who's ported there m7

[sledtahoe]

The m7 will need some TLC this summer thinking of porting it myself for a few extra ponies any thoughts or who does the best porting..

 

[diggerdown]

Don't really know who does the best but a friend of mine had his done by RKT along with a head, really ran great. Kelsey has a very good set up.

 

[ippielb]

I have an M7 that has the exhaust port opened by 1mm to the top. You need to run higher octane fuel with it, i run 91 octane. Raising the exhaust port, the higher the powerband range will be in the RPM range.

Here's what i took from RKTek

Take an engine with an exhaust duration of 182 degrees ATDC and install some domes (any domes) that yield.. say 170 PSI cranking compression.


OK, take another engine, exactly the same, except the exhaust duration is at 198 degrees ATDC (ie higher exhaust port) Now, install the SAME domes that the other engines has. Now, the cranking compression reads only 150 PSI.

Hmmm.... so does this engine require a different octane of fuel than the other one? Probably, but not what you think.. It , most likely, requires, a HIGHER octane fuel NOT a lower octane.

I know that the general conception among riders is that the higher the PSI .. the higher the octane needed.. Well, I just told you completely the opposite.
With the general consensus.. it would stand to reason that when ever you raise the exhaust port... you need to run a lower octane fuel because the cranking compression will, indeed, get lower with higher exhaust heights. Does this seem right?? What if you lowered the exhaust height? Would you then need a higher octane fuel because the cranking PSI would surely go UP?