Hello all!

I have a TH350 that I'm looking to pair with a 2200-2600 stall converter. As I look through the options I've noticed there are two diameters for those that are for the TH350: 10" and 12". How do I know which I need? Also, do all the converters that are for this transmission have the same spline count? If not, how do I determine which I need?

Thanks!

Bryon

 

A 12" is what your looking for if its rated 2200-2600 stall. The 10" are typically higher stalls starting as low as 2800 and up to 4000 plus normally.

Any TH350 converter will have the right splines as long as it is not the later Chevy 350-C lock up type. Also the TH400 is the same spline but avoid a TH400 only converter as it will have a larger bolt pattern that your flex plate may not accommodate although many flex plates are made with dual patterns of Th350/TH400 and also original TH400 converters are 13" diameter too big to run on a TH350. The preferred "BOP" 12" 2200-2600 converter like A Hughes GM25 (2500) BOP have welded on threaded lug bosses like OEM and use bolts. A lot of the Chevy style converters have brackets that requre nuts and bolts. You can find these 12" 2200+ plus converters as low as under $150 on Ebay under numerous brands.

 

Also, understand what you really need and what you are actually buying. There is no "exact" stall speed on a converter. The stall speed you get will be a function of engine torque as well as converter design. The same converter will have a higher stall behind a 455 than it will behind a 350, for example.

 

Yep that 12" will go 2200 on a 350 but a 455 easily 2600 in same car and gear. gear ratio and weight a big factor too. Run a tall gear and it will stall more if matches to say a 3.08 instead of a 3.42 as well. Hell my 12" GM25 in the heavy wagon with 3.08 and 455 will flash stall up to 2900 in my driveway just hopping it.

 

Thanks you guys. I noticed every "GM" torque converter says "chevy" - does that matter? Also, I noticed what seemed to be a good deal for a GM25 advertised at Summit called "Hughes Performance Street Master Torque Converters GM25" that should be in my range. Is this the converter you have,
GEARMAN69?

 

summit has a horrible search engine. This is the one you want, not Chevy. http://http://m.summitracing.com/parts/hup-gm25-bpo.

I have the same converter except mine is Heavy duty, very happy with it.

 

You know you can have your stock one re flashed to about 2500 right ?? We have a local shop here that will re build and re flash stock units for a very fair price. The best part is if there is any issues you dont gotta deal with phone calls and all that stuff. i would imagine that you could find a converter shop in your area. You just gotta talk to the local racers as they would know.

They do ship I have had this shop do converter work for me and i have been very happy.

http://www.torqueconvertertechnology.com/

 

Yes Sir , I have the BOP version of the Hughes GM25 except as 70Cutty mentioned it is the HD version of the BOP one. So far I have managed a 8.08-8.14 range out of it in my wagon in the 1/8th with 3.08 gear. Not as quick as the 10" converter was but not bad . May try again this Friday with some adjustments.

 

Hey GEARMAN69 and 70Cutty, what's the difference between the BPO GM25 above and the HD you all have? Does Summit have it somewhere in its twisted tunnels of parts that I just can't seem to find?

 

Look on the Hughes Performance web site (the manufacturer) instead of Summit (a retail outlet).

 

Here is the HD version

http://www.summitracing.com/parts/HUP-GM25BPOHD

 

I've been running this one with a 350cid/TH350 (3.73ratio) for about 2 years and am very happy with it