Thread: Exhaust manifold
10-23-2009, 01:09 AM #1
While cleaning up some parts and getting ready to start reassembling things, I started looking closer at the exhaust side of this engine. The exhaust ports on the heads are nice and short, fairly straight, and would be easy to smooth out and polish. What I didn't expect is a 'brick wall' in the manifold right in front of the center exhaust port. The mag and pto exhaust ports are relatively unobstructed, but why would they put this wall in front of the center port? Is it advantageous to reshape this center web to allow better center exhaust flow? I plan to smooth and polish all of the exhaust ports, what should I do with this manifold?
10-23-2009, 03:01 AM #2
- Join Date
- Jul 2007
- Cedar Rapids,Iowa
It is to redirect the 2 outer cylinders into the exhaust outlet,some have thinned it and smoothed it up. What you don't want is the 2 outer cylinders plausing each other in the middle. Port matching the cylinders and exhaust manifolds can't hurt at all.As cleaning up inside the ex. ports and pipe.
10-23-2009, 03:35 AM #3
I wasn't planning on major porting or anything, mostly just a nice cleanup and a smooth polish job on the exhaust end. It just seems like such a restriction in the center ports that I may just have to clean up a little more aluminum than I had planned! I won't remove the whole web, but reshape it a little to allow for better center flow while maintaining smooth flow from the pto and mag ports. Then polish the crap out of it till I can see myself in the exhaust ports!!!
10-23-2009, 05:49 PM #4
- Join Date
- Oct 2006
- Cleveland OH
There was a guy that came on here a long time ago and said the Polaris racing team use to cut down that web you speak of to free up more HP.
No one has ever proven him to be right or wrong.
I have actually done the mod to a 750 exh manifold already, just never tried it out.
As for the exh ports, clean them up, but don't enlarge the opening if you can.
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