Anyone port/polish rb25det head?

[CKs240sxNC]

Just wondering as the topic says. Since i need all new pistons cause they were damaged when i got the motor ive been doing powercoating on the valve covers and a very mild port and polish...Anyone know how deep i am able to cut? Sure as hell dont want to cut into the water jackets even tho ive only cut off barely anything as of now, just enough to polish it...

thanks

[Imissmyturbo]

There was a post on skylines of australia board about head work on the 25. From what I remeber them saying is to clean up the exhaust ports and leave the intake alone.

[JonPowell]

The turbo will overcome WHATEVER in the intake tract, exhaust is what you wanna optimize on turbo cars...

[CKs240sxNC]

ok cool, i havent done the intake side yet, just exhaust, iam only on the second port , used about 5 polish bits each and about an hour of polishing on each of them, but damn are they smooth and bling blingin hahah :lol Ill take pics next week when im done

[Slo_240sx]

I love hand porting heads. you can clean up the intake a little but but you want it rough to have air turbulance in it so it mixes better with fuel. Port the heck out of the exhuast though. The way you are doing it is a no no. Work on all the ports at 1 time. Do a little section then move on. That way they are all almost alike. if you cut too much out of one then move on they arent to similiar. So for example cut a little bit out of the top then move to the next and after all of them go back to the first one and make another cut. Also you get the most power out of the throat of the port. That is the section right behind the valve seats. Make sure you DO NOT damnage the valve seat because then you are screwed. If you are good enough though, grind the heck out of the aluminum behind the valve seat and about a 1/2 upward and make sure there are no big angles it needs to be all smooth. After you're dpone you should be able to flow some good cfm numbers.-Alex

[CKs240sxNC]

yea my father is going to do the bottom of the head where the valves are, maybe in a month when he has time lol

[Phat_Optimo]

I ported the head on my engine. I always tell people to work the sort turn radius. Thats is the area right under the valves where the air turns down to go into the cyls (floor). Remember air wants to flow in a straight line. I haven't looked at an rb25 head but I am sure they are similar. I shaped the intake side pretty good. Most of the work was on the splitter between valves and some work on the short turn radius. Exhaust side I removed the bumps and cleaned up the casting lines. Chambers were hit with sand paper and then buffed out with scotch brite. Good luck. The rb heads definately need some reworking.

[WDRacing]

I ported the hell out of my RB20 head. Both intake and exhaust. I don't know why you wouldn't port the intake??? More aire in...more air our. Simple concept. At the very least remove the casting defects and port match the manifolds.

You can also use a flexhone to hit the intake runners. Polish the exhaust and leave the intake slightly ruff and you'll be golden.

WD

[CKs240sxNC]

thanks guys, your the best! hehe