Bird won't stay running under a load

[booalou]

My 62 Tbird has been having some problems ever since I replaced the power booster and master cylinder. The car will start and idle without any problems but as soon as I drive it boggs down and shutdown like its staving for gas. At first thought I thought it was the gas filter at the fuel pump which was dirty so I replaced it and the car continued doing the same thing. So I decided since the carb and fuel pump were old and I'm in a restoration mode I would replace them as well. Put in the new fuel system and no change the same problem still exist.

So then I go back to the power booster thinking something with regards to a vacuum problem (even though the idle is good and no sounds of a leak) could be causing the problem. The only thing I could see is that the vacuum check valve I installed from the old booster had a diaphrame and the booster had one as well. Could having two in the system be the problem?

Finally I was told by a friend on the east coast who works on old cars that it could be the coil thats causing this. I put a tester on mine and it reads 6.5 volts DC does anyone know what the Ford Tbird coils should read? Note I have pertronix electronic ignition on this car for about a year.

Learning as I go!

[Petrolhead]

Hi

It's a bit hard to diagnose remotely. First up check that the non-return valve in the vacuum line is in the right way, not that I think that'd affect the way the car runs, more than likely it would affect how the brake booster works. I'd check that the vacuum lines are reinstalled in the correct place.
It's unlikely that it's the Pertronix, I haven't heard of one failing, and I imagine that if it did it'd fail completely. I'd suggest that it was a blockage in the carb when the carb comes off the idle circuit, but you've eliminated that too by changing the carb. Does sound like ignition, not sure what the 6.5 volts mean. I had an ignition that broke down under load and the coil was the culprit. Can you borrow a coil and try a different one?

[Texas Landau]

Petrolhead is right, it is hard to diagnose a problem from afar, that being said, here goes:It sounds like it may be your advance not working; this would allow a perfectly good idle, but cause the car to quit when you try to drive.

Pull your distributor cap off, disconnect the vaccuum advance line at the carb. While watching the distributor with the cap off, suck on the vaccuum hose. The plates in the distributor should visibly move when you suck on the line; this is the vaccuum advance. If it does not move, you have a bad vaccuum advance on your distributor and it must be replaced.

Hope this helps!
Randy

[bcomo]

Vaccuum advance is what I would also say is the problem.

Texas Landau gave the correct proceedure. It happened on mine and that's the way I found it was bad.

Voltage provided to the stock coil is between 6-9 volts. So, that's OK.

[Guest]

1. Get a vacuum gage and verify you have at least 18" of vacuum at idle.

2. On my car, I had the same problem because I hooked up the vacuum advance on the distributor to an inert "vacuum" port on the carb, anyway, sounds like a vacuum problem.

3. If you have a leak in the new vacuum brake booster, a vacuum gage will help you track that down.

Bottom line: Vacuum gage is indispensible for finding vacuum related problems. A cheap and very useful tool.

[booalou]

Thanks for everyones help. The problem was caused by having the wrong vacuum check valve installed at the power booster. My new rebuilt booster had the vacuum check valve diaphrame already installed in the port where the vacuum check valve scrwews into. I installed a check valve that also had a diaphrame. I guess they were working against each other causingt he car to shutdown under a load. I found an original metal check valve installed it and the problem was resolved.

Thanks for everyones help.