8.1 Custom Intake Manifold
 

Well guys, I've been researching this for a long time and I've finally bought materials. I want to build a runner style N/A intake for the 8.1L. I was doing this because of the Raylar intake being so far out of my budget, but I just saw the lower post of them making a cast intake to bring down cost (thank you Larry!!!!!). I should have waited, and got that, but I've already ordered materials so its too late now. This intake is going on stock heads, with mid length headers and a healthy cam (healthy as stock allows). I've determined my runner length and the ideal TB setup I want. I'm shooting for an ideal RPM of 4500-5000 do to the sport I'm in, this is where I need my power. Now what I can't decide on is the runner diameter and plenum size. I've read so much of different oppinions on plenum size but very little on runner diameter. Should they pretty much match the intake port on the head? Or be slightly smaller to keep velocity up? I know short fat runners are for high rpm (10k area) and long narrower runners are ideal for lower rpms. Just some insight would be helpful. If I make an intake that isn't tuned for my setup.....well I have a few people running FI that'll take it. So this is more of a fun learning experience.

Are you fabbing it from scratch or using a stock intake modified? Me and my buddy made our own plus i own a raylar one
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Just starting from scratch. I've seen your unit before and I really like it. But aren't you running FI? I know NA and FI intakes use the same guidelines but minor changes in a FI intake don't affect it as bad as a NA

Well I see the pics with just an intake breather. I should've looked closer.

yeah i did short runners when dyno compared to the raylar, the long runners of the raylar made more power n/a. I have not done a boosted comparison. mainly because it is such a pita to swap in my 1500's

also make sure you account for the ac bracket or alternator, me and my buddy both had to modify things to get stuff to fit

Right. I want as long if runner possible. 18"- 20" (minus the valve to top of the head length) to get my power range down in the 4k rpms. But that may be not possible....but hell, I wouldn't mind cutting up the hood a little either.

my buddy made his fairly long but i dont think he went that long

Did you start from scratch or did you use the original intake? Also what size runners are those? Diameter?

we both used the base, he used less then i did. I sent him a link hoepfully he can jump on and reply. I got lots of pics of a stock intake milled down