When I installed my new engine I used a Victor Jr manifold. It doesn't have a vaccum port on it for the modulator.

Do I need a vaccum modulator on a race only TH350? The detent cable is already disconnected since I have no use for down shifts but can I still manually upshift without the modulator?

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Follow my racing progress on Stephen's racing page
and check out the race car

87 IROC-Z Pro ET Bracket Race Car
383 stroker (carbed) with double hump cast iron heads and pump gas
454 Big Block almost ready for the 2001 racing season

Best results before the 383 blew up
Best ET on a time slip: 11.857 altitude corrected to 11.163
Best MPH on a time slip: 117.87 altitude corrected to 126.10
Altitude corrected rear wheel HP based on power to weight ratio: 476.5
Best 60 foot: 1.662

Racing at 3500 feet elevation but most race days it's over 5000 feet density altitude!
Member of the Calgary Drag Racing Association

87 IROC bracket car, 91 454SS daily driver, 95 Homebuilt Harley

 

In My experiance Stephen, No.

On a friends car, We accidentally knocked the Modulator Loose, and it would not Shift Into third, Manually Or otherwise. Th350 as well.


I coudl very well Be wrong Tho.

Any Reason You cant Hook it to a Source Of Manifold vaccum on the Carb ?



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60 Ranchero - Project ( Money Hole )
85 Sport Coupe LG4 - Daily Driver

Just another Hot Rod kid, or thats what they all tell me.
Livin' the Stereotype

 

If it won't upshift at all, yes I can port it onto the carb if I have to.

 

My experience agrees with Bort's. I thought I'd firm up the shifts on my '73 307 Nova and disconnected the vacuum line: after less than a mile, I pulled over and hooked it back up - I was afraid to find out what RPM's it would take to get it to shift...

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R. 2.93 limited slip. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 w/LB9 block, ZZ3 cam and intake, WP 305 heads ported & polished, Hooker headers & y-pipe, hi-flow cat).
57 Bel Air, my 1st car. 0.030 over 396, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & shift kit, 3.08 10-bolt, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.

 

A MANUAL valve-body TH350 will shift into any gear whenever you move the shifter lever... And leave the line in 3rd gear if your are not careful. If you have an AUTOMATIC valve body, you need the vacuum...

 

You should always use the modulator if possible. If you have the Trans-Go full manual kit installed in the valve body, then I would use the modulator. The modulator changes line pressure according to load (vacuum) conditions. If you do not use the modulator then the pump is putting out max. line all the time. This wears out the front pump in no time, especially with some so-called racing fluids (type"F"). You only need max. line pressure when you are on it, not when you are cruising at light throttle.
Some full manual valve bodies will not let you run a modulator, in this case run the best fluid possible such as Amsoil or redline or my Pro-Fluid at a 50% mix with Mobil Dexron 3 (not Mobil One). We have found these oils do well as far as wear is concerned. Hope this helps!!!

 

I'm running Dexron, not type F yet and I don't have a manual valve body or full manual kit installed in it yet. There is a shift kit from TCI when I last rebuilt it. I would like to install a full manual kit since it does the same thing as the full manual valve body and is cheaper and I don't want the reverse pattern shift feature.

The only cruising I do is around the pits and coming back up the return road.

I guess if I have to I can route the line up to the carb port. I haven't checked yet but I don't think I have much manifold vacuum with this new cam. ie. less than 10 inches

I should just rip the tranny out and install a 2 speed

 

You will need the vacuum line hooked up. I ran mine to the bottom port on the carb (you've got to be below the butterflies, ie manifold vacuum).

Are you going to put in a trans brake when you go to a manual valve body?

Miles

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88 427 Camaro
12.18 @ 113mph 1.75 60ft

www.koolmeister.com

 

Transbrake will be way down the road but will probably go in eventually. The torque converter isn't designed for it and I doubt the diff would survive a 3800 rpm transbrake launch.

If I move up to Superpro, a transbrake and delay box is almost necessary however our 5 place winner in Superpro last year is a foot brake racer so it just shows that you don't need the fancy stuff to win.

I know of a bunch of Pro class racers who use transbrakes also. Just time yourself to let go of the 2 step button to release the brake instead of letting an electronic box do it.

There are 3 vacuum ports on a Demon carb. A large one on the back for things like PCV or power brakes. 2 small ones on the right front where they're easy to access. The front one is ported. The rear is manifold. I can just port the modulator onto the rear one unless I get the brake booster removed soon. Then I can just plug it into the back of the baseplate.