1957 283/270hp dual quads drag testing on a 350
 

I'm drag testing an original '57 dual quad set up with the WCFB carbs.There seems to be a problem with how to deal with the secondary air valves. These are those seconday air-flappers with a counter weight outside the carb body. How did the class racers in the old days make these things run hard for the complete quarter mile? In testing the car launches normal (3700lb '57chev, 355cid, T400) with1.8 sec 60ft then about 100ft out those pesky air valves can't figure out what they are supposed to be doing. Once in high gear it runs great(high 12.8's at 105mph). Perhaps some old timer will read this and offer some tips. Thanks,Tom, Dallas/FtWorth

Re: 1957 283/270hp dual quads drag testing on a 350
 

I ran the same setup on a 265" in the '60s and early '70s. Some guys made a wire hook to hold them wide open. I tried that, but good ol' Red Anderson made me take mine off. The car ran the same both ways. If you think that is the problem, tie the weights up to see if it actually is. I saw guys drill holes in the thick (heavy) weights to lighten them, they came with two different weights. Mine all had the thin weights. I would be suprised if that is your problem.

Good luck, Ed

Re: 1957 283/270hp dual quads drag testing on a 350
 

I'll try the wire open suggestion. The real trick is getting the rear booster venturies flowing fuel without leaning out and stumbling more than before with the weights swinging loosly based on the air flow signal. The throttle linkage is set to open both carbs together. What are the other possible explainations for this mid range stumbling? Thanks for the help.

Re: 1957 283/270hp dual quads drag testing on a 350
 

To much fuel presure

Re: 1957 283/270hp dual quads drag testing on a 350
 

Mike Braswell runs this setup on his 57' Chevy Super Stocker. He reads this forum he may chim in.

Re: 1957 283/270hp dual quads drag testing on a 350
 

Do you run wedge plates between the carbs & the spacer/manifold? Because of the small bowls in the WCFB they may run out of gas for a split second then perk up when it gets fuel again. The angle plate helps with this.

Re: 1957 283/270hp dual quads drag testing on a 350
 

This setup is just like 1957 with 6 inch paper air cleaners.

More background, about 4 years back I called to order a set of Stahl fender exit headers. Fortunately I was able ask Jere Stahl about this dual quad setup as he had championship experience with his 56 Chevy wagon. He indicated the carbs would see a stronger vacuum signal with 350 cid and consequently higher velocity in the venturii meaning if anything it would not run lean with the needle and jet set for the mechanical camshaft specified back in '57. Well...since this setup was really a high performance option for passenger cars in 1957 the power valve booster piston spring is really-really weak in compression, meaning the weak vacuum signal of the 283 with the solid lifter cam would pull the needles down into the jets to allow low power economy and motor idle stability. So...I'm wondering if at the top of 1st gear of the T-400 the vacuum signal is strong enough to pull the needles into the economy position. Then as the motor loads and really starts making more power the vacuum signal degrades and the power piston is pushed up and giving the jets more fuel. I meant to test the k factor of those springs before I rebuilt the carbs last Spring but forgot. The other set of needles and jets I have are for the hydraulic performance camshaft from 1957 and its springs are stiffer. So I've got much more test and tuning. There are several next steps. First is to install a vacuum gauge near the tachometer.

Re: 1957 283/270hp dual quads drag testing on a 350
 

while testing, another option is to completely remove the metering rods and change jets to allow the correct mixture.

This is common with Q-Jet racers. [it is called "no rod jetting"] You remove the rods, remove the power piston spring, then reinstall the power piston in it's original location.

Danny Ashley has a formula that will calculate the need jet size. From memory, I "think" the primary jets will need to be about 7 - 8 numbers smaller. Another source of info is Oliver Race Carbs in Arkansas. Both of those builders have extensive experience with all the Rochester and Carter combinations.

Re: 1957 283/270hp dual quads drag testing on a 350
 

tom,
call me at 817-371-8874. i'm not sure i can help but i will try.
thanks,
mike braswell ssm/a

Re: 1957 283/270hp dual quads drag testing on a 350
 

Tom may be onto something. I never used those on a larger engine. After we were forced to go to SS (when they killed off Stock) the bigger cam caused low enough vacuum that at high elevations (even at Amarrillo) they would not lean out on the return road, and at idle. I removed the spring and set the lever under the metering rod "tree" to raies them all the way at WOT, no spring needed. It drove so well that way I never put the springs back in. Might try that to verify you not sucking the pistons and rods back down. We also had to wedge the carbs foward after going to SS (no more 7" tires) to keep the rear jets covered up on the launch. 4GCs like wedges too.

Re: 1957 283/270hp dual quads drag testing on a 350
 

Thirty-five years ago,I had a red .62 Impala hardtop with a 348/250 horse W motor with a 4 speed and 3.70 gears. It also had a WCFB, and I remember that doing performance driving(was there any other kind?)if you cornered hard, the carb would do a big lean-out on one side only.The engine felt like half of it ran out of gas,because it did. I never had the carburetor apart, it always seemed to run fine otherwise.Later, an AFB went on to replace it, more power,less gas mileage, but the WCFB was around for a while in the garage. I couldn't have imagined road racing a Corvette with it, but I guess that's just what some teams did. A few years later, I came across a 65 Impala convertible, 327/250 horse with a 3 speed on the column(remember those?) and it too had a WCFB. Seemed that the stick cars had the WCFB and the Powerglide cars had the 4 jet. If someone wants to see something amazing, Angelo De Carlo's Super Stock 63 Vette, 327/250 has a WCFB. Car got into the 9's at Indy. There's still got to be people who can make this work. Good luck,it's an interesting induction system.

Re: 1957 283/270hp dual quads drag testing on a 350
 

This is a testing update.
Tested the setup Sunday afternoon (6Sep09, 14:00-16:00) at the new Dallas Raceway on the 1/4 mile. Air temps were warm 94-97F or better described as hot from my perspective. The front power pistons with their weak springs were tied open on both carbs (the up position). Then the secondary air valves were tied open. This netted 2 runs in the 12.6 sec range at 106 mph (3700 lb). The engine really ran rough in the pits but gave .3-.4 second improvemnt in the quarter mile.
The bad news is the slight hesitation is still present till high gear. I'm begining to suspect the secondary jets are too small. The jet area vs. the venturi diameter comparison from the front to rear carb throats is vastly different. The rear venturies seem to have a 36:1 lessor and different ratio of jet area to venturi area compared to the front venturies. What I'm trying to say is the bigger secondary venturies don't compare in jet area to the primary venturies. Looks like I need to change the rear jets to a larger size to kill this hesitation. Comments?

Re: 1957 283/270hp dual quads drag testing on a 350
 

Do you have the angle plates under both carbs as well. As you said it sure sounds like it is running out of gas in the secondaries. Looking back in my records with my setup(single WCFB) I ran a .095 in the primary a .059 in the secondary & 75-1161 metering rods.This is at about 3400 feet elevation.
I suggest obtaining a 10-109 Carter strip kit putting in real "rich" secondaries like about .065 & see what it does.

Allan

Re: 1957 283/270hp dual quads drag testing on a 350
 

Allan,
There are no angle plates.

I suppose I could cut some wedges out of Oak wood for a test. But then I'd have to think about the angle so as not cause the floats to introduce a different problem.

But first I like to rejet the secondaries. Thanks for the numbers on the needles and jets.

With all the different things done in testing so far and the same-old dull hesitation regardless, I'm thinking about pulling both carbs down on the bench and blowing the passages with compressed air again. I'll try to get some oversized secondary jets.

Unfortunately for the next 2 weekends we are having the Texas Muscle Car Club Challenge series races here so I'll just have to see if I can just get it consistant until getting back to the serious testing.

Thanks to all,

Re: 1957 283/270hp dual quads drag testing on a 350
 

Well, I'm learning, Allan and others are right.
These carbs need the angle or wedge plates under hard acceleration. What convinced me was the bowl and float arrangement of the 50+ year old WCFB's after I re-looked at the bowl/float arrangement after re-lifting the carb top. I guess you have to see it to believe/understand it. That front bowl is going to shut down the fuel flow under hard accelleration then when things slow down during the acceleration run (high gear in my case) the front float then starts accepting fuel then all returns to normal and she runs like he%^. I kept wanting to enrichen the rear jets but at this stage wedge plates need to be installed before anything else.

I really want to thank the responders helping me on this old school carb science project. Thanks guys! I'll report an update upon further progress.

Re: 1957 283/270hp dual quads drag testing on a 350
 

Moroso sells the wedge plate under part # 65030.

I never noticed it running out of gas before I made the change but after I did the car picked up just over a tenth. Quite significant in my case.

Allan

Re: 1957 283/270hp dual quads drag testing on a 350
 

Tom,

Check your fuel pressure and the volume of the pump. We run this style carb like Allan. I our experience these carbs require more volume (in racing conditions) than you think. I did not notice, do you have bog, or flat spot when you take off?

Robert

Re: 1957 283/270hp dual quads drag testing on a 350
 

Robert,
Yes the hesitation and/or bog are very evident early in the launch. Then it all clears when the acceleration decreases and high gear is reached. I'll give an update after performing the changes the forum has suggested.
I don't really think this problem could have been solved without the help from all the CLASSRACER responders. Thanks.
Tom
And oh yes,
Allan,
I have ordered the wedge plates thanks to your information and tonight I milled some wood to a 5 degree angle to install for Sunday's race to get me going. Hope to get them on tomorrow, Saturday. The metal wedges will be to late for Sunday.
thanks to all,
Tom

Re: 1957 283/270hp dual quads drag testing on a 350
 

Tom

Good luck with the testing & keep us updated.

Allan

Re: 1957 283/270hp dual quads drag testing on a 350
 

Update as of Sunday PM; 20 Sep 09.
Installed wedges under the carbs made of wood I milled (Moroso wedges were back ordered). Was rained out last weekend.
Today the motor ran quite poorly very much worse than before the wedges. The car launches okay then really starts running bad. This time observers told me it was puffing black smoke during the early part of the accelleration. To me, at the wheel, it almost started to miss but simply stumbled. After the acceleration slows it starts running okay at the top end about the time it is shifted into high gear.
I'm thinking the carb wedges screwed up the float/fuel level geomtery in both carbs such that something is flooding under the acceleration phase of the run. I may need to reset the floats for the wedges. Any ideas?
Oh yes I blew the rear end gears today. At least 2 weeks maybe 3 to get back testing again.

Re: 1957 283/270hp dual quads drag testing on a 350
 

Tom,

how much wedge did you have? some manifolds have about 3 degrees made in them, it has been my experience I had to drop the float level if the angle got to steep. What intake manifold do you use ? I
also had different results with different manifolds,

Myron

Re: 1957 283/270hp dual quads drag testing on a 350
 

The tested wooden wedges are 4 degrees. The manifold is a factory stock original 1957 283CID/270HP. I don't yet know the gasket surface angle of the stock manifold.
Moroso 5 degree wedges are back ordered.

So....how much float level drop is workable?

Re: 1957 283/270hp dual quads drag testing on a 350
 

TOM,
that manifold has no angle, and those open moroso open wedges will not work right on that manifold, I have the float settings in my notes, I will look those up, feel free to call 765-342-9746

Myron

Re: 1957 283/270hp dual quads drag testing on a 350
 

Myron.
Not having much success contacting you by phone. Any chance you could send me a personal message with the requested help.

Also you are correct; the Moroso angle plates overhang the old manifold base giving a giant leak point. They would need to be modified to work.
Thanks

As a matter of information on the subject. A local GT class racer, Tony Cowell, advised me to reverse the front to rear bowl float settings as a starting point for my problem's solution and consider raising the fuel pressure higher than the current 4 psig I'm running.

Re: 1957 283/270hp dual quads drag testing on a 350
 

Tom ,
he is right that is not enough fuel pressure, if you pm me your phone number I will call you,
or call and leave me your number, I am on 4-12 shift right now , that might be why I missed your call.

thank you , Myron

Re: 1957 283/270hp dual quads drag testing on a 350
 

I'd like to offer a belated update. Several findings as of March 2010. The piston ring seal went away on one cylinder (7) last Fall all the others went down too, maybe due to unknownly running with antifreeze in the oil one weekend. Add to that the valve spring pressure was insufficient for the roller cam I am using. After the engine is refreshed with roller ready heads and gapless total seal rings with a medium grit Sunnen hone finish I'll offer an actual performance update.