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Thu May 02, 2024 11:03 am

Hey Guys, I would like to put non baffled chrome tips on my stock 1600cc dual port. Will doing this hurt anything.

Will my engine miss the back pressure from the stock pea shooters.

Thank you

Thu May 02, 2024 2:59 pm

If there's much of a flow difference with the new tips, I seriously doubt it'd be any worse than the tens of thousands of us that have put an aftermarket "performance" muffler or 4 into 1 header system on an otherwise stock engine. Actually might be better because if you're using an otherwise stock muffler, carb, and air filter you can retain your manifold heating.

Just make sure you set the tailpipes to the correct depth so as not to obstruct the low pressure side of the manifold preheat tubing system.

Keep in mind the combination of a better flowing exhaust and the increased ethanol content of many fuels available today miiiiiight call for a slightly larger main jet, depending on how close to optimal your fuel curve is prior to changing the tips. If you have a way to check AFR before and after the tips are changed that would be ideal. If not, a good old fashioned spark plug electrode reading done correctly should get you in the ballpark.

Thu May 02, 2024 3:39 pm

The "need for back pressure" on a 4 stroke cycle engine is an old wive's tale. There is no scientific basis to support it.

Thu May 02, 2024 3:44 pm

oprn wrote: The "need for back pressure" on a 4 stroke cycle engine is an old wive's tale. There is no scientific basis to support it.
Ever run a stinger with no baffle??

It bogs at low rpm.

Fri May 03, 2024 3:17 am

Years ago I used to pull out the baffles. However, if you do you will probably run into the same problem that I had: Spitting them out as you drive down the road. When you pull the guts out, they loose their strength, and ability to stay round. So after a couple of heat cycles, the tubes would form to the shape of the clamps, then there is no longer a clamping force on the tips, and exhaust pressure blows them out.

My solution was to weld a "small" tack from the tube, to a clamp half. You don't need to run a full bead, just a tack. You can use just about any welding process that you have available: silver solder, braze, oxy acet, flux core, tig, mig or stick. Just get a little blob on there.

Fri May 03, 2024 3:59 am

Glenn wrote: oprn wrote: The "need for back pressure" on a 4 stroke cycle engine is an old wive's tale. There is no scientific basis to support it.
Ever run a stinger with no baffle??

It bogs at low rpm.
Changing the flow characteristics of the exhaust can affect the tune mixture. You may or may not need to adjust it but there are no massive catastrophic consequences of lowering the back pressure on your engine. I removed the baffles in the pea shooters on my 1600 DP years ago with the only negative effect being that it was loud.

More recently I took the dual cannons off a 1600 DP and put a 4 into 1 exhaust and a stinger on. It eliminated the low end stumbles and farts.

There is a belief out there that if you reduce back pressure on an engine you will burn the exhaust valves. Poppycock! Any change made to an engine’s exhaust system comes with the need to review the tune. Failure to do so could result in a too lean or too rich condition that is harmful.

Take a look at aircraft engines. Multitudes of them out there with exhaust stubs 6 to 18” long and no mufflers at all. You can’t get back pressure any lower that that and you can’t find an application where engine damage is more critical than that!