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1turbo6
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248 Posts
Discussion Starter · #1 ·
Where can I find an procedure for DIY upper plenum mods? I just finished smoothing it inside and out but was wondering about boring the throttle body opening, size?
 

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Village Idiot
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Village Idiot
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No I don't bore the exit larger.

Would it help?

I doubt it. I've never seen any flow figures on the TB with the rear exit tapered out to 65mm but the chance that it will flow significantly more than a straight through 62mm is not likely IMO.

Does it complicate the boring process when done on a conventional lathe?

Greatly. Unlike the other vendor who did them, I don't have use of my employers CNC lathe with an automatic feed for the taper at the exit.

Does it complicate the plenum machining?

Yes. Besides the cleaning & beadblasting, There's both machine work and bench work with a die grinder involved in modfying the plenums and to open it up and transition it from 65mm at the entrance on back into the plenum body brings a risk of going too thin in an area along the top of the plenum unless you just make it a 45° angle there. I prefer less of an angle at that point.
 

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Village Idiot
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OTOH, if a person wants to have the TB exit machined, I'll offer to do it for an additional $40. Plenum portmatching would be an extra $25 over the standard price. Thanks. :)
 

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I'm not bitching, just curious...
Yes, I have one and yes I did have to spend some extra time with the plenum.
I just haven't had a chance to try one and was curious to know if anyone had. I know they were only offered for a short time, actually bought two but sold one to Bruce P., maybe he'll chime in.
 

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It's a 'G' thang
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So how much to port my TB and plenum Steve? :dunno: Also, what about shipping?
 

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Village Idiot
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Hey, I forgot about this mod I used to do on plenums back before the RJC Powerplate came along. This was basically a flow enhancement to get the air down quicker and help with the rear cyls lean / front rich condition. Probably put up the pics & info on the web 10 yrs ago. My old website has the pics at
http://home.att.net/~stevemon/Plenum.html
 

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1turbo6
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248 Posts
Discussion Starter · #10 ·
Thanx for the great info. I will bore the opening tommorow at work. I think I will hold off on the throttle body for now.
 

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stevemon said:
Hey, I forgot about this mod I used to do on plenums back before the RJC Powerplate came along. This was basically a flow enhancement to get the air down quicker and help with the rear cyls lean / front rich condition. Probably put up the pics & info on the web 10 yrs ago. My old website has the pics at
http://home.att.net/~stevemon/Plenum.html
thats what MPE does with their sheetmetal doghouse. he has a restrictor restricting air to the rear cylinders, from what i hear it works well. i have one of his plenums and 62mmTB but decided to go to a champion complete intake so ive been letting it sit and wait for somone to buy it lol
 

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It's a 'G' thang
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I can weld aluminum no prob, but I don't really want to cut out a piece of sheet metal. Steve, how much could you sell a precut piece of aluminum for, so I can do this at home. I would still have you port my TB of course. :)
 

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Village Idiot
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Should be $100 on the first one (and $20 each on those thereafter :wink: ) since I threw away the template I made for those weld-in plates.
I'll do it for $20. It may take some trial & error before I get one cut right but I got a big piece of aluminum given to me the other day so no problem.
 

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RealestVIN7 said:
I can weld aluminum no prob,
Then you might consider getting a spare lower intake, and welding up the areas between the runners, and then cutting the floor out. You can drastically, increase the plenum volume doing that. And, you also get rid of the rear cylinders running lean. I wound up adding about 8% more fuel to get the WOT AFRs back in line. It's also much harder now, to get the motor to detonate.
 

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It's a 'G' thang
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That sounds great and all, but I need to concentrate on getting what I got going right now. I can't afford a spare lower right now. I'll just do the plenum mods with a power plate for now. :)
 
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