After life derailing my plans for a month or so, I have resumed wrenching. I am trying to sort out what I think is a carb issue and could use some feedback.

69 427 390hp 4 spd cpe

a previous owner had swapped a Holley spreadbore on to the engine. Carb had more leaks than the titanic, both fuel and air. the air leaks appear to have been there from the begining as the carb was jetted insanely rich.

Since this car had been parked for a couple decades, went through and replaced plugs, wires, cap, rotor, fuel tank, fuel lines, fuel pump, fuel filters. Replaced other parts as well, such as brakes/lines, but nothing that would affect the engine, so irrelevant here. Holley was sent off to be rebuilt.

Got the car to fire up, but wouldn't idle. anything above 1200rpm and it was fine. Still seemed to be really rich, especially at lower rpms. When driving, it seemed to load up and want to die. WOT would clear it out. Holley went back for adjustments. (just the carb)

reinstalled, hard to start, won't idle. (yes, P.O. removed the mechanical linkage for the choke) Even after it is warm, won't idle. Still seemed to load up at idle when driving, WOT still cleared it.

Pulled Holley, swapped in the Qjet from the 68. Smaller carb, but as I have not been into it yet, I don't know how it is jetted. 427 fired up, still didn't want to idle, but was better than with the Holley. more responsive, although the throttle linkage wouldn't clear a bolt on the intake, so could not drive it.

Installed a reman Q-jet, thinking this was the solution. no dice. fit/linkage all are fine, but backfiring when cranking. Distributor has not been touched. 2 ft column of fire up out of the carb and both mufflers are split now. Granted they were old and going to be replaced, but damn! When I can get it to fire up, it will NOT run under 1200-1500rpm. At all. I am thinking vacuum leak, so I disconnected the vaccuum lines from the intake and capped them. battery is on the charger and I will try again tonight to see if it will fire up.

anyone experience this before?
thoughts?
ideas?
suggestions?
voodoo rituals?
anything?

Thanks in advance

 

Make sure the plug wiring is correct.

 

It sounds like the distributor is way out of time, the vacuum can is sticking or blown, or you still have a massive vacuum leak somewhere.

I assume you made sure the plug wires are on correctly as far as firing order? I've seen it where two wires were switched and it behaves exactly as you describe.

There aren't too many things that can cause your problems. It's a matter of methodically eliminating them.

 

verified the wires are in the order on the distributor that is cast into the intake manifold.

Pretty sure I confirmed it with the assembly manual firing order as well, but its been a couple months, so I will double check.

no obvious massive vaccuum leaks. no sucking air sound aside from the carb. vacuum lines to the carb ports (distributor and driver side PCV valve) are new. the remaining vaccuum port (tree) on the intake manifold is currently capped to hopefully eliminate leaks on brake booster, headlight doors, wiper door.

distributor was not removed or loosened, so it should be same timing as when it was driven last.

 

So, lots of variables here, but I'll start with the obvious (to me). Try one thing at a time! Good idea to disconnect all the vacuum hoses. Now, get a plastic spray bottle, fill it with water, and spray a stream around the base of the carb and at the intake gskets while it's running. It'll be pretty obvious if there is a leak.

Back fires through carb = retarded timing or swapped wires, blown mufflers = rich mixture + swapped wires or bad timing.

Loosen the Distributor, fire it up and "ear time" it. just turn the distributor one way or the other and it'll slow down and start to "labor" (retarded timing) or speed up and smooth out (advanced). You want it right in between, so when it just starts to smooth out. You'll still need to put a timing light on it, but it'll be in the ball park.

Sart with that and see what happens. I'm assuming you checked the point gap (if it still has them) and cap for cracks inside. After three (or 4, I lost track!) carbs that won't idle, I'm guessing it's one of the above mentioned problems. Hard to diagnose from here, but it's a start.

Hans