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.