I have a 58 Pontiac with a 261 six that is original and has never been apart. It has run flawlessly for over 20 years. I drove it to a show in Penticton BC (from Calgary) and it ran great going there. Half way back it croaked. It started missing a little, like dirty points. I stopped, cleand and gapped them and it ran ok for a little while, then it started acting up again. At first it would only "miss"when there was very light throttle or coasting, but it got worse. After going down a long hill and then entering a level part of the road it missed, bucked, and ran very rough. In about 5 miles, it straightened out and ran fine. I would go down another hill and it would act up again, each time worse. Finally at Revelstoke it died. Iinitially, it seemed to be electrical so I replaced, the cap, rotor and coil. That only seemed to make it worse. It was seriously flooding, but when I took the carb off and apart, everything looked ok. When the engine was cold it would run for about 3 minutes (perfectly) then it got goofy again. Finally I had it towed home. I have rebuilt the carb, to know avail. The compression of the engine is consistant but a little low (might be my gage). When I am able to get it to run (howenver breifly) the engine vacuum is no more than 12 inches. It smokes and is running very very rich. I am at my wits end. When it did act up, it did so going down hills which really increases engine vacuum, so I am thinking maybe an intake manifold gasket but I am grasping at straws. Any ideas out there? Thanks Bill
I've had that happen to me when I had a 54 Chevy with a 235. Turned out there was sediment in the fuel bowl of the carb causing grief. I rebuilt the carb and never had a problem. Going up and down hills probably moved a piece of sediment.
Replace your points and condenser, the condenser is often overlooked but time and heat make them do quirky things"like not allowing the coil to charge".
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pontiax- (canadian pontiac X frame)1964 Parisienne 2dr. Hardtop ,lagoon aqua metallic (Q) ,421 cid Dart Industries block and heads. 550 hp. 575 ft lb of torque.
My money is on the fuel system. Eventually I had to pull the fuel tank to flush out 20 years of accumulated crud (and I had it boiled and coated at the radiator shop), new pickup since the old sock was clogged so badly too, blow out the fuel line, new fuel pump, and rebuild the carburetor. Then the old 261 ran great. Before then, lots of problems, not unlike yours.
Oh -- welcome! We like photos, show your 58!
Dave
-- Edited by davelacourse on Sunday 24th of July 2011 07:06:37 AM
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1956 Pontiac Pathfinder 2dr sedan, 496 - dyno'd 545 hp, stick shift, 4.11 posi - Hot Rod
I will agree with Dave and add if you have already replaced your fuel tank pickup and sending assembly with a new one with a new sock the sock is disintigrating from the new gasoline. The new sock will plug the fuel line intemitantly and may be the cause of the problem. Disconnect the fuel line at the carb and blow air back in the fuel line to the gas tank. If it starts and runs after this procedure you will have to drop the gas tank and have it cleaned and coated. Remove the sock and install a clear inline gas filter on the fuel line so you can actually see the fuel and you can check for dirt.
Above ideas if fuel system problem plus bad pump or lobe possible, even sucking air w/ holes in fuel supply lines?. Confirm ignition components good then bypass fuel system w/ remote fuel supply directly to carb, supply is constant w/ container elevated higher than carb.. Line is disconnected between f'pump and carb so put a dead antifrz jug or something @ f'pump exit line to catch gas pumped w/ engine cranking/running... If good now, move backwards to isolate where problem beings or if still no go look more closely at carb again, intake leaks etc..
~ :smile
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I like real cars best...especially the REAL real ones! ----------------------------------------------------------------
I rebuilt the carb and replaced almost (note almost) the entire ignition system. I had a great spark coming out of the coil when I manually manipulated the points (almost stopped my heart). I double and triple checked everything. I didn't replace the condensor as I had such a good spark. At my wits end, I found an old condensor laying around, installed it and it ran fine. Lesson learned, don't look for the complicated when you have overlooked the simple. Thanks all for your comments, greatly appreciated. Bill
Keep the fuel tank/pickup in mind for possible stalling out problems down the road, and I forgot to mention what Al (Taylor55) said but add that too if you have to pull the tank and/or pickup.
Dave
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1956 Pontiac Pathfinder 2dr sedan, 496 - dyno'd 545 hp, stick shift, 4.11 posi - Hot Rod
1956 Pontiac Pathfinder 2dr sedan, 496 - dyno'd 545 hp, stick shift, 4.11 posi - Hot Rod