I am considering purchasing some oversized valves.
Does anybody have experience with these?

.5mm oversized:
http://cgi.ebay.com/ebaymotors/Supertech-S...1QQcmdZViewItem
1mm oversized:
http://cgi.ebay.com/ebaymotors/Supertech-S...1QQcmdZViewItem

Any comments on these? What would the outcome be? Naturally fitting more air in the engine would increase a little power, but are there other effects? Smoother performance maybe? I don't know... Are there any reasons not to do this? Would one NEED new retainers? Thanks a lot!

 

I would recommend upgrading the valves ONLY if you decided on increasing the compression in the motor. Oversized valves IMO won't help much on a stock internals with a bored out head.

Just my $.02 and I might be wrong.

 

Bump!

 

TTT... Surely more people have an input!

 

Another poster with no clue.

Head work when done correctly will give good returns NA and great returns FI. You must get the headwork done to see the value of the valves.

 

Consider the valves upgraded than! Thanks!

 

To get oversized valves, does one need to do other headwork (port/polish)?
Is there any gain or reason to go with lightweight Supertech OEM sized valves?

 

I'm not certain I understand this "oversize" valve issue.

Are you talking about intake and exhaust valves that are larger in diameter than the factory valves? If so, how much extra room is there in the combustion chamber to allow for a larger valve face?

From the pictures I've seen, there simply isn't any excess room to allow for a larger valve face.

Just wondering.

Drive Safe,
Steve R.

 

I think it's the doming in the face or the bottom contact surface of the valve to allow for more room? I am not sure, hence my inquiries!

 

Oversized valves go along with increases in the size of the bowl under the valve. (Yes you need porting) They also require new valve seats and usually guides be installed. Porting and polishing along with oversized valves will result in increased flow. Increased flow leads to increased hp.

Going with the light weight standard sized valves will give you no performance enhancement other than allowing more rpms prior to valve float. The combination with the titanium retainers results in a top end that can rev several hundred rpm more than stock safely.