DragStuff

What are the thoughts on 4/7 cyl swaps on BBC ?
Worth it or not ?

My new combo has one, but it is so different from my previous combo that I could not even compare them. March 06 Hot rod did a big comparison using two identical cams other than the 4/7 swap, in the same 492 ci bbc and the 4/7 did make more power, both peak and across the curve. One thing I will say is every chevy prostock car uses a 4/7 swap, and so does all of the new ls motors.

My take on it is that you're far more likely to make more power by getting the duration and lift exactly right than the swap will be worth.

Now say you're scienced out all that (and tested it) then yeah, there might be a little in the swap. Ten degrees in the wrong or right way is far more of a difference than if it's got the swapped firing order or not.

Another note, it's real hard for us old farts to remember the new firing order also LOL. I have 18436572 engraved in my head and find it difficult to remember the 4/7 swap order.

No doubt on the firing order. I got it right when I broke the motor in, but I screwed it up when I pulled the intake back off. DUMBAS_! When I called comp on my cam, I never specified a 4/7 swap, that is what they recomended with the grind I bought.

gave me an extra 30hp at the flywheel. i like the 4/7 swap myself