 2.0l Heads with 48/38- too big for a 2258? |
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| tornik550 |
 Aug 15 2011, 02:41 PM
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#1
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Senior Member  Group: Members Posts: 1,248 Joined: 29-January 07 From: Ohio Member No.: 7,486 Region Association: None  |
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? |
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Replies(1 - 10)
| yeahmag |
Aug 15 2011, 03:23 PM
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#2
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Advanced Member Group: Members Posts: 2,422 Joined: 18-April 05 From: Pasadena, CA Member No.: 3,946 Region Association: Southern California 
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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...
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| Jake Raby |
Aug 15 2011, 06:02 PM
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#3
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Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
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. |
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| tornik550 |
Aug 15 2011, 06:14 PM
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#4
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Senior Member Group: Members Posts: 1,248 Joined: 29-January 07 From: Ohio Member No.: 7,486 Region Association: None |
QUOTE(Jake Raby @ Aug 15 2011, 08:02 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. Ok thanks. Just what I was looking for. |
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| Jake Raby |
Aug 15 2011, 06:19 PM
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#5
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Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
Bigger isn't better.
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| r_towle |
Aug 15 2011, 07:11 PM
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#6
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Custom Member Group: Members Posts: 24,585 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States
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only fun at WOT.
The rest of the time it will just foul the plugs and suck gas. |
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| Jake Raby |
Aug 15 2011, 07:41 PM
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#7
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Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
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. |
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| Mike Bellis |
Aug 15 2011, 11:14 PM
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#8
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Resident Electrician Group: Members Posts: 8,345 Joined: 22-June 09 From: Midlothian TX Member No.: 10,496 Region Association: None 
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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 (IMG:style_emoticons/default/biggrin.gif) |
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| HAM Inc |
Aug 16 2011, 07:04 AM
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#9
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Senior Member Group: Members Posts: 846 Joined: 24-July 06 From: Watkinsville,GA Member No.: 6,499 Region Association: None |
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. |
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| Jake Raby |
Aug 16 2011, 11:08 AM
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#10
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Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
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 :-) (IMG:http://www.914world.com/bbs2/uploads_offsite/www.rdtlabs.com-1095-1313515111.1.jpg) This post has been edited by Jake Raby: Aug 16 2011, 11:18 AM |
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| r_towle |
Aug 16 2011, 11:21 AM
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#11
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Custom Member Group: Members Posts: 24,585 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States
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QUOTE(HAM Inc @ Aug 16 2011, 09:04 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. True, and lots of fun. Rich |
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