Oversize valve questions

[air]

I am going to have larger valves put in my head when it is ported.
I dune about 75% of the time and trail ride the rest.

I am looking for input on size +1 or +2
Best Brand?
Where to Buy

[Colorado700R]

Air,

I think part of this equation will depend on what head you decide to run and how extreme you want to go with P&P. 

Because of the different flow dynamics and overall chamber design philosophy differences, i don't think there is just a one size fits all valve decision right now.

Just my .02


Aaron

[air]

A local porter is doing it for me.
He ported a head for a stock bore 12.5 to 1 660 that used to kick my ass.
I will see what he recommends, just trying to get a jump start on the winter build

Is a x2 0r x4 cam worth the expense over a stage 3 hotcam

[Colorado700R]

If I was going to build my quad for your purposes, I think the x-2 is a great option.

Aaron

[air]

I have a stage 3 now.
just wondering if the gain is worth the $$$$$

[Tim Barker]

+2 in and +1.5 ex is what we have found works for us.

[air]

My build is a 11:1 stock bore 5 mil stroker, And I do not want to go too big

[DL700]

no such thing as too big of a motor  :grin_nod:

[Krandall]

SandDragon had Bo do a +1 (intake only) I believe in his 727. Bo found that the Exhaust side was already to big for what was needed.

[Tim Barker]

SandDragon had Bo do a +1 (intake only) I believe in his 727. Bo found that the Exhaust side was already to big for what was needed.

He has not found the airflow yet to need bigger exhaust valves.

         this is not a slam on Bo

[1badazz_700r]

I have the T-rex port with +1 intake valves, and X-4 cam, with je 12:5 piston. Im very happy with this combo/ I always want more though may do a big bore and stroke it over the winter. If not though im still happy knowing how strong mine runs

[VelociRaptor]

SandDragon had Bo do a +1 (intake only) I believe in his 727. Bo found that the Exhaust side was already to big for what was needed.

He has not found the airflow yet to need bigger exhaust valves.

         this is not a slam on Bo

None taken. I know were the flow is but chose not to pursue it since 90% of my customers are trail riders and 250cfm @ .400" exhuast flow is plenty for that application.

[Kenny]

 Stock size exhaust valves will work very well with +1mm intakes that have been mildly ported. A larger intake port with + 1 valves or exh with lower throat percentage will work well with + 1 exh valves. I personally use a smaller throat percentage on the exhaust than some, but I have a very tricky bowl shape. I know your porter has a wet bench, so you need to get with him on your goals and his preferences.
To make any kind of real recommendations that are not just generalizations, we need to know what throat % he likes to run on the intake and exhaust. If you haven't gotten to that point in the planning, just remember that the short turn shape, tulip angle, and valve seat cut angles(and widths of those cuts) go hand in hand.

I would recommend you using + 1 int and exh(to start) to make a good fuel pattern in a stock bore. There are ways to get a better pattern with big valves in the stock bore, but they are either a compromise or complicated. If your guy has the capability of flowing at 40 or 80 in/hg, do it.

Forget about high velocity. You will find out why with higher pressure drops. There are people out there doing high velocity style porting that are flowing air so fast that the fuel separates. Engine failures are not uncommon in these conditions. The only way to really study this is by observing the burn pattern on the piston(and chamber). These suggestions are only geared to the 700 based engine, and they are intentionally vague

[Tim Barker]

what does Kenny know

[air]

Thanks Kenny.