Leaky Rochester carb issues on a '66 DeVille

[stratogeezer]

Hi experts!

I've been wrestling with my Rochester carb for several weeks now. Even after a rebuild kit and taking it completely apart and soaking in carb cleaner, it continues to leak gas from a couple places upon re-installation at- the rear base of where the carb meets the manifold spacer, as well as in the top front where the fuel line connects to the carb.

By the way, it's a 66 DeVille with the usual 429 engine. No a/c.

But, the good news is that it starts easily now, and seems to idle decently. But, a leaky carb is of course, a dangerous show stopper.

I'm looking for either other "next steps" to try, or if I should consider a replacement and be done with it, or continue to try to bring this carb back to life. 

thank you!

[Ralph Messina CLC 4937]

Rob,

A couple of thoughts:

Did it leak before rebuilding? If so there may be cracks in the casting that open with heat or torque on the mounting bolts.

Have you tried tightening the mounting bolts after the car has warmed up? The gaskets do require tightening after being heated to fully seat..

Do you have a gasket on both sides of the Bakelite spacer?

Did you replace the brass fitting the fuel line attaches to? Is the leak where the brass meets the carb body or from the fuel line connection?

Let us know how you get along,

Ralph

[stratogeezer]

Hi Ralph and thanks for the guidance.

Before rebuilding the floats would not shut off the gas flow, so initially since gas was all over the place, it was hard to tell if it was leaking, or just soaked with gas spouting out of the top of the carb.

Gaskets were on both sides of the Bakelite spacer, but the rebuild kit shorted us one, so we had to use the original which seemed to be in ok shape.  And no, we did not know to tighten the bolts after heating the engine up so we can try that.

And yes, the leak on top is where the brass fitting attaches to the fuel line. Needs replacing, so I'll order a new one and filter insert (if they can be ordered).  We also experienced a lot of gas spraying from the air intake, that got slightly better following the rebuild but it still spurts some (less) gas from the top.

Rob

[stratogeezer]

This short video may or may not help the diagnosis. This is before the rebuild, but some gas still sprays out of the top of the carb.

http://www.youtube.com/watch?v=QJw7FwuEPrs&feature=youtu.be

[Glen]

Are you using an electric fuel pump?  If so check the pressure of the out put.  It maybe over powering the float valve.  I believe the carb needs no more than about 5 psi. 

[Ralph Messina CLC 4937]

Rob,

I believe Glen’s on to something. The video seems to show that the float/bowl system is not working properly…..Floats may have a leak or inlet is not seating and fuel is flooding into the bowl.

Ralph

[stratogeezer]

Are you using an electric fuel pump?  If so check the pressure of the out put.  It maybe over powering the float valve.  I believe the carb needs no more than about 5 psi.

Great point. Answer, I do not know. How would I check?  And if it is electric, is it adjustable?

[stratogeezer]

Rob,

I believe Glen’s on to something. The video seems to show that the float/bowl system is not working properly…..Floats may have a leak or inlet is not seating and fuel is flooding into the bowl.

Ralph

Gotcha Ralph. I could take the floats out again and check for leakage. Maybe allowing a pro to rebuild it may be an option too.

Let me ask you this this however....at what point do I think about just replacing it?  It's been on and off twice already, ant the top off once before then.  And, if I do replace it, do I need to stay with a Rochester, or does someone make a modern replacement that may be more modern - recognizing that impacts the "original" aspect? 

Sorry for all the questions!  This is very helpful to me though.  I'm learning!

[Ralph Messina CLC 4937]

Rob,

Both  Rochesters and Carters were used in ’66 as dual suppliers. Both had the same performance when new. My brougham came with a Rochester but I converted it to a Carter because it’s a much simpler carburetor, and I like simple.  My Eldorado came with a Rochester but I didn’t have another good Carter core to rebuild, so I kept what I had. I have a great rebuilder locally (NJ). He checked the castings for warping before investing in the rebuild. The body and cover castings of these vintage carbs can warp or crack over time which renders the parts useless. I suspect you have mechanical failure or damage to a component that a pro mechanic or rebuilder can spot and rectify. A rebuild is in the range of $200-250 complete. If you search this Forum, I believe there are favorable references and comments about “The Carburetor Shop” located in Florida ()
If you do rebuild the Rochester, you may have to tweak the accelerator pump adjustment. Mine idled and ran fine normally. However, flooring the gas from a stand still produced a tire burning surge for the first 30 feet followed by hesitation and stumbling. After much reading I discovered that Rochesters usually need to the maximum accelerator pump stroke. I moved the adjustment to the forward most hole and things are fine. Set up correctly, these cars are surprisingly fast and powerful off the line. 

If all else fails, Edelbrock makes new carbs that are similar to Carters. It will require a bit of rigging for an electric choke.

HTH,
Ralph

[stratogeezer]

I appreciate all of the insight, Ralph!

I'll work on it Saturday and see what I can do.  I had no idea how finicky these carbs can be.

Once I have success, I'll post more video.

Thanks again

[Glen]

Probably the best way to check for an electric fuel pump is to follow the fuel line from the carburetor to the fuel tank.  The original configuration has the line going through the mechanical pump on the side of the engine then down under the car and going back to the tank.  If you find something the fuel line goes through with wires on it; it is an electric fuel pump.  You can buy fuel pressure regulators if the pump is too powerful. 

If you do not have an electric fuel pump then there is something wrong with the float or float valve.