Modified / Enlarged 12 Valve Plenum & Runners; - Alfa Romeo Bulletin Board & Forums
 
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post #1 of 5 (permalink) Old 03-05-2011, 12:20 PM Thread Starter
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Modified / Enlarged 12 Valve Plenum & Runners;

Just as a matter of interest; we are out of the 50mm custom intake runners, but I sold my last set to a guy with a big-bore 12v project, so we modified the intake plenum utilizing two standard Milano / GTV6 intake plenums!

I sectioned the one off center-left and the 2nd plenum off center-right and had my TIG guy weld the two larger halves together. the bottom was jigged off of the position of the standard runners and then we made a brand new bottom plate, machined rings and welded them on, radiused the inside edges of the down-stubs and welded the bottom plate to the new plenum.

I had it finished in a 2000 degree thermal heat-barrier coating and now the customer can just source some 50mm silicone tube to cut his connector stubs and buy some nice T-clamps!

I figure the volume is about 40% higher.
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Full-Race 6-Speed Getrag 3.7 Litre 24v Milano; 1993 155 TS 2.0; 1999 24 Valve 3.0 916 GTV; 1995 164Q; 1987 Milano Verde; 1966 GTV Stepnose
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post #2 of 5 (permalink) Old 03-05-2011, 01:40 PM
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Nice work, JJ !
Are you taking orders or this time showing from a project? Have seen this solution on a 24V engine. Could these parts(yours) be used on a 24V engine also? The 3,2L GTA engine has an inner diameter of 43mm, so 50mm would possibly be too large?

Here a photo of a V6 24V with double plenum:
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post #3 of 5 (permalink) Old 03-05-2011, 01:42 PM
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Wow, that was a lot of work. I hope it gives good results. For what it's worth, I wouldn't bother with T-Bolt clamps there. They are difficult to work with in a tight spot, and the higher clamping forces are not needed in that location.

Greg
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post #4 of 5 (permalink) Old 03-06-2011, 11:03 PM Thread Starter
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Thanks!

Nah - the 50mm runners was a speculative project that I funded in part and it cost thousands of dollars to kick off initially!. We had to order 50 pieces (got two left - wonder why...!?) It took me 6 years to get my money back and I just sold the last full set (with this special, one-time, enlarged plenum), for a big-bore project down in Oz.

The solution works on a 24v and I like the symmetric look of the 12v plenums, but they are small and the flow to the two forward cylinders has always been a questionable issue... At least the enlarged plenum addresses the additional back-stop requirements of a larger displacement motor. Still, Id probably do a custom plenum instead, or convert to the flopped-over-to-the-one-side look of the 164-styl;e plenum with the enlarged / expanded section at the rear and the intake at the center of it all like I have done on my black 24v street Milano!

Right on the T-clamps Greg!

Full-Race 6-Speed Getrag 3.7 Litre 24v Milano; 1993 155 TS 2.0; 1999 24 Valve 3.0 916 GTV; 1995 164Q; 1987 Milano Verde; 1966 GTV Stepnose
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post #5 of 5 (permalink) Old 03-27-2011, 09:59 AM
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Mutant plenum! Or "plenumnum," if you will.

JJ, you didn't tell me about this Do you know the volumes of the stock and mostro plenums? I need some numbers to geek out on...

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