ChrisFormula355

Ok I'm not the one to normally ask carb questions (I'm the guy that usually rebuilds everyone's carbs and tunes everyones carb motor within the people I know) but this one has got me stumped. The secondary float bowl started to overflow today, so I figured a piece of junk got its way into the needle seat. Took it out, blew it out, carb cleaned the passages, and stuck it back in. Adjusted the float, and started the car, well guess what, it still over flows. So I figure its a bad needle seat, take it out, replace it, and start it again. SAME PROBLEM. Hmmmmm So Now I'm getting pissed, so I take the carb inside the house, tear it apart, put in new secondary gaskets, and clean the snot out of it soaking it in carb cleaner for 10 minutes. re-adjust the floats slightly lower than "even", and try again. hah, gues what, same stupid problem!! So Now I take the float out of the bowl, put it in a sink full of water and see if it has a hole in it. Nope, float works just fine. This has got me stumped. The only way I can even drive the car is to turn off the secondary needle completely by turning the needle all the way in. My only other guess would be high fuel PSI, but then why isn't the front one flooding? Its a stock 1985 trans am fuel pump too, so high psi is doubtful. Any ideas?
this is on my girlfriends t/a btw.

Damon

Water's heavier than gas. Float will have more bouyancy in water than in gas. Might want to replace the float on general principle.

Also, make sure there's no binding in the hinge and that the "tang" on the float pushes directly on the bottom of the needle valve AS INSTALLED in the carb-it's possible that it's bent and that it's pushing against something OTHER than the needle valve, even if the float setting is perfect. Also make sure the little "helper" spring in the hinge is installed correctly and that it's not bent/out of place and PREVENTING or RESISTING the float from coming up.

The new needle/seat you installed would be the typical one-piece unit used on 4150/4160 style carbs, right? if so, make sure it's got the little o-ring installed where it should be and that there's nothing down in the fuel passage that would prevent the o-ring from sealing on the metal that surrounds it.

ChrisFormula355

Going to replace the float tommorow, since everything seems to be fine. Then we'll see what happens. If that doesn't fix it i give up

ChrisFormula355

BTT. Please guys, I need help. I put in a new float and it still overflows on the secondaries. I'm clueless, I have no idea why it could be doing this besides fuel pressure. But how could the pressure be too high if the primaries aren't overflowign?? anybody????

RB83L69

Do you have the little "helper" spring on the float?

Is the float getting stuck on something, rubbing on something, maybe the little plastic fuel diffuser piece that goes around the needle valve assy? Is that piece in right?

Is the casting cracked around the lower neddle valve O-ring? Try a new fuel bowl; they're cheap.

Damon

I'm with RB. I think maybe you've got somethign wrong with the float bowl itself that's allowing a leak.

It is POSSIBLE that SLIGHTLY too high a fuel pressure could overflow the secondaries and not the primaries (although I think it's unlikely) since the primary side always has a little fuel being drained out of it from the engine idling. But that's way-out teeny- bopper bizarre stuff.

Again, check for any binding or something "hanging" the secondary float also.

ChrisFormula355

Ok, going to swap my 870HP holley from my firebird onto her car today and see if the problem is still there, that way it eliminates the fuel pump as th problem, we'll see what happens. I'm pretty sure its just gonna do the same thing cuz I always have thesse weird problems that are NOT solvable. Why me, ***, why me.

ChrisFormula355

Oh and btw, what effect would a worn cam have on fuel pressure? I know for a fact the cam in her car has a worn exhaust lobe, so its possible the cam lobe is worn too...but wouldn't that cuase lower fuel pressure with the stock mechanical pump?

Jester

Replace the N/S again. Just because it's new...doesn't mean it's good. If that doesn't do it just try replacing the bowl with the secondary bowl off of the 870...that will help you narrow things down more than swapping the whole carb.

ChrisFormula355

Whats up man, haven't talked to you in years. Well the 870 has custom float bowls, so they won't swap. Going to just swap the carb tommorow. The way I have my vehicles setup, carb swapping is a 5 minute job, where as jet changing/on vehicle tuning is a 30 minute job Will swap tommorow and let you guys know what happened. I would actually be happy if it turned out to be the cam lobe, since I'm swapping another Comp extreme 274 cam into her car anyways to fix the exhaust lobe. That would save me some money. Cam swap on her car is like a 1.5 hour job, seriously.

305sbc

iTrader: (3)

I was going to say this too. I seriously doubt your cam has anything to do with one bowl leaking.