Questions regarding siamesing the plenum...
Thread Starter
Melting Slicks
Joined: Jun 2001
Posts: 2,525
Likes: 1
From: Sarasota, FL
Questions regarding siamesing the plenum...
I have spent a few hours today porting and polishing my TB. Then I started on my plenum. Yikes is that alot of work with a die grinder! Tomorrow I am gonna put in a mill to hog out the big stuff. Now to my question...
I am contemplating siamesing the runner openings in the plenum. Then I was gonna port and polish the plenum end of the runners. Any thoughts on whether this would be a good idea or not? I can't think or any reason this would be bad, can you?
Thanks, Bob
I am contemplating siamesing the runner openings in the plenum. Then I was gonna port and polish the plenum end of the runners. Any thoughts on whether this would be a good idea or not? I can't think or any reason this would be bad, can you?
Thanks, Bob
Le Mans Master
Joined: Feb 2001
Posts: 6,398
Likes: 1
From: Loveland Co
Cruise-In III Veteran
Re: Questions regarding siamesing the plenum... (BobMachus)
hey hows it going, i am planning that mod soon, gotta wait to get a spare intake so i don't have to park the car. Check out the thread about that from a few days ago, i will see if i can find the link
Le Mans Master
Joined: Feb 2001
Posts: 6,398
Likes: 1
From: Loveland Co
Cruise-In III Veteran
Re: Questions regarding siamesing the plenum... (No Ordinary 91)
here you go bob
check it out http://forums.corvetteforum.com/zerothread?id=153200
check it out http://forums.corvetteforum.com/zerothread?id=153200
Thread Starter
Melting Slicks
Joined: Jun 2001
Posts: 2,525
Likes: 1
From: Sarasota, FL
Re: I can save you the hassle (89TripleWhite)
Actually..I was asking about siamesing the runner holes in the plenum, not the intake base (but that's coming!). Is there any reason that any of you can think of not to cut out the walls between the paired runner openings in the plenum? Thanks, Bob
Team Owner
Joined: Dec 2000
Posts: 90,675
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From: SE NY
Cruise-In II Veteran
Re: I can save you the hassle (BobMachus)
When I did my plenum I fluted the upper runners and opened up the plenum holes to match plus continued the fluting into the plenum.
If you are going to siamese the plenum, I suggest you extend the effort into the upper tunner flange, and round the separation in the flang to provide a smooth air flow transition. Of course you can take a sanding drum to the stock runner gaskets to match em up.
I see no reason to not siamese the plenum and upper runner flange. It just shortens the runner length a little (say ~1") and increases the effective plenum volume.
If you are going to siamese the plenum, I suggest you extend the effort into the upper tunner flange, and round the separation in the flang to provide a smooth air flow transition. Of course you can take a sanding drum to the stock runner gaskets to match em up.
I see no reason to not siamese the plenum and upper runner flange. It just shortens the runner length a little (say ~1") and increases the effective plenum volume.
Thread Starter
Melting Slicks
Joined: Jun 2001
Posts: 2,525
Likes: 1
From: Sarasota, FL
Re: I can save you the hassle (65Z01)
I see no reason to not siamese the plenum and upper runner flange. It just shortens the runner length a little (say ~1") and increases the effective plenum volume.
Bob
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Burning Brakes
Joined: Nov 2000
Posts: 1,040
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From: BowlingGreen KY
Re: I can save you the hassle (BobMachus)
I did this to my 90 last week. I cut down the EGR bumps in the front of the plenum and siamesed the plenum runner holes. I angled and rounded the walls that meet with the runners. I also contoured the runner openings and cut out a little of the divider between the runner tubes. You can get a whole set of oversized tpi gaskets from TPIS for $18. I've noticed that the engine reaches high rpms a lot quicker. I also removed my cats at the same time so that probably had a lot to do with the performance increase. I have not had a single problem from the porting though. :smash:
Le Mans Master
Joined: Jul 2001
Posts: 8,184
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From: Santa Maria, CA
Re: Questions regarding siamesing the plenum... (BobMachus)
I did this a coupla weeks ago also. If you think the upper is tedious, wait till you attack the lower! Wow it was a PITA but I did it. If you really stop and think about it, the work on the upper may not be necessary but then again, more is better(?). When my new motor is fully broken-in, I will do some runs to redline. It in theory should redline alot higher now.
Race Director
Joined: Aug 2000
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Cruise-In II Veteran
Re: Questions regarding siamesing the plenum... (89 Paul in cal)
Are you taling about cutting the wall down at the TB bores itself? Ive seen that done in a TPIS catalog...they siamesed the opening to the TB bores...however, look at the back of your TB and see where the gaskets cover..dont want to cut the middle wall down and find out the gasket is the only way to seal the back where the bores are,b from memory, this shouldnt be a problem.
Bt do check that first before cutting the middle wall down.
As for siamesing the runner holes themselves, thats fine...you can cut the walls down on the sides and open them to gasket size.You can also cut your gaskets siamese and slightly port back the runners themselves to form a "C" to sort of "divide" the incoming air into the runners, then just leaving them flat as they are.
May not do any real peformance gains but who knows? The more air you can fill into that plenum and runners can only help.
Bt do check that first before cutting the middle wall down.
As for siamesing the runner holes themselves, thats fine...you can cut the walls down on the sides and open them to gasket size.You can also cut your gaskets siamese and slightly port back the runners themselves to form a "C" to sort of "divide" the incoming air into the runners, then just leaving them flat as they are.
May not do any real peformance gains but who knows? The more air you can fill into that plenum and runners can only help.