1974 Dodge Dart Magnum Swap

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My car has the factory balancer that came on the motor and using the factory flex plate. The car doesn't really shake at idle or sitting still. It shakes at high way rpms. I thought it might be the wheels but if I kill the motor while it is still moving it stops shaking. Again factory balancer that came on motor, factory flex plate that came on motor, and a neutral torque converter that was in my darts 904.
 
If it is vibrating under power while driving look at the driveshaft/u joints. Make sure driveshaft still has weights on it and u joints are tight. Since it got worse after a gear swap i would swap the driveshaft 180 degrees on the rear yoke and see if it gets better, sometimes tolerances stack up and you get a vibration.
 
Rev the engine up to 2,000 rpm's. If it vibrating at 2 grand see my previous comments. Or continue beat yourself up.
 
I have had it at all 2000 rpm and actually at 2500 to set my final advance and doesn't shake at stand still.
 
Well, I believe most every rotating issue has been looked at. Given that it is a used engine I have not seen where you did any basics to check the operation of the engine.
Like: Pull the plugs to confirm the are the same color, New plug wires, New plugs, Dist cap. I bought 3 dist caps before I had one that was NOT cracked(new ones). Distributor shaft, is it straight? Rotor button? Compression Check, MOST important. Cracked heads? 5.9's are famous for cracked heads. Vacuum leaks. The intake is critical when it comes to the sequence and the small amount it takes to torque it. Cam lift, (worn lobe) pushrods, rockers, lifters. Blown head gasket, leaking from one cylinder to another.
The Scamp I bought with the 5.9 had a slight miss. And it would light up the tires. I never checked what the issue was since that 5.9 was not going to be used.
Hope for the best, expect the worst.
 
Well, I believe most every rotating issue has been looked at. Given that it is a used engine I have not seen where you did any basics to check the operation of the engine.
Like: Pull the plugs to confirm the are the same color, New plug wires, New plugs, Dist cap. I bought 3 dist caps before I had one that was NOT cracked(new ones). Distributor shaft, is it straight? Rotor button? Compression Check, MOST important. Cracked heads? 5.9's are famous for cracked heads. Vacuum leaks. The intake is critical when it comes to the sequence and the small amount it takes to torque it. Cam lift, (worn lobe) pushrods, rockers, lifters. Blown head gasket, leaking from one cylinder to another.
The Scamp I bought with the 5.9 had a slight miss. And it would light up the tires. I never checked what the issue was since that 5.9 was not going to be used.
Hope for the best, expect the worst.
If you think I put an engine in a car with out checking and changing all of the above you must think I am a complete jack ***. It was tore down to a long block on an engine stand and checked over before it ever had new parts hung on it. If you look at the picture you can see it has a brand new set of plug wires, cap, rotor, does have a brand new distributer, brand new carb, brand new intake etc. The car doesn't miss or sputter in the slightest, it shakes. Go read magnum swap website it tells you all info you need to know and I followed it to a T. I don't need that kit, head gaskets aren't blown, heads aren't cracked, etc.
 
Not saying anybody is a jackass. I have had 2 5.9's completely rebuilt. Machine work only. One for my 99 5.9 R/T Dakota, a spare and the 408. Bought the 408 used and was told everything is perfect. Knew the mechanic the built it personally, Jim Boostin, and I trusted his work. However, I had the 408 rebuilt be another machine shop and they found one piston with a broken ring land. Replaced the piston set. Jeff died of cancer 4 years ago. Got the 408 from his son. My point is, whenever you get a used engine, the unknowns can cause much grief. Rebuilt or not, and now you are experiencing it.
Just trying to look outside the box. Good luck with your project, hope you find the problem.
 
Where did you get this engine; from a truck you were able to drive and test, or did you get it already removed? I see you said it's the balancer and flex plate that came on the engine, but I am wondering if they gave you a mismatched flex plate, or balancer. Some of the descriptions are conflicting, making it harder to evaluate. It shakes at highway speeds, but not sitting in park with rpm at a steady 2500, and goes away when engine is turned off while at speed. At what vehicle speed and rpm does it actually show up? Is it worse when you floor it while it's happening? Do you feel it at all in second gear, before transmission shifts to third? Also, an early post said you were using a new converter, but a recent post said it was from your existing trans, so what's the story there? Sorry for all questions in one post.
 
Where did you get this engine; from a truck you were able to drive and test, or did you get it already removed? I see you said it's the balancer and flex plate that came on the engine, but I am wondering if they gave you a mismatched flex plate, or balancer. Some of the descriptions are conflicting, making it harder to evaluate. It shakes at highway speeds, but not sitting in park with rpm at a steady 2500, and goes away when engine is turned off while at speed. At what vehicle speed and rpm does it actually show up? Is it worse when you floor it while it's happening? Do you feel it at all in second gear, before transmission shifts to third? Also, an early post said you were using a new converter, but a recent post said it was from your existing trans, so what's the story there? Sorry for all questions in one post.
I got it removed but I tested it on the stand. Flex plate and balancer were bolted to the motor when I got it. I saw the motor running before purchase but no didn't drive it. It used to start shaking around 60 to 75 mph, now shakes at around 45 to 55 mph since lower gears installed. No it doesn't seem to shake when sitting still and yes if I shut it off it quits shaking. If I let out of the gas it shakes less and shakes more when back on the throttle. I couldn't tell you on the gear thing unless I took it out and drove it again. I am pretty sure it something to do with flex plate. I initially had a new torque converter but it was a balanced one so I got my old one out that was a nutral or unbalanced. When I put the flex plate on I had to make a couple holes bigger to get it to bolt up to the old style torque convertor. In doing so I think I may have it in the wrong spot in turn making the thing vibrate.
 
If the converter is neutral balance, with no weights on it, then your slotted holes in the flex plate should be fine, as it then doesn't matter what orientation they get connected together. Did you happen to get a picture of the flex plate before the engine was installed? Not worried about holes, but wondering which style it is and if it has the factory weights on it that many Magnums used.
 
That sure sounds like drive line to me. Did you try taking drive shaft off and turn 180 and bolt back on? I have had the same thing happen after changing gears. Shook bad at 55-60, rotated drive shaft 180 and it stopped.
 
I have had it at all 2000 rpm and actually at 2500 to set my final advance and doesn't shake at stand still.
This here says it all.
Firstly You may be cranking waaay too much advance into it, and It may be in way to early. And the if the Vcan kicks it's load in, then maybe this is just purely detonation. Try slowing the curve down to all in by 3200 And disconnect the Vcan. Then a roadtest
 
It's been a while since I have posted. Have had the car up and driving over the summer but still have a few kinks to work out. I have a horrible vibration in the drive line some where that got worse when I switched my rear end gear ratio. If I shut my engine off as I'm moving the vibration stops. I'm thinking something in the flex plate weights is off. Either way here are a couple pics.

View attachment 1715117985

View attachment 1715117986
Hey how did you eventually get your exhaust headers to fit? Were you able to get a master cylinder and booster in with your valve covers?
 
Actually I had time to look at it again and it does vibrate when you Rev the motor in neutral.
 
Put new u-joints in the driveshaft, report back.
Hell I just bought a brand new truck, vibrated at 68 mph, the factory did not balance any of the tires.
 
I think at this point, after re-reading all the details about your build and the vibration, and if you have already ruled out ignition timing, I would retest at same steady RPM with any/all belts removed, sitting stationary in park again. If it still shakes, get the balancer triumphman mentioned in post #48, Professional Products Part #80012. Install it with no weights first, then if it still shakes, try adding the Magnum weight. Another option would be installing a different style factory Magnum balancer than you have, if you can get it cheap. The newer one has a serpentine pulley integrated, so I am sure you don't have that one yet, but the Professional Products part will work with pulleys you already have, and it will allow you try three different balance setups with one part.
 
Hey how did you eventually get your exhaust headers to fit? Were you able to get a master cylinder and booster in with your valve covers?
I couldn't get headers I got from summit to fit so I got some manifolds off of a 81 Mirada. Never touched factory master cylinder or booster.
 
I am going to tear into it tonight and look at my flex plate and my torque convertor.
 
Do not know your latest situation. Did you go with all the hardware from an original 5.9 Magnum factory set up? FYI: AKA: serpentine. Everything fits.
 
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