Vibrations / Shaking / low power

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big&bad

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Hi @ all!

I'm sorry, but here we are very uncommon with V8- engines...

I've a problem - my 74 318 LA is running very rough. If I accelerate, it feels like the engine is shaking, it isn't running smooth.

We renewed all mountings, tried to tune the carb exactly, but it's still like an old tractor running. You really can hear every piston working.

The formerly owner told me that the engine has a 0.30 overbore,it had been completely overhauled.
The cylinderheads have been overhauled, too.

I'm running a 600 cfm Edelbrock carb on an Edelbrock intake at it.

One of our engeneers told me it would be sounding as if one bank of the engine isn't running the way the other one does.

Any ideas, any suggestions?
 
big&bad said:
The formerly owner told me that the engine has a 0.30 overbore,it had been completely overhauled.
The cylinder heads have been overhauled, too.
Click to expand...

Was the rotating assembly balanced?

Does it vibrate just sitting or only when driving?

Automatic? Correct torque converter?
 
Hmm. - rotating assembly balanced?

How to do this?

The TC is from Summit, direct replacement for the stock one.

It starts vibrating if I accelerate - when rolling without foot on the pedal it's rough, but no vibrations.

If I step on the gas it really feels like driving with a heavy trailer ehind it.
 
That's what the guys from Summit told me to use as replacement...

Brand:Boss Hog
Manufacturer's Part Number:53080
Part Type:Torque Converters
Product Line:Boss Hog Street Bandit Torque Converters
Summit Racing Part Number:APE-53080

Anti-Ballooning Plate:No
Lockup:No
Diameter (in):12.000 in.
Furnace-Brazed:No
Balanced:Yes
Hardware Included:No
Quantity:Sold individually.
In-Store Pickup:Choose In-store pick-up (OH, GA, NV) on our web site.
 
Start with a compression check for all cylinders and see if any cylinders are low and start there.


If you get some low readings, squirt a few squirts of oil in the cylinder with a squirt can and recheck the compression again to see if it makes any difference. Go from there.

In an unknown engine, you have to start with the basics and work your way up.
 
Check the distributor cap for water/condensation,, Check the spark plug wire firing order... 1,8,4,3,6,5,7,2.

as mentioned,, pull all the spark plugs,, keeping track of where they go,, and look for a spark plug/plugs that appear different.. post some pics here..

and compression test..

attachment.php


hope it helps.
 
krazykuda said:
Start with a compression check for all cylinders and see if any cylinders are low and start there.


If you get some low readings, squirt a few squirts of oil in the cylinder with a squirt can and recheck the compression again to see if it makes any difference. Go from there.

In an unknown engine, you have to start with the basics and work your way up.
Click to expand...

THE ABOVE

I would start with a basic checkup and tuneup and see where you "are."

Run a compression and leakdown test

Inspect the distributor cap and rotor for grease, dirt, moisture, and carbon tracking or physical damage.

Use a multimeter to test the resistance of all spark plug wires and coil wire

Replace spark plugs.

Check timing. "Lean" more towards more advance rather than less

Then with the engine completely warmed to temp, make sure the choke is completely open. Adjust the carb mixture screws for best / fastest idle or most vacuum on a gauge.

If it now does not idle smooth, DO YOU have some idea of whether it has a fairly stock factory cam, or a big "thumper"?

Perform a "backyard" cylinder load test. What you want to do is short the spark voltage out at each cylinder in turn, listen, and watch a tach. "Rig" it so you can do this. One way is to loosen the distributor boots and wires so you can easily pull the wires up out of the cap one at a time.

Use a probe or small screwdriver, grounded with a clip lead. As you pull the wire up out of the cap, ground the spark with the probe.

Watch the tach and listen on each cylinder. A cylinder which does not "drop" as much when shorted means that one is not firing, or not firing as "strong."

This could be due to a number of reasons, including ignition, vacuum leak, carb problems, valve leakage, or low compression from a few reasons.
 
Thx a lot...
During restoration all was renewed, new spark plugs, distributor, cables, sensors, thermostats, hoses. We sealed everything. My mechanic had the Dodge manual in front of him and tried to follow the official instructions.
If this problems would be at a Mercedes or BMW engine, I could fix it drunk, blindfolded, with my hands tied at my back. But american V8 are unknown territories, a new land.... I even wouldn't see the difference between a stock and a modified camshaft.
Next week I will sit with my mechanic and try to follow your instructions - maybe we will find what's going wrong.
 
Check to see if your harmonic balancer/dampner has separated(will make engine run rough/off balance)There is a rubber ring inbetween 2 pieces,if separated,get a new one(Pioneer..thru Summit)
 
Hey Guys, just looked on Summit racing at the part he posted. In notes it says this converter has weights. WRONG converter! Stop running this car and change to the right converter. Converter is the problem
 
Big&bad, looks like russhal may have pinpointed the culprit. Too bad if it is the wrong TQ, sounds like Summit may have fouled you up. BTW, I remember your build thread, good looking car you got there!
 
big&bad said:
That's what the guys from Summit told me to use as replacement...

Brand:Boss Hog
Manufacturer's Part Number:53080
Part Type:Torque Converters
Product Line:Boss Hog Street Bandit Torque Converters
Summit Racing Part Number:APE-53080

Anti-Ballooning Plate:No
Lockup:No
Diameter (in):12.000 in.
Furnace-Brazed:No
Balanced:Yes
Hardware Included:No
Quantity:Sold individually.
In-Store Pickup:Choose In-store pick-up (OH, GA, NV) on our web site.
Click to expand...

Right there boss, is your problem as others have stated. Do not run anymore or you will mess things up. 318 is internally balanced so therefore it does NOT need a balanced torque convertor.
360's are the ones that need the balanced torque convertor.
Hopefully you didn't run that too much, otherwise you might have problems there boss... :sad1:
 
I say BS. An out of balance converter will indeed make an engine vibrate BUT NOT ALL THAT BADLY. I once ran a 360 with a 340 flywheel and other than NOTICABLE vibrations at SOME RPM it wasn't earth shuddering NOR DID IT cause real loss of power.

NOTE:!!!!

This was way WAY before Al Gore invented the internet
 
It may not be the same, but we started a rebuilt externally balanced 340 with a 318 flywheel and new INSTANTLY that there was something wrong. Engine shook at idle and worse as you revved it up. Again, this was all before the internet.

I hope the torque convertor fixes your problem.
 
RedFish said:
Did it run right at one time and suddenly go bad ?
Click to expand...

This is exactly what I was wondering. If it's a sudden change, you might be passing a kidney stone through the fuel system. Do things get rougher as your engine warms?
 
If the converter is weighted as the notes say in the application on Summit, can't he just grind the welds and knock the weights off? Mopar performance used to have a weight and template kit to weld weights on neutral balance converters for external balance engines. My understanding has always been that all converters are neutral balance. They weld the weights on for external balance applications. It's not as high tech as you would think. The location for the weight and amount off weight is the same for all external balance app's. Just a thought.
 
67Dart273 said:
I say BS. An out of balance converter will indeed make an engine vibrate BUT NOT ALL THAT BADLY. I once ran a 360 with a 340 flywheel and other than NOTICABLE vibrations at SOME RPM it wasn't earth shuddering NOR DID IT cause real loss of power.

NOTE:!!!!

This was way WAY before Al Gore invented the internet
Click to expand...


I did the same on a car that I was just moving around the yard. At idle you couldn't tell. At 2000 rpm you could feel it in the seat. at 3500 the entire car shook and rattled. That was a 360 and a 318 torque convertor so it was only the back end of the crank that was not counterweighted.
 
I had a tq converter in a neutral balance application that was bad right out of the box. I wouldn't drive the car until I figured it out. It was just like he's describing. Pulled the trans and put a bellhousing and flywheel on it. Engine ran smooth. I replaced the converter. Car went from terse to beast.
 
Today we made a run on the "Autobahn"...

No fear, my mech was beside to tell me if something is going really wrong to stop me...

Standing, no feet at the pedal, it was like a Harley-Davidson a little bit. It sounds as if you could hear every ignition.

Accelerating with pedal halfway-down you could feel a little shaking, as if a tire is out of balance. Not so much, but the feeling was a little bit the same. Also, the needle of the odometer was hopping up and down, dancing difference maybe 3 - 5 mph. It felt as if a part of the power was lost somewhere.

Accelerating pedal to the ground you could feel that the engine fights. The shaking became less, to a small but notifyable vibration. It seems that there was still some power missing.

At 100 - 120 mph the engine run totally smooth...
 
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