Guest Straight eight Posted August 21, 2009 Share Posted August 21, 2009 :confused:Is it true that the float bowls on some Qudrajets leak from the plugs in the base and drain into the intake manifold, causing a fire hazzard? If you have an 85 with the V8 engine that cranks and cranks before starting in the morning, it is possible you are harboring a real fire hazzard and don't know it.How about some knowledgeable comments from some carburetor guys? Link to comment Share on other sites More sharing options...
Bill Stoneberg Posted August 21, 2009 Share Posted August 21, 2009 Dont know about the Q-Jets but I had lunch with a fellow the other day whose Buick burned because one of the plugs came loose on his Rochester.Also there was an article about the same thing in the Bugle last year. Link to comment Share on other sites More sharing options...
Guest pfloro Posted August 21, 2009 Share Posted August 21, 2009 (edited) Hello Everyone:I can't speak to the fire hazard but, from experience, I know the 'well plugs' can leak fuel which drips into the intake manifold. The plugs exist to seal openings which were part of the float bowl section casting process. The repair requires the carb to be disassembled and the plug areas cleaned & sealed with epoxy. If done correctly, the repair should last many, many years. Both the primary & secondary well plugs are involved here...As for the extended cranking required after an overnight rest, I think this has as much to do with the new reformulated fuel (higher vapor pressure) as it does with leaking well plugs. This fuel also causes percolation out of the wells and right through the main discharge nozzles & idle ports. I've seen the bowl lose significant fuel overnight in our Arizona summer climate. The fix is to install an electric fuel pump in place of the mechanical one. I installed a Holley 'little red' pump mounted on the frame near the fuel tank. I just let the pump run for several seconds before cranking each morning. The return line from the old mechanical pump is no longer needed. The Holley is internally regulated to 7 PSI so no external regulator is required. This pump is not super quiet but I can live with it... Unfortunately, reformulated fuel is not friendly to our carbureted engines but fine for fuel injection... I will post pictures later of my Q-Jet rebuild showing the sealed fuel well plugs...IMHO: Unless a well plug is leaking a ton of fuel, I don't think enough will pool & vaporize in the intake manifold to cause a fire...Paul Edited August 21, 2009 by pfloro (see edit history) Link to comment Share on other sites More sharing options...
John Posted August 21, 2009 Share Posted August 21, 2009 Leaking into the intake should not cause a fire; leaking externally onto the intake could. John Link to comment Share on other sites More sharing options...
carbking Posted August 21, 2009 Share Posted August 21, 2009 Pre-1968 Q-Jets CAN leak past the well plugs. GM fixed the issue with the 1968 models.More of an issue is the volatility of modern fuel, which causes fuel to leak between the throttle body and throttle shaft right after the engine is turned off.Jon. Link to comment Share on other sites More sharing options...
Guest Straight eight Posted August 21, 2009 Share Posted August 21, 2009 How about the computer controlled 85 Riviera V8 s with the Rochester 4bbl. quadrajet? Link to comment Share on other sites More sharing options...
Guest pfloro Posted August 22, 2009 Share Posted August 22, 2009 (edited) From research on the Internet, even the later Q-Jets (including the 'electronic' (E4MC/E)) units which appear on '81 - '90 engines have well plugs which can leak. It appears that it's SOP to epoxy the wells during a carb rebuild...The attached images show the areas to be cleaned, roughened up a bit and covered with epoxy. The little round button plugs can't been seen any more...There are six (6) plugs to cover: 2 primary wells, 2 secondary wells, accelerator pump well plug and one other which I think is part of the fuel inlet.So..., YES, the Q-Jet on your '85 Riv (307 Olds V8) could possibly have leaking well plugs. There is a very easy way to measure the fuel level in the bowl to see if it drops over a short time. Within a few minutes after the engine has been running:1) Shut off engine.2) Remove the air cleaner assembly.3) Cut a thin strip of cardboard from a manila folder (1/4" x 3").4) Gently drop this strip into one of rectangular slots on either side of the threaded shaft to which the air cleaner lid is secured (see RED notation on my photo). This strip will now rest on top of the float. If you press down GENTLY you will feel the pontoon submerge into the fuel. 5) Release the strip & with a pencil, draw a line where the strip meets the top of the slot.6) Every hour or so, see if the cardboard strip has dropped further into the slot. This indicates that the fuel level has dropped in the float bowl. If it drops 1/4" to 1/2" in an hour or so, the well plugs are leaking a lot. Then again, the drop may be due to fuel percolation.7) I can almost guarantee that if you let the car sit overnight, the fuel level WILL be lower. The bowl may even be empty... However, this may simply mean that the reformulated fuel has just evaporated.Unfortunately, the only way to be sure that the fuel well plugs aren't leaking is to pull the carb off, disassemble it & seal them.Hope this information helps... Keep us posted... Paul Edited August 22, 2009 by pfloro (see edit history) Link to comment Share on other sites More sharing options...
sosuzguy Posted August 22, 2009 Share Posted August 22, 2009 Bravo Paul - excellent information and visual aids! Link to comment Share on other sites More sharing options...
Jolly_John Posted August 23, 2009 Share Posted August 23, 2009 Yes! Very helpful information, Paul. Thank you for taking your time to share this with the Buick gang.A QUESTION FOR ALL: Has anyone experienced leaking well plugs causing an inconsistent or erratic idle on the 1979-1985 Buick and Olds V8's? John in Wisconsin Link to comment Share on other sites More sharing options...
Guest pfloro Posted August 24, 2009 Share Posted August 24, 2009 (edited) Thank you, Jason & John for the compliments... That Olds 307 gives me a connection to the '80s Buick gang...!I didn't experience an idle problem due to leaking well plugs. BUT... since the primary well plugs are exposed to manifold vacuum, fuel could be 'pushed' out by the atmospheric pressure above. This might cause the O2 sensor to see a richer mixture & the ECM would try to adjust via the Q-Jet's mixture control solenoid 'duty cycle'.One thing I've recently learned about the electronic Q-Jets is that they really need to be adjusted correctly (using the factory procedure). Once they are, the idle is amazingly smooth & the transition to part throttle is seamless. Before I realized that I only needed my dwell meter & the few special adjustment tools, I had my mechanic 'adjust' the carb to smooth a rough idle. It was better but I always had some hesitation coming off idle. After adjusting it myself using the factory procedure, the idle & transition to off-idle is way smooth...During the adjustment procedure, you can actually see how the ECM is trying to compensate for an overly lean or rich idle mixture setting. The dwell meter reading is a window into the computer's brain. It was very cool... Paul Edited August 24, 2009 by pfloro (see edit history) Link to comment Share on other sites More sharing options...
Guest TwoDoorBuickMan Posted August 24, 2009 Share Posted August 24, 2009 What type of epoxy is best for this procedure? I have been told that J B Weld is good and I have also been told there is a gas tank repair similar to Mighty Putty that works well. I would like to hear from someone that has had good results. I only want to take it apart once. Link to comment Share on other sites More sharing options...
padgett Posted August 24, 2009 Share Posted August 24, 2009 Back in the day the big problem with QJs was people who stripped the pot metal threads where the fuel line enters. This can cause a major leak onto (not into) the intake manifold. There were all kinds of fixes available but usually the carb was just junked. Link to comment Share on other sites More sharing options...
Guest pfloro Posted August 24, 2009 Share Posted August 24, 2009 JB Weld is fine. This is what I used. Be sure to clean the areas to be epoxyed using lacquer thinner or similar solvent. Then roughen up those areas a bit. It's best to apply the epoxy when the float bowl is upside down & level. Don't use too much as the JB Weld will 'run' a bit before it starts to cure. Wait 24 hours before reassembling the carb...Paul Link to comment Share on other sites More sharing options...
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