[twfreightman]

I need some advise from a good engine builder. I have a Heritage 2003 TC 88. I have a 95" big bore, SE HTCC heads, SE 10.5:1 HTCC pistons, SE 257 cam, Mikuni 42 carb with SE HTCC intake manifold, SE High performance ignition/plugs/wires, SE K&N high flow air intake, and a Python dual slash exhaust. I dyno about 100 lb/ft torque and 98 HP. Problem is from 2500 to 3500 RPM, my torque drops like a rock in a well. Then it takes off and runs at 3500 rpm. I am changing my exhaust to a V&H Pro Pipe HS 2 into 1 as I have been told this could fix my issue. Wondering if I need to drop back to a SE 211 cam? Also wondering if a Mikuni 45 would get me anything over my Mikuni 42? My goal is to hit over 100 Lb/ft torque and over 100 hp with a good smooth torque curve. Harley dealers seem to have differing opinions. Any advise?

[hotroadking]

You have a good combination, on the dyno run did you get an afr reading as well?

Can you post the dyno sheet with the afr it would help to see if you are going really lean or maybe reversion.

The pro pipe is a great pipe, you will make more peak hp and tq with the pipe, however you may see some dip in the curve, however it's typical of the 2:1 type pipe that isn't tuneable.

My thunderheader has the dip but it's so short you really don't notice it.

The other thing is the cams you selected are higher rpm power cams so what you really feel isn't the dip per se IMHO as much as it is the motor getting on the cam at 3500 or so rpm which is it's starting point.

Did the operator of the dyno do any tuning, ignition wise or jets in the carb.

You're close now so a few tweaks may get you in the power band.

[hotroadking]

Also a good tuneable ignition like the Daytona twin tech or Crane HI-4tc is a better choice as you can select the curves to match the fuel and motor build.

I would not go to the 45 as you may pick up some hp up top but it will not help the bottom, the 42 is better for that, if you want to switch go to the cv44 or cv 51 carb.

[twfreightman]

They did not give me an AFR reading. I am not sure what that is.
I will try to get my dyno run scanned and posted.
Joplin MO HD did my dyno with the help of a guy that travels around the country to rallies doing dyno tunes...."The Dynoman"!! (John something) They did jet the carb and modify the baffles on the dyno, but could not solve the problem without significant impact on max torque and max HP. That was when they told me my Pythons had to go. Said I needed to find a good 2 into 1 to fix the flat spot (drop) in the torque curve. Your advise on the ignition and carb sounds good. Thanks much!!

[hotroadking]

The guy you used is John Golden, Rolling Thunder Dyno, he tunes without the AFR been doing it for years, problem is when you have an issue like this it's one tool that helps get you to the answer.

AFR is the Air Fuel Ratio, it's a line that prints on the graph that measures the mix and reports it like the hp and tq curves.

13's are optimal for performance, higher is leaner, lower is too rich.

Did he pull the air filter out to see if that helped, John is good, if he thinks the pipes are the problem he may be correct.

[CD]

Additionally, are the Python slip on or Python III? Python III have welded baffles so modifying the is difficult at best.

The AFR ratio is essential but not an absolute necessity to diagnose reversion. I just makes life one heck of a lot easier. If AFR is not available you have to alter jetting at that point in the RPN / Throttle range and retest.

If you are using stock head pipes and Python slip on mufflers it is time to change to either a good 2-2 Cycle Shack, AR, Python III or a 2-1.

[twfreightman]

The Pythons were Dual Slash Cut 2 into 2 with removable baffles. John did work on my baffles but said the pipes were still causing the problem. I am switching to a V&H Pro Pipe HS 2 into 1. Then...I will either take it back to John in Joplin for tuning, or I found a place in Tulsa called Kinetic Playground that I might go to.

[CD]

That explains it a little better. The Python line is a house brand of Drag Specialties. The original Pythons and the Python II's were made by AR Khrome Werks and had removable baffles. Python III's are made by Vance and Hines have welded non removable baffles and a oretty significant design change.

The Python II did exhibit reversion like you are seeing and the best bet is to change them out. The Pro pipe is a good choice and we do sell a ton of them. Thunder header is also a good choice but pricier.

[twfreightman]

Got one ordered from you right now. Great on line web sight. Great price. Great forum. Looking forward to getting it on! Thanks much.