Originally Posted by dshevick
I'm installing a new engine and my new exhaust actually hits the cowl at the bottom. So I'm need to modify the cowl. I know I need to put some kind of fire shielding material on it and I read some threads on the different types of that. But what is the minimum clearance I need to modify the cowl to? 1 inch? Thank you David
Yep use metallic SS tape or other heat shield. The min clearance is what you end up with. There is no rule. The more space the better for your cowl. I think 1" clearance is fine but it depends on how hot the pipe is and airflow. Pipe is hotter closer to the head.
Engine, engine mount and cowl are constants. Not going to change those. New exhaust (what kind?) will determine clearance. Little you can do to gain more clearance unless you cut and weld the pipe.
I have 4 into 1 pipes exiting cowl butt-line zero. Where it exits cowl the collector almost touches. However there's a lot of air flow in the area and the pipe is cooler at that point. That does not mean I won't get cowl toasty over time... remains to be seen. Think of engine movement and clearance as well. Once you run engine check for touching and heat damage. You could get scientific and put a thermocouple on the cowl, check the temperature.
I think epoxy wet layup fiberglass is safe up to 200F to as much as 300F.... but again it will degrade over time. Use a IR temp gun after you shut down on the outside of the cowl. You might find cowl it gets very hot... all over. Even the old vinyl-ester cowls held up but would shrink....