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Intake manifold CSA

General engine tech -- Drag Racing to Circle Track

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MadBill
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Re: Intake manifold CSA

Post by MadBill » Sat Oct 19, 2019 10:33 pm

Knight rider wrote:
Sat Oct 19, 2019 3:18 am
...
The taper in the runners are only tapered one way so there a little oval in shape, I'm not sure how to work out actually the CSA in a oval shape...
Area of an oval = short radius x long radius x π.
Felix, qui potuit rerum cognscere causas.

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Re: Intake manifold CSA

Post by Knight rider » Sun Oct 20, 2019 6:41 am

cjperformance wrote:
Sat Oct 19, 2019 6:30 pm
Cool XC and intake, its great to see people make stuff and experiment rather than just buy catalogue parts.
With the small runners opening into a larger port, you get a velocity loss as the charge exits the runner. In an extreme case it essentially makes the runner/port overall length "look" shorter the the engine below peak HP so you loose some TQ potential, at peak HP you are then hampered by the smaller runner.
But for street use where partial throttle settings are used more often thus scenario "can" improve driveability especially if the port is on the big side for the combo.
Theres of course a ton more variables as with all things engine!
Thanks I do like to try a make things, I'm all to aware that I'm taking the long road but keeps it interesting and you learn stuff too. I like being different :)

I did start to make another after that one and that wasn't the first, was trying to keep the same layout but use larger diameter tubes for the runners but it wasn't packing right- ran out of room so the search goes on for a minn tunnel ram that performs well with a single carby.

I do have a couple of idea for mods before ditching that intake, like making the runners draw from the adjacent runner at the same time. I have tried that before more to balance the runners, engine ran the best it has with that setup but not faster. Cheers

By the way it's a ZG Fairlane-best car ever made !!

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Re: Intake manifold CSA

Post by cjperformance » Sun Oct 20, 2019 4:12 pm

Ah ZG ! Cool , i would have picked that (or XB) if I could see the master cylinder in the pic! Going by washer bottle and aircon pipes i knew it was XB or XC based (ZF/ZG) , then looking at top rad hose direction from the engine looked like its running a 90* t-stat housing, hence the XC choice. Yes ZG are cool, a little more refined than ZF and way cooler than ZH! I also like the ZA/ZB , and the early compact and US fairlanes with side by side headlights, im not a fan of the stacked headlight look.
Craig.

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Re: Intake manifold CSA

Post by Knight rider » Tue Nov 05, 2019 3:12 am

So I've started some modds on my intake I wanted to try, I've done similar before by linking the ports together but wasn't linked back to the plenum, it did seem to improve idle and drivability.

Would this help with max CFM available to the port, would it also draw easier at idle from the small port and help balance the feed to the runners ?

Blowing air down it it feeds the front and rear mostly which is probably what is needed with the design of the intake.
It's not pretty but I can work on that when it finished. Cheers


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Re: Intake manifold CSA

Post by Knight rider » Sun Nov 10, 2019 2:40 pm

I'm looking to get the manifold flow tested, how relevant is flow testing ? as from what I've read the actual air speed in the runner is alot higher than anything you see on a flow bench ?
I guess it will at least show some comparisons to other intakes and if I have it done with the heads to see how it effects the head flow.
I can block off the mods done too to see what effect they have as well

Will be getting Terry parker to do the tests so he'll have a good idea on how it's performs.

The mods done I'm only hoping to see maybe better low speed flow for idle and maybe even out the runners somewhat, I really have no idea how some effect it will have if any but interesting for me anyway. Cheers

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Re: Intake manifold CSA

Post by BLSTIC » Sun Nov 10, 2019 3:27 pm

I'm also looking at those runners (also with zero experience) thinking they could do with more radius. Is it possible to put a plate over the whole floor to build it up to get more material to make a better radius? It would immediately cost you in plenum volume though.

I take it you want to keep the carby style look too it all though? If you weren't and could have port injection you could easily go to side mounted throttles and have a lot more vertical room available (for said plenum volume)

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Re: Intake manifold CSA

Post by cardo0 » Wed Nov 13, 2019 1:09 pm

Knight rider wrote:
Sun Nov 10, 2019 2:40 pm
I'm looking to get the manifold flow tested, how relevant is flow testing ? as from what I've read the actual air speed in the runner is alot higher than anything you see on a flow bench ?
I guess it will at least show some comparisons to other intakes and if I have it done with the heads to see how it effects the head flow.
I can block off the mods done too to see what effect they have as well

Will be getting Terry parker to do the tests so he'll have a good idea on how it's performs.

The mods done I'm only hoping to see maybe better low speed flow for idle and maybe even out the runners somewhat, I really have no idea how some effect it will have if any but interesting for me anyway. Cheers
Well you could do your own testing by welding on (or even just screw on) some taps to measure wall static pressure where you want to look at it. I think low flow areas will match normal manifold vacuum and high flow areas will induce a vacuum reading where manifold pressure will reach atmospheric (zero vacuum).

BTW I have no idea what you are trying to do by cross connecting the runners. I think it would kill the pressure wave/signal you are trying to make with the longer runners.

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Re: Intake manifold CSA

Post by MadBill » Wed Nov 13, 2019 9:16 pm

Some points re dual plenum cross rams and connecting passages:
  • David Vizard told me that he and Terry Walters spent a week trying to tune up a BBC with an Edelbrock XC96 cross ram (dual plenum) and that when they gave up and switched to a single carb single plane, gained 100 HP.
  • I have one I'll be trying on my 495" BBC. The previous owner had fitted it with mechanical injection and added a 1" diameter balance pipe, the latter presumably for good reason.
  • Since I loved the factory cross ram I used on the SBC in my '70-1/2 Camaro and it had a single plenum, I'm in the process of fabbing a 3" square connecting passage for the XC96 and plan to tune with the passage open, then see what happens when I block it off.
  • I was looking at a magnesium Barton Hemi cross ram (single plenum) the other day and noticed that it has three connector passages of ~ 2"² area each cast in but sealed off at the ends, presumably to allow selective opening for experimentation. :-k
  • I assume the Barton worked pretty well, as the aluminum Hemi underneath it had "1125 HP" inscribed on the rocker covers.
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Re: Intake manifold CSA

Post by Knight rider » Thu Nov 14, 2019 2:23 am

MadBill wrote:
Wed Nov 13, 2019 9:16 pm
Some points re dual plenum cross rams and connecting passages:
  • David Vizard told me that he and Terry Walters spent a week trying to tune up a BBC with an Edelbrock XC96 cross ram (dual plenum) and that when they gave up and switched to a single carb single plane, gained 100 HP.
  • I have one I'll be trying on my 495" BBC. The previous owner had fitted it with mechanical injection and added a 1" diameter balance pipe, the latter presumably for good reason.
  • Since I loved the factory cross ram I used on the SBC in my '70-1/2 Camaro and it had a single plenum, I'm in the process of fabbing a 3" square connecting passage for the XC96 and plan to tune with the passage open, then see what happens when I block it off.
  • I was looking at a magnesium Barton Hemi cross ram (single plenum) the other day and noticed that it has three connector passages of ~ 2"² area each cast in but sealed off at the ends, presumably to allow selective opening for experimentation. :-k
  • I assume the Barton worked pretty well, as the aluminum Hemi underneath it had "1125 HP" inscribed on the rocker covers.
Thanks everyone for the input, I'm sort of running out of time to get it flowed as I need to put it all back together. I have no idea what it will do other than the similar thing I've done before which seemed to improve the idle and tip in throttle response, guess I'll see how it goes it's only something to try and not worried to much about the outcome as I have ideas for another intake anyway cheers

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