Engine Swap Question

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Bob Watkins

Bob Watkins

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I recently put a 1974 318 motor in my 64 Barracuda. It fit, but just barely. Unfortunately, the engine has a severe vibration/balance issue that we have to solve. Since the motor we rebuilt had some internal issues I may want to put in a different short block, and still use the aftermarket parts we put in, such as cam, 4 bbl, roller lifters, etc. My question is: What years of motors will bolt up to my 1974 A904 trans, still fit in the tight quarters of my A body, and allow us to use our parts? Can I run the newer fuel injected motors on a 4 bbl carb? Any suggestions? Thanks A-Body-ers for all of your great advice!
 
I would be willing to bet you have an externally/internally balanced parts mismatch issue.
 
All LA and newer magnum small blocks have same bellhousing pattern, all will bolt up to your A904. All LA and newer magnum engines are the same external dimensions. Yes you can put a four barrel on a newer fuel injected engine. My 5.9 magnum stroked to 408 with a 780 Holley.

IMG_4773.JPG
 
We noticed during rebuild that someone before us welded a steel weight onto the harmonic balancer, which tells me this problem could be deep and old. We also found it had thrown a rod at one time and did some minor? damage to the crank. Torque converter was the original one with this motor/trans combo, so it should match, but I don't know about its condition. We'll look closer this time.
 
Bob Watkins said:
Did you mean internally balanced torque converter?
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No you said the convertor, trans and engine was all from the same donor right? But you said there was a piece of steel welded to the balancer? But yes the convertor you have should not have weights on it.
 
SGBARRACUDA said:
No you said the convertor, trans and engine was all from the same donor right? But you said there was a piece of steel welded to the balancer? But yes the convertor you have should not have weights on it.
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I understand now. Yes the engine and trans were originally a pair. That weight on the balancer really puzzled me too. Really a shame too. It runs so nice, but at 1000 rpm and up it really shakes. Something is not right, so it's coming out. I'll check the torque converter for weights also. That's a good tip- thanks.
 
Hell can you knock the weight off the balancer and run it before you pull it? And you can see if there are any weights on the convertor from under the car. They will be on the flex plate side of the convertor if there is any.
 
SGBARRACUDA said:
Hell can you knock the weight off the balancer and run it before you pull it? And you can see if there are any weights on the convertor from under the car. They will be on the flex plate side of the convertor if there is any.
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I can inspect the torque converter, but I've already disconnected everything to pull the motor. Should have posted this earlier. Lesson learned! I have found so much good info here on A-Bodies, I should have known better to ask first. We'll pull it and give it a good going over. I If we don't find a problem inside the motor, I think I'll rebuild my T/C and get a new balancer. (Summit Racing is 10 minutes from my house) If you can think of anything else to check pass it along. I appreciate your knowledge and help!
 
Make sure your convertor hub that sticks into the back of your crank is the right size. 67 and older snout were smaller. Make sure it's not sloppy in the hole.
 
Just because it was mated when you got it does not mean it belonged. 68ish and earlier crank converter snout registers are smaller. That means if you have an earlier transmission mated to a later engine, the converter will not be properly piloted/ centered.

Mopar converters up until Magnums were weighted for external weighted/ balanced engines. All 273/318/340 that I'm aware of used neutral balance converters. A neutral balance converter may have small balancing weights, but not the larger one used on a 360. A photo would help

Same thing on the balancer. Who knows if it is original/ correct? Welding weights to "stuff" is ALWAYS suspect!!!!

I'm not an engine builder/ expert, but "it might be" that if you got some oddball crank/ rod/ piston combo it might be enough out of factory weight to no longer be balanced.
 
67Dart273 said:
Just because it was mated when you got it does not mean it belonged. 68ish and earlier crank converter snout registers are smaller. That means if you have an earlier transmission mated to a later engine, the converter will not be properly piloted/ centered.

Mopar converters up until Magnums were weighted for external weighted/ balanced engines. All 273/318/340 that I'm aware of used neutral balance converters. A neutral balance converter may have small balancing weights, but not the larger one used on a 360. A photo would help

Same thing on the balancer. Who knows if it is original/ correct? Welding weights to "stuff" is ALWAYS suspect!!!!

I'm not an engine builder/ expert, but "it might be" that if you got some oddball crank/ rod/ piston combo it might be enough out of factory weight to no longer be balanced.
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I am aware of the smaller snout- had a '65 273 that I couldn't match to my tranny- ended up selling it. There's so much we don't know about this motor, I'm now suspect of everything. If we can't find a "smoking gun", another engine might be the safest route. Evidence pints to the engine threw a rod at one time, was bored .060, and there's still some light scars on the crank. We used all the rotating parts, but you're right questioning them. I'll add a "post mortum" discussion when we figure it out. Also- I did check the flex plate/converter bolts and they were tight. Can't get to the crank bolts until we separate the tranny, but they look tight from what I can see visually.
 
67Dart273 said:
Just because it was mated when you got it does not mean it belonged. 68ish and earlier crank converter snout registers are smaller. That means if you have an earlier transmission mated to a later engine, the converter will not be properly piloted/ centered.

Mopar converters up until Magnums were weighted for external weighted/ balanced engines. All 273/318/340 that I'm aware of used neutral balance converters. A neutral balance converter may have small balancing weights, but not the larger one used on a 360. A photo would help

Same thing on the balancer. Who knows if it is original/ correct? Welding weights to "stuff" is ALWAYS suspect!!!!

I'm not an engine builder/ expert, but "it might be" that if you got some oddball crank/ rod/ piston combo it might be enough out of factory weight to no longer be balanced.
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20201109_105217[1].jpg


Here's pic of the welded weight on the balancer. Weld is pretty "funky", which makes me more suspicious.
 
SGBARRACUDA said:
That would have scared me off from building that one. At least without having the whole rotating assembly balanced.
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Being a novice, hindsight is a wonderful thing. Sometimes those lessons are pricey, but we're learning.
 
Bob Watkins said:
Being a novice, hindsight is a wonderful thing. Sometimes those lessons are pricey, but we're learning.
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Not busting your balls here. We all learn as we go. I could tell you about some of the genius things I’ve done that has cost me thousands. One in particular, 17,000.
 
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Ouch! Nice thing I've found, even the parts I've bought by mistake seem to sell, which lessens the cost of my education.
 
I know the potential for that is there, but fortunately I'm not upside down in this one yet, but it ain't over! That's why we started with a "driver" and not a concourse candidate. That was smart.
 
67Dart273 said:
Just because it was mated when you got it does not mean it belonged. 68ish and earlier crank converter snout registers are smaller. That means if you have an earlier transmission mated to a later engine, the converter will not be properly piloted/ centered.

Mopar converters up until Magnums were weighted for external weighted/ balanced engines. All 273/318/340 that I'm aware of used neutral balance converters. A neutral balance converter may have small balancing weights, but not the larger one used on a 360. A photo would help

Same thing on the balancer. Who knows if it is original/ correct? Welding weights to "stuff" is ALWAYS suspect!!!!

I'm not an engine builder/ expert, but "it might be" that if you got some oddball crank/ rod/ piston combo it might be enough out of factory weight to no longer be balanced.
Click to expand...
The exception to your list of engines would be the late'72 and '73 340 engines. Those are externally balanced.
 
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