i did a search but nothing to informative. i am in the process of building a high hp gsr hopefully in the 4-500 hp range. what valves are most of you guys running as in diameter wise. i called some places and they told me to use stock valve sizes. some other guys told me to go .5mm over on bot intake and exhaust, and finally my friend told me to go 1mm on the exhaust to make them same? btw i will be using gsr cams. tia. choiboi.

 

I'm no expert by far, but I have had good results using stock valves with Crower valve springs, retainers, and cams

 

no expert either but I will probably go with .5 over on the exhaust. recomended by a couple of socal head guys.

 

If your using a cam that allows oversize valves use .5 mm on the intake and 1 mm on the exhaust.

 

it's NOT the cam that aloows valve sizing, it's the placement of the valves. if you go more than .5mm overstock on both they have a higher possibility of touching udner load and high rpm, this causing a floating and blown motor. you could go 1mm on the exhaust or .5 on both but on most honda stuff anything more can be hazardous.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by oscarmayer &raquo;</TD></TR><TR><TD CLASS="quote">it's NOT the cam that allows valve sizing, it's the placement of the valves. if you go more than .5mm overstock on both they have a higher possibility of touching under load and high rpm, this causing a floating and blown motor. you could go 1mm on the exhaust or .5 on both but on most honda stuff anything more can be hazardous.</TD></TR></TABLE>

Actually it is the cam that dictates such a occurrence, let's not forget what pushes the valves down and what keeps them there for the desired amount of time ( A cam for those who don't know). And considering alot of the Hot Rod class racers have made 900+fwhp on stock cams this should be a consideration. As FKNED said 1mm exhaust, .5 intake makes a ton of power on FI apps, this knowledge comes from experience not guessing.
and, Size of a valve won't cause it to float, valve springs do this, make sure you use a quality valve spring package with any FI app.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by oscarmayer &raquo;</TD></TR><TR><TD CLASS="quote">it's NOT the cam that aloows valve sizing, it's the placement of the valves. if you go more than .5mm overstock on both they have a higher possibility of touching udner load and high rpm, this causing a floating and blown motor. you could go 1mm on the exhaust or .5 on both but on most honda stuff anything more can be hazardous.</TD></TR></TABLE>

Please explain to me how load makes valves touch each other??I must be missing something .And btw no matter what size valve it is stock or oversize if they float,(which is a valve spring problem not valve size,Thank you Dave), then they most likely will hit each other .