454 Rochester Internal Fuel Wells

[broncopower]

Hi Everyone,

I had an automotive mechanic (friend of a friend) rebuild the rochester carb off my early 90s GM 454. An electric choke has been hooked up as well, which works great. I recently got the boat back from a marine shop (Jaws Marine, Baltimore MD), and they noticed internal flooding & special attention needed to the internal fuel wells. What is the internal fuel well, and is this a part that would be overlooked during a carb rebuild? I took the boat out in the harbor for a few hours, and on the way back, encountered hesitation/stalling at RPMs above 2,000. Would this be from the carb flooding?

Any suggestions or advice on how to get this rochester working correctly would be much appreciated.

Thank you!

 

[fat fanny]

Re: 454 Rochester Internal Fuel Wells

I would suggest that the re-build was a bust and that the prep before re-assembly needed more attention to making sure all ports and passages were cleaned and probed. A re-build is a 50/50 shot of success as you will find if you use the search function on carb re-build. Disassemble,scrub with soapy water,blow out with compessed air,carb soak overnight and repeat before re-assembly. Good luck and post back.

 

[Bondo]

Re: 454 Rochester Internal Fuel Wells

I would suggest that the re-build was a bust and that the prep before re-assembly needed more attention to making sure all ports and passages were cleaned and probed. A re-build is a 50/50 shot of success as you will find if you use the search function on carb re-build. Disassemble,scrub with soapy water,blow out with compessed air,carb soak overnight and repeat before re-assembly. Good luck and post back.

Ayuh,.... Combined with the fact that Quadra-jets are notorious for leakin' welch plugs in the fuel bowls, 'n slop in the throttle plate shafts...

Were these issues addressed,..??

 

[Silvertip]

Re: 454 Rochester Internal Fuel Wells

Some kits came with a sealing plug (a rubber seal) that was placed in the carb to seal off those leaks. Some of those carbs had porous castings that could develop leaks over time. If that was the case the carb is not generally repairable.

 

[broncopower]

Re: 454 Rochester Internal Fuel Wells

I don't think these issues were addressed. The mechanic just soaked the carb, used & rebuild kit, and replaced the float. I will diss-assemble, clean, and reassemble. I do not have any experience with Rochester carbs. Does anyone have a rebuild step-by-step, or can anyone point me in the right direction. If there are any manuals with pics that you can recommend, that would be great.

The marine shop mechanic told me that he adjusted the mixture as much as possible, but that Rochesters are tricky, and the other mechanic probably didn't rebuild it correctly.

Thank you!

 

[broncopower]

Re: 454 Rochester Internal Fuel Wells

Silvertip,

Do you have any suggestion on how to diagnose the casting, and to determine if the carb is repairable?

 

[Don S]

Re: 454 Rochester Internal Fuel Wells

See if this covers your carb. Boatinfo - Mercruiser Service Manual nr. 15 - 1989-1992 - GM V8 Engines

Here are the plugs that are possibly leaking. Some use epoxy to stop the leaks as shown.

 

[broncopower]

Re: 454 Rochester Internal Fuel Wells

Awesome, the service manual is great! I'll make sure to post any problems w/pictures if I run into any. Thanks for the help.

 

[westportfish]

Re: 454 Rochester Internal Fuel Wells

The primary and secondary main well plugs should be sealed with epoxy on any rebuild. Marine Tex or J-B Weld work fine. I have found one that had a internal leak between the pump passage and power valve vacuum passage but these are very rare. I have rebuilt hundreds of Q-jets and all but the one was easily repairable.

 

[NHGuy]

Re: 454 Rochester Internal Fuel Wells

The Mercruiser manual is good in how it shows how our carbs are set up, but it leaves out some stuff I learned when I decided to rebuild my Qjet.
The well plug issue was corrected by Rochester in the very early 80's. It's not very likely to be a problem on a 1990's carburetor. And the sloppy throttle shaft issue is not very likely in boat carburetors cause they are not subject to the constant changing of throttle position that a car or truck carburetor experiences. An old 60's or 70's quadrajet out of a car can need bushings in the throttle shafts to correct air leaks from that sort of use.

You can correct a problem with the secondary internal wells by taking off the top of the quadrajet and cleaning the secondary feed system. It's the outer two tubes that hang down into the secondary fuel wells and the secondary discharge nozzles that they (vacuum) feed. Also while you are in there get a piece of wire and clear out the feed holes that allow gas from the central main fuel bowl into the 2 outer secondary bowls.
If there really is a secondary bog that may correct it.
Internal flooding could be a leaking fuel needle. The needle & seat can be bad or the float could be misadjusted, or it could be sinking. You buddy probably checked it and since he did the rebuild he may have a float gauge to check the internal fuel level. If he does not get one yourself and check the way the Mercruiser manual says. If it's off adjust it like the manual shows.
When you have the top off stick a bit of wire down the idle tubes and idle channel restrictions which are just inboard of the main nozzles. They are drilled passages with brass tubes pressed into them. The idle tubes are the ones that are rearward, they go down to the bottom of that main section of your carb, use enough wire to go a little more than 2.5". There is a fairly small orifice at the bottom which can get clogged.
If you want to do the whole thing get "How to Rebuild and Modify Rochetser Quadrajet Carburetors" by Cliff Ruggles. Just go through Cliff's process, when you come out the other end you will have a good working knowledge of the system. It's thorough and I found it very interesting and helpful. Plus he has a forum to answer your questions at cliffshighperformance.com.

 

[broncopower]

Re: 454 Rochester Internal Fuel Wells

Thank you for your experience and advice. I already purchased the Ruggles rebuild book on Amazon, and should be receiving it sometime next week. I have a carb stand, and will purchase the float gauge. Since it was just "rebuilt" by a professional mechanic with carburetor experience, can I re-use the parts (needle, float, jets, gaskets, etc?) I will make sure to clean those parts you specified with the wire, and check to see if I need to epoxy the well plugs.

 

[Don S]

Re: 454 Rochester Internal Fuel Wells

NEVER reuse gaskets. More leaks are started that way just because the gasket "Looks" good. It's not.

Float, needle and seat should be fine along with the other hard parts. There is also a float gauge in the kits, no reason to buy a special tool for that.

Marine carbs are not always rebuildable. They get a lot worse treatment in the marine world, especially if the boat is in salt water.
Then you have maybe a 50/50 chance of the rebuild working. Things get plugged with with salt water corrosion if salt water is allowed into the carb. All passages have to be verified they are clear and things need to be clean to work.
A lot inside of the carb can not be seen.
You flooding may be because of piece of dirt under the needle valve. Happens to the best.

 

[fat fanny]

Re: 454 Rochester Internal Fuel Wells

Remember the hot soapy water scrub between soaks and comp, air blow outs it helps the cleaning process. Also a torch tip cleaner is hany for this task cleaning out ports and such just don't force it!

 

[NHGuy]

Re: 454 Rochester Internal Fuel Wells

My Mercruiser kit did not have a float gauge, but it did have a little paper L shaped ruler. If you need a float gauge you can get them at various places. On the other hand Cliff's book will describe how to set the float height from the inside with a machinists ruler. It also shows how to test the needle and seat to confirm that the seat holds pressure. (You flip the carb over and apply vacuum to the inlet.)
The book tells how to check to see if the wells leak too.
Once you get the book do the reading and think a while a while before you order parts. If you figure out what you need and order your stuff once you will avoid extra shipping charges.
I would not reuse the gaskets from the previous rebuild, mainly because the carburetor is imperfect and it could be a gasket break that caused it. The gaskets in the quadrajet go in dry and can be reused if not run and stuck to the carburetor. But the one that goes between the top and middle sections is very detailed and any ham fistedness can botch it up. Just plan on changing it to be safe.
You also use the vacuum tester to verify that your choke pulloff is working, they often fail.
It's a little daunting but it's all logical and if anything fails to make sense you can ask Cliff or ask us here.