'67 283 2V Rochester Carb question

[Duluth67]

Currently working on a '67 K20 with a 283, 4 speed. I had the engine rebuilt, 60 over, "rv cam", put true dual exhaust on. Engine builder said the heads were "4 barrel type" but I had a 2 bbl intake mani.

I bought a rebuild rochester 2 bbl for (autoline brand) and installed it with a new gasket.

http://www.autozone.com/fuel-deliver...3032_123660_0/

Set timing with vacuum gauge. Set up with manual choke, as stock would be.

Truck always starts and idles nice, but when shifting gears, I will get a pop through the carb and a hard stutter. Also when cruising, there seems to be a slight surging.

What would I do to solve these running issues? Also, don't know what these trucks would have/get for fuel mileage/power, but right now it needs full throttle to go up hills and is getting around 7 mpg. 4.56 gears. Rockwell T221, SM465.

My original thought is maybe it is running lean, but I don't know how to tell for sure. If it is, could a main jet fix the problem, how do I know what one is in the Autolite? Better to switch to 4 bbl. If so, which one?

Thanks!

[Fitz]

Originally Posted by Duluth67

Currently working on a '67 K20 with a 283, 4 speed. I had the engine rebuilt, 60 over, "rv cam", put true dual exhaust on. Engine builder said the heads were "4 barrel type" but I had a 2 bbl intake mani.

I bought a rebuild rochester 2 bbl for (autoline brand) and installed it with a new gasket.

http://www.autozone.com/fuel-deliver...3032_123660_0/

Set timing with vacuum gauge. Set up with manual choke, as stock would be.

Truck always starts and idles nice, but when shifting gears, I will get a pop through the carb and a hard stutter. Also when cruising, there seems to be a slight surging.

What would I do to solve these running issues? Also, don't know what these trucks would have/get for fuel mileage/power, but right now it needs full throttle to go up hills and is getting around 7 mpg. 4.56 gears. Rockwell T221, SM465.

My original thought is maybe it is running lean, but I don't know how to tell for sure. If it is, could a main jet fix the problem, how do I know what one is in the Autolite? Better to switch to 4 bbl. If so, which one?

Thanks!

The easiest way to diagnose mixture is to read your plugs. A 283 is a pretty small motor. Much over 500 CFM will just swamp it. 4.56 gears aren't helping your gas mileage.

[Duluth67]

When should one check the plugs?

Engine cool?

After idling, running hard?

Doesn't matter?

Also, with the weight of the 4x4 should I expect to operate at full throttle routinely. Even with the low gears, it doesn't seem to have much for acceleration.

[geezer#99]

Check and set your timing with a timing light.
Vac gauge is not accurate especially at higher elevations.
Try 12 initial at first.

FWIW there are no 4 bbl or 2bbl heads on a 283.

[swamp rat]

Per the jetting if its pulling strong at wot the main jet is probably fine, if it feels like its surging the main could be too small, if its blowing black smoke it could be too rich. Make sure the float level is correct too.

If it feels sluggish just off idle it could be the air fuel adjust is off, but without proper timing adjustment messing with the carb can send ya in the wrong direction by slightly opening the butterfly and pulling fuel off the off idle circut instead of just the idle circut.

Vacuum advance? be sure to unplug the vac line from the distributor and plug the line before adjusting the timing, then readjust the carb.

[Duluth67]

http://67-72chevytrucks.com/vboard/s...14&postcount=8

There is some uncertainty as to the origin of the engine^.

I can't set timing with the light because the front pulley has spun a bit and the mark doesn't correspond to the tab on the front cover anymore.

I'll check the plugs tonight and see the color. How do you set the float height?

[notsolo]

How is the quality of the carb....bottom butterfly pivot tight not worn...mixture screws not loose without the springs..bottom mounting surface flat....I bought a rebuilt years ago that should have been scrapped....I hope yours is good..

[Duluth67]

It seemed to be pretty good, I don't have a lot to compare to, but it looked clean, tight, ect.

The real problem is running as it is coming off idle. Idles really nice then you let out the clutch and give it a little gas and it wants to buck before it comes back to life and then accelerates fine.

[Duluth67]

Plug color...

[Duluth67]

Any comments on the color of the plug?

[Steeveedee]

Pretty much right on, for mixture. See the chart up-thread to compare the colors. You can try setting the timing following this-

http://www.v8buick.com/showthread.ph...t=power+timing

It's a Buick site but the expertise applies to your engine as well.

[Alex V.]

You need to know timing is right before going after fuel. Backfiring through the intake and no power sound the same as what my 'Burb's 350 was doing, after swapping in a stock cam, before I realized my base timing was at -2. :-O SBC's can take generously more than factory timing - my dad's advice was to keep tweaking it up until it either spark-knocked under load or tried to kick back when starting hot, then back it off until those went away. Also, make sure you have a generous drop in timing when you disconnect the vacuum advance line at idle.