question for you guys (I posted this in the All Motor forum too, but no response; and it is H related):
If I am currently running valves that are 1.00 mm oversize, but the installed seat width is the same as a stock size installed seat width, do I need to do any machine work or can I just pull out the super size valves and throw in the stock size ones?

 

To be frank....I don't know how to answer your question....
What's your setup? I don't think it's too wise to run oversized valves if you have any aftermarket camshafts - what's your purpose for running oversize valves?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AJBurks &raquo;</TD></TR><TR><TD CLASS="quote">To be frank....I don't know how to answer your question....
</TD></TR></TABLE>

So why'd you reply?

 

well, when i picked up my motor a couple of years ago, that was the beginning of the whole "oversized valve" trend. not that i'm trendy, but it just happened when i built my motor.

my point being, the stock valve seat sizes are intake .075" and exhaust .080". the valve seat size for my oversize valve spec out to the exact same; hence my question if it is possible to just pull the super size ones and throw in some stock size ones. valve job aside, i don't see any issues, but i would like to get some opinions from some head builders or those who know.

setup:
JDM SiR/S-spec head and bottom end. BIG cams going in; won't work with the oversize valves. $2k invested in the head already, hence my questioning.


Modified by iakona at 11:21 AM 3/11/2005

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LudeyKrus &raquo;</TD></TR><TR><TD CLASS="quote">

So why'd you reply?</TD></TR></TABLE>

Why don't you read my entire post and then answer the question yourself...stop being a dick - i asked him what he was trying to accomplish using oversized valves...

AND WHAT WAS YOUR REPLY FOR? YOU DON"T HAVE AN ANSWER EITHER I ASSUME.....SO WHY'D YOU REPLY?

 

If you did no machine work when putting in the oversize valves I would see no harm in putting back in stock size valves. If you had machining done when you added the oversize valves I would assume you should stick with the same size valve from that point on.

 

right, and i don't know if there was additional machine shop work done or not. i know that from the specs Manley gave me that the stock size valve seat and the oversize valve seat are the same. i'm thinking they will work.

 

The seat should touch the vlave in the middle (more or less) of the 45 grind on the valve. You can put machinist's blue (or sharpie) on this angle of the vlave and then rub the valve on the seat to see where it is contacting. If the head has a couple valve jobs already, then oversize valves will help maintain this contact position in addidion to sitting up a little higher on the seat (which helps compensate for seats that have been cut down some due to valve jobs). So short answer is: stock valves will probably work fine, but if the head has been worked over significantly or you just want optimum conditions then you should do some inspection and see what fits propperly. Also, more info on what has been done to the head, what you are trying to accomplish, pictures, etc. will help place your question in context and give people who want to help you more to go on.

 

thanks.

i don't have any pics because he neglected to take any in build process and the head was sent off, so i don't have much to go on except for what was relayed to me.

the purpose of the motor is to get as close to 230whp as possible (that's the goal anyways) on the stock JDM SiR bottom end pushing 11.2:1. head has full p'n'p, port match, everything. you name it. and this time when it comes out, it's getting fully balanced rockers, some more port clean up work, a full inspection, combustion chamber clean up work, and a thorough going over. it is my intention to not pull this head again for upgrade reasons.
it has Manley high pressure dual valve springs, Ti retainers, and valve locks. it will be getting JUN cams, STR gears, Ferrea valves, bronze guides, new seals, the aforementioned head work, rail, regulator, injectors, s200, P28, oil cooler, and more.
things i've wanted to do for a while i can finally get around to doing.

i hope this helps for more background on the motor.

QUESTION: if the seat has been cut back .005"/.06mm, are the stock valves still usable with the proper valve job?

 

Considering your performance goals and that the head has been fully ported, I don't think stock valves are what you want to use. It's hard to say for sure without measuring things, but my guess is that the seat has probably been opened up along with the port with oversize valves in mind. If you use stock valves, they will probably be heavier, they will seat deeper (affecting valve spring installed height), and will seat out near the edge of the valves. Weight alone is usually a compelling reason for aftermarket valves because you can usually save more weight with valves than with Ti retainers.

 

i was looking into the Ferrea sodium filled competition valves. lightweight, lighter than the oversize ones, and stronger material.

so why not a stock size valve then? i figured less material, lighter material, and better quality material at that. pardon my ignorance. i've spent the last week trying to bone up on my valvetrain knowledge to make the right decision.

one more quesiton: if the seats have been cut back, can i just replace them and then have full control over the new valve and seating surfaces?