DIY big block intake manifold

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MOPARMAGA

MOPARMAGA

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Hey folks, I'm planning on building a dominator flanged intake for my 471 stroker, most likely in between typical tunnel ram height & tall single plane height. Maybe 8 inch runners. I figure I'll get a little more room for my tig torch to maneuver.
Anyone on here have any experience doing this. What's the recommended runner thickness, I think I'll use 1/2 inch on the port mount surfaces & 1/2 inch to bolt the carb onto,
3/16 for runners ? Not sure. Anyways pictures would be cool too. Home made preferred, I'm a diy'er
 
3/8 -1/2 is a good flange thickness. Your runners can be made thin or as thick as your comfortable welding. I did mine in steel as I can weld steel but AL would be much lighter. 3/16 AL sounds good, nice thickness and strength. Plan the build out so as to address the torch angles and access as you dont want to get stuck with a weld that you cannot get to (between runners). Run the runner up into the carb box and weld from the inside as well as at the flanges. you can always grind the welds flat at the flange and the carb box will be hidden with the top plate. Are you going to run it natural finish? If not you can use a bit of filler on the joints to smooth it out and then paint. You may want to consider using straight runners that are already fabbed, ie. extruded AL square or rectangle tube. Curved fabbed runners will be alot of work, especially in AL.
 
pishta said:
3/8 -1/2 is a good flange thickness. Your runners can be made thin or as thick as your comfortable welding. I did mine in steel as I can weld steel but AL would be much lighter. 3/16 AL sounds good, nice thickness and strength. Plan the build out so as to address the torch angles and access as you dont want to get stuck with a weld that you cannot get to (between runners). Run the runner up into the carb box and weld from the inside as well as at the flanges. you can always grind the welds flat at the flange and the carb box will be hidden with the top plate. Are you going to run it natural finish? If not you can use a bit of filler on the joints to smooth it out and then paint. You may want to consider using straight runners that are already fabbed, ie. extruded AL square or rectangle tube. Curved fabbed runners will be alot of work, especially in AL.
Click to expand...
Thank you pishta Yes, I was planning on getting rectangular tube closest size to my ports. I think that it was a tiny bit bigger than the trickflow 240 ports, so I'd blend the head ports too. That's a great idea having the tube go into the flanges. How big of plenum do you think? This will be for a 3400-7400 rpm engine
 
plenum on my 6 intake ended up the displacement of the motor, 225! That was for a dry intake with a formula that was online. Wet intake, no idea. Id keep it as free flowing as possible. You dont want A/F making right angle turns as you lose suspension. Drys are totally different..they can go though a maze and still work. Slightly larger runners are acceptable if you blend them at the flange. Use fuel proof epoxy. Duals would be nice as you could position the carbs over the 2 groupings of runners for better distribution, even dual 2bbls or a split Dominator. Probably not in your cards. 3-7400 probably wont mind the single 4 over 10 inches of intake runners.
 
pishta said:
plenum on my 6 intake ended up the displacement of the motor, 225! That was for a dry intake with a formula that was online. Wet intake, no idea. Id keep it as free flowing as possible. You dont want A/F making right angle turns as you lose suspension. Drys are totally different..they can go though a maze and still work. Slightly larger runners are acceptable if you blend them at the flange. Use fuel proof epoxy. Duals would be nice as you could position the carbs over the 2 groupings of runners for better distribution, even dual 2bbls or a split Dominator. Probably not in your cards. 3-7400 probably wont mind the single 4 over 10 inches of intake runners.
Click to expand...
I guess while I'm at it I could have different plates machined for top plates, single -multi carbs. Well the other design I want to try is a split dual 4 bbl like the ram horn design . although the linkage will be another fun build.
 
Ram horn is better for low end, you can tune to high but the shorter runners of a street ram are better for that. original Ramcharger formula on a small stock cam was N x L = 84,000, where N represents the desired engine rpm to tune for and L is the length in inches from the opening of the ram tube to the valve head. For a hotter cam duration it changes...NxL=80,300 @ 224 duration @ .050. I researched a formula and it took valve duration into effect as a constant. Here is a plastic intake for a 4.7 Ford, dry of course. Tuned for GT350 peak power.
GT-350-Intake-manifold.jpg
 
pishta said:
Ram horn is better for low end, you can tune to high but the shorter runners of a street ram are better for that. original Ramcharger formula on a small stock cam was N x L = 84,000, where N represents the desired engine rpm to tune for and L is the length in inches from the opening of the ram tube to the valve head. For a hotter cam duration it changes...NxL=80,300 @ 224 duration @ .050. I researched a formula and it took valve duration into effect as a constant. Here is a plastic intake for a 4.7 Ford, dry of course. Tuned for GT350 peak power.
View attachment 1715563964
Click to expand...
Alright thanks for that info.
 
pishta said:
Ram horn is better for low end, you can tune to high but the shorter runners of a street ram are better for that. original Ramcharger formula on a small stock cam was N x L = 84,000, where N represents the desired engine rpm to tune for and L is the length in inches from the opening of the ram tube to the valve head. For a hotter cam duration it changes...NxL=80,300 @ 224 duration @ .050. I researched a formula and it took valve duration into effect as a constant. Here is a plastic intake for a 4.7 Ford, dry of course. Tuned for GT350 peak power.
View attachment 1715563964
Click to expand...
It sounds like a dual 4 tunnel ram will be the easiest build. It will take any bending out of the equation. Give good powerband I think
 
copy this and extend the runners to 8", chop them on a horizontal plane and put a dominator box on top. If its too tall, increase the angle out the flange. Crude but easy chop saw cuts and welds. Clean it all up and paint or polish. Your intake ports will be very wide once you do a horizontal cut.
20180901_162600-jpg.jpg
 
pishta said:
copy this and extend the runners to 8", chop them on a horizontal plane and put a dominator box on top. If its too tall, increase the angle out the flange. Crude but easy chop saw cuts and welds. Clean it all up and paint or polish. Your intake ports will be very wide once you do a horizontal cut.
View attachment 1715564174
Click to expand...
Cool thanks
 
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