SI valves

[SappySE107]

Ill CC the SI vs stock valves in a bit and let you guys know the difference. Eyeballing it, it looks like it will have less dish, as the width of the flat part around the face of the valve is a little more than the stocker. Depth looks the same, but only measuring it will tell us anything accurate:P

[TurboGTU]

I got about 8cc on the stock MPFI 2.8/3.1 intake valve. !!!

[Fedaykin]

I ordered the "Portflow" valves from them... do you guys know if they are lighter than stock?

[SappySE107]

Whatever valves Corey bought (SI, probably stock replacement series) are 8 grams lighter. I tried to CC the chamber last night but screwed it up so im about to go out there now and give it another shot. The margin is thinner on the SI valves, so its up in the air on compression changes between these and stock valves.

How much are the portflow valves? I think they just undercut the stem some..which weakens them. Ferrea is the way to go on quality valves. Not sure what they may have for pushrods, but they say they have nothing for the DOHC.

[Fedaykin]

well mine isnt a DOHC, i was thinking about ferrea...

the portflow series are twice as much as the stock replacements....

so you think that the valves are giong to be weaker? shiZA!! does this mean that I cant rev as high or what? i dont want to break a valve and wreck my engine... what is your suggestion?

[SappySE107]

You need to ask SI how they do their valves. They are cast, not forged, and they grind them down so if they grind down on the stem, its gonna get weaker. Ferrea compresses theirs so they strong. If the portflow are 25 each, ferrea should be about the same. I would definetly go with ferrea over SI.

Maybe SI does compress theirs as well, but I highly doubt it.

[Fedaykin]

that sucks. I should have called ferrea. damnit.

[SappySE107]

I could be wrong, and their valves could be more than adequate even cut down for their port flow series if in fact its what im thinking of. I just know the stock replacement series really needs an angle cut in the backside of the valve to get back to stock valve shape. The machine shop I use for valve jobs told me SI valves cannot be undercut or ground on the stem as the portflow series are. So perhaps they do it differently, but you need to contact SI and see what is up. Thats the only way to know for sure.

[SappySE107]

Ok, measured the displacement with stock valves and with SI valves, using the same combustion chamber. I got 27cc for SI and 28.2 with the stock valves. Ill probably be checking this again after I do my combustion chamber work on these heads to verify the 1.2 difference.

[Fedaykin]

that gives us more compression! AWESOME!@!@

on another note... I removed a little material doing my grinding inside the combustion chambers.... I wonder if i fubarD the compression ratio.... not much, i just smoothed some lines, etc...

[SappySE107]

Show me a picture and ill be able to give you an idea once I do my work on these heads and compare. I gotta match them and its my first time measuring them let alone matching:P Ill have plenty of practice CCing chambers when im done, thats for sure:P

[Fedaykin]

i dont have a good pic right now, i'll take em this week sometime.

[TurboGTU]

Did you use a pexi glass a dropper and a needle?

[SappySE107]

I used a burrette, plexiglass, and some grease.

[Fedaykin]

Well I emailed SI valves with questions about their product....

"Hi, i just recieved some of your portflow vavles for my 95 3.4 camaro. I was wondering how you make your valves and how they handle RPMs.... I guess i'm looking for some reassurance that they can handle 7000 RPMS or so... I dont have a race engine... but i'm hoping to build a street engine with 7-7500 RPM goals, and I will be turboing later...

other companies such as ferrea compress their valves for strength when narrowing the stems... what is your approach and what do you do to avoid weakening the portflow series valves?"

And their response was:

ERIK,

THERE IS NO SUCH THING AS "COMPRESSING A VALVE" TO INCREASE IT'S STRENGTH. WHOEVER TOLD YOU THAT HAS NO IDEA WHAT THEIR TALKING ABOUT. VALVES ARE MADE FROM STEEL OR STAINLESS STEEL FORGINGS FROM BAR STOCK. THESE FORGINGS ARE DONE WITH THE MATERIAL NEAR WHITE HOT. THIS FORMS THE HEAD OF THE VALVE AND THE STEM AS ONE PIECE WHICH IS VERY STONG. ALL OTHER VALVE FORMING OPERATIONS ARE DONE ON GRINDING AND MILLING MACHINES FOR FINAL SHAPE. UNDERCUT STEMS ARE DONE BY GRINDING. THERE ARE ALSO TWO PIECE VALVES WITH THE HEAD AND THE STEM JOINED BY FRICTION WELDING. THESE ARE USED MOSTLY IN O.E. APPLICATIONS TO CUT COSTS. THE VALVES YOU GOT FROM US WILL EASILY WITHSTAND YOUR RPM REQUIREMENTS.

THANK YOU,

PETER WIGBELS
GENERAL MANAGER