The Stovebolt Site Forums The Parking Lot Big Bolts split manifold performance on a big bolt

I wanted to know what the performance difference would be if I installed split exhaust manifolds on my 1954 chevrolet 1-1/2 ton with a stock 1962 1/2 ton 235 sm 420 transmission w/a 2-speed rear. I like the sound of the split six and plan to route the exhaust through 4-inch stacks. the truck will be loaded with construction tools and may pull a trailer with a skid steer loader,etc. I heard that the split manifold may affect my bottom end torque but will increase my top end power. I plan to upgrade to a 261 later on.

As long as the 4" stacks are just for cosmetic effect, and you use small-diameter pipes off the manifold flanges, the low-end torque shouldn't be affected much. Run pipes about 1 3/4" or 1 7/8" diameter from the manifold to the stacks, and adapt them to the larger pipes for visual effect. Any semi-low restriction mufflers will produce the sound you want, guaranteed to give you a headache if you drive it very far.
Jerry

IMO: If it is sound you want I'd say go for it. But in my rig, the rear axle is so geared low in either position that it can't go any faster no matter what you do with the pipes. I've got plenty of motor it just can't go very fast but it will pull anything you want!

do the mufflers have to be 1-3/4" or 1-7/8" inlet/outlet?

Not necessarily, but the pipes off the manifold flanges don't need to be very big or you'll mess up the back pressure and possibly draw cold air back to the exhaust valves as the pressure pulses cycle. A split manifold only has half the pulse frequency in each pipe as a single exhaust, and the pulses occur every 240 degrees of crankshaft rotation. That's what gives a split manifold six the characteristic "BRAAAAAPPPPP" sound, but it can also warp valves with cold air if the pipes are too big.
Jerry