front end vibration

[fireguyfire]

I am looking for suggestions on how to trouble shoot my rebuilt 383 in my 68 charger. The car struck a tree on the front drivers side in the early 90's, was disassembled for repair and was never put back together. This is how I bought the car and have done a full restoration on it.
As for the engine, I had a high end engine shop do all of the machining and reassembled the engine myself, with the assistance of a professional mechanic/engine builder friend of mine.
After start up last year I have been working out some bugs on the car. There was a good vibration at the crankshaft pulley; I pulled the pulley and determined it must have been tweaked in the accident as it had a slight wobble I was able to diagnose out of the car. Anyway, I sourced another 4 slot crank pulley and determined that it was straight before installing on the car. That made the vibration noticebly better, but there is still a mild vibration on the front of the crank. My engine builder buddy is not happy and says over time it might hurt the engine even though it is fairly minor now.
Anyway, I pulled out the receipt for all of the engine work and the shop did rework the crank so I am confident that the crank is true or else they would have caught it.
To me that leaves only 1 other real option, which is the harmonic balancer which appears to be original to the car. I was looking at replacing it, but some of the info I was finding on the internet was really confusing regarding forged cranks vs cast cranks and internal vs externally balanced engines,
I am looking for inputs on how to go about diagnosing what my problem really is before throwing money/parts at the problem hoping to fix it.
Could this be anything other than the harmonic balancer? The crank is good, the crank pulley is good, the torque converter is brand new and is the right one for the engine and a 747 torqueflight.
Are there both internally and externally balanced 383's? As you can tell I am not a master engine builder and want to be able to figure out whats going on and fix it.
Thanks for any suggestions in advance!

[crj1968]

Your 383 would be internally balanced.

I would take it back to the high end engine building shop. They should be able to diagnose it

[will]

My damper took out a bunch of stuff when it let go. I have the 440 source damper, no shaking up front. I have to change the water pump, the shaft is a little tweaked. Make sure you check the torque convertor for weights, there should not be any. The 68 is an internally balanced engine.

[b5blue]

Ron recommended this for my 440. I think is the same for 383.
http://www.summitracing.com/parts/pfs-80013/overview/make/dodge

[Nacho-RT74]

Wrong damper.

Or

Lost rubber isolation on damper. This can move the two pieces damper assembly

The damper science is easy. Thick counterweightened ones for cast cranks, thin neutrally balanced ones for forged cranks.

the usual on 383 is find them find them forged. But since 70 they began to offer cast for low performance engines

[mopar0166]

AS im sure people are saying above, the  harmonic balancer  is different for a internal verus external balance engine.  that has to be determined first.  once you know which crank you have everything else has to matched.  flex plate, converter,  harmonic balancer  etc.  Hopefully if it was internally balanced the shop balanced it with the rods and pistons you are using.   if its externally balanced then you need to look further in to the  harmonic balancer  and flex plate .   


Good Luck 

[fireguyfire]

Found this (not great) photo of my crank when I was tearing down my engine. Can anyone confirm that I for sure have a forged crank? This is a 68 383.

[crj1968]

Check this out

[Nacho-RT74]

Cast crank...was changed sometime in the past, because AS FAR I KNOW, all were forged by 68!

I guess, you must have unweightened TC ( if you bought telling by the engine year, and not the crank facts ) and neutral damper?

[fireguyfire]

You are correct about the TC and the damper. The TC is brand new but the damper is very old.
Crap!!!! This is not what I wanted to hear; I just assumed that because it is a 68 383 it would be a forged crank for sure.
I guess my next step will be to try and find a forged 383 crank.
Anyone got an idea how hard it will be to find one, and how expensive it will be?

[fireguyfire]

Perhaps I need to pull the harmonic balancer and confirm that it is neutral; could be a weighted one. This engine was rebuilt along time ago and it didnt occour to me that the crank may have been swapped out then. This car was driven for years after that rebuild so maybe it has a weighted balancer on it, and had a weighted torque converter to make it balanced? Maybe my vibration is from putting in a non weighted torque converter after the tranny refresh based on assuming the 68 383 had a forged crank and that threw out my balance. I need to do some checking to see just what I have before making drastic decisions; perhaps the best option will be to change out the converter to a weighted one and have an externally balanced 383 with a cast crank. I would hate to tear into the freshly rebuilt and tight engine if I dont have to.

So with the cast crank, this engine would need to be externally balanced; 1) external harmonic balancer, 2) weighted torque converter in the torqueflight. I believe there is something with the fly wheel too? If so how can I identify which type of flywheel is in the car?
As I said I now suspect this thing was externally balanced when rebuilt back in the day when the crank was swapped, and when I put a non weighted torque converter on I made the vibration.
For purely street driving would there be any solid reason to go through the major surgery of swapping to a forged crank over getting the external balance right on the cast crank?

[fireguyfire]

Found another photo of the engine after rebuild and in fresh paint. This shows the harmonic balancer that is on it now. Can anyone identify if this is a neutral or an external weighted balancer?

[Nacho-RT74]

Forged crank damper

[Nacho-RT74]

Rockauto uses ( or used ) to sell stock replacements forged and cast cranks in an affordable price ratio, already machined and bearings included. If you search to your car by year, just will get forged option. The used to be in between 250-300 rate. Not really expensive if you think it is ready to go into engine, no machine shop or anything else required with parts included and something you can do by yourself at home.

Otherwise, ebay is a good source. You can get them in several conditions, from 80 to 120 or so.

Actually for stock street use car, cast is quite enough, and stock dampers for these are cheap. What is it involved? Get one with non symmetric pulley bolts setup. I can't recall if they really exist in fact, because was really early in The 70s when they become to be symmetric, and your car BY THE YEAR, was non symmetric. You could enlarge the respective bolt hole on pulley anyway to match it. Not hard to do.

You can also get an aftermarket damper for these, which gets balanced on use.

about TC you can either get the weights and weld ( usually original weights are available with templates to locate the weld position, sold by Mopar Performance way back ) or get a balanced flywheel, sold by several aftermarket tranny parts manufacturers, such as TCI, B&M etc... Actually it calls flexplate.

You can also send back the TC to get it balanced for the cast cranks.

The cheaper &/or easier? Get the balanced parts!

The correct? Get the crank.

[Nacho-RT74]

Tech info about stock balancers

http://www.440source.com/dampers.htm

Reading the link, just checked non symmetric cast crank damper it does exist.

[crj1968]

Yeah it'd be easier to get the balanced parts and just bolt them on.

That's what I'd do since everything else is rebuilt and all put together. But that's just me.

[fireguyfire]

I've decided to go the external balancing route, even though it might create a major headache in regards to my front 4 groove pulley lining up.
Was able to find a cast crank 400 damper today

[Nacho-RT74]

ok, still will need to consider the TC balance ( if your one is not weightened )... the easier and cheaper... get the flexplate for it

it should look like this, which is also valid for several TC setups ( 11" and 10" ) in one piece



This flex plate gets the cut on the opposite side of the weights should be, to make the balancing.

I always try to be correct on anything on my car with just some exceptions for upgrades, and being a 68 would get a forged crank.

But that's just me LOL

[Nacho-RT74]

another option, a bolt on counterweight

[fireguyfire]

Thanks for the tips guys. The car is in show car condition after a full 2 year restoration so the last thing I want to do is pull the engine out and apart now that she's runs like a top other than this small vibration.

[fireguyfire]

Thought I'd give an update. I put an external balance harmonic balancer on the engine and it is WAY better but there still is a slight vibration. I've sourced a local tranny shop that has been balancing flywheels for 35 years so I'm hoping once I get the weights tacked onto the flywheel the engine will be good.

[b5blue]

Good luck with the next step!