So long as there is enough length to get at least two full pulses from the same housing in the pipe before collecting. So, multiples of about 11 to 12 inches. Both pipes exactly the same length to the collector. Push a length of hose into the pipes and mark the length with bits of tape. Same angle into the collector. 1 7/8" to 2" ID. Long collector gives broader power band (good) short collector peaky power, not so good. In the early days of no porting the correct primary length was 102" inches of 2" ID pipe. A bit long for an airplane. Check your Racing Beat catalogue. Their headers are good sized and cheap, but carbon steel (crap) and will not hold up in an aircraft. Work fine on street cars.

 If the engine is solid mounted the pipes can be mounted solid. If the engine can move the pipes will move and allowance must be made for that movement. All stainless of course.

 

Lynn E. Hanover

 

 

 

Lynn:

In the past you have discussed on the list how to optimize the exhaust system, with the optimum length from manifold to header being 22-24 inches (depending on RPM desired).  I have fairly limited needs and only desire to produce between 160-180 hp for my RV-9A.  I have a 2.17 PSRU (without intake porting) so should I shoot for an exhaust pipe length of approx. 24 inches to the point where my 2 into 1 collector attaches?

Thanks.

Doug Lomheim

OK City, OK