Cadillac 472 Fuel System Part 1 - This Is What Leaky Quadrajet Well Plugs Look Like

#impalamansgarage1
If you suspect your Rochester Quadrajet is leaking gasoline from its well plugs, watch this video. I remove and disassemble the Cadillac Quadrajet for inspection. I found pretty severe well plug leaks and excessive play in the primary throttle plate rod. I also found left-over gasoline and varnish sitting on top of the intake manifold which is clearly evidence of well plug leaks. The idle of this car is quite jittery which tells me that raw gas is dripping into the manifold while it is running.
Parts and Materials Used for these repairs:
Epoxy
www.jbweld.com...
Bushing Kit
cliffshighperf...
Carburetor Kit
www.oreillyaut...

[@TheRds797]

Thank you! I'm working on my 69 convertible carburetor right now.

[@mattiroth5902]

H Nice Video, thanks! The proper fuel filter is at the other end of the fuel line, after the fuel pump.

[@ImpalamansGarage]

Correct! I had forgotten about that. Been a while.

[@ImpalamansGarage]

In retrospect I had assumed the filter on this Caddy was like the one in my other old GM vehicle, which is in the carb inlet. Was reading the service manual this morning and it clearly indicates the filter residing in the pump.

[@wernerdanler2742]

It's been a lot more than 10 years since I rebuilt a carb. Like around 50. I don't think I ever did a Rochester. They were always considered way to complicated to use. How are those casting plugs put in? Just pressed in or what? Hope you continue on this soon now that you have me hooked. Lol

[@ImpalamansGarage]

Yeah they were just pressed in at the factory. This is a common defect repair for a quadrajet from this era.

[@bigcurt011]

Getting my “quadraDRIP “ for my 68 Cadillac rebuild as we speak

[@ImpalamansGarage]

lmao

[@storyoc]

i learned how to work on quadrajets on a 1975 caddy eldorado quadrajet-got a book from amazon-i never tried sealing the well plugs but i have one on my 78 chevy k10 that i think is leaking-im gonna try permatex gas tank sealer-says is ethanol resistant-comes in a 2 part kneadable stick-also gonna replace the float with a brass one s i think is absorbing gas and flooding -its one or the other or both-

[@ImpalamansGarage]

According to Cliff Ruggles, Marine-Tex is the best sealant for this job.

[@ImpalamansGarage]

cliffshighperformance.com/product/bottom-plug-kit

[@brdnsky6417]

It looks to me some one had already been in the carb. The carb was way to clean after looking at the engine. I believe some one could have tried to adjust the float, causing the needle valve to stick open. That could be why you see so much gas in the intake. Also I didn't see any ball fall out when you turned it over. The EGR is what opens the choke when the engine reaches a certain temp. Also a quick way to remove the carbon is to use water in a spray bottle. You start the engine and turn the idle screw up, then spay mist of water in the carb while the engine is running. Don't spray it so heavy that you flood the engine enough to stall it. This will help remove carbon build up on valves and plugs.The old timers use to do this and I have done it and it works.Ronnie.

[@ImpalamansGarage]

I think you are right about someone being in this carb before. This is a 71. No EGR. This car uses a divorced choke with the bi-metal spring down inside a pocket in the manifold.

[@ImpalamansGarage]

EGR (Exhaust Gas Recirculation) has nothing to do with opening the choke on cars that employ an EGR valve. A choke is either opened by engine heat or an electric heater on the bi-metal spring. The hot air chokes are either divorced (spring is down inside a manifold pocket) or they are hot-air (bi-metal spring is located in a canister on the side of the carb and there is a hot air tube running from that manifold to the canister)

[@brdnsky6417]

@@ImpalamansGarage That is what is hooked to the carb to open the choke.

[@brdnsky6417]

@@ImpalamansGarage That is what pulls open the choke using the spring.

[@brdnsky6417]

@@ImpalamansGarage That divorce choke you call it is your EGR valve. And that is what opens your choke through exhaust gas.

[@Closdmon]

Where you getting all you ac stuff worked on?

[@ImpalamansGarage]

I can do a lot of it but there is a shop in Birmingham AL that I would trust. Southern Armature.

[@robertjackson7590]

Carbon on the throttle shaft, poor PCV system maintenance if any at all.

[@beastrabban]

you can get the new hardline from www.classictube.com also, the reason the little hose is there is because undoubtedly the line rusted solid to the fitting going into the front of the carb. not sure about 71 but on later caddies that's where the fuel filter lives. BUT I haven't finished watching the video yet.. you may have discovered all this :-)

[@ImpalamansGarage]

Yeah I suspected there must have been a problem in the past and the previous owner put the rubber line there. Works fine. Doesn't leak. Looks kind of crappy though. lol

[@ImpalamansGarage]

I've had fairly good success bending my own steel lines in the past. It's a fair amount of work, but very cheap to do. I'll check out the classic tube place. Thanks !

[@beastrabban]

@@ImpalamansGarage awesome. hey if you need shop manuals, I have them over on my facebook page - facebook.com/groups/854176278059863/ I don't have the '71, but I do have the '72.. and they're just about identical.

[@beastrabban]

@@ImpalamansGarage yup. you'd try to break that fitting and would twist and crush the line right about where your rubber line is.. then you'd get a hacksaw and 'fix it' with that rubber hose patch while swearing at yourself and GM.

[@ImpalamansGarage]

@@beastrabban Thanks. I have the complete 71 factory service manual. I should probably go read it. lol

[@Coodeville]

I have a leak on my fuel inlet. Replaced the gasket and did nothing. Any suggestions?

[@ImpalamansGarage]

It may be leaking from the compression fitting. In "Cadillac 472 Fuel System Part 6" I install a new fuel hard line I got from Classic Tube. That might be the ticket.

[@Coodeville]

@@ImpalamansGarage i replaced that. Its leaking between the carb body and big fitting. I see some guys use JB to fix that. Thry remove the filter inside and use an external one

[@tannernichols2024]

How do you get to the left mixture screw on the carb when tuning for max vacuum? Seems tough to get any sort of flat head in that tight space.

[@ImpalamansGarage]

For passenger side screw, re-route any vacuum lines which may be in the way. Then use needle nose pliers to come at the mixture screw from above. Works well. Just tweek the screw a little at a time. The drivers side mixture screw can be adjusted with a small flat head screw driver. (Very small).

[@tannernichols9451]

@@ImpalamansGarage thanks. After I commented I saw your video explaining so. Is your vacuum gauge connected to your transmission vacuum line for manifold vacuum? I don't believe the brake booster vacuum line is manifold.

[@tannernichols9451]

I plan to tune my carb later this afternoon. I just wanted to be sure it was transmission vacuum line and not something else. Thanks..

[@ImpalamansGarage]

@@tannernichols9451 It was the smaller port on the back of the carb that connects to the transmission vacuum modulator. (As I recall) Which ever it was, it must be full manifold vacuum.

[@ImpalamansGarage]

​@@tannernichols9451 All vacuum powered brakes get full intake manifold vacuum. (On any car) This does not necessarily mean that the port supplying the vacuum to the brakes must physically reside directly on the intake manifold. It can reside on the carburetor as well. The carb has several ports which are full manifold vacuum. The large port on the back of the carb is full manifold vacuum. It supplies the brakes. It would be fine to use for engine tuning in the shop. The port on the driver's side front of the carb is ported. It only supplies vacuum in off idle conditions. (The port is above the throttle plates) On these cars, this ported vacuum port is meant to supply vacuum advance to the distributor. I've plugged this ported vacuum source on my carb as I prefer full intake vacuum to the distributor. I use vacuum from the front passenger side port which is meant to supply vacuum to the choke pull-off. I have a tee installed there to send full intake vacuum both to the choke pull-off and the distributor.

[@dgoldman2846]

NOOOOOOO DO NOT REPLACE R12 with R134. Get the system checked for leaks and once there are none put R12 back in it........ it's still available!

[@ImpalamansGarage]

No one has R12 around here. R134a is cheap and works just as well. I plan to convert it properly with new POA valve and hoses which can handle r134a. My 300SD was converted and it puts out air in the mid 30s.