Proof of the smaller exhaust valves of Turbo heads?

[douglas vincent]

I have two sets of turbo heads. Neither looks smaller too me compared to the 4 sets of NA heads I own.

I set of heads is 93. The other is off of Brandos,

[206er]

so you measured the valves and NA are the same? are the ports the same size?

[Matt Monson]

Yeah,
Did you measure them? I was the one who put that information out there, and it was because I measured them. The difference is +/- 1/16" IIRC. And I believe the ports are the same size.

But just look at the valves themselves if you don't have a caliper to measure them. The valves definitely have different casting stamps on them...

[douglas vincent]

Ok kids.

I measured two sets of turbo heads and two sets of NA heads.

Turbo heads have:
Exhaust 1.10 OD and are marked EX2S
Intake 1.22 OD and are marked lN1

NA heads have:
Exhaust 1.10 and are marked EX2
Intake 1.28 and are marked lN2

So we have two different sets of marked valves, although the exaust valves ARE THE SAME, but we have a 1/16 bigger intake valve on the NA heads.

As for the ports, I do not know.

[Matt Monson]

http://bbs.legacycentral.org/viewtopic. ... rent+heads

Well, not the first time I have gotten confused around here. I had it right the first time, but somewhere along the line someone (and it could have been me) got intake mixed up with exhaust, and it became urban myth...

[douglas vincent]

I wasnt accusing you.

[Legacy777]

Interesting.....that blows the smaller exhaust valve, more exhaust velocity theory out of the water.

So what effect does the smaller intake have? Maybe to limit power....

[evolutionmovement]

Improved low end torque?

Steve

[nzKAOSnz]

rememeber than a turbo is called forced induction for a reason, and even with a smaller inlet valve - will flow more through into the cylinder.

Im thinking it might have something to do with improving the top end of the rev range for the turbo (less mass so less chance of valve skipping), whereas a NA needs more air because it has to suck it in.

[Matt Monson]

I wasnt accusing you.

I didn't feel accused. I just wanted to own that I may have mixed people up.

Legacy777,
I don't know why this would throw out the port velocity idea. To my thinking, it actually supports it, and it going to lead to the crisp low end torque the Ej22T is known for...

[Legacy777]

I was meaning it throws out the exhaust port velocity theory. The only way I can see it have any affect is in the cylinder scavenging....

[musketeerracing]

Soooo, you might recall that I bought this SS and it turns out to have an open deck EJ22 block but I've measured the valves and the heads appear to be turbo.

I have the option of putting the engine back together with the turbo heads or the NA heads that I also have. I suspect I'll have a larger turbo soon too, and other mods.

So, what's the opinion out there on intake valve size? Is bigger better? Is the NA intake:exhaust valve size ratio inferior to the turbo valves? Was it maybe an emissions thing, or engineered to 8lbs of boost, or to provide longevity on certain fuel ie all things we don't care about?

Or does it matter?

A.