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Author Topic: Plenum Porting  (Read 8718 times)

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Offline smackc4

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Plenum Porting
« on: April 15, 2005, 12:45:01 PM »
I'm in the midst of getting to my injectors on the '85 (good fun) - Have cleaned the plenum while it's off but here's the question :

WHY does each port (behind throttle body) have metal in the way of the airflow, at sides and bottom?



My ONLY 2 thoughts are:

1. Time saving on G.M.'s behalf

2. It actually helps 'swirl' the air before it meets the intake port...

I'm biased towards the second reason, but only because I don't want to grind it away and find my idle quality or performance/economy suffers!

I've searched the forum but only find mention of grinding it away once...Can someone who's DONE IT, PLEASE give me a learned answer on this ASAP before I put it all back together?

The setup as it IS, sort of takes away the theories of TB airfoils, smoothbore MAF -> TB etc when there's a dirty great blockage at the plenum!!!

Many thanks!
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Offline Vette Obsessed

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Plenum Porting
« Reply #1 on: April 15, 2005, 12:58:52 PM »
I can't answer WHY that metal is there but I ported it all out on my old plenum.

No difference to the idle and no other problems/issues.

I didn't feel a difference but I think L98's are a motor where if you make a lot of little changes they will add up to an increase.
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Offline MrC5

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Plenum Porting
« Reply #2 on: April 20, 2005, 10:30:41 AM »
If the engine is standard, porting the plenum chamber, will do very little to increase the power for the amount of labour out laid, even increasing throttle body size will have little effect on power for the money out laid.
BUT if you improve the heads, cam and exhaust system all these modifications will be felt as torque and top end power.
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Offline Ausrs

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Plenum Porting
« Reply #3 on: May 06, 2005, 09:01:35 PM »
that and some large tube or siamesed runners !!
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Offline 87Z51

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Plenum Porting
« Reply #4 on: July 21, 2005, 01:02:51 PM »
Ridges are there immediately in front of EGR entry holes so as to create swirl to mix EGR  gases.
Can be safely removed and whole of front entry smoothed with no ill effects if EGR system deleted.
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Offline 87Z51

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Plenum Porting
« Reply #5 on: July 21, 2005, 06:07:10 PM »
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