67 gal with 390? Can somebody help with a degree of angle?

Originally Posted by lnmrmn

I just didnt know if gravity affected the amount of fuel that way I could easier and cheaper fix it by leveling the carb with a spacer rather than shimming up the transmission to change the angle of the motor.

First, ascertain the engine and transmission mounts are in good shape. These will cause incorrect geometry. If you decide to level the carb pad by shimming the trans mount, you will upset the driveline angle and have to chase that.

Put the car on a level surface, and lay a torpedo level as best as you can at the carb mounting pad. If excessive angle, use a wedged carb spacer.

It is possible that if there is an extremely lean fuel mixture that it will not be distributed throughout the intake correctly. The key here is that the fuel bowls must be level as entire carburetor calibration depends entirely on this factor. FI engines can be tilted somewhat with no complications.

Something no one touched on here, is that the angle shouldn't make a lot of difference. Gravity dosen't play into this problem nearly as much as VACUUM does. Think about it for a second...what pulls the fuel into the cylinders? It's the piston going down on the intake stroke creating the vacuum that pulls the fuel thru the intake. Are there any vacuum leaks? But I agree with the others that it looks to be more about a mixture problem.

Originally Posted by bcuz1998

Something no one touched on here, is that the angle shouldn't make a lot of difference.

The carburetor having to sit @ level (on the mounting pad) has everything to do with this problem. If not level, the fuel level(s) in the fuel bowl(s) will not be correct and throw the calibration (fuel mixture) off, resulting in either lean and/or rich fuel conditions. If the mixture is lean, it may be possible that all cylinders will not have a full draw (even with a dual plane intake) and result in plug readings he is describing.

Look at competition engines. Staggering jet sizes and rocker arm ratios trying to obtain even fuel distribution is a given. One cylinder can rob fuel mixture from another. One reason competition engines run fat.

Gravity is not a factor.

I was just looking at shimming the transmission at the cross member, you must be psychic. I will try the carb wedge first and see what that does.