New Member, New Owner of a 425

[JGZahn]

That's a great place to start a fire

When I saw it glowing in the dark in winter after plowing snow for a while I wondered if it might be a little on the restricted side.

 

[marrt]

View attachment 701187
Here’s a dissected Power-Trac muffler, btw.

WOW! Looks like somebody at PT believes in the myth that engines like this need backpressure. This looks WAY too restricted to me. While a large header/exhaust pipe can reduce power at low RPM's due to reduced exhaust velocity and scavenging, a lot of back pressure is not needed in a 4-cycle engine. I'd be much more comfortable with Subaru's stock system since there was probably a degree of engineering applied to optimize flow velocity and scavenging. I'm not saying PT didn't optimize with this...but I doubt it given the use of square tubing and right angle turns. I have the same setup on one of my PT's...so, thanks for confirming my suspicion. I'm have a stock Subaru exhaust system around here somewhere if I didn't throw it away, which I probably did because I thought I'd never need it. This is before I bought another 425 with the Subaru engine. I better go look for it.

 

[JGZahn]

WOW! Looks like somebody at PT believes in the myth that engines like this need backpressure. This looks WAY too restricted to me. While a large header/exhaust pipe can reduce power at low RPM's due to reduced exhaust velocity and scavenging, a lot of back pressure is not needed in a 4-cycle engine. I'd be much more comfortable with Subaru's stock system since there was probably a degree of engineering applied to optimize flow velocity and scavenging. I'm not saying PT didn't optimize with this...but I doubt it given the use of square tubing and right angle turns. I have the same setup on one of my PT's...so, thanks for confirming my suspicion. I'm have a stock Subaru exhaust system around here somewhere if I didn't throw it away, which I probably did because I thought I'd never need it. This is before I bought another 425 with the Subaru engine. I better go look for it.

The stock Subaru pipes sweep up and out. I put a EH72 FI in my friend’s PT425, had to modify the engine cover so the hoop where the pipe exits is taller The pipe also had a bend and flange on the end I cut off and extended it with a straight piece. I found a tractor muffler on line, I needed an adapter because it’s inlet pipe size is larger than the Subaru pipe. The pic is from when it was still a work in progress about 4 yrs ago.