air flow thru intake manifold runners

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swampbuggy
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air flow thru intake manifold runners

Post by swampbuggy »

I would like to know what you guys have found in this area, for those of you who have already done this testing. S.B.C. single plane, cast alum. individual runner airflow testing on like a super Victor for example. Stock as cast (or) ported ?? Was wanting to know how much difference (if any) you have seen between #1 runner vs. #3 runner or maybe #6 vs. #8 ? This would be with manifold bolted to the cylinder head with all of the head ports flowing almost identical, with all runners blocked off except the one being tested. Testing done at max. flow lift point of valve. Thanks for any answers in advance, Mark H. :wink:
Belgian1979
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Re: air flow thru intake manifold runners

Post by Belgian1979 »

Not related to a victor Jr, but on an ITB, one can see one cyl affecting the next, especially if they are close together in the firing order. This effect was even visible in the way my vacuum reservoir affected things. I ended up dividing the vacuum reservoir in 2 and connecting the vacuum lines such that they were arranged as per dual plane manifold. It made a noticable difference.

Things tend to even out the higher the rpm is.
swampbuggy
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Re: air flow thru intake manifold runners

Post by swampbuggy »

Thanks , Belgian . Anybody else have any comments ? Mark H.
user-30257

Re: air flow thru intake manifold runners

Post by user-30257 »

I have seen years ago on the bench, being able to even out the outer cylinders to within 15cfm. Tuning was easier. The nitrous guys didn't care because they were spraying what the engine made in power, they adjusted the pills accordingly.

Now days I just use the eyeball, fingers and past experiences. I try to get the straightest shot to the head. Big block Chevy was terrible. But now you can get off the shelf intakes that take 50hours of welding and grinding out of the equation.
zums
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Re: air flow thru intake manifold runners

Post by zums »

SBC SPVB #3 bare port 288-cfm
Super Victor/ GM Eliminator stock 234cfm avr csa2.58
2814 Edelbrock stock 265cfm avr csa 2.78
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Re: air flow thru intake manifold runners

Post by user-17438 »

swampbuggy wrote: Sun Apr 29, 2018 12:05 am I would like to know what you guys have found in this area, for those of you who have already done this testing. S.B.C. single plane, cast alum. individual runner airflow testing on like a super Victor for example. Stock as cast (or) ported ?? Was wanting to know how much difference (if any) you have seen between #1 runner vs. #3 runner or maybe #6 vs. #8 ? This would be with manifold bolted to the cylinder head with all of the head ports flowing almost identical, with all runners blocked off except the one being tested. Testing done at max. flow lift point of valve. Thanks for any answers in advance, Mark H. :wink:
This can be misleading if porting the runner, because if you get them to flow the same, chances are you ruined the runner and increased cross section in the wrong way, sure flow went up, but the fuel may now fall out of suspension, now you need to make dams or divots to reintroduce it. This is where sometimes if the casting is limited you are better off having an equal taper vs going for best flow at the head. It can throw your tuning off
B Original
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Re: air flow thru intake manifold runners

Post by B Original »

Most of the engines are build I don't need this get into the detail of porting intake trying to get that extra HP, butt I do analyze egt's and or the O2 readings depending on who's dyno I'm using. If I get something too far out of line that's when I give it attention. On SBC sometimes I have to bias the 5-7 runner entrance.
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Re: air flow thru intake manifold runners

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B Original wrote: Sun Apr 29, 2018 3:17 pm Most of the engines are build I don't need this get into the detail of porting intake trying to get that extra HP, butt I do analyze egt's and or the O2 readings depending on who's dyno I'm using. If I get something too far out of line that's when I give it attention. On SBC sometimes I have to bias the 5-7 runner entrance.
Reading this thread I was thinking this very thing then got to the bottom and just smiled ...

As long as the intake is not a major restriction the unevenness will tend to broaden the power band a bit and make the engine a little more flexible ... I have spent hours/days /weeks making intakes perfect flow and mix ... it's a lot of work for not much of nothing
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Re: air flow thru intake manifold runners

Post by B Original »

Scotthatch wrote: Mon Apr 30, 2018 11:48 am
B Original wrote: Sun Apr 29, 2018 3:17 pm Most of the engines are build I don't need this get into the detail of porting intake trying to get that extra HP, butt I do analyze egt's and or the O2 readings depending on who's dyno I'm using. If I get something too far out of line that's when I give it attention. On SBC sometimes I have to bias the 5-7 runner entrance.
Reading this thread I was thinking this very thing then got to the bottom and just smiled ...

As long as the intake is not a major restriction the unevenness will tend to broaden the power band a bit and make the engine a little more flexible ... I have spent hours/days /weeks making intakes perfect flow and mix ... it's a lot of work for not much of nothing
The main reason I consider port bias on adjacent cylinder firing in order is to protect the a single cylinder if all else is right but pushing the envelope. In some cases I have had that cylinder's EGT's run as much as 120-150+ degree's hotter than all the other ports and the inverse port being the coolest. When the 2 cylinders are on the same corner of the carb a jetting change affects this phenomenon minimally.
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