View Full Version : Exhaust ?

12-18-2010, 1:58 PM
How short can you go with exhaust pipes before it starts to burn valves? I want my pipes short
just don't want to burn the valves.

12-19-2010, 11:18 AM
my father was an aircraft mech during WW2, he told me the rule was 12" of exhaust to keep the valves from burning, and a "cool down" period before shutting off...[idle for a minute] my buddie TRI-MIKE just did a biuld and his pipes are cut at the lower bend [2nd bend from the head on TRI down pipes] so far so good, hasnt cooked a valve YET!
i would be more worried about what this will do to your state of tune! Know that all the factory triumph race bikes won with the smaller diameter pipes, seems they like the backpressure some! i have long high pipes on my performance modded chop and it took some experimentation to get just the right restriction in the pipes as this thing was SERIOUSLY "peaky" @ top end, seemed to "hunt" a stable RPM.....just a little backpressure smoothed this engine out and now it sounds fuggin great [runs great too!]
surprisingly, TRI-MIKE`s bike isnt that loud,i still suggest somr restriction for performance sake!

12-19-2010, 11:41 AM
Short pipes don't burn valves ! In proper jetting , cam timing , fuels and valve materials does . If you cut your pipes very short you end up with very little velocity to scavange the cylinder . but it makes great low end .
Besides Triumph valves pitt anyways and depending on the year of the head the seats are probly crap with only one angle ground into them . So unless you are rebuilding your head to I wouldn't worry about " burning " a Valve since the face is most likely pitted already .
One issue that people call " burning " your valve is when it is hot and you drop throttle and egine brake you can suck cold air in and aneal the face is small areas causing them to wear away but that is not burning up a valve since it was not over heated it was just softened by cooler air .

12-19-2010, 12:17 PM
I would like to cut them off right after the 2nd bend headed towards the rear. I my go with left side high pipes
but I like the blueish/purple look of the pipes I have. I plan on rebuilding the whole engine bottom to top. I don't want it to run like piss and not hold a tune with short pipes if I go that route.

12-19-2010, 1:03 PM
Optimum length for triumph headers is 36 inch longer or shorter you lose power

12-19-2010, 2:33 PM
If you go through rebuilding the engine and want it to hold tune as you say then why the F#$% would you run short pipes ? Thats like building a turbo charged motor then only running 1/2lb of boost it makes no sence .

If you just want a look then do it and suffer a bike that is finicky to run and try tuning it forever unless you understand theometrics and air fuel velocities so you can come up with a cam design to work with such short pipes
If you plan on riding this thing then run ex. pipes they to look cool you know . if you want to build a hot rod of a motor then make a 2 into 1

12-19-2010, 2:53 PM
I like the look of the high pipes so that's prob what I will end up with in the end.

12-19-2010, 4:44 PM
"I would like to cut them off right after the 2nd bend headed towards the rear."
TRI-MIKE`s pipes are cut right before the bend,,,, they blow straight down.......
heres one of mine: