Long story short, I put a 496" RB in my 69 Road Runner. It was exactly the same combination as I ran with a std. stroke 440. The old combo ran a best of 11.17@ 120.5 mph. With the additional 60 or so cubic inches, and a switch from ported and polished 452 heads to Super Stealth (CNC heads)...I could only run 11.55 @ 117 MPH. I suspected a converter issue as I did switch to a new converter when I installed the stroker motor. When i ordered the converter from a reputable company in PA, I told them that the car is mostly street driven, but does see the track once or twice per year. The original converter (10") had a stall of 3800 RPM. It was loose at low RPM, and loose at the top of 3rd gear. I suspected a problem when I noticed the car running only 117 MPH, but spinning to 7000 RPM in doing so.

I called around to a number of companies looking for the right new converter. Eventually I settled on Frank Lupo's Dynamic 9.5" unit. It cost me $699 delivered to my door. I had it in one week. I installed it last Wednesday night, and ran the car at Cecil Co. yesterday.

What a difference!!! The car ran it's best 60' and ET of all time. It's also much tamer on the street as it is tighter down low and at top end.

Below is a comparison of the best passes on the stroker motor. First with the old converter, and the second is with the Dynamic. Thank you Dynamic. I would suggest Dynamic to anyone with a heavy street strip automatic car!

Old 10"
60' 1.671
330 4.741
1/8 7.352
MPH 93.61
1000' 9.625
ET 11.551
MPH 117.49

Dynamic 9.5"
60' 1.593
330 4.561
1/8 7.072
MPH 98.05
1000 9.238
ET 11.071
MPH 122.89

The best news of all is how nicely this car drives on the street now. It seems to act like a car with a stock converter. It's tight on the street. No high stall at take off, and it seems to lock up much sooner than the old unit. ET gain of almost half a second, and MPH gain of 5.4. Best $700 spend on the car to date!

As you discovered.......with the wrong converter(especially when it's really wrong), it's pretty hard to overcome the loss of performance it brings to the combo.

Depending on the way the car is set up, I feel it's usually the #2 item on the list of importance.

Of course the more data you can provide, the "closer" the builders can come to meeting your needs. Still doesn't stop me from trying different ones Converters are like shoes to your wife.... you can't have too many .

Transmission Specalties missed mine by 60 rpm when I sent mine in to have adjusted this year but knowing your combo, past ET's, and having RacePak info helps a lot. I love how they cut it apart and clean it and call to talk to you the next day. A few hours later it's on the truck headed back to me

...Thanks. Funny how there's so little discussion about this topic. If I can pick up 5 tenths, and 5 mph from a converter swap, how many others are out there that could benefit from an improved converter?? It would take lots of HP, and $$ to gain that kind of improvement by looking towards the engine alone.

...just out of curiosity, what is the number 1 item?

I agree but most casual racers aren't going to go to the work of testing converters. The converters are expensive to buy and they aren't much fun to change, especially at the track. Some high end bracket cars are set up with sliding mounts and stuff like that so the converter can come out a little easier but for most guys you are laying on your back in the heat and dirt getting a bath from hot tranny fluid.

Other thing is that unless guys have a racepak or some other data recorder they don't really know what their converter slip is. Without the data it is harder to justify spending $700 plus a full day under the car changing the converter.

I called around to a number of companies looking for the right new converter. Eventually I settled on Frank Lupo's Dynamic 9.5" unit. It cost me $699 delivered to my door. I had it in one week. I installed it last Wednesday night, and ran the car at Cecil Co. yesterday.

What a difference!!! The car ran it's best 60' and ET of all time. It's also much tamer on the street as it is tighter down low and at top end.

Below is a comparison of the best passes on the stroker motor. First with the old converter, and the second is with the Dynamic. Thank you Dynamic. I would suggest Dynamic to anyone with a heavy street strip automatic car!

Old 10"
60' 1.671
330 4.741
1/8 7.352
MPH 93.61
1000' 9.625
ET 11.551
MPH 117.49

Dynamic 9.5"
60' 1.593
330 4.561
1/8 7.072
MPH 98.05
1000 9.238
ET 11.071
MPH 122.89

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Thats what I run in my car and my sons which is the Luppo Dynamic 9.5 street/strip type converter they build. I have been running the same converter in my 63 since 2006 and the Luppo Dynamic 9.5 converter in my sons Dart has been in it since 2005. Both are still working great and going strong. And as you said Tommy mine drives like a normal converter driving on the street but will flash to about 4200 at the track when I nail it. I like their converter's a ton as they work great in our cars. Ron

The motor obviously....... It's pretty tough to reach a certain ET goal
If you don't have the power to weight ratio to get it done.

However....... If the converter sucks, as in the case of your first one...... Then upgrading the converter gets moved into the number 1 spot........ Cuz extra power never fixes a crappy one.

My concerns would be why you only picked up a tenth in the quarter. You added a stroker engine, Stealth heads and went from 11.17 with your stock stroke iron headed 440 to an 11.07 with your stroker with Stealth heads and you're happy with that? Maybe I'm missing something here but I would have expected quite a bit more from a stroker engine than 1 tenth of a second.

My calculations show .48 ET gain and 5.4 MPH gain

He said his old combo ran 11.17 and the new combo ran 11.07, that comes out to a tenth in my math.

I have one converter that slowed the car slightly.... but 60's 1.34 everywhere. Made the car incredibly predictable and definitely helped us go rounds last year. The other lower stall piece has given me a 1.29 and my best et, but the launch isn't nearly consistent as the first one. Just got my 904 converter Friday so we'll see how that pans out this fall over the 727.

The old stock stroke motor ran a best of 11.17, the new stroker motor with that same converter ran a best of 11.55, the new motor was blowing through the old converter

Godscountry, I agree. You are correct. I did only improve from an 11.17-11.07. I neglected to say, the old combo was 13.2:1 and ran on race gas. The new combo is right at 11:1 and runs on pump gas. Additionally, I have done zero test and tune on the new combo to date. I simply ran it the way it was set up for the old engine. I also neglected to say that the 11.17 (old motor) was run with open headers. The 11.07 is through the pipes. I haven't run the new combo with open headers, but in the past, open headers have gained me more than two tenths with my system. Thanks for the comments.

Tommy D, Thanks for the added info, that explains the difference. I'm sure your new stroker will have your car deep into the 10's when you get finished sorting it out. A low 11 second street car is a rocket and will scare the crap out of most people, especially the person in the front passenger seat. Keep up the good work.

That person is usually my 15 year old son. He's dying to get behind the wheel. He won't be starting with an 11-second car though...just like I didn't. I don't know about being a low 10-second car, but a 10.99 would make me feel justified in spending for the new cubes! I'll wait for fall and the cool, dry air. Tommy

A good tail wind will put you in the high tens. I foresee 10.7's in your future.

Be careful that your progressives friends around you don't try to get after you for child abuse
Neither one of my children wanted to drive any of my drag cars or hot street cars, they both loved riding two and three wheelers though