318/360 flex plate

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Dartvader440gt

Dartvader440gt

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Hi all,
I'm scrolling around and I noticed the doing a 360 swap will require either the 360 torque converter OR flex plate. So if I am already using a 360 torque converter in a 727 will the stock 318 flex plate be good?

Also, should I replace the stock 360 harmonic balancer with another stock unit or is there a more preferable aftermarket unit?

It's basically a stock 79 360 truck motor with a 4 barrel and headers. Nothing radical.

Thanks
Tim
 
Pretty sure that you will need an externally balanced flex plate. Believe that the 318 is internally balanced.
 
Here's the deal:
LA flexplates are LA flexplates.
From the factory, the engines that were externally balanced had weights attached to the torque convertor to balance the motor. Internally balanced engines did not. No change to the flexplate.
The confusion comes in when you start talking aftermarket flexplates- B&M (and others) make specially weighted flexplates that allow you to run neutrally balanced (also known as internally balanced) torque convertors on externally balanced engines. These are not factory, though.
So, to answer your initial question, if you already have a 360-specific torque convertor (unmodified, with the factory weights still intact) and a factory LA flexplate, you're good to go.
As far as the harmonic balancer goes, if yours is in good shape, and the rubber isolation ring isn't rotted or the outer ring hasn't slipped for some reason, you're good to go.
 
go-fish said:
@Dartvader440gt Stay away from factory replacement. They are flimsy and will break. I had a bone stock 1976 318/727 flex plate break in my D100. After looking up the issue on here and posting about it, many people said they have encountered the same with the same point of failure. Make sure you use blue Loctite 242 and torque the flywheel bolts to spec.

Here is the best , most economical option Mopar Chrysler SB 318 340 360 BB 383 440 Internal Balance Heavy Duty Flexplate | eBay
Click to expand...
Have you used this flexplate in the past? I actually have had a stock one break one of the tabs back in the day.
 
Professor Fate said:
Here's the deal:
LA flexplates are LA flexplates.
From the factory, the engines that were externally balanced had weights attached to the torque convertor to balance the motor. Internally balanced engines did not. No change to the flexplate.
The confusion comes in when you start talking aftermarket flexplates- B&M (and others) make specially weighted flexplates that allow you to run neutrally balanced (also known as internally balanced) torque convertors on externally balanced engines. These are not factory, though.
So, to answer your initial question, if you already have a 360-specific torque convertor (unmodified, with the factory weights still intact) and a factory LA flexplate, you're good to go.
As far as the harmonic balancer goes, if yours is in good shape, and the rubber isolation ring isn't rotted or the outer ring hasn't slipped for some reason, you're good to go.
Click to expand...
The harmonic balancer on the engine now is a little worn. Since I am putting this all together I'd rather just replace it to be safe. Do it while the motor is out of the car. Easier that way.
 
Dartvader440gt said:
Have you used this flexplate in the past? I actually have had a stock one break one of the tabs back in the day.
Click to expand...
Yes, I use it on a hot 318 with an Air Gap and ported Speedmaster heads, 2400 stall converter, and a performance built 727.
The tabs is where they all break. I believe it has to do with vibration making the bolts lose torque then the holes in the flexplate at the tab get stressed and cracks. I like the O-shape flex plate better than an X-shape flex plate.
 
go-fish said:
Yes, I use it on a hot 318 with an Air Gap and ported Speedmaster heads, 2400 stall converter, and a performance built 727.
The tabs is where they all break. I believe it has to do with vibration making the bolts lose torque then the holes in the flexplate at the tab get stressed and cracks. I like the O-shape flex plate better than an X-shape flex plate.
Click to expand...
Great thanks, I'll order it right now.
 
I think going this route attempts a correction in two areas. The Loctite (blue) will help keep the bolts from being affected by vibration and the round style flex plate adds strength where there is weakness in the cross-design OE flex plate.
A win-win in my book. :thumbsup:
 
bear in mind the 360 torque convertor you were using behind the 318 almost certainly had the (360) balance weight removed. if not it would cause nasty vibration when used with a 318. as mentioned if there's no balance weight on the torque convertor there is a flex plate available that achieves the same 360 specific balance you need without a weighted convertor.
 
mygasser said:
bear in mind the 360 torque convertor you were using behind the 318 almost certainly had the (360) balance weight removed. if not it would cause nasty vibration when used with a 318. as mentioned if there's no balance weight on the torque convertor there is a flex plate available that achieves the same 360 specific balance you need without a weighted convertor.
Click to expand...
It's a new 360 torque converter. I'm having a 727 built to replace the original 904.
 
go-fish said:
@Dartvader440gt Stay away from factory replacement. They are flimsy and will break. I had a bone stock 1976 318/727 flex plate break in my D100. After looking up the issue on here and posting about it, many people said they have encountered the same with the same point of failure. Make sure you use blue Loctite 242 and torque the flywheel bolts to spec.

Here is the best , most economical option Mopar Chrysler SB 318 340 360 BB 383 440 Internal Balance Heavy Duty Flexplate | eBay
Click to expand...
I'm almost ready to put the new 360 back in. Do you happen to know the torque specs for the flexplate to crank bolts?
 
55 ft lbs, crank flex plate
270 in lbs converter to flex plate

Note difference between foot and inch lbs.
 
270 = 270/12 = 22.5 ft/lb

Better check bolt size on converter, they have different diameters sometimes, so don't go strictly by a book as reference.
 
The balancer on my 360 looks really good but has a bit of a wobble to it. I was thinking about getting this one.
www.summitracing.com

DODGE Summit Racing SUM-163318 Summit Racing™ OE-Style Harmonic Dampers | Summit Racing

Free Shipping - Summit Racing™ OE-Style Harmonic Dampers with qualifying orders of $109. Shop Harmonic Balancers at Summit Racing.
www.summitracing.com www.summitracing.com
There are also some neutral balance ones that takes weights for different motors including the 360LA.
 
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