Motor Questions

[chevjayfsd]

72 Chevy SWB
355 SBC
Vortec Heads
Comp Cams XE262H Cam (.462/.469 lift)
Performer RPM Intake
TH350
Puny Q-Jet
12 Bolt Rear with 3.08's, non posi


Alright, basically we are going to be bracket racing the 72 a little and we want to be able to run pretty consistent times... We like the cam and heads, but what can we add to tweak the motor just a bit? We are going to be putting a 4.11 posi in to replace the 3.08's, so that should help out a bit... Also would a little stall help out? What exactly is stall? And what does a converter do? How does it feel and how does it make the truck drive differently?

Does anyone have a setup close to this? What does it run in the 1/8th? 1/4?

Thanks everyone

[67_C-30]

Stall is the mount free-rev (flash) before the converter engages and the truck actually moves. For instance a 3500 stall (in theory) should flash to 3500 at WOT before it moves. It would help 60 ft and overall ET tremendously. For that cam a 2400 - 2500 would be ideal with no bigger than a 2800. As far as the way it feels, it kinda feel like a slipping clutch until engages. Just because it is a 2500 rpm or 3000 rpm convertor doesn't mean it won't pull at lower rpm when driving normal. The flash point is applicable only at WOT and it usually takes stickey tires to see the full flash point.

A Holley double pumper carb would be better for bracket racing than any vacuum secondary carb as well. Don't screw around with a Demon or an Edelbrock if you want all out performance, go ahead and get the old un-glamourous but rock-solid reliable Holley double pumper. (That is years of bracket racing myself and experience with all the above carbs talking.)

With 4.10's and a little stall mid to low 13's should be acheivable with mid to low 8's in the 1/8.

[67_C-30]

Here's a few examples of stall. Notice how the engines rev before they take off. Its kinda like dumping a clutch in a stick shift car.

YouTube - Testing the new stall converter

YouTube - 4k Stall first samples

[chevjayfsd]

Awesome bro,,,

Thanks for your help... Couple more Q's..

What kind of CFM on a Double Pumper? I see a ton of them on ebay... I do not drive the truck every day, as far as the street go's.. I probably drive it 15-30 miles a month on the street... Would a Double pumper be suitable for even that moddest of street driving?

thanks a ton!

[67_C-30]

Oh, yeah. If driven normally a double pumper isn't too much worse than a regular Holley, although its hard not to open the secondarys on a truck like that. A 650 would ideal, and would still be appropriate if you decided later to go with a bigger cam or intake. That set-up would probably be good for 350 - 375 HP at the flywheel with 9.0 - 9.5 : 1 CR.

[chevjayfsd]

Is this the carb you reccomended? The Holley Double Pumper 650 CFM 4777c?

http://cgi.ebay.com/ebaymotors/HOLLE...mZ270255476071

[hotrod 80]

Yes , 4777 Holley or 650 Speed Demon . The parts between these 2 swap back and forth . Basically the same carb , but the demon has better features IMO . With the 4.11's going in it and the power level your at and the limited street driving you do , i would go at least 2500 on the converter . Add a posi unit when you do the gear , as an open rear axle will not be consistant . This may be apples and oranges , but i had a1980 Camaro @ 3700 lbs ,355 cid , th350 , 2200-2400 stall ,vortecs , performer rpm , edelbroke 750 , 268H cam , headers 3.73 posi , on drag radials it would run 13.20's . Car even had a/c .