Intake manifold port size?
Thread Starter
Instructor
Joined: Aug 2009
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From: Waco Texas
Intake manifold port size?
Can anyone tell me the size of the stock intake port on an 89 L98 with stock heads? I've been searching and searching but cannot seem to find an answer. Maybe even the stock gasket port size? 
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From: Overland Park Kansas
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I'm pretty sure they use a 1204 gasket (1.23" x 1.99") Seems like they're 163cc and flow about 185cfm at peak.
Oh yeah...40lbs lighter than iron headed predesessors
Oh yeah...40lbs lighter than iron headed predesessors
Race Director
Joined: Nov 2003
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From: Overland Park Kansas
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That's funny (that you think it's funny) because AFR180's have a 1.23" x 1.99" intake port. And, they're considered direct replacement for gasket/port match. http://www.airflowresearch.com/index.php?cPath=24_25
1256/1204 are the same port size IIRC.
1256/1204 are the same port size IIRC.
Safety Car
Joined: Feb 2000
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From: Austin Texas
That's funny (that you think it's funny) because AFR180's have a 1.23" x 1.99" intake port. And, they're considered direct replacement for gasket/port match. http://www.airflowresearch.com/index.php?cPath=24_25
1256/1204 are the same port size IIRC.
1256/1204 are the same port size IIRC.
My stock heads on the original 43k mile motor have at least 3/16" material between the edge of the gasket and the port...my ported heads took it all the way to the gasket.
Racer
Joined: Oct 2007
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I measured a port on a stock TPI intake. This at the gasket surface and the ports vary somewhat.
1.155" width X 1.778" tall. The port narrows as it leaves the gasket surface. So the inside area is not near this large. I can measure inside if you want.
Edit: I could not stand my spelling anymore. very=vary
1.155" width X 1.778" tall. The port narrows as it leaves the gasket surface. So the inside area is not near this large. I can measure inside if you want.
Edit: I could not stand my spelling anymore. very=vary
Last edited by 1989TransAm; May 12, 2011 at 09:30 PM.
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Race Director
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From: Overland Park Kansas
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My STOCK heads CNC-ported just barely flow 230 CFM...comparing those AFR's to a stock head is a joke. They flow 260 CFM in street trim, and 270 CFM in Competition trim...so they are FAR from a stock flow. And just slightly bigger in size than the stock ports as well.
My stock heads on the original 43k mile motor have at least 3/16" material between the edge of the gasket and the port...my ported heads took it all the way to the gasket.
My stock heads on the original 43k mile motor have at least 3/16" material between the edge of the gasket and the port...my ported heads took it all the way to the gasket.
I still say the 1204 (or 1256) gasket is the most commonly sized gasket for replacement. (No idea why the OP wanted the measurements).
Safety Car
Joined: Feb 2000
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From: Austin Texas
When comparing AFRs to stock, I was ONLY referring to port size. You said the dimension I posted were too small. (Oops, they're smaller.)
I still say the 1204 (or 1256) gasket is the most commonly sized gasket for replacement. (No idea why the OP wanted the measurements).
I still say the 1204 (or 1256) gasket is the most commonly sized gasket for replacement. (No idea why the OP wanted the measurements).
I said the ports were too small (tongue in cheek) period. I wasn't referring to your post AT ALL. The stock ports are too small to make any reasonable power for an L98...
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From: Overland Park Kansas
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)Reasonable power is a relative term. 350hp is the number most commonly associated with the 113 heads (e.g., their so-called-limit w/o porting).
Safety Car
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From: Austin Texas
New C6's come with 430 HP standard. If you want to play with anything newer, 400 HP is a minimum of what you need.
Just my opinion...
Thread Starter
Instructor
Joined: Aug 2009
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From: Waco Texas
I'm trying to figure out if the intake manifold I have will work with my stock heads, because it has been gasket matched to a 1205.
P.S. 350hp seems pretty reasonable for an L98 on stock heads. Especially when they're rated at 245. That's like 100 shot
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The 1205 is a good amount bigger than the factory ports on the 113 head. I am having my heads matched to the 1205 gasket because the intake I am using an intake matched to that gasket as well. I think it will work, but its not ideal.
Thread Starter
Instructor
Joined: Aug 2009
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From: Waco Texas
Dang. So many options. I can either run with what i got, save up and wait for new heads, or pull mine and match them. How much difference do you think there would be by just slapping this superram on?
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From: Overland Park Kansas
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I remember seeing 1 or 2 reports of increases in the 40-50hp range from an intake-only swap (to a SR). I would expect that to have included a port match though!
Who knows how much it would hurt to put a 1205 intake on stock heads. My guess is you'd lose up to half the potential...meaning you wouldn't be terribly impressed with that swap alone. You'd feel it though.
Cam, port match, bowl-blend, and a SR would be worth it though!
BTW...1205 is 1.23 x 2.09"
Who knows how much it would hurt to put a 1205 intake on stock heads. My guess is you'd lose up to half the potential...meaning you wouldn't be terribly impressed with that swap alone. You'd feel it though.
Cam, port match, bowl-blend, and a SR would be worth it though!
BTW...1205 is 1.23 x 2.09"
