Hello all,

I have a 1972 Dart Custom that I cannot get to go over 55pmh. I was on a long drive and blew a manifold gasket and lost pressure. I replaced it and everything seemed ok, but. a couple hours later I started loosing a lot of power. Topping out at 25/30mph up hill and 55mph on flat land. Its been sitting for some months and starts right up. It idles fine but drops when put into drive. I have to rev it to keep it from dying and it will eventually get there. Does just fine in all other gears. Havent been able to pressure test it as my tester just bit the dust. Waiting on another I'm in a VERY remote small town so everything takes quite a while. I've been told by a couple people that it sounds like the timing is off. Any ideas?

If it idles smoothly then I wouldn't suspect a burned valve. Have you checked and reset the valve lash? I would also check for excessive exhaust back pressure, but this requires a back pressure gauge and drilling a small hole in the exhaust pipe ahead of the muffler. Also, before you do anything make sure the throttle is opening all the way, with the engine off of course. Report back with your findings.

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63 Plymouth Valiant Wagon

This could be a ton of different things. You might try replacing the fuel filter and/or blowing out the fuel line from the back of the fuel pump back to the gas tank. Good idea to check the ignition timing. Pull out 2-3 of the spark plugs too and look for dark and sooty appearance or speckled with dots of aluminum. Can you post pics? Start taking some "measurements" and give us more data on the engine.

Best wishes,
Lou

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Home of Slant6-powered fun machines since 1988

Thank you so much for the suggestions! I will start trying these out and hopefully one of em works.

Remember to go simple and cheap first, Willsy. Things I would look at include:

Blocked exhaust/muffler--you can do a fair amount of diagnosis just holding your hand over the tail pipe. If you blew an exhaust gasket, there could well be something causing too much back pressure.

Check your head gasket--is their water in the oil? You can do a lot with a rubber hose to listen through around the head as well. I thought I had an exhaust gasket problem but it turned out to me a head gasket blown out under one of the manifold studs.

Make certain there aren't any vacuum leaks or leaks around your carburetor throttle shaft. Vacuum leaks and throttle shaft leaks can sometimes let your car idle okay, but then when it needs more fuel, it isn't able to get the correct mixture.

Best of luck,
Joe

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Joe Hoppe

71 D100 225 Super Six 727 AT on 2008 Crown Vic CopCar frame

64 Valiant Wagon 225 904 AT 3:23 8.75"

"blew a manifold gasket and lost pressure" the engine produces vacuum not pressure. Is this a boosted application?