to port or not to port, that is the question

[mtn goat]

So what does porting a head really do for you, Its a 258 and just wanting to know if its worth the work.

[linskej]

A good three angle valve job would also improve the overall flow of the head. Don't expect a huge HP increase, but it should help. The factory usually doesn't smooth the valve area of the head. By porting the head, the insides of the valve area is smoothed so that the flow of both exhaust and air/gas mixture flows better without restrictions. Besides if your engine has any ware on it then it probably needs head work.

Hope this helps,
John

[JeepFreak]

The 258 head design was not the best to begin with. The intake port makes a 90 degree turn from the intake into the cylinder. It will never flow real well no matter what kind of porting you do. This is why allot of folks are adding the 4.0 HO head to the 258. Is said to add 40 to 50 horses just by bolting it on.

[Rogue]

with the right person doing it, it can do a lot for you. i'm not trying to discourage anyone from backyard engineering BUT if you change the shape of the ports in the head the wrong way then you can actually slow down air charge velocity causing fuel droplets to fall out of suspension(atomization) and cause uneven flame fronts in the combustion chamber actually causing you to have less power then when you started. since it would take a lot of material removal to actually see gains in airflow it is a tricky balancing act. before any of the nay sayers come out of the closet i learned this the expensive and hard way! i ported my own heads after reading a how to article, took them down to the shop to see how good of a job i actually did only to find out I didn't! :mad: the HO head sounds like a good option