BBC output overview.

General engine tech -- Drag Racing to Circle Track

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Erland Cox
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Re: BBC output overview.

Post by Erland Cox » Mon Oct 15, 2018 4:16 pm

Keep to the topic of porting BBC heads instead of discussing opinions.
Of course a canted valve head is better than a inline head but why mess the thread up by discussing that instead?
Looking at the two graphs, the flow and the cd graph.
Why do we need the cd graph? The flow numbers tell everything.
Please explain.

Erland

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Re: BBC output overview.

Post by Frankshaft » Mon Oct 15, 2018 4:27 pm

Stan Weiss wrote:
Mon Oct 15, 2018 4:12 pm
Headguy wrote:
Mon Oct 15, 2018 1:59 pm
David Vizard wrote:
Mon Oct 15, 2018 1:25 pm


Joe,

A point of reference here - telling it the way it really is from actual data does not universally win you friends ---------------- and that's a certainty!!!
DV
Then explain to me why a Big Block Mopar with B1 heads is down huge to a Predator head?
Getting old, memory is not what it used to be. Didn't the B1 win a few Pro Stock championships?

Stan
Not a b1 original, like referenced. The B1 T/S head did though. Which was a raised, spread Port canted valve head. And they needed nitrous to do.it. 😉
Last edited by Frankshaft on Mon Oct 15, 2018 4:32 pm, edited 1 time in total.

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Re: BBC output overview.

Post by Erland Cox » Mon Oct 15, 2018 5:05 pm

He is wrong on that but the porting discussion can become interesting if there aren´t to many side paths.

Erland

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Re: BBC output overview.

Post by cjperformance » Mon Oct 15, 2018 5:36 pm

Why not start a thread on the various inline and canted valve heads out there and compare port efficiencies in stock and/or ported form, maybe based on flow, mcsa, port face csa, valve diameter and bore diameter. Trying to forget port volume due to the differences in port length and therefore different volume fo 2 equal flowing ports but on 2 different engine platforms.
This would be way more interesting and constructive than just saying , this is better than that, no its not, etc.
Chev, ford, chrysler, fiat, who cares.
Craig.

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Re: BBC output overview.

Post by David Vizard » Mon Oct 15, 2018 6:47 pm

Erland,
Your comment----'Looking at the two graphs, the flow and the cd graph.
Why do we need the cd graph? The flow numbers tell everything.
Please explain.---'


The red CD curve flattens out at the inflection point thus indicating- with no further testing just to see if it is so, that the port needs more bias.

Once you know that, you can go ahead and grind more bias to achieve something like the blue curve.
Don't forget if you are testing a port like the red curve then you have not got to the blue curve yet so you can't compare the flow curves.
DV
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Re: BBC output overview.

Post by David Vizard » Mon Oct 15, 2018 6:54 pm

Erland Cox wrote:
Mon Oct 15, 2018 5:05 pm
He is wrong on that but the porting discussion can become interesting if there aren´t to many side paths.

Erland
Because you are coming at this as a racer you are wrong on the red part of your quote. If you start thinking this out as chief engineer for a production line engine you will find a different outcome.
As for the blue part of your post - that is right on the money!
DV
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Re: BBC output overview.

Post by Erland Cox » Mon Oct 15, 2018 7:13 pm

David Vizard wrote:
Mon Oct 15, 2018 6:47 pm
Erland,
Your comment----'Looking at the two graphs, the flow and the cd graph.
Why do we need the cd graph? The flow numbers tell everything.
Please explain.---'


The red CD curve flattens out at the inflection point thus indicating- with no further testing just to see if it is so, that the port needs more bias.

Once you know that, you can go ahead and grind more bias to achieve something like the blue curve.
Don't forget if you are testing a port like the red curve then you have not got to the blue curve yet so you can't compare the flow curves.
DV

Please explain, how do you know that it needs more bias and not something else?
From the flow curve it is easy to see that something is wrong with the port as it stops gaining flow with more lift.
As I am not used to the cd curve it doesn´t tell me anything.
Not that I cannot learn but to complicate things there must be a good reason.
Bias is mostly used because that is the only direction you can port, there is water and another port on the other side.
Usually I gain flow by centering the valve more over the port.

Erland

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Re: BBC output overview.

Post by digger » Mon Oct 15, 2018 9:24 pm

The other question I have is how can you be sure that what works on a flow bench works in an engine? The discharge coefficient at "high" lifts is fairly heavily dependent on the pressure ratio and the flow bench produces a mere fraction of the pressure ratio that occurs in the engine.

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Re: BBC output overview.

Post by Geoff2 » Tue Oct 16, 2018 5:15 am

David,

Please keep going with the thread. There are those who are generally interested. The usual suspects are behaving as....well...the usual suspects; hopefully they will get bored with it & go & colour in their comic books.....

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Re: BBC output overview.

Post by MELWAY » Tue Oct 16, 2018 6:33 am

Erland Cox wrote:
Mon Oct 15, 2018 7:13 pm
David Vizard wrote:
Mon Oct 15, 2018 6:47 pm
Erland,
Your comment----'Looking at the two graphs, the flow and the cd graph.
Why do we need the cd graph? The flow numbers tell everything.
Please explain.---'


The red CD curve flattens out at the inflection point thus indicating- with no further testing just to see if it is so, that the port needs more bias.

Once you know that, you can go ahead and grind more bias to achieve something like the blue curve.
Don't forget if you are testing a port like the red curve then you have not got to the blue curve yet so you can't compare the flow curves.
DV

Please explain, how do you know that it needs more bias and not something else?
From the flow curve it is easy to see that something is wrong with the port as it stops gaining flow with more lift.
As I am not used to the cd curve it doesn´t tell me anything.
Not that I cannot learn but to complicate things there must be a good reason.
Bias is mostly used because that is the only direction you can port, there is water and another port on the other side.
Usually I gain flow by centering the valve more over the port.

Erland
Thanks DV for the great info and pics

Erland. With your last comments about gaining flow by centering the valve to port. Do you think this is due to a straight line of sight or less energy due to less change of direction
Would the gains from bias in an inline 2 valve head be partly due to the direction the flow comes from in cylinder as piston rises?
3370lb Sedan 9.89@136MPH 358chevN/A

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Re: BBC output overview.

Post by Frankshaft » Tue Oct 16, 2018 11:39 am

RevTheory wrote:
Sun Oct 14, 2018 12:07 pm
Well, those are the prettiest damn seats I've seen. I'm guessing you've got the "fuel shear" argument addressed- perhaps forthcoming?
Radius intake seats flow a little better than a multi angle seat. But they don't make as much power from my testing. Or Rheere and Morrison's, Cfe's, Bes's, Sonny Leanords, Kasse's, Mbe, Frankenstein, Slick Rick, , Brodix, etc etc. With the exception of Brodix, I have NEVER seen a radius intake seat from any of them. Brodix USED to cut radius intake seats, many years ago, but have switched to multiple angles. I wonder why?

Dart has the most sophisticated wet flow testing rig in the industry, ask Richard Maskins what he says about radius intake seats. You don't even have to, not ONE head comes with a radius intake seat from them.

I have seen numerous sets of heads from Hendricks and Rcr over the years, EVERY single one had multiple angles on the intake seats. Ask Warpspeed if they use radius intake seats.

So, I guess, we are all doing it wrong.

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Re: BBC output overview.

Post by Ron E » Tue Oct 16, 2018 11:43 am

digger wrote:
Mon Oct 15, 2018 9:24 pm
The other question I have is how can you be sure that what works on a flow bench works in an engine? The discharge coefficient at "high" lifts is fairly heavily dependent on the pressure ratio and the flow bench produces a mere fraction of the pressure ratio that occurs in the engine.
I only offer this based off drag and round track motors. From big solid rollers to rules mandated flat or hyd roller cams. All with open exhaust.
I use EA pro looking at cylinder PSI vs. exhaust port PSI. When the sonic period is over, you're back to turbulent conditions. No reason a bench won't help you there. Optimize from there. Also, do what you can do keep the port as calm as possible. You usually wind up with a fairly large throat. Use a flow pipe to avoid that expansion train wreck. Understanding that with a flow pipe you're on your own. They all flow different and you just look for your own gains. No comparisons. I can't offer you any A-B-A graphs, etc. But, that recipe gives good results.
On the bias. Most everything we've tried liked the bias as DV describes. (not hemis). Picture the majority of the air to be approaching from the center of the chamber. Its not lined up to the port. The bias helps this transition.

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Re: BBC output overview.

Post by David Vizard » Tue Oct 16, 2018 12:24 pm

Erland,

A reply to your last post.

I am going to be blunt and too the point here as questions like this are stalling me going to the next phase of my BBC stuff.

Q:- Please explain, how do you know that it needs more bias and not something else? 60 years of flow testing and data/trend mining the results.

Q:-From the flow curve it is easy to see that something is wrong with the port as it stops gaining flow with more lift. Sure you can see things are not optimal but saying exactly what is not so easy. What happens at the inflection point can be very informant.

Q:- I am not used to the cd curve it doesn´t tell me anything. I know you are jut more than smart so now might be a good time to learn.

Q:- Not that I cannot learn but to complicate things there must be a good reason. You are right - there is - and you need to let me push forward on this post to some logical conclusion before bombarding me with qestions.


Q:-Bias is mostly used because that is the only direction you can port, there is water and another port on the other side. Absolutely not so!

Your comment:- Usually I gain flow by centering the valve more over the port. This sounds like something you got from Grumpy's book. The times I spent with Grumpy were great learning experiences for me but some of his air flow stuff was out of line with the data I had. I told him about the fact that my tests with applied bias showed a centered valve was not the way to get best hi-lift flow. I did not see Grumpy for quite a while (maybe two years) when I did he pointed at me and said 'Mr. Vizard - that biased tip worked just the way you said'.


Erland - patience please - let me get on with the theme of this post. As I have said before we need to talk.
We have not done that for some years now.

Take care,
DV
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Re: BBC output overview.

Post by David Vizard » Tue Oct 16, 2018 12:42 pm

digger wrote:
Mon Oct 15, 2018 9:24 pm
The other question I have is how can you be sure that what works on a flow bench works in an engine? The discharge coefficient at "high" lifts is fairly heavily dependent on the pressure ratio and the flow bench produces a mere fraction of the pressure ratio that occurs in the engine.
In all probability I am possibly the only one posting on this site who has any kind of meaningful experience with a 'super-sonic' capable flow bench. Where DATA LEARNED FROM THAT IS RELEVANT I TAKE THAT INTO ACCOUNT BUT OTHERWISE TRY TO STAY WITH THE POINT OF THE ORIGINAL POST WHICH IS HOPPING UP BBC'S.

DV
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Re: BBC output overview.

Post by prairiehotrodder » Tue Oct 16, 2018 1:29 pm

I'm all ears for helpful info to make my BBC go faster. I'm using the AFR 335 CNC heads and just this winter stepping up my program. Any experience with these heads and where their limits are ?
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