What will happen with no back-pressure? How much is enough?

 

Well, I've heard that too little backpressure builds less torque, and at lower RPMs less horsepower. However, too much backpressure, and you also loose power, especially on the top-end. The trick is to the right size exhaust system given how your engine is built.

For example, a top-fuel dragster is best suited with a 3" straight pipe off dumping off each exhaust port, while your average V8 is happy with headers and dual-exhaust. If you put the 3" straight pipes on the V8, it would actually make less usable power than with the full exhaust system.

That was probly more information than you wanted, but I hope I at least partially answered your question. I've never heard of an engine being damaged from too little backpressure, but I suppose it's possible.

 

My 250r cracked a piston from noy having enough back presure.I am sure being a 14 year old piston had something to do with it also.

 

Thanks. That's exactly what I wanted.

 

ALSO YOU CAN BURN VALVES

 

sorry caps was on