SBP chamber + stock header pipe ?

[danlandberg]

That's what I thought! In a post above, '' 12'' is a good starting point''. I'll be starting with 8.o'' because I'm going to cut .5'' above mufler, (In case I have to sleeve and weld it back together). The longer the header pipe, the harder it is for sound wave to return to ex. port for optimum scavenging!

 

[Ghost0]

First, the critical distance is from your exhaust port on your engine to the beginning of the expansion chamber, the muffler has nothing to do with this. Our pipes are designed to work at around 12 inches plus or minus an inch or so for tuning. Altering it 4 inches, shorter, or 12 inches longer, making the 24 inches I noted earlier, will be detrimental to the proper tuning of the pipe. It is all about timing and the speed of sound. 24 inches doesn't make if harder for the sound waves to travel it just takes longer which is why it destroys the tune of the pipe. For the sake of example, if you went to 24 inches. The timing of the sound pulse would be delayed to the point that your exhaust port would be closed by the piston when the sound wave is supposed to close it. This will defeat the purpose of the sound wave closing the exhaust port when it is open keeping the unburnt intake charge from leaving the combustion chamber creating a better more powerful combustion. So say you go with the 8 inches you are looking at. At 8 inches the pulse would hit the exhaust port too early and do approximately the same thing. A 1/4 inch difference in header length can make a difference in power band so I hope this explains that 4 inches from the recommended 12 inches will be well passed the effective length to make the most power out of your engine. Will it run better than a stock pipe? Yes, but are you really taking advantage of what a tuned pipe is supposed to do? No

 

[danlandberg]

Thanks Ghost, Like I posted before, I do no YET how long the header will need to be. If your chamber is set up for a 12'' header, I'll have to add 4'' to the stock pipe. And see how it works. If I want a low end-mid range power band, do I go longer or shorter? This is a learning experance for me. And I love to learn what is right and wrong!!! (Frome people who know)!!!

 

[Ghost0]

Longer equals more torque and shorter equals more top end.

 

[danlandberg]

Thanks Ghost Like I said it's a learning thing. (and I want to learn) What increments at a time?

 

[Ghost0]

Like I said 1/4 inch can make a difference but you are pretty safe working 1/2 inch at a time.

 

[danlandberg]

I'll start out with Adding 4''. I want mid to top end power , but I'm in the break in period right now. After break in , I'll cut as I go!

 

[AussieSteve]

Dan, you need to stick to Jim's 12" recommendation, then tune the pipe itself for the rev range that you're after.
Especially, don't use a 2 foot header or you'll waste the tuned pipe.
(Yep, I'm still alive. Just thought I'd poke my head in for a look-see.)

 

[danlandberg]

Good to hear from you Steve! I'll have to add 4'' to the stock pipe to get to 12'' Going to try it this week!

 

[danlandberg]

I tie wrapped the chamber on, to get an idea of where it needs to be. (but from the bolt flange to the chamber is 11'') The question I have now is, Will the silicone tubing hold up with out the header pipe inserted into the chamber? (the tubing is about a 1/2'' extension added to the stock pipe). It allows some flex for alignment. I'll post pics later!