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Old 04-29-2013, 02:01 AM   #5 (permalink)
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Originally Posted by Frank Lee View Post
I'm amazed too. It had a 2bbl Rochester, TH350.

My '59 Bel Air, 283, 2bbl, Powerglide gets low 20's too. However my driving is not intense city like yours.

8 mpg indicates something is very wrong. Could be the driving, could be not running on all 8, who knows. No burnouts or stoplight gran prix are allowed if you are seeking to maximize your economy.

You suspect alignment cuz it pulls left, but if the tire wear is even then I'd say your front left brake caliper is not releasing. Jack it up and see how easy the wheel spins. Check 'em all. Make sure the tires are all aired up properly.

Put a manual choke in. Or in CA you should be able to disable the choke altogether. The 59's choke is disabled; I just pump a few times to start. It hasn't been an issue (thus my failure to fix it or add a manual choke).

There is probably nothing wrong with the intake, although the crossover passage for intake heating could be plugged up. That would hurt mileage. There is also a crossover thermostatically controlled valve in the exhaust system that needs to be freely working if that warming system is to be functional.

It is said that a 4bbl can achieve better fuel economy than a 2bbl IF you can stay outta the secondaries. I haven't tested that theory.

You suspect excess PCV contamination. Maybe there's a stuck piston ring, or excessive wear throughout. Do compression and leak-down tests.

Maybe it's flooding. They can flood and still manage to run decently. Could be a hung-up or not floating carb float.

Could even be a fuel leak somewhere.

Does the motor oil stay clean or does it get diluted thin with gas?

Your trips are too short. That big V8 lump is not getting to operating temp. NO I'M NOT SUGGESTING YOU LET IT SIT THERE IDLING TO "WARM UP". The big old carb'd stuff was simply far worse in that respect than today's EFI stuff. To mitigate it some you can use a block heater, engine compartment blanket, convert to e-fan, perhaps some grille blocking, perhaps a warmer t-stat.

But seriously- trips of only a couple miles are better done on bicycles, scooters, or any number of things more suited for the task. What you have is a hobby car more than a daily driver.
Frank, this is all good stuff. I'll diagnose all this ASAP. thanks again!
1971 El Camino
Chevy 350
TH350 transmission
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