Help me out with this Convertor issue

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7duce swinger

7duce swinger

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Okay fabo i am having a bit of a hard time getting this across to a buddy of mine. Hes swapping a 360 to where a 273 once lived. What im trying to get help on is trying to give him info on this swap lol so here goes....

My understanding is that the 360 is balanced differently than a 273 external vs internal , does the 360 have the convertor weighted? And a neutral plate? Correct or false?

Now his buddy who he says knows more, is telling him to use the convertor from the 273 and original flexplate with the 360 and itll be fine. Also that he can knock the weights off?

I know b&m sells the plate, but is that to use with the 273 convertor right?
So how does he go about this? Buy the b&m plate and use the existing convertor or buy a 360 convertor and use the existing flexplate? Also is there any difference in the pilot holes
 
You are correct, not the other guy. I think the best bet is to buy the B&M plate that's weighted to properly balance the 360 engine. It's cheaper doing it that way and if he decides later he wants a high stall converter he can buy a standard neutral balance converter.

BTW: what year is the car he's working on? Specifically the trans? Before 68 they used a 19 spline input shaft with a small torque converter hub (1.55" vs. 1.81" o.d. in 68 and later). If he has a 67 or earlier trans. he'll also need an adapter ring to install on the torque converter pilot hub so it fits in the 360 crankshaft properly. Only place I know to get them is e-bay. Look up the seller "torqueflitepatty"

BTW: it sounds to me like your friends other buddy is a chevy guy due to him not knowing how Mopar balanced things. And what's the crap about knocking the weights off?? That makes no sense at all. If he puts it together it'll shake like a blender with a Tasmanian devil in it.
 
Thanks fishy 68, the car is a 65 barracuda, its a 727 trans, he also said the seller was giving him a convertor but it wouldnt seat on the shaft properly.
He just told me two people told him it was fine to "knock off" the weight and one of them is a diehard mopar guy.
I told him it would shake like an 1800s wagon and eventually fail, but hes stickin to what theyre saying since theyve been friends longer. I just dont want him doing all the work for it to fail in the end if you know what i mean.

Sorry thats what i meant about the pilot holes in the crank, i shoulda clarified that, its a bushing right?

So the b&m plate is his best bet thanks, ill let him know.

Btw: i was stumped when he said they told him to knock the weights off, lol i was like wtf? Lmao he even said he was gonna run it with the original 273 stuff with the weights "knocked off" and it would run fine they said.
 
Wow! Well you tried. That's all you can do sometimes. He'll have to learn the hard way. The one odd thing that strikes me is them saying to knock the 273 weights off?? To my knowledge all 273's were all internally balanced so they had no weights. 360's have weights on the converter because their externally balanced.

I incorrectly assumed since you said it was a 273 car it'd have a 904. The 727 didn't have the pilot size issue like I described above, only 904's had the small pilot. But 66 and older 727's had a 19 spline input shaft so a converter from a 67 and up won't work.
 
Well thanks fishy68, hes gonna buy the b&m unit, and be done with it.He told me his buddy, said he had forgot about buying the plate so he actually does need it lol he sent him a picture.
 
Quick question: my buddy is getting the 360 done, and well my head is scrambled right now, he has purchased the flexplate already.
Hes telling me his convertor has no weights, this is right correct? Theyre not supposed to have weights being internally balanced?
 
A 360 is externally balanced unless the shop that's building the engine built it internally balanced. He needs to ask the shop how they balanced it. If it's still externally balanced like it came from the factory it either needs a weighted converter or a B&M conversion flex plate.
 
My bad fishy68 i meant hes finishing it up, so its still factory balanced he told me, the new plate is heavier than the factory winged style, its a full circle instead of the 4 wing style plate. Idk if its a b&m piece.
 
7duce swinger said:
My bad fishy68 i meant hes finishing it up, so its still factory balanced he told me, the new plate is heavier than the factory winged style, its a full circle instead of the 4 wing style plate. Idk if its a b&m piece.
Click to expand...

Ok. Sounds like the flex plate is just a heavy duty replacement. If it were the conversion plate it'd have a chunk taken out of it on one side. He needs weights on the converter with a flex plate like that cause it's a neutral balance plate
 
Just back off and let your buddy sink or swim. You keep givin him advice and somehow if something messes up it'll all be on you. Let him learn the hard way.
 
Thanks, fishy68 i cant imagine how it'll run if he wont get the right plate, I guess its a few months temporary motor. I just wonder if it will last 5 or 6 months of daily driving..

..And yea, you might be right RustyRatRod, i just have that damn thing in me that has to help a friend out to keep them from doing stupid things. God knows why.Ah, i guess you cant help everybody.. But you can try! Lol

Thanks guys

7duce
 
I know what you mean. I absolutely love helpin people. But I swear, sometimes it's worse than talkin to a brick wall. That's when I just shake my head and walk off.
 
I hear ya man, people being stubborn can screw up alot of things im just trying to get him to do things right so he wont have to spend money twice.

He keeps telling me his friends are saying go for it. So im just gonna take your advice and back off this one before it backfires on me..

Although i am curious and wonder how their mopars are running if theyre giving him this type of advice lol.
 
The 273 converter will have a small crank snout. If you use this, you need an early to late crank adapter ring, or make one. This is not the same as a brass (stickshift) pilot bushing

The 273 converter will be "neutral balanced," and may have small weights to get it into balance in the same way that tires/ wheels are balanced.

A 360 LA converter is not "balanced." It is in fact UN balanced so that the combination of the weighted converter, the unbalanced rotating engine assy, and the weighted 360 dampener causes the entire assembly to be "in balance."

The factory weights on a 360 converter are quite large

In the photo below, you can see the 360 weights in the lower right quadrant. A "neutral balance" converter may not have any weights, or may have much much smaller weights

attachment.php


In order to use a neutral balance (273) converter behind a 360, you need a B&M flex plate. There are several for different engine combos so get the right one, IE 360 Magnums are weighted differently than 360 LA. Early model BM flexplates are round with weights, later ones have a half moon shaped cutout to act as the balancing weight

Later BM flexplates look like this:

m6tUq-DNI6BhHL3CES8pCDA.jpg


Early ones look like this, and have welded on weights

mkssXxq87Hf495cWpZtlRWw.jpg
 
67Dart273 said:
The 273 converter will have a small crank snout. If you use this, you need an early to late crank adapter ring, or make one. This is not the same as a brass (stickshift) pilot bushing

The 273 converter will be "neutral balanced," and may have small weights to get it into balance in the same way that tires/ wheels are balanced.

A 360 LA converter is not "balanced." It is in fact UN balanced so that the combination of the weighted converter, the unbalanced rotating engine assy, and the weighted 360 dampener causes the entire assembly to be "in balance."

The factory weights on a 360 converter are quite large

In the photo below, you can see the 360 weights in the lower right quadrant. A "neutral balance" converter may not have any weights, or may have much much smaller weights

In order to use a neutral balance (273) converter behind a 360, you need a B&M flex plate. There are several for different engine combos so get the right one, IE 360 Magnums are weighted differently than 360 LA. Early model BM flexplates are round with weights, later ones have a half moon shaped cutout to act as the balancing weight

Later BM flexplates look like this:

Early ones look like this, and have welded on weights
Click to expand...

Apparently they've also swapped the trans. to a 727 (as noted in post #3). All 727's had the large pilot hub. I have never seen the early B&M plate you speak of. I wonder if that's what he's got?
 
fishy68 said:
Apparently they've also swapped the trans. to a 727 (as noted in post #3). All 727's had the large pilot hub. I have never seen the early B&M plate you speak of. I wonder if that's what he's got?
Click to expand...

No, I may be the one confused, I missed post 3.

I have an early B&M plate. I believe it's simply a change in BM manufacturing---easier to take a bite out of a round blank than to weld on a weight, LOL
 
is it correct that if the converter he is using has the weights like the red one pictured he needs to use a factory flex plate or the round one pictured?
 
bOb shingler said:
is it correct that if the converter he is using has the weights like the red one pictured he needs to use a factory flex plate or the round one pictured?
Click to expand...

The round one I was referring to has weights welded to it. The photo may be "representative" I was trying to point out the differences in BM manufacturing

A weighted converter would require either a factory "star" flex, or a neutral balance aftermarket flex which may be circular but NOT weighted.
 
The full round plate, he bought is a b&m plate but he checked and accidently bougt the internal balance plate, not the one with the notch missing. He is using the convertor that came with the car along with a 727 and not a 904.
His converter has no weights and the plate he bought which is the full circle doesnt either. He will be returning the plate and getting the correct flexplate as he doesnt want to get the other style converter.

67dart273, do you mean you bought it along time ago when you say earlier? And the one with the notch is newer?

I believe my buddy is on fabo now but i dont know his user name.
 
Damn,Fishy what would we do with out members like you.... I was about to make this big mistake my self....904+318 converter behind fresh 360 not gonna be pretty..

Thanks ...................................PETE.............................
 
7duce swinger said:
67dart273, do you mean you bought it along time ago when you say earlier? And the one with the notch is newer?.
Click to expand...

Yes, exactly. I have one "somewhere." As far as I know, it was simply a manufacturing change at B&M

To reiterate, make sure you get the right one. Magnums, LA, etc are balanced with different weights.
 
Its not my build its a friend of mines, i was about 95 percent sure about the balancing and weighting between the la's, so i just posted it and fishy68 confirmed it for me.
.And yea hes gonna be getting the proper flexplate to work with his converter...

Thanks guys
..7duce
 
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