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Lenny Bruce

Senior Member
I’m so sorry everyone I just posted and should have been more specific about my issues. Our coupe was running great but had a very loud backfire once in a while out the exhaust. I found the intake was broken. I had the exhaust manifold resurfaced and installed a new intake and gaskets. Now the car runs worse. Tried multiple rebuilt cleaned soaked carbs with same issue. Runs rough
And adjusting the GAV doesn’t help. Fuel flow is great! Re gapped the points and that made it even worse! Bucks and shakes no power running warm and smells lean. The car ran beautifully except the occasional backfire before replacing the manifold and gaskets. Now it has all these issues and I’m stumped!!!
 
I will inspect the distributor today and reset the timing. I will also replace the condenser.
If that doesn’t work it may be time to remove the valve cover?
 
remove it and spray PB Blaster in there and work them back and forth. put MMO in your gas, if you havent already.
 
If you haven't already done so it would be a good idea to do a cylinder compression test and a leak down test. These will confirm or rule out a possible cause. I'm with ronn in thinking it's a possible sticking valve or possibly even the cam timing gear has broken/jumped a tooth.
 
  1. Do the compression and leak down test as B Butturff advised in Post #10
  2. Make sure the intake and exhaust manifolds are co-planer at the surfaces that mount to the engine as Gary said in Post #8.
  3. Check for vacuum leaks by spraying carburetor cleaner at various places where the intake manifold bolts to the engine.
  4. Check the timing and condensor as you said you were going to do in Post #6.
  5. Use a vacuum gauge to check for abnormalities in the intake manifold vacuum at idle.
 
You said "I had the exhaust manifold resurfaced and installed a new intake and gaskets." I'm curious, did you have the exhaust and intake resurfaced while bolted together? They both have to be on the same plain.

I see Gary WA already asked this question in post #8, but I have not seen an answer.
 
That loud backfire is a clue. This can happen if you have in intermittent short in the distributor that cause a few spark cycles to be skipped, letting unburned gas in the muffler. When the short resolves itself, the burned exhaust ignites the gas in the muffler and boom, a backfire. Ray64 said check the lower plate pigtail wire in post #2. That is a common place for a short to occur. The insulation could have chafed or cracked, and as you move the spark advance lever the bare wire can ground out to the distributor body, and if you move it some more it could break contact with ground.
 
To much going on chasing your problem! Start with the original problem Manifolds! Terminal box next! Was running good prior to manifold cracked!
 

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Yes it was running great just backfired now and again. Broken intake manifold was what I was assuming the sole issue but apparently not. I will check off all the boxes. Thanks everyone!
 
Just got done removed the manifolds,cleaned them up along with the block. Popped the valve cover off all the valves seem to be operating properly. All back together still runs like crap! So tomorrow I will dig into the distributor. I peaked inside the top of it. Nothing seems to be disturbed. I’ll have to dig into it. See if there’s a shorted wire go from there.
 
Lenny, I just got back from an attempted trip of approximately 100 miles. I made it about 15 miles. The car was running really rough. I traced the fault to really burned points, so burned that they could not be filed. I suspect that the condensor failed to cause the points to fail. After replacing the points and condensor with new ones that I carry in the car, it ran great on the way home. I aborted the trip because it was getting late, the temperature was in the 100's, and I think the humidity was up close to 100% too. And black clouds were gathering.

This happened without warning. One day it was running great and the next day really badly.
 
Nkaminar sorry your trip was cut short but we don’t like them black clouds! I’m going to replace the condenser today and set the points and timing. Do you know anyone who has installed an FS modern distributor on their car? This is my wife’s sport coupe I’m tempted to make it more user friendly for her. I’d love to get some feedback. We like to keep them mostly stock but also would like to make them more dependable. Thank you for reaching out I love learning more about these old pain in the Butts Hahahaha
 
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