Size of plenum openings
Thread Starter
Burning Brakes
Joined: Mar 2007
Posts: 976
Likes: 24
From: Raleigh NC
Size of plenum openings
Where can I find the size of stock L98 plenum openings for throttle body and runners at the plenum? I have a plenum that is ported inside and I want to verify the openings are the stock size.
Could not find this in the FSM or any other documentation I have.
Thanks,
Ed
Could not find this in the FSM or any other documentation I have.
Thanks,
Ed
Last edited by eogel; Jul 7, 2016 at 09:04 PM.
Safety Car
Joined: Jan 2014
Posts: 4,017
Likes: 492
From: Poughkeepsie New York
I've got a stock one I can measure but I'm on vacation at the moment. I'm sure someone has these measurements for you. I'll be back next Thursday if not. You might be able to find it online.
Team Owner
Joined: Sep 2003
Posts: 25,398
Likes: 2,742
OP - post the dimensions that you've measured that you'd like compared. You're looking for information so "show us" what you've got.
Have you compared new stock gaskets to your plenum?
I have an idea of what I'd expect if it were me but I've never owned a L98 so I've nothing just laying around to measure.
Have you compared new stock gaskets to your plenum?
I have an idea of what I'd expect if it were me but I've never owned a L98 so I've nothing just laying around to measure.
Last edited by WVZR-1; Jul 8, 2016 at 07:29 AM.
Thread Starter
Burning Brakes
Joined: Mar 2007
Posts: 976
Likes: 24
From: Raleigh NC
Good point WVR-1, thanks.
The openings where the throttle body attaches to the plenum measure 2” and the side openings are 1 9/16”. I did find what I believe is a stock gasket that goes between the throttle body and the plenum. The holes in it are 2”. This is the plenum I am trying to verify has stock size openings.
I have a second plenum, which has 2 ¼” openings at the throttle body mount and 1 11/16” openings on the side. Obviously this one has been more aggressively ported.
Both have been smoothed / ported inside to remove the rough edges that cause turbulence in the air flow.
Ed
The openings where the throttle body attaches to the plenum measure 2” and the side openings are 1 9/16”. I did find what I believe is a stock gasket that goes between the throttle body and the plenum. The holes in it are 2”. This is the plenum I am trying to verify has stock size openings.
I have a second plenum, which has 2 ¼” openings at the throttle body mount and 1 11/16” openings on the side. Obviously this one has been more aggressively ported.
Both have been smoothed / ported inside to remove the rough edges that cause turbulence in the air flow.
Ed
Team Owner
Joined: Sep 2003
Posts: 25,398
Likes: 2,742
I'd say it sounds as if it's "stock" or very near on the "runner"ports. I've seen tubes mentioned at being just under 1 1/2 (1.47) I believe so the 1 9/16 sounds to be what I expected. I would have mentioned Metric and 48mm is a stock TB and maybe 40mm or just short of that for the "runner" ports.
Your second sounds as if it's done for a 58mm TB.
Your second sounds as if it's done for a 58mm TB.
Last edited by WVZR-1; Jul 8, 2016 at 10:16 AM.
