1970 Pontiac Firebird

This car has been sitting for YEARS… It starts and runs but runs rough at idle. With some throttle its better. Electridal and timing components are new, carb rebuilt… I can hear some liffter noise. I’m trying to get it running without pulling heads. I think I have a couple collapsed lifters.?? It’s 1967 326ci

Flat lifters is a pretty likely one issue. Vacuum leaks from the intake manifold is another. A biggie is the fuel we use now has 10% ethanol that eats away the fuel lines, carb seals, gaskets and fuel pump diaphragm from this era. It also makes the mixture lean. Fuel injection can compensate but the carb cannot. It may require slightly larger jets to make it run correctly. And what carb IS it? Rochester 2 barrel? 4 barrel Quadrajet? Replacement Edelbrock or Holley? Some models are easier to get parts for than others.

Plan on replacing all the fuel lines and the fuel pump. Might not hurt to just replace the fuel tank with a brand new one. They are available and this old tank may shed rust like crazy and cause you endless problems.

Timing gears on this era Pontiac is also an issue as they use nylon gears to quiet the timing chain and they fail.

Why does this 1970 car have a '67 326 in it, BTW?

As far as the lifters, I just checked an old repair guide. Heads do not need to be removed to R&R lifters. I agree with Mustangman’s comments on fuel system issues. Once those issues are address you MIGHT be able to free up the lifters using an additive to the oil. Others on this forum recommend Seafoam, I have no personal experience with it, but I would be concerned Seafoam or other additive would freeup crud in the engine that might interfere with other oil passages.

The car is a 1967 Firebird. The website would not let me select a year older than 1970???
Thanks for the help.

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Was the fuel tank was drained and cleaned before you started the car?

@Mustangman is right. Old fuel is never going to run well. It’s a surprise that it runs at all. You really do have to get rid of the old gas.

Since it does run, you might as well check the compression. It’s critical because if the compression is poor in one or several cylinders nothing you do to the fuel, valves, ignition, vacuum hoses or anything else is going to help much.

When you dig out an old car it’s really helpful if you can find out why it was abandoned in the first place. That can be a big clue in figuring out what needs to be done. You can spend months on a rough engine, finally get it right, and then discover a blown transmission or a broken frame or some other very expensive problem in the running gear.

If you run old varnished gasline into a rebuilt carburetor it’s quite possible that you will have to go back into that carburetor and clean it out.

Old gas will not ignite or not ignite readily. I’ve seen some gas samples dumped on to a floor with a match thrown into it. Won’t burn a bit.

With lifter noise try adding a can or two of Seafoam to the motor oil and run it a while to see if the SF cuts any lifter sludge loose. As mentioned the lifters are removeable without puling the heads if that’s the case.
Remove valve cover, Remove rocker arm, Use a lifter removal tool to fish it right out.
Another possibility is that ends of some pushrods may have collapsed due to lack or oil.sludge. Lubrication goes away in the lifter and the pushrod doesn’t last long.

Cool car. First year of the Firebird and Camaro and should be worth some money even not running. Mechanically speaking, they’re bone simple to work on.


Concur w/ @ok4450 above , unless all the old gas was drained out and the inside of the tank was cleaned before the carb was rebuilt, likely the carb has gummed up again. The symptoms are definitely consistent w/that. With owning a similar vintage truck, ask me how I know … lol … It might be possible to de-gunk the carb without having to totally rebuild it again, but get the fuel delivered to the carb in pristine condition first. I’m presuming the fuel filter was replaced when the carb was rebuilt. Even so, it might have to be replaced again. When I was solving a similar problem on my truck I had two fuel filters in series until I was sure the incoming fuel was clean.