The "8-inch stacks" are necessary on the diesel to carry away all of the black smoke from the diesel!!! wink

A smaller pipe would quickly be stopped up from the pollution!!! wink

Do the diesels still have the tap on the bottom of the stacks to draw off the carbon, now that computer software has dramatically cut the demand for pencils? wink

Jon.

Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify.
If you truly believe "one size fits all," try walking a mile in your spouse's shoes!
The Carburetor Shop