anyone know what is the largest valve I can upgrade a set of ls6 heads? (or even if that's possible)

looking to increase flow here and figure well doing a pp might think about throwing in bigger valves


... any thoughts?


btw I cant seem to find ANY information on this via the search engine.

 

YES and NO.

Bigger valves will get you more volume of flow, but less velocity of air flow ( ie more but slow air flow vs less volume but faster)flow More volume of air that is moving slower, will be felt in loss of low end tq and less throttle response.

Some heads flow better at lift .600 then others, but do not flow as well with the lift of .200 to.550

same with different cams provided different results.

Ask yourself what you want your car to do? Then talk to a engine builder for suggestions.

There are some very good PP LS6 heads out there. TSP, Patriot, ET, Trick Flow and of course AFR.

Good Luck

 

thanks.

Sorry if I wasn't being clear, I was trying to find out about clearance to the cylinder wall .. i.e. could i go with a 2.02" intake / 1.570" exhaust and be okay. I think I might call a pro shop with that question though. I realize it'll reduce the velocity and might affect the swirl but I figure a nice cam will a steep ramp can help in that area.

just so you're aware I'm going the way of the poor man's mods and doing it myself. I figure these companies had to start somewhere .. so why not.

I plan to do a P&P on a set of 853s or if i can find a cheap enough set I'll do the 243s either way I'm going to take a gamble on it. I've been reading a lot of literature about it and finally feel I have a good understanding of what's going on.

I've got a nice cam in mind based on a ThunderRacing cam, their Cheatr cam, which will give me .601 lift on the intake, I don't want their cam specifically though I will see about doing a custom grind so I can get exactly what I want.

I'm mostly looking for power above 2k so if it's not really strong off idle, that's okay with me. I'm starting to look into road racing this beast

and I figure the reduced throttle response I can maybe compensate with a ported TB.

Incase you can't tell by now, i've been thinking about what I wanted to do for a while. lol

thanks for everything.

oh and btw ... your advise regarding the brake fluid was great (about 2 years ago now) I've been running the Motul 600 and my brakes are still great.

 

Good Man. Lots of reading and asking questions before you begin.

Good Luck on your project. Post info when you can.

and your welcome .

 

I have the PP LS6 STAGE II heads. They have 2.02" intake and 1.57" exhaust valves.I was told that they are worth about 5cfm.I am running a custom cam with them that is slightly bigger on the intake duration than the cheater cam.I am running headers so I cut down on the exhaust duration.Throttle response is fantastic with this setup.The trick IMHO is the CR. I am running 11.2 CR and this realy helps low end torque and throttle response. My mods are in my sig.

 

thanks for the input. your setup is pretty close to the one I want to run.

I was however thinking of doing slightly larger exhaust valves. maybe the 1.60" but I still have to get in contact with a rep. builder before I go ahead.

I have read bigger valves aren't necessarily better but then it goes on to say unless you're running above a .600" lift .. lol so in my case, maybe they will be better.

nice times btw .. esp from an A4.

 

The trouble with larger valves is it can start to get some valve shrouding against the combustion chamber wall, which will reduce air flow. So combustion chamber size plays a factor into it. Also bore size.
IF you are doing your own work, maybe you can unshroud the valve a little without going past the bore size, and then mill the heads to bring the compression back up.