Lost a lot of performance
 

I am slowly taking the streetcar from running 11.70's back to basically stock. I have not changed anything on the engine yet other than the carb. I took the th400 with race converter out and replaced it with a 200r4 OD trans and stock 12" converter. I also changed from a 750Holley DP to a 750 Holley vacuum secondary carb. I did not think it would lose that much performance. Seat of the pants feels like I lost 100hp. Just very surprised.
Guess the $800 race converter was worth every dime I paid for it.

A converter of the needed stall to get a given motor into a cam’s power band has a big time effect.

For every 200 to 300 rpm you gave up in stall speed you probably need to go up 5% more in rear gear ratio to get that 1st gear punch back..

How’s it in gear idling? Is the cam big enough it’s surging?

Lost a lot of performance
 

Eginemasters did a dyno test of 750 Brawlers recently. DP vs vacuum secondary. Can’t remember the exact numbers but there was a noticeable loss with the VS on peak power. I’ll see if I can find it.

ETA, I’m too dumb to link it on Tapatalk. It’s episode 121. Double pumper was up 20 HP over the vacuum secondary at peak on a 500 HP small block Ford of some kind. It’s a pretty good episode.

Murf

The cam that's in the 455 now is 236/244 at .050 on 112ls. Installed straight up. I don't think it has enough bottom end for the 1800 stall. Also have to check the spring on the secondary's in the carb. I still have the 3.73 gear in the back. When it's in 4th with the lock up the rpms are at 1600 at 55mph. In a month I will be pulling the 455 out and installing a 400 with a 68 cam.

Just surprised at the difference the right converter can make. The one that came out was a custom ATI tree master that stalled about 3800. It use to smoke the tires from a roll.

Re-install the good carb. Sell the weak carb for beer money.
Feelin for ya on the TH400 converter removal. I got lucky with the Stock 4L80 Converter.

Does your 200r4 have lockup torque converter capability? If so you can run an aggressive converter and have it lockup under light throttle. Best of both worlds.

I was playing around with a car on a chassis dyno, about 10 years ago, RWHP in the lower 300's. Had a nice VS Holley, a DP, and a nice running Qjet. After adjusting the AFR on each, they were all really close. DP did the best, but only 4 or 5hp more.

On my first 67 Firebird, which had a 326 with too much cam, going from a stock torque converter to a "3000" (which flashed to MAYBE 2800 behind the torqueless 326) knocked nearly 2 full seconds off the e.t. (from high 16's to high 14's).

I am a big fan of having the right converter for the application. The "right one" for my car put it on the rear bumper pretty much.

I switched my low 11 second ‘63 Lemans over to a 200-4r from a TH350 last year. I bought a TSP converter through Cliff Ruggles. Haven’t had it to the track yet but doesn’t feel like I’ve lost any power. It’s a lock-up and with 3:90 gears I’m 2200 rpm at about 75mph. According to Cliff the converter clutches will handle full power lock-up after 1-2 shift. Hoping for some track testing next year.