Hi. Just finished building the 455 for a '72 Riv. It really hauls with the Crower cam we put in. Put on a temporary Q-Jet just to get it down the road, and it ran really rich, but o.k., for a while. Then something weird started happening. It would be fine for 5-10 miles and then start a horrible low rpm bog, maybe go another 1/4 mile and bog. Ignition good, cleaned out all the fuel lines - fitting tightly. Obviously it's the Frankenstein sitting atop the motor, but why the delay? I took it apart, everything o.k., secondaries adjusted (bog doesn't let me get to the secondaries once it starts happening anyway), no leaks detected besides driver-side well plug-been epoxied. Why the horrible bog after a delay? I let the car warm up to 180 dg. before I drive it, so it doesn't seem to be an issue with that. The choke is disconnected. I am going to put another carb on today, but I am still wondering what's going on. Thanks, Gabe
Try another carb, my original did similar things and I F'ed with it for years. Finally spend verry little money for a new one and Ill never mess with an old funky carb again. For the price even including the core charge its a steal and so pleasing. All I did was take it out of the box, bolt it on, nail it and smile. You could re-sell their parts for a profit easy. http://www.nationalcarburetors.com/
Thanks for the reply, 70sLark. I threw on another carb that I know works and the problem returned. Same thing, runs great until about 10 miles down the road and it cuts out and bogs, stumbles, idle lowers etc. I tried a new ignition coil, checked wires, connections. Maybe bad fuel pump? I pretty sure the carb is getting fuel, and why the 10 mile delay? I know it has to be something stupid like an arcing wire.
Hi, doc. Vacuum advance diaphragm is good and the connecting rod is not frozen. I'm assuming it is doing it's job as I can feel the difference from when it's not connected, and the weights and springs of the mechanical are moving freely(nothing missing or stuck). It's also hard to start when this problem happens, normally 1/2 key turn and it lights right up.
So it has to cool down to run good, then 10 min later it does that? Or what need to happen to run good for a bit good again??? ID think a fuel pump would be funky all the time but check it too. Could be heat related, maybe the coil gets flaky once workin for a bit? Heat is their enemy.
Hi again. I just read in my shop manual that a condenser will fail if it gets wet, and the problem does not show itself until the condenser gets hot. I live in Oregon and it gets wet here and the little window on my distributor cap is off. I do not know if the problem goes away when the condenser dries out, but it seems to go away when it cools. Likewise, the fuel pump might be getting hot and starting to fail. The car can idle and rev in the driveway and the problem never arises. Maybe try both, condenser and pump, but I'll try a new condenser in first! Thanks
along with that, now that we know you are dealing with a points distributor, very carefully check the wire from the points to the coil. Over the years, the breaker plate's twisting back and forth with the vacuum advance can either break the wires inside the wire jacketing, or rub through the jacketing so the wire arcs on the breaker plate when the vacuum advance twists the breaker plate to just the right position. The kicker is when the engine stumbles, the vacuum changes, the breaker plate twists, and the problem goes away. The 10-miles down the road problem could be is your vacuum advance is still connected to the temperature controlled solenoid (TCS?) that won't allow vacuum advance until the engine is at a certain temp.
Thanks for all of the help! Changed the condenser (which was wet), but the problem's still there. What if there is debris in the pump? It does seem to pump fine though. I pulled off the fuel return line when the problem came up again hoping for a pressure release, but nothing. I disconnected one of the vent tubes off of the gas tank thinking a clogged vent be causing it. It seemed to run better - almost more effortlessly, but the problem came back. I tried blowing on the fuel return line, and found it to be restricted. I have to blow on it very hard to get fuel or air though it, and a couple of times, some flaky black pieces came out. Maybe clogged? Is the fuel return line supposed to be so hard to blow out? I really want to see this car run. Thanks.
This post triggered a memory. A Buddy had a 67 GTO stick car that had a similar problem, It would hardly run when warm. But his would make a noise when the fuel cap was removed. A mud dauber wasp had somehow plugged the vent at the tank. After he found and fixed that it was fine. So you may be on to something with the lines, vent, etc.
Good call. There are plenty of reasons you can still have fuel delivery probs with a perfectly good pump in place. Devon
yep, just a few months back I had a dirt dauber nest in the pick up on my 65 lark gs....also the gas cap on some cars used to have the vent in them....
Good call on a vented fuel system, if he had a Virago it would of been a first suggestion. Bad vent causing vapor lock, and when the cap is removed you hear air rush in. Only FI or a ventless system should make noise when the cap is removed. Which would be like 85-86+ and newer???
Yup, stuck vent or debris in the tank...after running a while the debris clogs the sock. After you let it sit a while, the debris releases from the sock and sits on the bottom of the tank. Start it up and presto, slowly the debris gets sucked back onto the sock.
Never replace your qjet with a rebuilt other or even new type. The 71-74 era Buick 455 carbs were the best period. They are 800 CFM. Most others were 750. They can almost always be rebuilt to good as new.
I agree. The last q-jet I tried to tune with the APT like shown the picture ended up being replaced by an earlier model. A lot more friendly for modifications. Devon
That is just a pic of my carb, they will send you any style you want for any year. mine is an 80, so I got an 80 style carb but with the older base. If you want an 800 you order one for a 800 car. And they all come with the older base with easy adjuster screws if you ask or not, its standard.
