Stack Pictures

[Jeff122]

Amigatec:
We're always ready to BBQ.

[Guitar Guy]

Those stacks and pipes look pretty cool. I'm wondering, when adding a different muffler or pipe that what came stock on the engine, doesn't that change the back pressure seen by the engine?

I know when adding more open pipes to a Harley, the carb. usually has to be re-jetted. Just wondering how this is measured or determined for the Kohler engines, and if there is a chance for damage.

Josh P

[westofb]

Originally Posted by Guitar Guy

Those stacks and pipes look pretty cool. I'm wondering, when adding a different muffler or pipe that what came stock on the engine, doesn't that change the back pressure seen by the engine?

I know when adding more open pipes to a Harley, the carb. usually has to be re-jetted. Just wondering how this is measured or determined for the Kohler engines, and if there is a chance for damage.

Josh P

Josh, see post number 1 in this thread, he stated he had to drill out the mainjet, tractor was running lean with the stack!

[Guitar Guy]

Yes, I saw that about drilling the main jet, but I was just wondering for different types of mufflers which may create different amounts of back pressure, how does one determine how much to drill, or how to actually measure / tune the system for proper flow.

Josh

[Matt G.]

If you have an adjustable carb, you don't need to do any drilling, just readjust the carb.

[AMCJavelin74]

One thing that wasn't mentioned are turns and bends...

I know a lot of guys like 'blackpipe' but I really think using it impedes exhaust flow (as it's OD is the same as 'normal exhaust pipe' but the ID is smaller. This creates a hard angle for the exhaust gases to manuver around as it narrows down- even if you use a straight section.

......s are to take up space as some formatting keeps my diagram from turning out how I'd like.

------------
................L___________
exh. port........blackpipe ID
................____________
................I
------------


While the above is up to debate as to wether or not if would affect engine efficency or power significantly, the elbows are what scare me.

Look at the inside of a blackpipe elbow at the hardware store, then find a nice angle or pressure bend pipe. Which would exhaust gasses flow easier through? As for 'standard exhaust pipe' bends, at the worst is crush bent. The inner radius of this bend is all crinkly. Normally found in parts store bins. Then they have pressure bent pipes, which the inner radius is smooth, but a smaller diameter than the straight sections of pipe. I think this is an ideal 'bang for buck' bend. And of course we round it off with mandrel bends, which keeps a diamter consistent through the bend. I'd go with this (a little pricier) if you have a competition engine.

Just my two cents.

[drysumpjet]

In my case, I had to drill out the main jet to obtain adjustment, utilizing drill bits from a numbered (not to be confused with fractional) drill set. I can't rememember the drill size, but it ended up 2 sizes larger than the stock jet.

The carbuator was from new old stock, 1" bore #30, I'm not sure if the main jet was sized specifically for a 14HP or 16HP or if it's the same for both motors. Surely others may be able to chime in on that.

Also note, in my case, the motor has been "ported" and has valve reliefs machined into the combustion area of the block.

Interesting note, due to the configuation of the fuel ports in this carb, if the high speed mixture adjustment needle is screwed out more than approx 4 turns, it plays HAVOC with the idle circuit fuel feed!
What happens is the upper threaded body portion of the adjustment screw blocks the idle circuit fuel feed port. (Observe the idle fuel passage starts at the top of the high speed mixture adjustment screw)
Suspect symtoms of this condition is the idle being too "lean" where-as screwing the idle mixure adjustment screw out further has little/no effect on the idle quality.

A larger main jet allowed for the high speed mixture adjustment screw to be adjusted "in" further, which took care of my issue.

As always, "Your Results May Vary!"

[Sugarmaker]

Most probably seen these. Wanted to get them into the right thread to maybe help some one else in this area. I know that the previous posts and many pictures on the subject of stacks help me a lot.
Here are some shots of the 147R custom stack I built. Questions/Comments always welcome. I made some improvements based on what folks recommended.
The first shot is the components I used. SST 2 inch tubing, some stainless fitting, and some fab work. Second shot is first attempt when it was a tad to close to the hood. Remaining shots are from revised stack design. Which means trying to make something out of the parts you already have
I followed the guidlines of a added support plate off the top of the head studs. I like this it seems very stiff and secure.
This stack is loud and may have to have a baffle put in for any type of normal use
Regards,
Chris

[70Cub]

That is is awsome!! looks very well made that's for sure. Really good fab work!! Makes me what to do this even more now.

[Sugarmaker]

70 Cub,
Thanks!
Your only 10 minutes from me. Stop by!
Regards,
Chris