[Chevyragtop57]

I have 4 barrels in all of mine. Mike

 

[jmg283]

I would get a good distributor and make sure the secondary side of the carburetor is opening up.
That happened to me with Dad's 55. I pulled a 327 from a 68 Impala that hadn't ran for 5/6 years. I put it along with all new points, plugs, cap, wires, and coil. It idled smooth and had good throttle response, but just didn't set you back in the seat. I finally took it to a guy known for rebuilding Quadrajets and he said it was running on the front half of the carburetor because the secondaries weren't opening at all. It was like a different engine afterward.
Also, set the timing where it runs good, don't worry about numbers.

 

[Machev]

My car is the super quick two barrel car Johns talking about. :sign0020:
Car was restored about 25 years ago, including engine. As far as I know, engine is stock apart from being bored out slightly. Everything else remains original except for the electronic distributor and flex fan. It runs Standard powerglide and diff, and dual exhaust with no mufflers, just hotdogs.
So if any of you big 4 barrel guys are up for a drag, bring you cars down to Melbourne. I'll show you what this little big, big, little two barrel can do.:sign0020:
John you forgot to mention how good my power steering was.:tu

 

[DavidY]

Chevy put dual quads on some of those 283's and at no time were they outperformed by a single 2 barrel engine.
Differences in carbs is probably not the reason yours is outperformed by a 2 barrel version.

They also equipped those engines with higher compression heads and cams that allowed a better air/fuel flow than the 2bbl engines.

 

[johnonetrillion]

[QUOTE John you forgot to mention how good my power steering was.:tu[/QUOTE]

Yes ... well ... that's another story. And pretty hard to replicate original for a RHD.

 

[oldchey57]

2 vs 4

Sounds like somebody would be embarrassed to be beaten by a 2bbl. I don't think this will ever be settled.

Joe

 

[johnonetrillion]

I sent Chuck Smith an email last night and he kindly replied with:

1. A four barrel operates like the first two barrels are like a two barrel carburetor, the second two barrels are like flushing the toilet, it just dumps the fuel in.

2. The timing when using the four barrel carburation should be @12 degrees BTDC with a two barrel you can get buy with a lessor amount advance.

I'm going to look at this piece by piece. Firstly, my distributor is not actually quite right – we can't change the timing at the moment, and is stuck on 4 degrees. (The motor engineer thinks it might be the modulator.) So will look at that and get the timing advanced and see where we stand.

 

[jmg283]

Are you talking about setting the dwell (point gap)? The ignition timing is changed by turning the distributor itself. I can't understand how anything inside the distributor would prevent advancing the timing. Is the vacuum advance hitting the intake manifold so the distributor can't turn counterclockwise?

Also not sure what modulator you speak of? Maybe the vacuum advance?

Chuck Smith has forgotten more about carburetors than I know, but the engine has to suck fuel through the rear jets just like the front 2 bbl. It is just two 2 bbl.'s in one body. The Carter or Rochester 4 bbl has no accelerator pump in the secondaries to dump fuel in like a toilet. A Rochester 4 jet has spring loaded butterfly valves to prevent the secondaries from opening until the engine is running enough rpm to use the extra air/fuel. not sure about the WCFB.

 

[johnonetrillion]

Yes, JG, it's the vacuum advance I was referring to.

Just to clarify, the local mechanic was turning the distributor ok, but it was not changing the timing or the RPM. So I asked the engineer about it, and all he could think of was a faulty vacuum advance. (Plenty of clearance between the vacuum advance and the manifold.)

 

[DraginMain]

My 56 that I owned 10 years ago all original 265 power pak would blow the doors off my 55 265 with 2brl. Both stock and original. I think mileage was better as well with the 4 barrel. Time for a complete tune up.:anim_25:

 

[jmg283]

Yes, JG, it's the vacuum advance I was referring to.

Just to clarify, the local mechanic was turning the distributor ok, but it was not changing the timing or the RPM. So I asked the engineer about it, and all he could think of was a faulty vacuum advance. (Plenty of clearance between the vacuum advance and the manifold.)

I'm going to have to wait on ideas from others because I can't imagine turning the distributor changes nothing.

40 years ago we didn't even use vacuum advance on our "hot rods". (Not saying it was smart) It needs to be unhooked and the line plugged to set the timing with a light, so I don't think that's your problem.

It's sounding more likely to be a timing issue, is there any way you could find another distributor? any chevy v8 distributor up to 74 should work and would eliminate that.

I wish you were not thousands of miles away, this is intriguing to me and I'd love to figure it out with you. It has to be something simple. :confused0024:

 

[johnonetrillion]

Hehe – I'd like to get the engineer, mechanic and car guy in the same workshop to figure it out! Yes, it has to be something simple. I'll get there!

 

[angs1957]

What type of vacum advance do you have on the distributor?

 

[johnonetrillion]

The original type – not the GM replacement type.

 

[CJS57]

Something is wrong with the OP's car! 2 bbl. is less hp than 4bbl. and 2x4 bbl.'s is yet even more. 2 WCFB's is not too much for a healthy stock well tuned 283. There is something wrong with your car! Go back to basics. Compression check, cam flat?, timing, plugs, carb, everything! The difference between 2 bbl and 4 bbl is seat of the pants! Chevrolet did not make a mistake in 1957!

 

[stoveboltgeek]

John, there's nothing wrong with your '57 that I haven't seen on mine. So, why don't you bring the car by my house on Saturday and I'll have a look?

:sign0020:

There are a pile of issues here, and only a few have been covered. Here's some that come to mind:

1. '57 2 bbl and 4 bbl distributors are different. They have different advance curves, both mechanical and vacuum.

2. The "standard Chevy" vacuum advances sold most everywhere are WRONG for the 4 bbl. They don't have nearly enough advance. You should be hitting 12-14 degrees at 16-18 inches of vacuum. Most have about 6-8 degrees.

3. There is a NAPA advance that uses a rubber vacuum line that's pretty close to the original 4 bbl specs. It was used on 1970 Chevelles and Camaros with a 350. Now, I recognize you probably don't have NAPA stores in Australia but my point is - there is one obscure vacuum advance that'll work.

4. Since the total advance = initial setting + vacuum advance + centrifugal advance, if you have the wrong vacuum advance, you have the wrong total advance at idle and low speed.

5. A 4 bbl carburetor usually only operates on the front 2 barrels, which are smaller than the comparable ones on the 2 bbl carb. So, low end performance can actually be better on a 2 bbl.

6. The secondary 2 barrels only operate at heavy throttle. All the additional horsepower tends to be concentrated at higher RPMs. This is where I can tell the difference between a 2 bbl vs. 4 bbl '57 - the 4 bbl will "take off" under these conditions. The 2 bbl will accelerate, but not with the same burst of power. I don't even have to open the hood to tell you which one the car is equipped with. All I have to do is get the car cruising steadily at about 60 mph under light throttle, and then floor it.

7. When diagnosing some major pain in the a** drivability problems on my '57, I bought a rebuilt distributor from Advance Auto for very little money. It was actually a mid '70s distributor with minimal advance curves. The car ran well, but the performance was unimpressive because of the lack of advance.

8. Are you sure you have the correct weights and springs on your centrifugal advance? Do the weights move smoothly?

9. Do you have a Rochester 4GC or Carter WCFB? Both have their quirks. I've learned far more about these quirks than I ever wanted to know.

10. Both the 4GC and the WCFB have a "lock out" that prevents the secondaries from opening unless the choke is fully open. Your problem may be as simple as the lock out is mis-adjusted, preventing the secondaries from opening. The same can be said for the adjustment of the linkage to the secondary throttle.

 

[jmg283]

Stovebolt, he's saying that he cannot change the initial timing, turning the distributor body does nothing to timing or engine rpm. He said it's stuck at 4 deg btdc.
I'm not sure whether something is lost in translation of terminology, but there's no way turning the distributor in the block isn't going to change the timing and rpm on a running engine........IS THERE?

 

[stoveboltgeek]

Stovebolt, he's saying that he cannot change the initial timing, turning the distributor body does nothing to timing or engine rpm. He said it's stuck at 4 deg btdc.
I'm not sure whether something is lost in translation of terminology, but there's no way turning the distributor in the block isn't going to change the timing and rpm on a running engine........IS THERE?

Ummm...that ain't right....

"Lost in translation" is quite possible - hence my joke about John bringing the car from Melbourne (Victoria, Australia) to Raleigh (NC, USA) on Saturday so I could take a look for myself.

First things first:

1. Make sure the vacuum advance line - be it metal or rubber - is disconnected from the distributor and plugged.

2. Then, make sure the setting is at least 4 degrees ahead of TDC at no more than 450 rpm. (A 4 bbl distributor's centrifugal advance will kick in below 1000 rpm, so this is important). 450 rpm or less, no vacuum advance.

3. If it's wrong, loosen the bolt on the distributor clamp, and twist the distributor back and forth until correct. Then, retighten and recheck. (it may move when you tighten the bolt)

4. You may have to re-bend the metal line to hook the vacuum advance back up. (a significant down side to this design)

If he cannot twist the distributor back and forth, then someone probably used gasket sealer on both sides of the distributor gasket.

If he can twist the distributor back and forth, but the timing doesn't change, something is VERY wrong with the distributor.

 

[Rick_L]

First off, the 35 hp (or whatever the difference is supposed to be) is very real.

Second, the secondaries on a 4 bbl. carb don't dump fuel in like "flushing a toilet" - they work exactly the same way as the primaries except there's no idle circuit. As already said, the secondaries don't open until the flow opens the counterweighted air valve.

I suspect that you may be setting the timing with the vacuum advance hose connected. You should pull the hose off the distributor and plug it when setting the timing, then put it back afterwards.

You also may not be getting any mechanical advance at all, and you might not have vacuum advance either. Both need to be verified.

If you are setting the initial timing at 4 degrees, you may be able to increase it to 10-12 degrees.

Electronics to replace the points won't affect power at all relative to a points setup in good condition. But they will stay right all the time.

You've been getting some bad advice and comments from your "mechanic" and "engineer" (and to a lesser degree from some here). Seek out someone who understands this stuff and can help you. They aren't.

 

[stoveboltgeek]

Also, just to make sure there's no confusion - you are setting the timing mark on the harmonic balancer between the "0", and "A" - right? Not between "0" and "R"?

See the picture on http://chevy.oldcarmanualproject.com/booklets/56top06/5606top32.html (which describes setting at 8 degrees at 1000 rpm).