Effect of Overlap on Pipe Choice

[Tail Ridr]

In matching up components for a better build...what would be the difference in pipe/slip-on choice between a low to mid 20's overlap to a mid 30's overlap, or even on to an overlap in to the 40deg range, to keep more area under the curve? Does IVC effect the choice as well, rather than choosing a combo for the sound or looks?

[Don D]

As overlap increases the pipe choice becomes more critical. When adding overlap you have to be sure the pipe design and timing events compliment each other. When done properly the overlap assists in pulling in new mixture, air and fuel. The pipe works well with the timing events to assist in initiating intake flow approaching and ATDC on the intake stroke. This is a critical point and one that gets screwed up often. When messed up the intake draws in exhaust or the pipe pulls out mixture. Back pressure is an influence as is the corrected timed pulse that initiated the negative pressure during the overlap period. Remember an EFI engine will have a little different requirement than carbureted engine as it is fed fuel mechanically and timed by program. The carbureted engine works on demand, and hopefully a cooperating pipe, to bring in the mixture.

[1FSTRK]

As overlap increases the pipe choice becomes more critical. When adding overlap you have to be sure the pipe design and timing events compliment each other. When done properly the overlap assists in pulling in new mixture, air and fuel. The pipe works well with the timing events to assist in initiating intake flow approaching and ATDC on the intake stroke. This is a critical point and one that gets screwed up often. When messed up the intake draws in exhaust or the pipe pulls out mixture. Back pressure is an influence as is the corrected timed pulse that initiated the negative pressure during the overlap period. Remember an EFI engine will have a little different requirement than carbureted engine as it is fed fuel mechanically and timed by program. The carbureted engine works on demand, and hopefully a cooperating pipe, to bring in the mixture.

This speaks volumes and should be re-read by most until understood.

I would add that once understood it is more forgiving and can be tuned to work with errors in the rest of the package.

[Tail Ridr]

As an example, what pipe and/or muffler differences/changes are required as you would build into any of these particular overlap areas, of say 10deg increments? For example...my stock HO at 13deg overlap, a CR575 at 22deg, Kury 24D at 34deg or something like a Rocket 584 at 46deg...what changes from one to another would be needed to compliment either of these from any of the others?

[gordonr]

You need to focus more on CI and RPM for pipe choices. And also where you want your power, early or late. If your ok spending a few bucks buy "pipe max" on line and use it in single cylinder configuration. You will be able to answer this question as well others you come up with.

[wfolarry]

example

[Nastytls]

I've never seen that before, very cool. Thank you for posting Larry.

[98fxstc]

I've never seen that before, very cool. Thank you for posting Larry.

Thanks Larry

[Phu Cat]

Putting parts together that aren't known for complimenting each other is a waste of time and money.  Why not call the cam and pipe manufacturers and see what they recommend?

PC