GT550 74' port timing.

[durgam]

Ive been reading various posts about raising the cylinders (and milling the top of the head the same amount of raise)on the 750's to better port timing. Is this or a similar practice feasable on the 550's as well. Im running Jemco's, Uni pods and its jetted for the both. thanks.

[ja-moo]

A very good Kawi tuner did dyno testing with lift kits. Didn't see much "gain" if the windows weren't worked over. And you still have to lower the port floors. It might save "some" work time, but is it really worth it. The 750 have problems with breaking into the water jackets. Normal porting might be a better way to go.

[tz375]

JA is correct. The reason for the lift plates on a 750 is because the water jacket is too close to the roof of the port and porting it is likely to break through.

Lane has had great results with a lift plate on his 750, but the 550 is a completely different animal. The trick is to plot all the ports and the pipe dimensions and then work out a BMEP/HP target and that defines the port time areas you need and then input the data into either TSR or MOTA and play with things like port direction and width, and blowdown timing until you get close to the target and then you will know what has to be done to the ports.

The other way is the empirical way - try it and see.

If you send me the port plot and pipe dimensions a few other details, I can do the number crunching. I will need to know what your objective is in terms of how much hp at what RPM and do you want it all top end or a super hard acceleration or sweet on the street or??

PM or email me and let's see what we can do to that bad boy.

[durgam]

Ill have to pull the cylinders obviously to get the plots. Ive gotta pull the right side anyways, to fix an exhaust stud. You just need the chamber dimensions right? length and diameter of each section of pipe?