Carb replacement

[Sundowner]

Any information on a replacement carb for a 283. It came with a 4 barrel Carter WCFB. Looking for info on bolt pattern CFM and any other carbs that will fit the angle plate

[Paul P]

I can't tell you where to get a proper replacement carb right off hand, but I can give some advice about getting one too big. Anyone running a stock CC Small or Big Block with anything bigger than 600 is going WAY overboard. The 427 CC motor came with a 625, and even that was oversized a bit for the 4000 max rpm these air pumps were pumping. If the Edelbrock marine 1409 marine is good for the 427, it's going to be way too big for the 283, or any other small block Chevy motor.

Here is the forumula for calculating CFM requirements.

CFM = ( RPM X CID ) DIVIDED BY 3456

Example 4000 X 283 = 1132000 divided by 3456 = 328 cfm

rpm = max rpm the engine will see

This readily dispells the myth that a (stock) Small Block will need a 750 cfm carb (or a 600). Naturally if the motor is highly modified and producing lots more power, the carb must be upsized to meet the demand.

You dont want to go too big, because then it reduces the velocity of air into the carb, making for a weak signal for the carb.

Because the actual engine efficiency is less than theoretical, you can downsize another 10-15% and not be too small. However, bear in mind that vacuum secondaries may open early on smaller carbs, unless properly set up with stiffer springs in the secondary side. A weak signal..low velocity/vacuum..causes incomplete atomization of the fuel, and low vacuum causes the power enrichment circuit to operate, which hurts economy.

Therefore, the solution is not to buy an Edelbrock 600 CFM carb for a 283. I suppose it would work, but it would require internal modifications and then the throat may still be too wide for the proper running.

This is just one more reason why we should keep the automotive guys away from the boats. You can go into any autoparts store in the USA, ask anyone at the counter what carb is appropriate for a Ford 427 marine engine, and after they get done discussing among themselves if Ford actually ever produced a 427, they're going to give you a 95% probability that it's the 750-CFM carb, which is dead wrong for the Chris Craft application.

The Edelbrock will bolt onto the 283 motor, I believe, but it would require a discussion with the tech department to be sure you got the correct downsized jets, springs, etc. YOu would be better served to get a carb that was intended for that beautiful small block motor.

Good luck

Paul