• When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.

Strange 360 LA

Diz TheFiddler

Well-Known Member
Local time
1:45 PM
Joined
Sep 14, 2019
Messages
84
Reaction score
45
Location
Rohrbach
Hey Folks,

let me tell you my story.

I bought a 360LA which ran in a offroad jeep until then. The guy said it is internally balanced, but google says every 360LA is externally balanced. The harmonic dampener at the front is for a internally balanced engine. The flexplate that came with it is symmetric too. But i never saw the converter.

So i assume this 360LA is really internally balanced, since it ran a while in that jeep according to the seller. And he said this was a military engine. They made internally balanced 360LAs only for military. Maybe thats the answer to the other strange thing here.

Today i checked the numbers of the engine. Its definitely a 360LA, but the casting number on its left side is 4006830. I found some casting number lists (which worked great for the heads), but this number is listed nowhere. And usually only the 440 big blocks had a casting number beginning with 400...
The heads are from 75-76 and have the number 3769974, by the way.


Im interested if you guys know something about that.
 
A 360 can be internally balanced with aftermarket parts (Eagle, Scat, etc..). All OEM 360LA engines, military or otherwise, are externally balanced.
 
Thank you guys, this really helps. Reading the link, i was surprised to find a closed chamber 360LA head (heart shaped). Thought they were all open chamber?!

Correction: Yesterday i took a closer look at the harmonic balancer. It is not perfectly symmetric, as i thought first. The 2 radial drillings are not exactly opposite and they have a different depth. So maybe its externally balanced.

Does the converter or the flexplate manage the balancing usually? because the flex plate that came with it is symmetric and definitely for a internally balanced engine.
 
If the balancer does not have an external weight on the front (OEM) or bolted on the rear I believe (aftermarket), it is neutral balanced. Just because the drill holes are not symmetrical (180 degrees apart) or the same depth, means nothing. The drill marks are strictly there to finish the balancing by removing material. This the same thing they do when they balance a crankshaft. As far as the converter/flexplate goes, an original Mopar converter will have a weight for external balance, and no weight for internal balance. Aftermarket converters I believe have no weights as they are usually on the new flexplate (HP). An OEM replacement flexplate will be the same as the original. The reason that the engine is externally balanced is the there is not enough material in the end crank counterweights to balance, so external weight is added to the front and rear of the crankshaft to counteract a lot of the rotating weight, and is fine tuned with removing the rest out of the crankshaft.
 
Thanks a lot!

Just contacted the seller again. Guy said he ran it without counterweights at the back (with a chevy trans) and he knows the pre owner and he assures me, that there was never put another crank in it or balanced it.

So i guess there are 2 possibilities:
- they ran it with the wrong converter and harmonic damper
- i have a unique engine

Is there a possibility to find out the correct balancing without disasembling it and bring it to the machine shop? I dont really trust the installed harmonic dampener. Good chance that it has been changed in 44 years....
 
Drop the pan and verify the Mopar crankshaft. If it is an original 360 Mopar crank, put the correct 360 Mopar (or aftermarket equivalent) on the front. If you are going to put a Mopar trans behind it, either get an original (or OEM aftermarket replacement) flexplate and use the 360 converter with weights. You can also get an aftermarket flexplate that has weights on it, and use a neutral balanced converter. If you are using the GM trans, I assume the aftermarket flexplate was a Mopar and converted for a 3 bolt GM converter. Get an aftermarket flexplate with weights, and use/adapt to the GM converter.

B&M 360 Mopar with neutral converter and 727 Trans: https://www.summitracing.com/parts/bmm-10236/overview/make/chrysler
B&M 360 Mopar with neutral converter and 904 Trans: https://www.summitracing.com/parts/bmm-10239/overview/make/chrysler
ATP OEM style for weighted converter: https://www.summitracing.com/parts/atp-z197/overview/make/chrysler
 
Thank you my friend!

How do i identify that the crank is original? Think i saw a pic that there is "360" casted in or stamped in, but i cant find it any more.

The plan is to put a NAG1 from a 5,7 gen3 hemi behind the engine. Since i couldnt find any fitting flex plate or other conversion kit (gearstar only sells the whole trans kit for more than 5000$, which are about 8000€ when its here in austria) i think i have to make a fitting flexplate.

So I just need a flexplate without the holes (the big one in the middle should be already bored, because it fits gen3 hemi and LA) and the needed counter weight/balance.
 
Aftermarket cranks look nothing like OEM cranks. There are no casting numbers, and the craftmanship is different. Just google Scat or Eagle and look at their cranks for an example. Here are two pics of an original crank for reference. You can also google the casting number you find to ID it.

IMG_3951.jpg
IMG_3952.jpg
 
Auto Transport Service
Back
Top