Rochester 4GC flooding problem

[huug]

Guys,

I have a '58 Belair 348 with a Rochester 4GC on top. I did a rebuild of that carb in christmas holiday one year ago, which wasn't quite difficult (I did it for the first time). After installing it ran fine and it didn't need much adjusting. Vacuum read 19 inches mercury.
But now I have a flooding problem, only when my engine runs hot. So it starts nice, but when the temp needle raises to normal position, the flooding starts. I checked the floaters, but I can't see anything unusual. All the stated measurements on the floats seems to be OK.
The carb kit I used for the rebuilt came with a sort of valve with a little gasket on it that stops the fuel inlet, instead of the original neelde & seats. I'm thinking of placing the original needle & seat assemblies back. Is that a solution? Or should a bend those floater arms some more? It's hard to determine if and where the floaters interfere in the bowl...

Hugo

PS: sorry for my English. I live in the Netherlands.
PPS: My 58 Belair is on http://drive.to/Belair

[walkerheaders]

i wonder if the base gasket is wrong and the exhaust crossover in the manifold is boiling the carb? isnt there a stainless isolater plate there to seperate the heat? check that first. your english is fine.

[Rockfish39]

What Bob said....

Sounds to me like you're boiling the gasoline right out of the carb too.

Here is one really cool solution that I found out about in South Texas, years ago...

Pull the intake manifold off of the engine. fill the exhaust crossover ports with molten aluminum (an old piston melted down works great) When cooled, sand the port or machine the port FLAT... Paint and re-install the intake

You're problem will be forever solved and you wont end up burning the paint right off the intake.

There are trade-offs in doing this, for example, your warm-up time goes from 2 minutes to about 8, but no big deal. That aluminum is a good conductor of heat and will warm that intake just enough!

OPTION-2 Buy a 472 truck intake and use that... It accepts the same carb the intake you have but has two slick side benefits.

a) the plenum and runners are a bit larger than the ones you have

b) no port passages leading up to the bottom of the carb to boil your gas !!!!

Rock :cool:

[huug]

Hmmmm, boiling my gasoline... Do you really think so?
And why should that occur right now after 45 years of normal operation? Does it has to do with the new core in my radiator? I didn't notice a higher engine temperature, it should be lower right now.

I've checked my exaust crossover valve, it is rusty, does not move and should be replaced, but it stays fixed in the open position.
And that crossover port is just needed to quickly heaten up the carb so the gasoline evaporates fine and does not dilute the engine oil, as to be read in the shop manual.
I like the original setup in my car, so filling that with moulded aluminium...

I'll check the availability of such a isolator plate, maybe they'll come with and without crossover port holes. Any (web)stores recommended?

Huug

[Southtowns27]

I've never heard of the molten aluminum theory, but it sounds like it works! On the circle track cars we don't want all that heat up to the carb either. We cut a small piece of aluminum flashing (beer cans work too) and use gasket adhesive to stick it to the intake manifold gasket to cover the port. Works really slick! A carb spacer would do the same thing for you and probably give you some more torque. It's a whole lot easier to install too! Good luck :cheers

[Rockfish39]

Originally posted by Southtowns27
I've never heard of the molten aluminum theory, but it sounds like it works!


Southtown, Ive done this on small block intakes, lots of times....In fact a old circle track guy in San Antonio taught it to me.

Its a little extra work, granted, but is optimal for the following reasons....

1) Ideal for show intakes that you dont want to fry the paint off of.

2) Filling those passages with molten aluminum takes any air in those passages out and fills every nook and cranny with light
metal... In the late 'teens' I think 1919, Chevrolet engineers started playing around with copper cooled engine designs. IE using a solid metal to dissapate heat instead of a liquid. Revolutionary idea for its day.

Aluminum was very expensive to manufacture at the turn of the last century, so that wasnt even tried. Aluminum's thermal properties are even better than copper's is. What ends up happening, is that the heat that the exhaust system is introducing to the machined ends of the cast aluminum starts conducting though the metal and starts to transfer into the iron that surrounds it until it reaches an ambient temperature at full warm up. Your choice of thermostat has alot to do with this too!

The slick part of the physics is that the heat transfer into the cast iron now occurs at a much more controlled rate. That warms the bottom of the plenum to nearly an optimum temperature for good cool air density charge, yet warm enought to prevent puddling.

In the heat of the summer, this techniques solves alot of carb problems, like vapor lock.

Unless you live in the Yukon and have to keep it running in the dead of winter too.... but that's another problem

End of Physics lesson

Rock :cool:

[Southtowns27]

Learn something new every day... :cheers

[60convert]

I am not sure what kind of float you have but if it is a brass one you coul of gotten a hole in it and now it is sinking as it filled up with gas on the inside???

also on filling the crossovers in the intake with aluminum will that work on a cast iron intake just curious of the best way to do it for circle track racing??

Jesse

[huug]

OK Guys, thanks for the advises!

I've been working on the vehicle all this weekend, and I could slap myself on the forehead.

I had the car parked for a longer period (it's winter) and I got a hint from another person to pour a bottle of alcohol in the fully filled gas tank to prevent it from getting rusty on the inside. A good one, I thought, untill I remembered this action and that this could be the cause of my "boiling" gasoline in the carb, resulting in the flooding. So I drained the fuel tank, and the bucket beneath it showed the alcohol on the bottom of the gas, not mixed in any way. As it is on the bottom, it should be in my carb too, and drained that one also, happy that I found the cause :) . So after that I filled my baby up with fresh gasoline and tried again... still flooding! :mad:
So I took off again my Rochester 4bbl and took it apart on my home made fixture at the kitchen table. And that showed a leaky float..... On the secondary side one float was heavy and filled with gasoline, got in there through a very small, hardly notified crack. It must have taken a long time to got filled, so I thought the flooding has to do with the engine temperature. But it was "just" a leaky float. :rolleyes:
So I "steamed" out the gasoline from the brass float, as to be read on http://www.thecarburetorshop.com/Carbshop_parts.htm It took al long time and got me a severe headache of the gasoline smell. But finally it was empty and I soldered the hole. Assembled the carb, not needing the new kit. Back on the car an tried again: working! I made a test trip and touched the 100... :D
Still have to check all the adjustments, but I'm happy to be back on track again.

Huug

[Rockfish39]

Originally posted by 60convert
....also on filling the crossovers in the intake with aluminum will that work on a cast iron intake just curious of the best way to do it for circle track racing??

Jesse

Jesse,
Works just fine on a cast iron intake. Here is the technique

1) Block off the carb mating flange with a flat piece of steel. Tighten the plate down, so molten aluminum doesnt flow everywhere you dont want it to go.

2) Turn the intake up on its side to take advantage of gravity as you pour. You pour from the intake port down towards the carb flange. I personally recommend a 12" vice to do this.

2) Use an acetelene torch setup and a ladle, to heat up and melt the aluminum.

3) SAFETY, SAFETY !!!!!!!!!!!!! remember this stuff is 1000 degs F in molten form, and WILL burn you if you contact it !!!!!!
SO wear approved welders clothing, welding gloves and eye protection. I cant emphasize safety enough!!! DONT TAKE CHANCES!!!!!!!!!!!

4) pour the aluminum and let cool (about 15 minutes) then do the other side.

OPTION 2

Call Ed's Automotive , and have them do it for you !!!! This guy does great work!!! and is reasonably priced.

(915)-692-5261

Address: 5550 Hwy 277 South
Abilene, TX 79606

Good luck!!!!!

Lou


:cool: