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oversized valves

gsxin

Proven Member
76
0
Jan 13, 2005
McCook, Nebraska
due to my poor macanics work my head has to be rebuilt. Theier putting in oversized valuves. can I expect to see an improvement in performance? :)
 

DsMWookie

Proven Member
360
0
May 3, 2004
Birmingham, Alabama
not with poor mechanics skills........

Honestly I'd look into a port and polish if your doing all that and just standard sized valves with 3-5angle valve job. really depends on ur mods.
 

project_tsi

DSM Wiseman
2,699
113
Sep 4, 2004
Eau Claire, Michigan
yeah, you will not noticed any large power differences in +1mm ovesized valves unless your making some serious serious power, like the other guy said, a good porting and polishing job w/ a nice 3 or 5 angle valve job will yeid you more noticeable power than just adding +1mm oversized valves. hope this helps
 

eclpsd1

Proven Member
21
0
Dec 11, 2003
Westerville, Ohio
According to Slow Boy you will actually flow better with stock size valves than oversize valves on an otherwise stock flowing head. It will take a good amount of head work to make oversize valves worth it.
 

Polk

Proven Member
92
1
May 9, 2002
+1mm valves will hurt power unless the head has been worked over and running bigger cams. The stock size (aftermarket) valves will out flow +1mm at lower lifts (up to .350 lift).

Polk
 

eclpsd1

Proven Member
21
0
Dec 11, 2003
Westerville, Ohio
No you should use at least 272s and you will still need a lot of port work to make them worth it. Its not the lift alone that warrants their use.
 

dsmpower1

Proven Member
122
0
Sep 30, 2004
omaha, Nebraska
how much of a difference will 1mm o/s valves have on a ported polished head with valve job and proper head internals. what would be the difference with or with out them. :dsm:
 

lucuc0212

Proven Member
86
1
Jun 17, 2009
Abbotsford, BC_Canada
This question never got answered and not trying to thread jack, more adding to it anyway when running o/s valves would their be more lag. Just like running a large smim or
T.b., fmic ect it takes a bit away down low but give back up high is it the same or with proper p&p no matter the turbo ect. You'd just see gains. I understand that it's been said with out p&p, opening the throat, ect you'd get more from std size but what if u did yhe head work properly but
were only running a 16g would u just see gains all the way through. I'm running a 20g now but plan to go bigger (biggest 35r scale) so if all things the same if heads done right getting o/s would be good idea
 

pacn91

Proven Member
133
1
Sep 23, 2013
dallas, Texas
some consideration can be taken into having the valves unshrouded, (modifying the area in the combustion chamber, around the valves) when switching to oversized valves. As it will affect the size of the chamber This isnt favorable for guys who are looking the most compression possible.
 

JacksonAuto

Proven Member
753
126
Nov 21, 2005
Hanover, Maryland
Make sure the shop installing the valves knows how to do a proper valve job. Too often I see heads with oversize valves on a standard size seat. All this does is kill the flow and make the head perform worse than stock. Make sure they enlarge the seat using a Serdi type machine. When done properly you will see an improvement in airflow.
 
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