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Discussion Starter · #1 ·
Anyone who is going to do any mods to the upper engine should consider porting and polishing their intake manifold. The chills and inclusions that are left in at the factory foundry are more restrictve to smooth air flow than most people imagine. The ports do not match well to the heads. there is about a 1mm shift that can easily be seen thru the manifold when the supercharger is removed. Correcting these two things alone will result in improved performance.
 

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I know I read somewhere that gasket matching the intake manifold and heads was bad if your heads were stock. It said that you'll actually lose power gasket matching unless you had headwork done.

EDIT: From intense's website, "If your cylinder heads are still stock, this mod is NOT for you. If you make the intake ports larger than the cylinder head ports via gasket matching, you will actually LOSE power due to airflow disruption" Referring to gasket matching.
 

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Discussion Starter · #3 ·
You don't want to make the intake ports larger than the head ports. You want to make the intake smooth and all six ports the same size. If you try and remove so much material that you compensate for the shift you will accomplish nothing. You want to move the intake over so that the ports line up with the head ports. 1mm is only .039" applying pressure on the intake as you tighten it down is usually enough to line them up. There is enough clearence in the roll dowels that time the intake to the head to make this possible.
 

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Since we're on the subject of intake manifolds...

Looking at the stock L67 intake manifold, it bugs me that the center cylinders (3 & 4) are favored since the they're the closest to the intake's opening. I wonder if there would be any gains if somebody designed a turtle back to help direct a smoother and more consistant air flow to the cylinders 1,2,5 and 6.

Nikos
 

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Discussion Starter · #5 · (Edited)
I believe you may be onto something. I use what us old guys call an "old man" to line up the ports. But, a turtle back (or spider as some people call them) would make it much easier. And probably be more effective. I can't help but believe it would help performance as well as add some uniformity to the air flow. I've never seen one offered anywhere for a 3800 engine. If anyone has,I'd be interested in where.
 

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Discussion Starter · #7 ·
You lost me. Your suggestion is a great way for port line-up. (Much easier with a die grinder though) But, how does that substitute for a turtle back?
 

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My responce was more for the port and polish part.
As for uniform airflow I doubt your gonna get it even with that due to the length differences of our runners. I think we are actually helped some by the blower pressurizing the mani is that respect though.
 

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Discussion Starter · #9 ·
Shawn,
I think we're helped a great deal with the blower pressure. Got to thinking about a spider style manifold. Though I think it would help on flow distribution, you wouldn't be able to close the hood. It barely closes with an intercooler. Guess thats why you can't buy one for our GTP's.
 

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The problem is really simple and there isn't much you can do about it. The runners would all be equal length and have roughly the same curvature to make it work wich would mean they would al be longer than the shortest runners we have now and maybe even longer than the longest. I just don't think any solution will help becuase you'll actually be bringing the flow DOWN to match the worst areas.
 

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Discussion Starter · #11 · (Edited)
You are correct. They would be longer. The formula they use to figure that (according to a well known manufacturer) is 1.3 time your longest runner.That takes into account the crossovers and the rise for your carb and or blower.
 
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