Greetings Formula Brothers !

One quick lesson I learned about repowering my Formula, that I wanted to share.

If you are installing a "performance engine with O2 sensor " in a Formula with a swim platform, make sure your exhaust tails are 4 to 6" out past the transom. Myself, and a few others I know have had a unexplained vortex backdraft when using the short 2" tails we like to run sometime

Just food for thought

What is the length of your 4" exhaust from where it bolts to the header to the end of your 2" tailpipe and then to end of your new tailpipe ?

I may / may not have answers for you on why this is happening.

Old pipes where 16" total length from header
New pipes are right at 20" total length from header

3rd Harmonic = 38.8 inches long ... more bottom-end Torque
4th Harmonic = 19.4 inches long ... highly recommended , best Torque Curve
5th Harmonic = 9.7 inches long ... reduced Torque , more top-end HP sometimes
6th Harmonic = 4.9 inches long ... reduced Torque , not recommended

Tuned Lengths= 19.4 best and also 9.7 or 38.8


Look like you are good now !

I guess "right at 20" and 19.4" are pretty dang close LOL

Thanks SB ! Should have called you first!