Change from 8" to 10" converter
 

New pump gas combo it making more power than the old race gas combo. Trying to set up new combo to run a 10.00 class. Went out Saturday with the small 850, tailpipes and 260lbs of ballast in the car. Ran 9.87/135 with a 1.33 60'. It was 90+ degrees with a da of 2000.
Running an 8" ATI MRT converter that stalls at 5000. I have an ATI 10" laying around from the street car that stalled at 3500 with 500hp engine.
What do you think the 10" converter will do vs the 8". I know I will loose some 60'.
Thinking it might stall higher with more hp and be a little tighter down track. By the way I am launching with a trans break at 3800 now. Shifting at 6200 and going thru the traps at 6700.

Mike convertors for me are still black magic. The 8" loose A1 I had in my first sold roller 455 would flash to 5000 60 ft low 1.5s . Same convertor behind the 500" 690 HP motor only flashed to 4500 and felt tighter! 2 other 8" in it have all done the same even though were suppsoed to be loose .
The 455 I put in the TA was a little milder HFT and was a 10" Contential convertor. Would only 60 in the 1.6-1.7 range but ran the same et and MPH . Did not slip pulling on the car trailer like the 8" did.

From previous experience about three tenths but take that with a grain of salt. It will most likely change your reaction time noticeably.

The torque is what will change the 'stall' of the converter.
I'd go with Paul's opinion.
I'd say the 10" will stall higher than 3500 if you have more torque now.


MPH may increase with a loss of some ET?


:confused:

Without knowing the full specs on both converters, there's a lot of variables. There's a lot more than just stall speed. The 8" will tend to rev quicker (less rotational mass) with all things being equal. 10" should run cooler, compared to your old combo should probably stall around 3900. It's worth a try, may pick up some MPH, as mentioned above you will have to adjust your driving to the different converter. If your reaction times are much slower, try bumping in a little more before getting up on the brake.

I'm with Paul, you'll be in that 10 class right on the edge but...

It might be easier to just reduce current 8" stall and try
2 Step 3500rpm (easier if you have EFI/Holley etc)
TBrake 3500

And find the sweet spot for a 10.0 in the same combo. Then you can always go back and forth between launch rpms and get your 9.8 back when wanted.

Not a race application, but for conversation...

My previous 4.210 stroke / 462 cid combo with a Performer RPM intake and HP950 carb produced 580.2 HP at 5800 rpm.
Mild ported 313 cfm Edelbrock heads in conjunction with a 254 degree solid roller cam. Headman 2-inch headers.
TH400 / 3.73 gears

Same track in similar conditions with no changes other than the converter. Foot brake application. Race weight about 3700 lbs.
Both shifting at 6000 rpm. Sorry, I don't recall the stall for either converter.

Continental 10-inch: 10.94 at 123.59 / 1.59 60-ft
Hughs 8-inch converter: 10.88 at 124.28 mph / 1.60 60-ft


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You could try some Hy Guard tractor fluid to tighten your current converter and see how the car responds. Changing from TYPE F to the Hy Guard changed my 8" PTC from 5200 RPM to 4700 RPM.

Just curious, did your car go faster with the converter being tighter?

I hate to hijack a tread but has anyone heard of Michigan Transmission is Saginaw. I ordered a 10" 3000 stall with anti-balloon plates back on '01 and have never run the car. Life got in the way. IIRC it was an ad from the back pages of a mag. Any thoughts would be great, BTW it was $218.45 with no core back in '01.

It was .09 slower, with .05 of it being in the 60ft. I used the standard Hy Gard with a qt of Type F for color. The car did pick up 1 MPH and firmed the shift.
I was seeing if my converter was too loose for the combo. Apparently Lane at PTC got it right first shot.

I am just going to leave the 8" converter in. Love the way it launches now and have the reaction times where I want them.

I will be going back to a restrictor plate under the carb. I was using them under the 1050 and worked but now have an 850 so need new plates.

Would love to soften the middle of the run but don't want to use a timing computer, want to keep it old school and simple.

Can always short shift it if you aren't too far off the index. Problem with restrictor plates is if the DA changes drastically in the middle of the event, you could run off the number too far and won't be able to make it up. I've added weight to run a number, depending on placement it can help traction/consistency as well. Lots of ways to cut back power, easiest is a throttle stop. Log your data and you can predict your package based on track condition and DA within a couple hundredths.