So , I have my "B" motor block heading to shop soon for clean, check , bore +.030 etc . Crank and rods already mag'd and turned .010 and will be going to get balanced etc . I am seriously considering selling my 4 speed stuff and going with auto for the "B" motor so I'll be needing a flex plate . Probably th350 or th400 . Standard good quality new flex ? SFI flex ? Looking for suggestions . Thanks for any info . ---------------------------------- 76 350 - block , crank , rods , 70 cast heads ( TA SS big valves , some port work , good TA dbl springs etc ) , diamond piston kit , TA 1.6 roller rockers . Have a good used crower solid cam , may use that ?
Stock replacement from TA would be fine unless your going to wing it to 7 grand or more. I have a stock TA flexplate, I will wing mine to 7000 rpm in first, no issues, but I should have an SFI Plate on it, ‘course there’s a lot of things I should do.
I bought the SFI flexplate I had 2 stock ones crack on me in the past the SFI been on there 28 yrs. I would put in the T350 and not the 400 the 350 is lighter and if you really want something neat get a 2004r trans and have over drive. I have had that in there since 2005 blasted it with nitrous a bunch of times and still going strong.
The TA 350 SFI plate is pretty pricey, http://taperformance.com/proddetail.asp?prod=TA_2032 Compared to the standard flex plate, http://taperformance.com/proddetail.asp?prod=TA_2031 You can get one even cheaper at Rockauto, https://www.rockauto.com/en/catalog...1379707,transmission-automatic,flexplate,8608
Send your pistons with block to the guy doing the boring. He should mic pistons and depending on material, may bore .029, .030 or .031 depending on clearance needed for that piston composition.
Here's an SFI INTERNAL flexplate that should work... if you're going internal balance. https://www.ebay.com/itm/2831264929...EcNVg3TRSm&var=&widget_ver=artemis&media=COPY
ok thanks for all the info . i have a couple nice looking used plates but i'd rather not risk it . i think oem is external balance - correct ? i see TA lists both in SFi versions but not the oem version ? also have a nice used ATi balancer and a new oem balancer , need to figure which way i'm going there . i like the ATi but i think there is a spacing thing to figure out . that is quite alot taller than the oem . and i am kinda leaning towards a TH350 , have a take-out core . and i like the smaller-lighter aspect . i should check my trans length for all three , not that getting a new length driveshaft is a big deal . .
Compare trans here (Not gonna say it...) https://help.summitracing.com/app/answers/detail/a_id/2501/~/gm-3-speed-transmission-dimensions
Any reason in particular you're going from manual to auto? I'd like to to go the other way! Let me know if you really end up selling your 4 speed setup, I'd be interested!
my original plan was for a TH400 , but , i ran into a nice muncie , lakewood , etc bunch of parts and the car was a three on the tree originally so clutch stuff was there . and i have had a couple 4 speed cars - liked them . and it goes ok but i just miss that simple auto setup and the "40 in first" snap into second gear . had a 70 skylark i put a shift kit in - went real nice . After army had a 65 Impala 396 , kit in that , also nice . and a 65 coronet with a mod'd 69 340 and fairbanks reverse pattern manual shift 727 - loved it . ------------------------------ I'll be driving car a little until probably mid October ? Remind me after that . Still head-scratchin' . edit : so looks like TH350 is 27 spline output , M-21 and TH400 are 32 spline . the 400 is about an inch longer which might work ok because my drive shaft needs a little length - ok but i'd like to see it into the trans another inch maybe . am i gonna run into a "room" problem in the 65 if i use a TH400 ? less trans mod's needed .
