Simple chamber mod that can get overlooked

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Simple chamber mod that can get overlooked

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Re: Simple chamber mod that can get overlooked

Post by steve cowan »

Nice video, makes sense once your 1/2" lift with the chamber shrouding in that area.
Good pick up and smoothed the curve some
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Re: Simple chamber mod that can get overlooked

Post by williamsmotowerx »

Doesn't Vizard say not to touch the area modified in video?
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Re: Simple chamber mod that can get overlooked

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Yeah I've seen that, anything can be overdone, but its not the first time I've had it help a head.
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Re: Simple chamber mod that can get overlooked

Post by Bigchief632 »

williamsmotowerx wrote: Sat Mar 18, 2023 3:06 am Doesn't Vizard say not to touch the area modified in video?
I'm pretty sure he says that for Vortec iron sbc heads, which may be true for his testing, but, Mummert said what the key is. To let the short turn work. That's the deal on the sbc head, his short turn still needs work, so you see that. I have a really big problem with set in stone rules with this stuff, because guys stake it for gospel and then we end up with 40 year wives tales that will never die.
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Re: Simple chamber mod that can get overlooked

Post by Tom Walker »

If you have a quantifiable gain, how can anyone argue with that?
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Re: Simple chamber mod that can get overlooked

Post by Wesman07 »

Good video. I’ve found that to be a sensitive area on a similar set of heads. As you pull that area back, flow continues to pick up and then it will start be detrimental. It’s kind of like finding spark MBT.

I believe a small air stream heads back up the valve in that area and tucks under the short turn… creating separation. By leaving it partially shrouded there is no room for revision at the valve to happen.
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Re: Simple chamber mod that can get overlooked

Post by BobbyB »

Tom Walker wrote: Sat Mar 18, 2023 10:54 am If you have a quantifiable gain, how can anyone argue with that?
Not that I disagree with you Tom, but some successful porters believe certain changes that increase flow, hurt power. I don’t have enough experience to know which is which.
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Re: Simple chamber mod that can get overlooked

Post by hoffman900 »

BobbyB wrote: Sat Mar 18, 2023 11:47 am
Tom Walker wrote: Sat Mar 18, 2023 10:54 am If you have a quantifiable gain, how can anyone argue with that?
Not that I disagree with you Tom, but some successful porters believe certain changes that increase flow, hurt power. I don’t have enough experience to know which is which.
This is true, but I usually like Mummert's takes as he has the dyno data and also is pretty in touch with the chamber side of stuff, which I think many aren't. Might be his powersports experience showing here? He can elaborate.

I'm pretty sure he says that for Vortec iron sbc heads, which may be true for his testing, but, Mummert said what the key is. To let the short turn work. That's the deal on the sbc head, his short turn still needs work, so you see that. I have a really big problem with set in stone rules with this stuff, because guys stake it for gospel and then we end up with 40 year wives tales that will never die.
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Re: Simple chamber mod that can get overlooked

Post by Tom Walker »

Yes BobbyB and Hoffman900, I absolutely agree.
An increase in CFM flow does not necessarily equate into a guaranteed power increase.
Quantity of air flow does not always trump quality of mixture preparation.
It would be very interesting to know what his 10 CFM increase resulted in.
Anyway, thanks for digging for more accurate statements about subjects presented on Speed Talk, makes a better place for all of us.
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Re: Simple chamber mod that can get overlooked

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Mummert wrote: Sat Mar 18, 2023 3:22 am Yeah I've seen that, anything can be overdone, but its not the first time I've had it help a head.
Good info, I believe DV's comment was that area helps flow but hurts swirl but clearly thats not always the case.
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Re: Simple chamber mod that can get overlooked

Post by Tom68 »

Don't touch it you'll hurt it, that assumes it was optimised in the first place.
Ignorance leads to confidence more often than knowledge does.
Nah, I'm not leaving myself out of the ignorant brigade....at times.
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Re: Simple chamber mod that can get overlooked

Post by Mummert »

This video isn't really to say that this mod fixes everything. As much as it is to say that all rules cant be bent. I love the swirl meter because is gives an accurate representation to directional changes of the plume. The main thing that causes directional changes is the short turns relationship with the the valve. If you pull the valve out and put in up side down I've seen the swirl double.
These heads had a radius chamber cut that may have altered the way the air is coming off the top cut. All in all improved stability which shows up in flow as well as lower swirl makes me think the mod is sound in this case.
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Re: Simple chamber mod that can get overlooked

Post by blykins »

Bigchief632 wrote: Sat Mar 18, 2023 10:14 am
williamsmotowerx wrote: Sat Mar 18, 2023 3:06 am Doesn't Vizard say not to touch the area modified in video?
I have a really big problem with set in stone rules with this stuff, because guys stake it for gospel and then we end up with 40 year wives tales that will never die.
Exactly. And the internet perpetuates it all.
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Re: Simple chamber mod that can get overlooked

Post by juuhanaa »

GARY C wrote: Sat Mar 18, 2023 4:14 pm
Mummert wrote: Sat Mar 18, 2023 3:22 am Yeah I've seen that, anything can be overdone, but its not the first time I've had it help a head.
Good info, I believe DV's comment was that area helps flow but hurts swirl but clearly thats not always the case.
Will the increased flow come also at the expense of increased velocity difference around the valve?

When people talk about pressure recovery, they dont necessarily visualize the direction of mass flow, and may also pay too much attention to changes in wall angles thinking it will keep things under control. Does a difference in speeds at the port entry vs the minimum csa cause a problem? What if velocity gradients are measured streamwise and cross-sectionally? Yea it make a difference, but this was just my 2 cents..



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