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Posted by: tornik550 Aug 15 2011, 02:41 PM

My buddy has a set of 2.0l heads that have 48mm intakes and 38mm exhaust valves. I am using weber 44idf's, My cam has .500" lift.

I intend on using my car for street and auto x.

Is this a reasonable set of heads for my setup or should I go smaller?

Posted by: yeahmag Aug 15 2011, 03:23 PM

Those are HUGE. I'd post over in Jake's forum, but I suspect that is too big for almost any engine. Your port velocity would be next to nothing...

Posted by: Jake Raby Aug 15 2011, 06:02 PM

That big intake valve just gets in the way of true performmance.. Its heavy and hard to control.

I don't use a valve that big on a 3 liter.

Posted by: tornik550 Aug 15 2011, 06:14 PM

QUOTE(Jake Raby @ Aug 15 2011, 08:02 PM)

Posted by: Jake Raby Aug 15 2011, 06:19 PM

Bigger isn't better.

Posted by: r_towle Aug 15 2011, 07:11 PM

only fun at WOT.
The rest of the time it will just foul the plugs and suck gas.

Posted by: Jake Raby Aug 15 2011, 07:41 PM

And it won't even make power at WOT.

Bite the bullet and buy good heads, else you'll waste lots of time and effort.

Posted by: kg6dxn Aug 15 2011, 11:14 PM

You could buy them and make a turbo T4... Velocity would not be a problem then...

Oh wait, I forgot... You can't turbo a T4

Posted by: HAM Inc Aug 16 2011, 07:04 AM

If the heads have been welded so the intake ports can be enlarged enough to support the full potential of a 48mm valve, and you have the right cam and exhaust with more induction than was listed and want to turn some revs, then the large valves will work okay. Otherwise you will not have as much engine as if you ran the HAM/RAT LE-200/V4.0 heads with 44x 36mm valves along with the appropriate cam, exhaust, and induction.


[quote]You could buy them and make a turbo T4...[/quote]
Controlling those giant (heavy) intake valves under boost would be a challenge at any boost levels/rpm's worthwhile for such big valves.

quote]Velocity would not be a problem then...[/quote]
N.A. or Forced Induction, velocity is always important.

[quote]Oh wait, I forgot... You can't turbo a T4 [/quote]
Any engine can be turbocharged. My professional opinion is that the T4 is not a good candidate for it, at least not with any bore over 91mm. The heads don't have the strength for it.

Posted by: Jake Raby Aug 16 2011, 11:08 AM

Just like Len said.. The port can't support the valve without welding at anything above the 44mm valve size range.. Using a valve with more potential than the port that can feed it, does nothing... Except add valve train mass, require more spring to control, add friction and other mechanical losses and REDUCE power.
Here is a proper port to support a 48mm valve with shape, volume and velocity all taken into consideration.
The result was 284HP on pump gas, normally aspirated and at less than 6,500 RPM.


And now a port optimized for a 56mm intake valve :-)

Posted by: r_towle Aug 16 2011, 11:21 AM

QUOTE(HAM Inc @ Aug 16 2011, 09:04 AM)