tunning for open headers

Is there a base line on how many jet sizes and or timing increase/decrease when uncapping a motor tuned with mufflers?

i run mine a tad rich all the time. About 2 jet sizes at the very most. Timing is the same

When you remove the mufflers, you should ALWAYS put an 18 inch long collector extention on the header flange. I have seen cars gain one half a second with this extention all by itself. This will keep your jetting in line with what it waas through the mufflers,

JOE SHERMAN RACING ENGINES

Originally Posted by BIGJOE

When you remove the mufflers, you should ALWAYS put an 18 inch long collector extention on the header flange. I have seen cars gain one half a second with this extention all by itself. This will keep your jetting in line with what it waas through the mufflers,

JOE SHERMAN RACING ENGINES

Man that is old school. But it works.. Keeps your torque curve up and was a ole super stocker trick decades ago. Use to make them longer than 18', like 26" and put a white paint line down the lenght and where the paint changed colors you would cut them off there. I believe that was in a old Hot Rod magazine article in the late 60's. Joe, thanks for the flash back....

Jeff

Originally Posted by JN-Motorsports

Man that is old school. But it works.. Keeps your torque curve up and was a ole super stocker trick decades ago. Use to make them longer than 18', like 26" and put a white paint line down the lenght and where the paint changed colors you would cut them off there. I believe that was in a old Hot Rod magazine article in the late 60's. Joe, thanks for the flash back....

Jeff

A old roundy track racer told me long ago that the used a crayon and at the spot it stopped melting thats were they cut off the exstension.

I believe the same concept of marking a crayon on your exhaust when your installing an H or X-pipe. Whereever the crayon part stops melting is where the H or X-pipe needs to go.