951 pipe question

faster7581 · 02-20-2010, 09:53 AM

hi bill,
i was wondering if you've done any mods to a stock pipe xpl, ski will be pretty much stock, just flame arrestors, and rejet and mild compression increase.. what are some good mods for the stock pipe, cutting the manifold, adding a stinger, opening it up, and hard jetting? ... i've had several ss 800's with hard jetted pipes, so im aware of keeping the inline filters clean and jets clear... racing pretty much took a dump around here, so im just putting together a nice stock boat to have fun on the weekends, but i cant leave anything stock..
thanks
mike b

Mr. Bill · 02-20-2010, 08:14 PM

If you look back over the posts here a month or two back, I outlined what some guys have done to modify their stock 947 exhaust pipes. I'd hate to spend an hour or so rewriting it.
I have personally not spent much time working with the stock pipes as most everything I have built had a Coffman or twin pipe setup on them, so up to date details of what is working out for those who use them is really not within my scope of expertise. But, what has worked on the 787 and other models is basically the same direction where you get power from a stock pipe.
I do not think enlarging the stinger diameter is the right direction for a stock motor, but someone else may know better than me about what works best on the 947 pipe. I had some limited sucesses using hard jetting and a slightly smaller stinger sleeve, and a bit of grinding into the manifold and headpipe to enlarge the passageway through them has proven beneficial too.
You should really talk to someone who is more current on these stock pipe mods, as I did it back in 1997-'98 when there were no aftermarket alternatives for the 947 engines.

faster7581 · 02-22-2010, 12:41 PM

thanks bill, i've searched and asked around, i got the info i was searching for

Mr. Bill · 02-22-2010, 07:58 PM

And what was it that you found out ? Care to share it ?

faster7581 · 02-23-2010, 10:16 AM

same as what you said, rules dont allow much, add a fitting to the stinger, dry it out up top.. get it hot.

ohell · 02-23-2010, 10:21 PM

extrude hone & swain coating - swaintech.com - legal??

Mr. Bill · 02-24-2010, 09:41 PM

I doubt it, as it is just a different way of porting the manifold and pipe, but who's looking that would notice such a change ?

Another trick is putting a reducer into the coupler hose instead of the stinger. They might check the stinger, but I've never seen anyone look at the exhaust coupler hose............ I'm just say'n, not avocating cheating

. That may or may not help the performance of any certian setup, but you never know until you try it. Probably not too good of an idea for the really big bore kits in the stock classes that may need the stinger enlarged, not reduced.

I have used water to trick the pipe into working like I reduced a stinger. By using a fiiting without the normal water reducer placed into the stinger, and by using a pressure valve like the Jetwoks water valve, you can control when the water is injected into the stinger so as not to flood the muffler for the holeshot. Then by making the exhaust gasses exit through the same hole along with more water, it tricks the pipe into acting like the stinger has been reduced.
I think the rules say you can add a stinger water fitting and also you can restrict the water being injected into the mid pipe fitting by use of a jet in placed into the brass fitting. So take most of the water away from the midpipe to allow the chamber gasses to rise in tempeture, then cool it with more water as it exits the stinger to keep from burning the couplers and hoses beyond the stinger. May or may not work for your setup, but you never know if you do not try.

These are the type of things that seperate the fast guys from the also-rans. I love grey areas.