jtranger

Just picked up a pair of 2x4 carbs. 6-1299 tops, 049 bowls, throttle plates are 1483 and 1486. These throttle plate bases seem thinner than the non 2x4 bases. Are these the thinner bases for the 2x4's? Thanks!

tach drive 61

yes they should be thinner bob kunz should know best and rebuild your set good luck

Frankie the Fink

The base plates have numbers too if you want to take out a few screws and check them. Proper 245hp/270hp dual quad plates should be 1-1387B. You are missing some choke/fast idle linkage and these carbs are hooked up "shotgun" instead of "progressive"...that's bad mojo...unless you're racing.

jtranger

Yeah Frank, this guy had these rigged up on a truck. What a waste! I would do them up right.

Where do I find the base plate numbers and parts for these? Don't mind pulling few screws. These have the 45 degree discharge nozzles as well.

Frankie the Fink

Then you've hit the jackpot - they are real deal 270hp carbs !!
See attached for base plate numbers. They are hidden on an assembled carb but just inboard of the idle speed adjustment screw...

jtranger

Nice photo. Thanks Frank!

Solid Axle Guy

How does a person tell the diff between 245 hp 2X4s & 270 hp 2X4s? Thxs Pics if possible please.

Steve59

Frank the Fink answered that question with pics about a year ago. Look at the jets. The ends are cut differently, I believe that the higher HP carbs, the jets are at an angle and the lower hp jets are vertical ( I may have that backwards)

Frankie the Fink

Primary nozzles are cut at 45* on 'real deal' 270hp carbs and the counterweight arms/weights are different to compensate for the lower engine vacuum in Duntov-cammed, solid-lifter cars. Those are the chief, easily-identifiable characteristics. See the green circles in the first pic in the attached article.

Solid Axle Guy

Thxs Frankie U R the best

Thmprr

Just checked the 4346 Fuel Pump pressure, 5-1/2 to 6 psi. No surprise that it's that high, actually I was expecting it higher, should be 4-1/2 - 5 psi.
I've now received the new needle valve seat assemblies so I'll install them and see how it goes, they say that they cope well with higher pressures, so we'll see.

Frankie the Fink

That is borderline high for these carbs but not "off the charts". Your flooding may be due to other issues (contamination, floats not centered in bowl, float height incorrect, leaky float, etc).

The needle valves are held shut by the buoyancy of the floats providing pressure on the valve against its seat - nothing else; so; I'm skeptical your new needle valves will help but worth a try I guess.

vettepoor

I did a pressure check on my fuel pump for my 57 with dual wcfb's. It was between 6 and 6 1/2. I was also having ongoing flooding issues. Turned out to be problem with seating surface on air horn body for needle seat (rough surface). I was able to hone surface to get a nice seal. No more flooding issues, even with higher pressure pump. Good luck.

John

Thmprr

That's interesting, I'll check that. cheers, Rod.

Frankie the Fink

Well then - if we are going there then you should note that the fiber needle valve round gaskets should fit tightly around the valve. In fact, they should almost need to be screwed on and not be so loose they just slide down the needle valve shaft. A good seal at the base of the valve is essential...

Thmprr

I got around to removing the carburetor tops, I then fitted the new needle seat assemblies.
When I did the same to the rear carburetor, the secondary float was noticeably heavy on the LH side. Of course it sunk like a stone when I tested it, so that threw me for a loop. The RH side was fine, so I was puzzled how this thing ran at all!
I had a parts WCFB, so I took a secondary type float from that and tested it, it came out fine.
Today I completed the re-assembly and test ran it. What a difference, oddly enough the idles were spot on. No black smoke anymore or erratic idling. It makes me a bit mad though, that I did not find this out sooner.
Incidentally the new needles and seats that came from Chicago Corvettes seem to be controlling the high fuel pressure fine, I did set the floats about 3/32" lower to compensate.
We'll see how it goes after a few test runs.

Frankie the Fink

Leaky float - as I suggested in post #12 above - they can be repaired BTW.

That was your problem....the Chicago Corvette "improved" needle valve and seat are the ones Daytona Parts has sold for several years - I run them and they work well. Its critical you use the correct number of gaskets under the seat; that's why they give you three.

If you now suffer fuel starvation on hard acceleration you'll want to set those floats back to spec - just keep an eye on it.

PAmotorman

back in the day I found that the 270 HP carbs worked better on the street using the 245 HP jetting. 270 HP carbs were jetted for open exhaust at the track.

Thmprr

I will drill the side of the float where it was soldered up to drain the gas, then I'll make a small jig up to hold the float so it wont collapse under heat, then use a heat gun to resolder the joint. Always good to have a spare.

GTOguy

I've always had excellent results with brass floats using a regular soldering iron. A heat gun is liable to melt all the solder in all the seams. Just sayin'.....