5.9 Magnum Flexplate help needed

[Justin Angle]

So I've been running an LA B&M (10236) flexplate behind my 5.9 magnum not knowing any better. The car has always had a high-speed 75+mph vibration. So since they no longer make a B&M flexplate for a 5.9 that I'm aware of, I have a stock 5.9 magnum flexplate from Scram Speed that is going into the car but have a couple of questions.
The with the new flexplate held against the PTC converter, the ring on the outside of the flexplate is holding the flange on the flexplate maybe less than a 1/16" (Included a pic but still hard to see). Anyone hit this? Also, does anyone know how strong these flexplates are? Making sure it would hold up behind 460hp/460tq engine hp car that is frequently bracket raced.
Thanks in advance

 

[MoparLeo]

I would find an SFI rated flex plate. They are out there.

 

[Bobzilla]

The SFI certification on older B&M flex plate will be expired, so there is no point searching one out, other than direct fitment.

Hughes Engines and Mancini Racing are both offering Magnum balanced flex plates the are modified versions of the solid neutral balanced or 360 LA balanced flex plates that are still being produced. But they are expensive. You are basically paying for a flex plate and the modification cost, but they fit and work well.

The stock style Magnum fuel injection flex plates are fine for stock Magnum swaps, but do not run one with that much horsepower and torque. And especially not since it is getting beat on as a race car.

Are you running a 727 transmission or 904 transmission? If you have a 727 and want to start over, you can get one of the solid neutral flex plates that have three bolt patterns and then modify to match an old B&M 10241. I put a picture with measurements in the this thread below, post 98.

Flexplate is not fits the torque converter

 

[Justin Angle]

Thanks for the replies. Called Hughes and Mancini and both said they no longer sell the SFI flexplates for 5.9s due to lack of demand but said told of a place that may have them called A&A transmission. I've been playing some phone tag with them but I'll post up what comes of it.

 

[318willrun]

Thanks for the replies. Called Hughes and Mancini and both said they no longer sell the SFI flexplates for 5.9s due to lack of demand but said told of a place that may have them called A&A transmission. I've been playing some phone tag with them but I'll post up what comes of it.

That's a shocker. I thought there were lots of 5.9 magnums in the bracket circuit.

 

[Bobzilla]

Thanks for the replies. Called Hughes and Mancini and both said they no longer sell the SFI flexplates for 5.9s due to lack of demand but said told of a place that may have them called A&A transmission. I've been playing some phone tag with them but I'll post up what comes of it.

Mancini Racing is their own worst enemy. Every time someone asks about those Magnum flex plates they are told by salesmen that item is no longer available or they try to sell the LA balanced versions. I guess there would "appear" to be lack of demand if they won't sell one.

You still have options. You can make one as I said. You can remove the Magnum weight from the factory style EFI flex plate and weld it to the converter in the exact same placement it would sit with flex plate mounted to the converter. You can have proper Magnum weight welded to your converter by a competent converter shop.

 

[Justin Angle]

Mancini Racing is their own worst enemy. Every time someone asks about those Magnum flex plates they are told by salesmen that item is no longer available or they try to sell the LA balanced versions. I guess there would "appear" to be lack of demand if they won't sell one.

You still have options. You can make one as I said. You can remove the Magnum weight from the factory style EFI flex plate and weld it to the converter in the exact same placement it would sit with flex plate mounted to the converter. You can have proper Magnum weight welded to your converter by a competent converter shop.

If I cant find an SFI 5.9 mag one, which looks to be the case, I most likely will try to go about having a local converter shop weld the weight off the factory flexplate onto the torque converter then going with a neutral balance converter. It looks like there used to be a 5.9 magnum torque converter weight kit you could buy but thats unavailable now to it appears. Thanks for the detailed responses

 

[TT5.9mag]

I noticed blueprint engines is selling LA balanced flexplates that are replacements for the B&M version. I wonder if they’re going to make magnum balanced ones as well. @Johnny Mac what says you?

 

[Bobzilla]

If I cant find an SFI 5.9 mag one, which looks to be the case, I most likely will try to go about having a local converter shop weld the weight off the factory flexplate onto the torque converter then going with a neutral balance converter. It looks like there used to be a 5.9 magnum torque converter weight kit you could buy but thats unavailable now to it appears. Thanks for the detailed responses

PRW neutral flex plate can be easily modified with the measurements in the link from post 3, and it's only 56 dollars from Summit. I think I put the wrong part number in post 3. The B&M 10241 was the smaller diameter 904 flex plate for Magnum. The B&M 10242 was the larger one for 727 transmission flex plate for Magnum. The modification in the link for post 3 won't work on the smaller diameter flex plate because the cutout is a different size.

https://www.summitracing.com/parts/pqx-1831800?rrec=true

 

[Justin Angle]

PRW neutral flex plate can be easily modified with the measurements in the link from post 3, and it's only 56 dollars from Summit. I think I put the wrong part number in post 3. The B&M 10241 was the smaller diameter 904 flex plate for Magnum. The B&M 10242 was the larger one for 727 transmission flex plate for Magnum. The modification in the link for post 3 won't work on the smaller diameter flex plate because the cutout is a different size.

PRW Power 1831800 PRW Gold Series Flexplates | Summit Racing

Ok so just to be clear, your saying the modification can be done on the PRW flexplate in the link for a 904. Also are those measurements in the picture from the other thread taken from the centerline of the bolt hole to the start of the cut measured point to point or around the radius of the flexplate? If that makes sense...

 

[Justin Angle]

Ok just spoke A&A Automotive and Transmission out of Indiana and they still offer one. So I went that route. Appreciate the help

 

[TT5.9mag]

Another thing to consider, as soon as you modify, in any form, an sfi certified part, you invalidate or void the sfi certification.

 

[TT5.9mag]

Ok just spoke A&A Automotive and Transmission out of Indiana and they still offer one. So I went that route. Appreciate the help

Link? What do they offer?

 

[Justin Angle]

Link? What do they offer?

Here's the link. I couldn't find the Magnum flexplate on their website as it seems a little dated, but when I called they did some searching and had it in stock. Not sure how many they keep.

Home - A&A Transmissions

 

[Matts440]

Thanks for the replies. Called Hughes and Mancini and both said they no longer sell the SFI flexplates for 5.9s due to lack of demand but said told of a place that may have them called A&A transmission. I've been playing some phone tag with them but I'll post up what comes of it.

I just bought a new B&M flex for my motor from current SFI tag too. Had to modify the holes since I have a 8 bolt TC. I'll have to see where I bought it from, thought summit but wasn't from there

 

[Johnny Mac]

I noticed blueprint engines is selling LA balanced flexplates that are replacements for the B&M version. I wonder if they’re going to make magnum balanced ones as well. @Johnny Mac what says you?

Since we only sell engines with LA balanced cranks, we only have the LA balanced flexplate. I was going to suggest PRW, but looks like they are already being talked about. WILCAP may still do some custom flexplates if someone wants to do some googling.

 

[Bobzilla]

Another thing to consider, as soon as you modify, in any form, an sfi certified part, you invalidate or void the sfi certification.

Absolutely agree. Just be clear for everyone else, my suggestion to modify a PRW plate is simply because it’s cheaper since we would be voiding the SFZi very.
If keeping the flex plate SFI certified is needed, add weight to the converter and use a neutral SFI plate.
Hopefully the A&A flex plate is correct because that will make easy for everyone.

 

[Woody500]

PRW neutral flex plate can be easily modified with the measurements in the link from post 3, and it's only 56 dollars from Summit. I think I put the wrong part number in post 3. The B&M 10241 was the smaller diameter 904 flex plate for Magnum. The B&M 10242 was the larger one for 727 transmission flex plate for Magnum. The modification in the link for post 3 won't work on the smaller diameter flex plate because the cutout is a different size.

PRW Power 1831800 PRW Gold Series Flexplates | Summit Racing

You can edit your post to change the part number. Click on three dots at lower left for drop down menu, then click edit. Then change post, then click save.

 

[RAVano]

When I ran a PTC converter with my 5.9 magnum I ended up having the flexplate milled down where it was hitting that ring on the converter.