Hey guys, looking for a SFI flexplate for a SBM 408 with internal balance for a 904, B&M says they do not have one, only external, what are you guys using?
Thanks in advance!

Last one I got was from Mopar Performance, but it was a while ago.

Isn't flexplaes the same for 727 and 904 ? I used the same neutral balance flexplaes when I switched from 727 to 904z

Correct me if I am wrong, but in my experience the stock V-8 flexplates (6 bolt) are all the same whether they are for a 904 or 727, BB or SB, Internal or External Balance and only differ in the diameter of the converter they are designed for. The converter is weighted and so is the harmonic balancer on the external balance engines and the special plates are made to be used with a neutral balance converter. Before the B&M and others SFI plates, we all used the SB stock flexplate with small converters. So why can't you use one of them? Of course, I never raced with a 904, so I don't know.

Same thing here... try Mancini's
EDIT
Your looking for P/N P4529751 for a 6 bolt crank
P4529752 is for a 8 bolt crank... both for race conv
(has larger bolt holes for the 7/16" bolts

This is my first 904,(actually a A500), always used the B&M 10230 on my 340 and 440's with 727's. The outside diameter is wider for the 727, but I didn't know (and neither did B&m) if that plate would fit in the bellhousing. I know the convertor bolt circle is smaller on the 904.

Thanks guys, and Mike, always so helpful and a wealth of knowledge, hope you make DW, I registered for the west coast version, Hot Rod Drag Weekend, is having out here at the end of October, I don't believe its sold out by the way.

not on my race converters...... my 904 N balance and 727 N balance flex plates are the same size. B&M also makes a flex plate for cast cranks that has a cresent cut out of it. Just gave one to a member here to try as he had a solid round flex plate on his cast crank 360. Said a lot of vibe gone now using it.

Don't know if they still have them but I have been using a Mopar Performance SFI flex plate for years now with no issues, bought mine thru Jegs, but I am sure Summit and Mancini will fix you up, they had a 8 bolt version also if that is needed.

I've used the TCI flex plate with no problems.

B&M number is 10230.

Stock flexplates are either big TC pattern or small, but interchange on 6 bolt cranks. They match to the TC bolt pattern, not the trans type.

Thanks everybody, I thought the B&M 10230 would work, but couldn't check clearance to the bellhousing or starter since its at ProTrans getting built.

I used the B&M flex plate for a 727 in my cast crank 340 and 904, it cleared as long as I used a newer starter off a magnum small block, would not work with old style starter.

I plan to use a Dakota starter, so that works

my trans has been over that way for over a month now.... hope it isn't too much longer.

I know Dave and Darren are busy, I figure a couple more weeks for mine, I still need to get a convertor, probably like 3500 stall speed range, the motor is done on the stand, RHS headed 408.

I used the B&M flex plate with a 408\A500 combo worked fine, used a mini starter. I had to clearance the starter a little by the gear a little to clear the outter edge of the flex plate.

Have you bought the converter yet? If not I would suggest you don't buy a off the shelf converter for that combo.

I would also ask Dave if you could barrow a empty case + OD to test fit in the car.

B&M 10239
http://www.summitracing.com/parts/bmm-10239/overview/

Joe, I think you got your #'s mixed up:

Summit/B&M 10230

It seems to me that B&M use to have a small diameter neutral flexplate for a 6 bolt crank. It didn't have the outer-most bolt holes. Looks like the 8-bolt neutral flexplate, but for a 6 bolt crank application. Or like Joe's pic, just neutral balanced. The smaller diameter makes it easier to put washers between it and the converter, when/if needed and has less weight.

Of course, the solid Mopar style flexplates can be used for the inner bolt pattern converters. But the B&M style are stronger.

Joe's pict is the flex plate for a cast crank..... that's the one I had in my 360, until we found a crack and went forged which required the solid "N balance" plate.

http://www.summitracing.com/parts/bmm-10239/overview/


corrected 360-904 cast crank

Yeah, the 10239 is for a external balance, B&M used to make a 904/internal balance, but discontinued it.
A buddy has done this swap in his daughters Demon, showed where I have to cut out the crossmemeber, and he made a template to build a new one, so I will borrow that in the next few weeks to prepare, got the engine bay primered yesterday, hope to paint that, so I can install the motor/trans.
I haven't decided who to order the convertor thru yet.