sspeed
12-11-2009, 04:20 PM
Been search around on the various Subaru forums and see lots of references to port and polish, but no real guts as to what that means at a granular level. For instance, do people usually just port match? Both intake and exhaust? Any bowl work? I had found this article and was looking at it as a guide....
http://www.popularhotrodding.com/engine ... index.html (http://www.popularhotrodding.com/enginemasters/articles/hardcore/0602em_cylinder_head_porting/index.html)
Here's my situation. Just bought a '98 Outback 30th Ltd. (DOHC) with a burned valve for a song. Have the engine almost out and will take the heads off and have them refreshed. I was thinking of doing a little porting and polishing while in there but want to narrow down specifics on what has worked for others... I found this interesting in the article, "Boundary layer airflow physics tells us there is little flow to be gained from surface finish, but in practice, significant flow gains are sometimes seen from polishing the ports."
I was also wondering, the new '05+ 2.5i seem way less sluggish off the line although the engine specs are nearly identical to the '98, is that all in the programming of the ECU which make them feel more powerful? Is there anything that can be swapped over from a different model for small gains? Forgive that question, I come from a DSM world where we put larger 1st gen throttle bodies on 2nd gens, 2nd gen TB elbows on 1st gen, 2nd gen axles on 1st gens, etc and every little bit had awesome improvements...
I went through the swap forums and though the WRX/STI swaps are interesting, the wiring and disassembling of the interior are not, so I'm just looking at small things while the engine is out...
http://www.popularhotrodding.com/engine ... index.html (http://www.popularhotrodding.com/enginemasters/articles/hardcore/0602em_cylinder_head_porting/index.html)
Here's my situation. Just bought a '98 Outback 30th Ltd. (DOHC) with a burned valve for a song. Have the engine almost out and will take the heads off and have them refreshed. I was thinking of doing a little porting and polishing while in there but want to narrow down specifics on what has worked for others... I found this interesting in the article, "Boundary layer airflow physics tells us there is little flow to be gained from surface finish, but in practice, significant flow gains are sometimes seen from polishing the ports."
I was also wondering, the new '05+ 2.5i seem way less sluggish off the line although the engine specs are nearly identical to the '98, is that all in the programming of the ECU which make them feel more powerful? Is there anything that can be swapped over from a different model for small gains? Forgive that question, I come from a DSM world where we put larger 1st gen throttle bodies on 2nd gens, 2nd gen TB elbows on 1st gen, 2nd gen axles on 1st gens, etc and every little bit had awesome improvements...
I went through the swap forums and though the WRX/STI swaps are interesting, the wiring and disassembling of the interior are not, so I'm just looking at small things while the engine is out...