why is my motor shaking like crazy.

[65stang289]

This thing just started shaking like crazy for some odd reason. I put new plugs in and a cap it did help the missing but not for long. IT all started after my trans swap. I would Idle it up it would stop for about 20 seconds and come back. Do you think it is my carb I can put my hand on top of it and it will run for 15 seconds befor it will die I thouht it would as soon as you put your hand on it.

 

[Ronstang]

What kind of tranny swap? Sounds like you have the wrong imbalance flywheel.

 

[65fastback2+2]

What kind of tranny swap? Sounds like you have the wrong imbalance flywheel.

His sig says "C4 streetfighter". So he just put in a built c4. Shouldnt be the wrong imbalance then eh?

 

[slackr]

if not the flexplate, then what about the vacuum line to the modulator? the modulator itself?

 

[302 coupe]

the flexplates have counterweights also, wrong weight will cause some shakin', or if the flexplate is loose, or if the torque converter is loose, the list goes on....

its not the modulator, and its not the carb, neither of those would cause a cyclic vibration.

 

['69Stang]

I would check your plug wires and distributor first because it sounds like the spark is getting to the chamber at the wrong time. Have you had the distributor out lately? The other thing could be a very lean carb, maybe that’s why when you take away the oxygen it runs better. Also, the carb could be malfunctioning.

 

[65straightsick]

Timing....My step dad was a royal dumba$$ and pressure washed the engine in his F-150 because he is about to sell it. Well one of the coils got fried....replaced it, along with a new sparkplug and that baby is as smooth as ever. Seeing is how the cars we have don't have a coil per sparkplug....i would check the wires. It sounds like the same kind of misfiring that was happening in his.

 

[C0V3R]

Sounds like you have a bad vacuum leak if your engine will run that long with your hand over the carby.

 

[xoxbxfx]

i was thinking flexplate too.. Were you the one that just converted from a C6 to C4?? IF so, did you get a late model or early model flexplate. Later model 302 needs a 50oz balance flex and an early is 28ox. Just a thought

 

[VictorII]

Also check the vibration dampener. Mine came loose and I had to put a new one on since the keyway was damaged. The end of the crank was slightly rounded off too. Good idea to check it as soon as you can. Then work backwards throught the ignition and carb. Off the top of my head, sounds like a vacuum leak between the carb and the manifold or something in the ignition. Also, maybe a PCV valve if you have one. When they go, you can get some shaking. If you suspect ignition, put on some gloves and pull one plug wire at a time until you find a dead cylinder and then replace the wire with an old one that you know is still good. Doesn't matter if the resistance is the same, it'll still fire if that's what it is.

 

[65stang289]

Yeah that was me that went from the C6 to the C4. I know for a fact that the flywheel now is a 28oz what it was befor I dont know I just know that mine is 157 tooth too. I will mess with the timing of the car.

 

[69PaleHorse]

If you have a 28 ounce flywheel, you have just pinpointed your problem...

As xoxbxfx mentioned, you need a 50 ounce.

 

[slackr]

the old ones (his 289) take a 28 oz...
he is good there...
the 50's started in '81-'82 302's.

 

[69PaleHorse]

Bah, got it all twisted in my head! Right, late models use 50's, early use 28's.

Ok, I need coffee.

 

[Ozsum2]

I vote for a vacumm leak as well.

 

[mhjo]

You have probably lost the rubber padding under the trans mount. Try looking under the car on the brace that holds the Trans. It should be a rubber pad betwwen the brace and the Trans. If it is gone, you get real shake.

 

[65stang289]

Is the 164 tooth flywheel 50 oz? if so I need to change the harmonic balancer to match it then right. Thats what I was told I could change that to the 28oz to match the flywheel. So my motor is off balance now? On top of this now I just came in to take a break and when I went to go put it into park it did not go at all it just rolled :damnit: You name it and it has happened to me. I will stay up all night if I have to so I can race on Friday.
This is what happenes to me every time I play to go to the track it breaks.

 

[slackr]

there are 164 tooth flexplates in both 28 and 50 oz... did you swap the flexplate when you swapped trannys? the c6 should have been a 164 to begin with...

you would also have had a 28oz balancer on the front originally, too...

if your flexplate is off balance, it will shake the whole car... i just had to swap mine out for this as someone put in the wrong one on mine...

if it is just the engine shaking (not so much the car), it's probably missing for one reason or another already stated here...

good luck

 

[302 coupe]

compare the size of the counterweight from your old C6 flexplate to the counterweight on the C4 flexplate. The counterweights should be the same size, the 50oz weight is nearly twice as big as the 28oz weight-obviously. I believe nearly all C6's have 28oz flexplates, they only way it could have a 50oz flex would be if it were put behind a 302 in a 82-up pickup truck/van. Don't start mixing and matching parts until you know exactly what you already have. If you have a 28 oz imbalance engine, you must use a 28oz harmonic balancer and a 28 oz flex/fly. You cannot put a 50oz balancer or flex/fly on a 28oz engine, it doesn't work that way. The crankshaft determines whether you use 28 or 50oz.

Not to be one to kick you when you're down, but its really important to do research before you start a project like this. And by research I don't mean to ask Bubba at the quick lube. Find out the facts from a legitimate source and it makes things alot easier. You also need to know exactly what you already have. The 'Ford Parts Interchange Manual' is a valuable resource and will save you many headaches. It covers just about all the different V8 engine configurations, tells what will or won't swap, and has part numbers and descriptions.