carchitect

iTrader: (1)

On most multi-valve engines, I've found the OEM cams to be the largest restriction to flow. Increasing the port surface area or flow characteristics usually doesn't yield much of an increase unless you install larger cams. What I've seen a lot of flow increase happen at the installing more valve angles on the valve seats. I usually use 5-7 angles on the intake and exhuast and they have always worked out great for me. On the bowl side, at the exhuast side I use a 35deg and the intake side I prefer a 30deg. The valves are generally a non-interferance fit so 45 deg seats are whats usually recommended. The port side I use 60,67.5, 75, 80 and 85 deg cuts. Fortunately, Toyota has stuffed some large cams on the IS350 engine and I think the increased lift will overcome a lot of the casting flaws and imperfections since once the VE of the cylinder has reached its upper limits, porting the heads will only start to hurt the performance rather than help it. Race heads for this reason, as stated by Lobux, are not ideal for everyone.

BTW, there are two things I hate to do on vehicles. Thats porting heads and body work. Everything else I can do. But head porting and body work throw dust everywhere and I absolutely hate to do them. I'd much rather pay someone to have them done.

-Joe

lobuxracer

iTrader: (2)

The number of angles helps, but the most important thing is placement of the contact ring on the valve and the face width on the valve. A narrow face (1.3 - 1.5mm) with a properly positioned seat contact line gives a pretty big improvement. Stock cams are one of the things I mean when I say, it depends on what other things you address. Cams can help a lot, but they can also change the power characteristics, so choosing a cam profile is all about what you want from the engine. Four valve engines don't seem to like a lot of timing like two valve engines do, and if you don't measure port flow, you could easily install a cam with more lift than actually works (anything over 10mm better be going in a fully tested race head). I've seen this lots of times with 2JZ-GTE heads. Unless you do a lot of work to the exhaust ports, there's no advantage to anything over 9mm of lift. You're just adding unnecessary stress to the valve springs (and a lot more work calculating coil bind, preload, etc.).

Porting is probably the thing I like to do best out of all engine work. But I never do bodywork. I suck at it.