4/7 swap cams

[danoone]

At what RPM level is a 4/7 swap cam become an advantage?

[randy wilson]

Originally Posted by danoone

At what RPM level is a 4/7 swap cam become an advantage?

Don't really know. Use a lot of them, and 4 cylinder swap. Does it help? Don't know. Does it hurt? No.

[Jeff Jewell]

While I don't have an answer on the RPM level, I had an interesting observation with my oval port headed 427 BBC a couple of years ago. This combo was shifted at 7400 and trapped around 7600. I had a standard roller cam in it when I had to pull the engine early due to a cylinder head issue. When the engine was taken apart, we found the cam was soft and starting to wear prematurely. The cam manufacturer had a bad run of standard cam cores. They couldn't get me a replacement in a standard cam right away, but they offered me a replacement in a 4/7 swap (no charge for the replacement cam BTW). The cam was identical to the original cam, except for the 4/7 swap. Put the engine back in and the car ran exactly the same. No gain or loss. Only change I saw was that the engine seemed to idle smoother.

[CFMCNC]

The only way to evaluate firing order is on the engine dyno with Wideband O2 sensors on each cylinder.followed by track testing.Gains from correct firing order are in thermal balance,crankshaft loading and smoothing intake manifold traffic.We have done testing where a firing order swap along with staggered jetting has shown gains and or connected to slight manifold fixes to balance cylinder to cylinder AFR.Bill C.

[danoone]

Thank you for the answers. I had wandered because I saw Top Fuel also swaps two more cylinders because of rpm and crank load. I have been intrigued few years with trying a 4,7 swap but figured I may not be running high enough rpm to take advantage of it.

[V M Kauffman]

On the Ford 302 and 351 firing order change that was done to improve #1 main bearing loading. Too much loading with driving Ac, Alt, Water pump and thermactor.