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dmir55 · 04-06-2015, 05:06 PM

Mike, Your primary tubes should be 1 7/5 inches. The collectors should be 2 1/2 inches. If you use a merge collector the 2 1/2 inches should be the minor diameter. The major, or larger size, can be almost any size you want. I know this sounds awfully small but we set national records with this formula. If you don't think it works just bolt a street reducer on your 3 1/2 collectors [3 1/2 to 2 1/2] and see what happens. This the cheapest way and I think you will be be surprised. Hope this helps and good luck.

04-06-2015, 05:06 PM	#5
dmir55 Junior Member Join Date: Jul 2014 Location: northern Minnesota Posts: 64 Likes: 0 Liked 0 Times in 0 Posts	Re: Header size Mike, Your primary tubes should be 1 7/5 inches. The collectors should be 2 1/2 inches. If you use a merge collector the 2 1/2 inches should be the minor diameter. The major, or larger size, can be almost any size you want. I know this sounds awfully small but we set national records with this formula. If you don't think it works just bolt a street reducer on your 3 1/2 collectors [3 1/2 to 2 1/2] and see what happens. This the cheapest way and I think you will be be surprised. Hope this helps and good luck.