73 Duster motor shake

[goofy73duster]

1973 Plymouth duster factory 318 car has 53,000 miles took off the two barrel put on a four barrel brand new distributor brand new plugs wires everything is new. The timing is dead on the car has great compression for the first 30 seconds. The car runs great and smooth once it warms up the whole entire motor shakes and the car shakes, like I said, it’s not a miss it’s a shake

 

[RustyRatRod]

What's the vacuum gauge say? Is the engine stock? Mild cam? Radical cam? Throw us some bones here. From your description, I'm guessing the engine is stock.....but I hate to guess.

 

[goofy73duster]

The engine is completely stock all I did was put a four barrel on and headers. I did a leak down test. There are no vacuum leaks all brand new ignition system and I did a compression test the first 30 seconds it runs at high idle there’s no miss and the motor doesn’t shake as soon as the car warms up the motor gets a violent shake.

 

[Bewy]

[1] Check that the dist cap is on properly.
[2] Check the firing order.
[3] Check the p/up air gap, should be 0.008". Check in 3 places, shaft could be bent or out of round.
[4] Say a prayer to Allah....

 

[junkyardhero]

did you upgrade everything at once: the intake/carb & ignition system + headers or was all that existing and all you did was snap on a 4bbl & carb?

 

[niceolddart]

did you upgrade everything at once: the intake/carb & ignition system + headers or was all that existing and all you did was snap on a 4bbl & carb?

Good question above. It sounds like your carb may be the problem. The carb may be sucking vacuum somewhere (Throttle shaft, gaskets, etc.) or not adjusted. What kind of carb is it? It looks kind of funky in the pics & it may be a defective/crappy one. Try a known GOOD 4bbl & see if that fixes your problem.

 

[RustyRatRod]

The engine is completely stock all I did was put a four barrel on and headers. I did a leak down test. There are no vacuum leaks all brand new ignition system and I did a compression test the first 30 seconds it runs at high idle there’s no miss and the motor doesn’t shake as soon as the car warms up the motor gets a violent shake.

Why would you do a leakdown test? You changed nothing that would affect that. How have you verified no vacuum leak? Have you had a vacuum gauge on it? What is this "I did a compression test for the first 30 seconds" mess? Can you expound on that? I don't even know what that means. I can't do a compression test on one cylinder in 30 seconds. We can't help you if you speak in riddles.

 

[Ant]

Motor mounts?

 

[4mulas]

Likely:
- big vacuum leak from manifold, the carb, or both. If not major jetting issues
-plug wires in the wrong order or something wrong with your ‘new’ distributor. What brand is it? Tell more about the distributor.

 

[OldmanRick]

I'll take a stab at it... I see a electric choke. Maybe it's way out of adjustment.

 

[AJ/FormS]

Here's another stab,
Remove the mixture screws and blow out the circuits