head porting

[ww228king]

does anybody have any info on porting a 400ex head...i have finished my exhaust side and was wondering about the intake...i know they say to leave it rough so the air and fuel can mix, but can you port that side a lil too?

[zeppelin]

you can but it would be smart just to let someone do that side for you, the intake is much more touchy than the exhaust side you dont want to ruin the whole head

[ww228king]

thanks.....anybody else?

[bwamos]

A agree with the above.. you really need a flow bench to do intake side porting.

Intake velocity is more important than volume. Air is elastic. You want the intake to keep drawing air for a short while after your piston hits BDC.

If you want intake porting, I'd reccomend taking it to a pro. It's honestly one of the few things on the quad that is NOT a do-it-yourself job.

[kingdingaling]

As long as you don't hog out the ports or change the shape of the ports too much, you will be fine. As stated before, you can't really do a professional port job without a flowbench, but you can still increase airflow without hurting velocity. I haven't seen a 400ex head but on my 250x I nife edged the divider, cleaned up the casting, and did a little bowl blending. I felt a major increase in performance.

One of the most important thing to remember while doing a port job is that it always easier to take away material than it is to put it back!

[DEVINF450R]

My brother is a honda/polaris/kawasaki mechanic and he did mine with a dremmel tool, aluminum sand paper, and a solvent washer. I get GREAT results from mine, but we made sure to not take too much off. only smooth out the burs and casting seams

[bwamos]

Aye, if you just clean it up, that would be fine.. remember to leave it rough in the intake side. ;)

[kingdingaling]

As long as you don't take anything finer than a cartridge roll to the ports, then
you'll be fine. Also, a trick I learned the other day: If you take sandpaper or DA paper and sand the exhaust ports, starting with about 120 grit and working your way down to about 400 grit, it polishes the ports up real nice. It also lets you feel if there are any low spots.

I don't know if the power gains are worth the trouble, but anything helps right?

[1fst400]

I have a vilocity port job on my 400ex. This is what it looks like on the intake.


About every 6 months I like to take the head off and cleen the carbon build up out of the exaust ports with a dremel and a felt tip.