would explain your weird driveability (sp?) issues too.

 

[AR67GTX]

I've had some issues with Holley accelerator pumps where the height of the manifold pad is low and the pump cover is just barely above the manifold. Heat off of the manifold expands/boils fuel in the accelerator pump and pushes it out the accelerator pump squitter (this isn't referring to my GTX). I've tried packing insulation between the cover and the intake with limited success. It usually starts dribbling/spitting fuel out in about 5 minutes of shut off. Makes a stink in the garage.

With the car running and fan air blowing over the motor it's not an issue - just happens on shut down and heat soak.

I wonder if plastic accelerator pump covers are available?

 

[oldbee]

Go on Summit's site and look up ac-delco carb gaskets. They make one with a thin gskt on each side of an aluminum plate that sticks out past the frt& rear of carb about 3".Has to stop some of the heat soak.

 

[beanhead]

Thanks guys..I was thinking this or maybe a carb spacer. Carb's sitting up a little already (rpm intake) but I'm figuring on using a 6pack hood anyways

 

[oldbee]

Ya gotta love those hoods!! Had one on mine years ago. ( oh, if you use a hunk of foam rubber to seal the opening; remember to take it before starting engine it stalls pretty quick!)

 

[AR67GTX]

Go on Summit's site and look up ac-delco carb gaskets. They make one with a thin gskt on each side of an aluminum plate that sticks out past the frt& rear of carb about 3".Has to stop some of the heat soak.

I actually have that (Mr. Gasket) installed and still having the same issue - but not as great. Shoved a piece of Be Cool insulation between it and the Mr. Gasket aluminum plate and slowed it a bit more. But still a little spitting and leaking after about 5 minutes of heat soak. My carb bowls are usually about 130 to 140 F when I shut down. It doesn't take much heat with today's fuel. It only takes 5 or 6 drops on a hot carb throttle plate to raise a stink for awhile.




I'm told you can drill a small relief port from the accelerator pump to vent back to the bowl but I never had the courage to try that.

 

[oldbee]

AR67--that's the gskt I was thinking of. Bad fuel,bad fuel; never gonna stop!

 

[beanhead]

I wonder if a return line helps? Though I always figured the separator/return line setup was for just vapor lock issues...kind of a bummer seeing as how the warmest day was just touching 70° so far, we run lots of 100°+ here in central CA...

 

[oldbee]

Not from what you're talking about, IMHO.

 

[Fran Blacker]

How about a phenolic insulator it doesn't conduct heat. https://www.summitracing.com/search...=Ascending&autoview=SKU&keyword=phenolic&ar=1
And ar67's aluminum gasket.

 

[beanhead]

How about a phenolic insulator it doesn't conduct heat. https://www.summitracing.com/search...=Ascending&autoview=SKU&keyword=phenolic&ar=1
And ar67's aluminum gasket.

Thanks I'm going to try spacer...easy enough

 

[AR67GTX]

AR67--that's the gskt I was thinking of. Bad fuel,bad fuel; never gonna stop!

A lot of it is today's fuel. Most of today's fuel is already starting to vaporize at around 140 degrees from what I've seen posted. That's not the same as boiling but if it's vaporizing it's expanding and venting off. If you shoot the carb bowls on a carb on a warm engine they are usually right around 140 F if not hotter. At least the stuff doesn't foul plugs and combustion chambers as badly as the good old leaded stuff we used to have.

 

[PeteBell68]

I put a phenolic spacer on it cured the heat soak . My car used to stall almost at every stop light
And would do the same fuel hiss after shut down .
Cleaned the carb and put the spacer on re checked timing and all was good .
It's today's fuel that does it .