Mild tuning cam

[Penner]

Left side is the stock intake cam
Right side the stock exhaust cam

For some reason Triumph made the exhaust cam bigger
As there will be quite a few cams around that have been replaced by tuning cams, it should be easy to get a stock ex-cam and use it at intake.
The power gain will not be huge, but if you are doing valve check anyway, it is not a big job.

Prost

 

[Claviger]

Is there any mechanical reason the exhaust cam won’t work on the intake side? Has anyone done this yet?

Seems a very economical way to pick up a few ponies without having to change out springs.

 

[1olbull]

The profiles look very different to me. What would this do to the duration and lobe centers?

 

[Penner]

Don´t worry. It will work.
The gain will be something like 10hp.
Anyway you won´t have to change springs with most tuning cams.
Stock springs are ready to take much more.

 

[Penner]

I have made a lot of the 1050cc Triumphs engines with the hotter 955 cams. Good results and no issues. They were made for that.
With the Rocket engine it is pretty the same.
I am absolutly sure that they made it for about 180-200 hp.
Then some ***** marketing guys told them to keep it at 140.
That is why compression is so low and cam timing is ridiculous. They even had to use some electronic restrictions.
But the rest of the motor is still willing to take much more.

 

[DEcosse]

At least per the Std/Classic specs the lift is the same for both cams (8.3mm) - the duration (at 1mm lift) is only slightly wider for the exhaust cam at 232 deg vs 220
I doubt this will make much difference

There is well documented mod of using 955 Daytona exhaust cam as inlet on 1050 engines, and swapping 1050 inlet to the exhaust - this gives a good difference in lift and duration vs stock 1050 but certainly is much more than the difference you propose on the R3 motor.

 

[Penner]

You are right.
A 10hp gain is quite optimistic.
And I have never tried it as I always used bigger tuning cams.
232 to 220 is about 5% improvement.
As the stock intake cam is very restrictive any longer opening will do a good job.
Considering a unrestricted Rocket with stock cams, Y-pipe and Ramair making about 150hp, I think it will be at least 5 hp.

 

[DEcosse]

... 232 to 220 is about 5% improvement.
As the stock intake cam is very restrictive any longer opening will do a good job.
... Considering a unrestricted Rocket with stock cams, Y-pipe and Ramair making about 150hp, I think it will be at least 5 hp.

You are taking simple math in the opening duration and applying that same factor directly to the peak hp
You may in fact have ~5% duration increase but this is at very modest opening i.e. 1mm
However you can see the profile is wider coming up to max lift, so sure, the valve will be open wider for longer.
But sorry, I doubt that is going to transpose directly to 5hp gain.

 

[Penner]

Simple math with 5% longer opening would mean a 7,5hp power increase at a motor that has 150hp.
But you are right. It is not that simple.
There is another point to consider. Dynamic compression.
If you have a look at the torque graph you will see, that load at higher revs is pretty low.
If you improve that, compression will go up too.
I am pretty sure it will be at least 5hp, but we will have to see.

 

[ThingKing]

I like the idea of it. Very simple, cheap and neat.