#1  
Old 01-09-2023, 03:20 PM
Mike S's Avatar
Mike S Mike S is offline
Ultimate Warrior
 
Join Date: Dec 1999
Location: Vineland,N.J.
Posts: 1,513
Default 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.

The Following 2 Users Say Thank You to Mike S For This Useful Post:
  #2  
Old 01-09-2023, 05:03 PM
25stevem's Avatar
25stevem 25stevem is offline
Ultimate Warrior
 
Join Date: Jan 2022
Posts: 1,744
Default

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..

__________________
I do stuff for reasons.
  #3  
Old 01-09-2023, 05:37 PM
grandam1979 grandam1979 is offline
Ultimate Warrior
 
Join Date: Feb 2005
Location: Ohio, Findlay
Posts: 1,428
Default

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

  #4  
Old 01-09-2023, 06:08 PM
Murf Murf is offline
Ultimate Warrior
 
Join Date: Aug 2000
Location: St. Marys Ks. U.S.A.
Posts: 1,486
Default 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


Last edited by Murf; 01-09-2023 at 06:32 PM.
  #5  
Old 01-09-2023, 06:58 PM
Mike S's Avatar
Mike S Mike S is offline
Ultimate Warrior
 
Join Date: Dec 1999
Location: Vineland,N.J.
Posts: 1,513
Default

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.

  #6  
Old 01-09-2023, 07:09 PM
Half-Inch Stud's Avatar
Half-Inch Stud Half-Inch Stud is offline
Ultimate Warrior
 
Join Date: Jul 2000
Location: BlueBell, PA or AL U.S.A.
Posts: 18,457
Default

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.

  #7  
Old 01-09-2023, 09:04 PM
MatthewKlein MatthewKlein is offline
Senior Member
 
Join Date: Aug 2011
Location: NW Illinois - The Great Cornifield Wasteland
Posts: 153
Default

Quote:
Originally Posted by Mike S View Post
I took the th400 with race converter out and replaced it with a 200r4 OD trans and stock 12" 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.

  #8  
Old 01-10-2023, 06:19 PM
Lee's Avatar
Lee Lee is offline
Ultimate Warrior
 
Join Date: Dec 1999
Location: Crosby, TX (East of Houston)/Texas/USA
Posts: 2,054
Default

Quote:
Originally Posted by Murf View Post
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.

Murf
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).

__________________
'73 T/A (clone). Low budget stock headed 8.3:1 455, 222/242 116lsa .443/.435 cam. FAST Sportsman EFI, 315rwhp/385rwtq on 87 octane. 13.12 @103.2, 1.91 60'.

'67 Firebird [sold], ; 11.27 @ 119.61, 7.167 @ 96.07, with UD 280/280 (108LSA/ 109 ICL)solid cam. [1.537, 7.233 @93.61, 11.46 @ 115.4 w/ old UD 288/296 108 hydraulic cam] Feb '05 HPP, home-ported "16" D-ports, dished pistons (pump gas only), 3.42 gears, 275/60 DR's, 750DP, T2, full exhaust

My webpage http://lnlpd.com/home
The Following User Says Thank You to Lee For This Useful Post:
  #9  
Old 01-11-2023, 02:40 PM
Mr Anonymous's Avatar
Mr Anonymous Mr Anonymous is offline
Senior Chief
 
Join Date: Dec 2004
Location: Waynesville, OH
Posts: 394
Default

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.

__________________
Clutch Guys Matter
_______________________________________
53 Studebaker, 400P/th400/9"
64 F-85
72 4-4-2 Mondello's VO Twister II
84 Hurst/Olds #2449
87 Cutlass Salon
54 Olds 88 sedan
The Following User Says Thank You to Mr Anonymous For This Useful Post:
  #10  
Old 01-11-2023, 11:49 PM
Tom63LeMans's Avatar
Tom63LeMans Tom63LeMans is offline
Senior Member
 
Join Date: Feb 2004
Location: Northeast Ohio
Posts: 193
Default

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.

__________________
Tom

1963 Lemans -428 +.030, SD Perf KRE heads, turbo 350, 9" Ford 3:90, 11.01@121

1956 Chieftain gasser, 461 stroked 400, SD Perf ported E-heads, turbo 400, Dana 3:70 10.40@125
The Following User Says Thank You to Tom63LeMans For This Useful Post:
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 01:21 PM.

 

About Us

The PY Online Forums is the largest online gathering of Pontiac enthusiasts anywhere in the world. Founded in 1991, it was also the first online forum for people to gather and talk about their Pontiacs. Since then, it has become the mecca of Pontiac technical data and knowledge that no other place can surpass.

 




Copyright © 2017