Thermoquad help - primary overfueled, boiling over on shutdown

[Secret Chimp]

I almost have my Thermoquad running right. It's not overflowing into the primaries any more while it's running, but it's still running stupid rich and the driver's side primary is getting way too much gas.

I've repaired the primary wells and they don't leak any more. O-rings are fine.

I've installed brass floats from quadrajetparts.com at both just over 1 inch and 29/32nds and the thing keeps getting too much gas in it. The level's getting high enough to where it will bubble over and drip out of the passenger side throttle shaft opening after I shut it off. Gas starts welling into the primary bores and fogging up even if I crank it for a few seconds without it starting (it ALWAYS slightly floods the engine on shutdown).

See further below for the fuel level on my current floats. I have no idea if I ought to use a super-low float setting with these or what.

Perhaps more concerning, the driver's side primary keeps getting way too much fuel. I can see gas welling up around the driver's side metering rod if I leave the covers off while it's running, and after the carb has filled up to the set level I can barely crack the throttle and it starts spraying fuel in like a garden hose. I adjusted the tree to 1.5 turns off of when the piston just started moving, no difference. Seating both idle screws won't kill it. A drop of fuel will come and go from the venturi tube.

I know the needle and seats are fine, I pressurized it with a bike pump on the bench again up to like 10 psi and they held. I have my fuel pressure at just under 3 psi.

No idea if this helps, but I plugged the jet with a float pin wrapped in scotch tape and filled up the driver side bowl to see how these floats float. The fuel level with the float in there was just lapping up the very rear step on the body.

http://imgur.com/hcexP

Buoyancy level for the float (upper squiggle on the left side, I messed up)

http://imgur.com/Gx4TE

Any idea if this warrants different float settings?

ALSO (I know I write too much)

I've read that gas will find its way out to the main venturis if any of the vents are plugged up. I'm wondering if this is why I've kept getting weird behavior out of the driver's side venturi - seeing gas wick up the metering rod and it seeming to be overfed compared to the other side despite it also being too rich.

I've poked pretty deep in all of the holes I can find, but I don't really know what I've poked (said the drunk in the brothel the next morning).

How can I check and see if maybe the driver's vents are plugged up completely or intermittently? I'm not sure which tubes are which.

I swear I can get this stupid thing to work. When I first ran it the bores would completely fill up with gas. Work Thermoquad work!!!

 

[RustyRatRod]

What kinda fuel pressure are you runnin? Thermoquads don't like much over 5.5 PSI, or it forces the needles off the seats.

 

[Secret Chimp]

Just under 3 psi.

 

[RustyRatRod]

I would say that's certainly not the problem then. It's also really not enough. But I wouldn't change it yet. What make was the kit? A LOT of the kits now are absolute junk. The needles and seats are crap and won't seal. I get mine from a local O'Reilly's. They carry Borg Warner kits. I've had good luck with them.

 

[Secret Chimp]

It was a Walker kit. Came with X-style o rings and all that. I tested on the bench with some carb cleaner to fill the inlet area and a bike pump - it held over 10 psi with the weight of the floats on the needles. They (edit: the floats) aren't very buoyant in the bowls until you submerge them completely but its not overflowing until I shut it off and heat gets into the gas. If the N/S werewak shshouldn'tt start flooding as it idles?

 

[RustyRatRod]

That almost sounds like a heat soak problem. Do you have a heat shield of any kind? Also, what type gasket do you have between the manifold and the base plate? If it's the thin one, that right there could be the whole problem. You need the really thick one with the plastic o rings in the mount holes.

 

[Secret Chimp]

I'm using the thick gasket. Heat soak alone doesn't explain my rich idle/garden hose driver side booster though. I can hear it bubble after I shut off the car but its fine to idle stinky rich for 10 minutes without overflowing.

 

[RustyRatRod]

So it only does it through one booster? I would suspect that side float was compromised.....new or not. I've seen it before. At any rate, something is causing the fuel level to rise. Have you watched the fuel pressure after you cut it off?

 

[Secret Chimp]

The drivers side booster did this before I rebuilt it, after I rebuilt it with the original foam floats and after I installed new brass ones. I've switched the floats side to side, same with the needles and seat pairs, same thing. The drivers side bowl looks like it carries more fuel than the passenger one even if you consider thespace the accel pump body takes up so maybe too high of a fuel level shows up on that side sooner?

And pressure slowly drops off when I shut down.

 

[RustyRatRod]

Have you tried lowering the float level on that side? If it keeps doing it regardless, I think I would maybe look for a compromise in the main body, or the bottom of the carburetor top. Did youcheck the main body for warpage?

 

[Secret Chimp]

I've tried running float levels on both sides as low as just past 1 1/4 and I still got this behavior. The main body has a slight corner-to-corner wobble to it but it all goes together easily & I've been using Demonsizzler's recommended tightening sequence. I can't be certain but it doesn't look like either float will hang up against the side of the body as I drop the air horn on.

 

[RustyRatRod]

I put all of my main bodies on a thick piece of safety glass I have. If they wobble, I lay a piece of sandpaper on the glass and correct them. I do that until I cannot get a .002" feeler gauge under it anywhere.

David is a good guy. I've dealt with him some and corroborated with him as well. He's pretty sharp alright.

 

[Secret Chimp]

Oh, so the method is to have the sandpaper fixed on something and move the body? I was never sure of what people were talking about.

How might a warped body be causing some of my problems? Metering rod never dropping in all the way or something?

 

[RustyRatRod]

Oh, so the method is to have the sandpaper fixed on something and move the body? I was never sure of what people were talking about.

How might a warped body be causing some of my problems? Metering rod never dropping in all the way or something?

Possibly allowing fuel to leak into the venturi. I'm just guessin of course, since I don't have it in front of me.

Alright.....give it up. Where'd "Secret Chimp" come from? lol

 

[Secret Chimp]

I saw it as somebody else's username in a screenshot from a game in a magazine a long time ago and I thought it sounded funny. I later learned it referred to this guy:

 

[Meep-Meep]

I think you're on to something with the buoyancy. Put new OEM floats in and start over with factory settings. No cracks or deformation in the plastic main body? As long as you're checking stuff, the epoxied main well cap is not leaking?

In my opinion fuel level should be checked with the main jet unplugged so the fuel gets into the main well. The whole purpose of the correct float setting is to have the fuel level at the proper height in the main well.

 

[Secret Chimp]

I think you're on to something with the buoyancy. Put new OEM floats in and start over with factory settings. No cracks or deformation in the plastic main body? As long as you're checking stuff, the epoxied main well cap is not leaking?

In my opinion fuel level should be checked with the main jet unplugged so the fuel gets into the main well. The whole purpose of the correct float setting is to have the fuel level at the proper height in the main well.

Ah! That is something I've been trying to figure out and suspected, but I had no idea what to actually look for.

Whenever I take the air horn off with the rest of the carb mounted, the fuel level in the main wells is almost at the top edge of the plastic if I place the floats back in the fuel. Sometimes the fuel will spill out into the bore depending on how quickly I get the carb apart (fuel evap and all that). The floats sit at a much steeper angle in the fuel at this point vs. the setting I have them at when I'm measuring the height with them installed on the air horn.

Where exactly should the fuel level be in the main wells? Near the top or just below? I'd like to try and figure out a float level that will work for these floats before I throw even more money at this thing.

As for your other q's, there is a slight bobble in the body I only noticed yesterday. The wells were leaking when I got the carb but I've since re-epoxied those and they're still holding just fine, no wet spots on the base plate after I dab off the gas from any post-shutdown spillover.

 

[Someotherguy]

this has got to be a issue with the floats(no buoyancy) or the needle/needle seats not closing off fuel....

if you still have the old floats, stick them back in it, set them to proper height..and give it another try...

 

[Secret Chimp]

I'm pretty sure my original foamies are sunk too, they sat pretty low and weren't very buoyant. How can I tell if whichever floats I get next are any good weight/buoyancy-wise? Where should the fuel level in the wells be if they're holding correctly?

 

[Someotherguy]

the foam type floats should weigh between 7-8 grams each...not sure about the well height..the brass ones should weigh 10.5 each...