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1G 6 bolt head intake port diameter?

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El Cuervo

15+ Year Contributor
576
25
Nov 7, 2004
Omaha, Nebraska
Hey guys what's new? I have a quick question here that as simple as it sounds, I haven't been able to find the answer. What is the inlet diameter of the intake ports on the 6 bolt cylinder head? I believe the exhaust poertse are something like 1.5 to 1.75 inch in inlet diameter, not too sure but I whae i would like to is the intake ports diameter on the 6 bolt cylinder head.

Thanks
 
Ah thanks. So if converted to a round shape, would it be about 2 to 2.1 incles in diameter? I'm asking this because I might build my own intake manifold and would like to know the runners inlet diameter.

Thanks
 
Not sure I understand what you're asking.

If you back-calculate for a circle shape with equal cross-sectional area, you're somewhere around a 2.21" diameter circle -- ignoring the radii in the corners. If you don't ignore the radii -- since I don't know exactly what the radius is -- the cross-sectional area can range anywhere from 3.78 in^2 for 6mm radii to 3.57 in^2 for 14mm radii.

If you mean the largest circle that will completely fit in the intake port, you're at about 1.5" diameter circle.
 
Thanks Brian. That's what i wanted to know. So a 2.21 diameter pipe will flow about the same as the rectangle intake ports? I could use the same rectangle shape for the intake runners but its hard to find rectangular shaped pipe, so i will just try to source a circle shaped pipe of closer to 2.21 in diameter. Either way, thanks for the help Brain.
 
You will take the round pipe and make it rectangle

A press, some heat and a couple of thick steel bar and some practice and you will be able to make a round peg fit a square hole.
 
Ah I see.. nice! Thank you very much Dale! Now, about the steel bars that you mentioned. Are these used as a mold of sort? Someone should just sell these rectangle to round aluminum pipes for intake manifolds.
 
Maybe check vibrant's catalog too, I think magnus or stm sells a manifold inlet flange.
 
I do not know if anyone makes/sells a die form.

The few times I have done it, I used a chunk of steel flat bar from a scrap barrel

About 8"x4 by a .500 thick
 
Thanks guys. I already have a flange that I purchased some time ago. I'll check the website that Brian posted. If i can't find what I'm looking for, then I will have to do what Dale suggested. Finding 2 1/4 aluminum piping could be a challenge. I only see piping with increments of 1/2 inch such as 2, 2.5, 3, etc. I will continue looking, no problem.

Thanks for the help everybody.
 
Could make a thick 'ring' of sorts with the hole of proper shape and size to match the rectangular opening in the flange plus thickness of metal of the pipe. Then cut that ring in half and you will have a mold for either a vise or a large C-clamp that will help you get those pipe ends to the exact size and shape. A downside to that would be the fact that you will have to spend time and effort making the thing, the upside is obviously more consistent straight even ends.

You might have some luck finding something here: http://www.rossmachineracing.com/intakepartspage.html
At least they have 2.25" aluminum pipe, though expensive it is ($15/ft).
 
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Well, I was thinking of 12g but don't know if thats too thin for runners or even 10g or smillar size. This would also be for the plenum.
 
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