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Old 10-06-2020, 05:02 PM
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Default Interesting port volume vid

Saw this vid https://youtu.be/PZSQ5KdJ2fc and thought it was interesting. Just made me think about the Jim Hands days with his d-ports vs e-heads back then and how things have progressed to where they are now.

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Old 10-06-2020, 05:10 PM
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Yeah Steve Brule has done that test a few times in the past on BBC's and found that the bigger ports actually don't hurt the low rpm torque like many are led to believe, least at WOT on the dyno anyway .

I went that direction on one of my own BBC's, with a small 454 using large 305cc AFR heads. General consensus is that these heads work best on 502-540ci engines, which is one reason I bought them with bigger plans later.

However they have proved to be just fine on the 454. Low speed light throttle drivability is very crisp and responsive. There is no lack of torque down low and nothing soggy about them putting around town. Which is one of the questions Richard didn't have an answer for on the dyno.

I can say, at least on mine, that it's absolutely not an issue at all.

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Old 10-06-2020, 09:06 PM
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I appreciate a lot of his work, but sometimes he could do a better job of eliminating variables. He switches between "as-cast" and cnc, which can certainly play into velocity and mixture motion in the runner as well as the combustion chamber. I also didn't hear him confirm if the chamber volumes are exactly the same or not to keep the compression consistent (unless I missed it).

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Old 10-06-2020, 09:53 PM
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There was another test they did on a Ford that did a little better job of what you're referring to Mike. It was pretty much the same result though using a handful of AFR heads on that one. Started with 165's and went up to 195 and then either 220's or 235's. Torque was still excellent down low. The interesting part is that the 165's and 195's were almost identical throughout.

I think Steve Brule even did an episode on Engine Masters about this theory.

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Old 10-06-2020, 10:49 PM
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Quote:
Originally Posted by Formulajones View Post
Yeah Steve Brule has done that test a few times in the past on BBC's and found that the bigger ports actually don't hurt the low rpm torque like many are led to believe, least at WOT on the dyno anyway .

I went that direction on one of my own BBC's, with a small 454 using large 305cc AFR heads. General consensus is that these heads work best on 502-540ci engines, which is one reason I bought them with bigger plans later.

However they have proved to be just fine on the 454. Low speed light throttle drivability is very crisp and responsive. There is no lack of torque down low and nothing soggy about them putting around town. Which is one of the questions Richard didn't have an answer for on the dyno.

I can say, at least on mine, that it's absolutely not an issue at all.
I know that port cc's only tell some of the story and one needs to know port center line length also. But weren't the rectangle port heads Chevy put on the 396 ci 375 HP and 427 ci 425 HP right around that port volume / size?

Stan

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Old 10-06-2020, 11:03 PM
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I know that port cc's only tell some of the story and one needs to know port center line length also. But weren't the rectangle port heads Chevy put on the 396 ci 375 HP and 427 ci 425 HP right around that port volume / size?

Stan
Yeah somewhere in that range if I remember correctly.

That's why it struck me as odd, I guess it's been more than 15 years ago now, when the general thought process was that these 305's were better suited to 500" and larger engines. And I still hear that even today.

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Old 10-07-2020, 08:11 AM
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I enjoy the engine masters series and gladly pay my money every month to Motor Trend. For the technical EM content alone, it is a bargain.

Dyno testing is nice, but is there a way to measure part throttle response? I've driven some stuff with monster HP numbers up top, but they were pure misery down low and in between.

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Old 10-07-2020, 08:44 AM
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I think a big part of what people are missing, and I think Steve Brule even touched on this in one of those Engine Master episodes.

Most people building these performance engines put them in front of automatic transmissions. With that in mind, they are also using some form of a custom stall converter and at least a mild rear gear (3.23/3.50/3.73)

So even if one is worried about part throttle below 2,000 rpm or even 2500 rpm it's really a non issue because as soon as you touch the throttle you blow right through that rpm range in most cases, even light throttle application.

My chevelle is that way with it's 454 and these large AFR heads. I run a very efficient 10" Continental converter in it that is nearly locked solid at cruise speed but even at light throttle application putting around town at 35 mph, as soon as I touch the throttle to accelerate normally, the engine is on 2000 rpm and going through the gears moving the car with ease. I can push the throttle at any low speed and the converter will flash higher (flashes 3400 at the track with traction) It exhibits no low speed issues at all, in fact on regular street tires it can be downright dangerous to drive if you aren't careful at anything below 60 mph.

I think the only way to test part throttle is to just build it and drive it. If the rest of the combo is built around the engine I don't think you'll notice with an automatic. A stick car would be a better scenario and even then I'm not convinced it's a huge problem. In some cases it could be a blessing with people complaining about traction. Just some thoughts, Lots of ways to look at it.
With a Pontiac 455 and it's 4.210 crank it's even less of an issue. My BBC ci wise is the same, but with larger bore and shorter 4" stroke. Technically on paper it should be worse in this scenario, and a better example of how low speed torque could be affected.

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Old 10-07-2020, 03:40 PM
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I think a really important part is being missed here when comparisons are being made on the dyno.
Unfortunately due to pretty poor processing power, and sampling rates, the industry (Superflow? ) settled on 300 rpm / sec as the default test rate.
This is extremely slow and does not compare to actual acceleration rates in vehicle. Often these are thousands of rpm per second, and an engine will respond very differently under these conditions.
If the intake CL remain nearly the same, and volume goes up, so must CSA.
Often cylinder filling with larger CSA heads can be less effective at low rpm, but the slow rate of acceleration on the dyno allows this to "recover" somewhat.
At the track the lack of bottom end, may be made up for with increased performance in the higher ranges, resulting in similar ET. (mph may be a good judge of this?)
I would like to see the tests carried out at higher rates, ie 900 rpm / sec and 1500 rpm / sec, but alot of dyno setups probably couldn't maintain that?

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Old 10-07-2020, 04:21 PM
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"It's possible to provide inlet passages that may show increased airflow on a test bench but reduce net torque from a lack of in-use flow velocity. It is at this point (typically based on over-sized passages) that more flow doesn't produce more power. There's simply insufficient velocity to build V.E. and create increased torque."
Jim McFarland

Noteworthy, If anyone can get access to back issues- In the Oct & Nov 2000 issues of Circle Track Magazine Jim McFarland wrote a series titled "Basics for getting a head". He discussed port sizing in part 1 of this series.

Tid bits here:

https://books.google.com/books?id=9J...arland&f=false


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Old 10-07-2020, 06:31 PM
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Quote:
Originally Posted by 455-4+1 View Post
I think a really important part is being missed here when comparisons are being made on the dyno.
Unfortunately due to pretty poor processing power, and sampling rates, the industry (Superflow? ) settled on 300 rpm / sec as the default test rate.
This is extremely slow and does not compare to actual acceleration rates in vehicle. Often these are thousands of rpm per second, and an engine will respond very differently under these conditions.
If the intake CL remain nearly the same, and volume goes up, so must CSA.
Often cylinder filling with larger CSA heads can be less effective at low rpm, but the slow rate of acceleration on the dyno allows this to "recover" somewhat.
At the track the lack of bottom end, may be made up for with increased performance in the higher ranges, resulting in similar ET. (mph may be a good judge of this?)
I would like to see the tests carried out at higher rates, ie 900 rpm / sec and 1500 rpm / sec, but alot of dyno setups probably couldn't maintain that?
The rate of RPM Change will not only change from 1 gear to the next but vary in each gear. The rate will increase as you go up to peak torque and then will decrease after peak torque. The 300 and 600 RM per second ranges are what many may see in high gear.

Stan

This is from some years ago on the Bo Laws Inertia engine dyno.


__Weight_(or_Req._Inertia)_=_335.0#____Radius_=_12 .0_Inches____Rear_Gear_Ratio_=_1.0

____________________________Rear_____Aero_____Roll ing____________Rear_W__Accele___Time___Rate
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Inerata
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Old 10-07-2020, 06:57 PM
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Originally Posted by Formulajones View Post
Yeah Steve Brule has done that test a few times in the past on BBC's and found that the bigger ports actually don't hurt the low rpm torque like many are led to believe, least at WOT on the dyno anyway .

I went that direction on one of my own BBC's, with a small 454 using large 305cc AFR heads. General consensus is that these heads work best on 502-540ci engines, which is one reason I bought them with bigger plans later.

However they have proved to be just fine on the 454. Low speed light throttle drivability is very crisp and responsive. There is no lack of torque down low and nothing soggy about them putting around town. Which is one of the questions Richard didn't have an answer for on the dyno.

I can say, at least on mine, that it's absolutely not an issue at all.
Makes me wonder if having a large diameter pipe bringing water into your house hurts if you only run the faucet partly open. Would water flow faster if the pipe were smaller at part open???But faster air flow could keep air cooler, but at low rpm would condensation form if too cool taking fuel out of the charge? Too many variables for me.

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Old 10-07-2020, 10:41 PM
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Originally Posted by dmac View Post
Makes me wonder if having a large diameter pipe bringing water into your house hurts if you only run the faucet partly open. Would water flow faster if the pipe were smaller at part open???But faster air flow could keep air cooler, but at low rpm would condensation form if too cool taking fuel out of the charge? Too many variables for me.
LOL Opens up a pretty interesting subject doesn't it?

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Old 10-08-2020, 08:04 AM
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I watched the those videos a while back. A slightly different topic that reminds me of these videos was a discussion about dyno pulls that were made with heads that have poor low lift flow, and they edged out heads with good low flows at those low speeds. Was that a similar result do to the dyno cell loading and acceleration?

My experience with 2 heads that flow the same, but one has a smaller port volume (on the same engine). More often than not the smaller port volume head outperforms the bigger head cc. Especially true on ported heads.

I like what extra port volume usually brings to the table though. We run a fully ported Max Wedge port 445 cid mopar with pretty big ports. In a Pontiac it would be equivalent of close to 360 on the port volume. With the big converter we run, most of the port work we have done has seemed to indicate it wants more port volume yet. We seem to be able to compensate for the big port volume some with extra compression and a decent cam.


Last edited by Jay S; 10-08-2020 at 08:26 AM. Reason: Edit
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Old 10-08-2020, 10:17 AM
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There are a few of ways to compare different heads for the same make engine, let alone different make engines.

A couple are: Coefficient of discharge and CFM per sq inch.

Stan

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Old 10-08-2020, 11:52 AM
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Stan are there guys using the coefficient of discharge for something other than the port window and valve size? I thought that was more for orifice’s?

I remember using the coefficient of discharge calculations to come up with orifice diameters back when we built our flow bench. I tried to use similar data to find optimum port window in the head. I don’t recall having any luck with that. My ME fluids class memories aren’t all that fresh anymore either.

We took one d port 16, and ported it with the expectation that it would be ruined, just seeing where the port volume would would kill low lift flows. It was a little hard to tell what the port volume end up being because they had lots of leaks. I kept welding and brazing, and reshaping the port, making it bigger and bigger. Totally went through the ceiling. I was expecting to find a place were the low lifts flows tanked. The .1” flowed went down some, everything at the higher lifts just kept going up. Maybe someone else’s flow bench would say something different, we were pretty surprised. IRC we were up around 320-330 cfm when we quit, it was getting difficult to find metal to grind out.

Rocky Rotella let me look at the port work from one of the ported 64s that Jim Hand had on his car when he clocked at 11.30 @117. Lol, the only thing I learned is I am not worthy. 11.30 @117 with pump gas, in a 4000 lbs and a flat tappet cam using a 166 cc port volume d port. Holy cow that was fast for that set up!

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Old 10-08-2020, 01:07 PM
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Jay,
Coefficient of discharge is another way of looking at CFM per sq inch. If I say a port flows xxx CFM per sq inch we do not know if that is good or bad without knowing the depression it was flowed at. If I say I have a Coefficient of discharge of .8888 it does not matter what the depression was.

In the FLOW / IOP program that I did with David Vizard we calculate CD and let the User graph it against a different Flow test. Because we correct all flow data to to 28" of water we can also do the same for CFM per Sq Inch.

As a side note. When you have a junk head and some time track what happens to low lift flow just by increase the valve / seat angle.

Stan

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Old 10-08-2020, 06:37 PM
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Originally Posted by Formulajones View Post
There was another test they did on a Ford that did a little better job of what you're referring to Mike. It was pretty much the same result though using a handful of AFR heads on that one. Started with 165's and went up to 195 and then either 220's or 235's. Torque was still excellent down low. The interesting part is that the 165's and 195's were almost identical throughout.

I think Steve Brule even did an episode on Engine Masters about this theory.

Yes, I remember that one. Found it again: It was a 408 and they tested 165cc, 195cc, and 220cc AFRs. The 195cc produced the best peak torque AND peak hp (10+HP over the 220s). And on the 2500rpm start of the pull, the 195CCs matched the 165CCs for torque. Now, it was a mild camshaft so probably with more cam lift, might have seen an advantage on the 220CC for peak HP. Their results seem consistent with some of Vizards published results if you scale the runner size for displacement.

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Old 10-08-2020, 10:41 PM
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Originally Posted by amcmike View Post
Yes, I remember that one. Found it again: It was a 408 and they tested 165cc, 195cc, and 220cc AFRs. The 195cc produced the best peak torque AND peak hp (10+HP over the 220s). And on the 2500rpm start of the pull, the 195CCs matched the 165CCs for torque. Now, it was a mild camshaft so probably with more cam lift, might have seen an advantage on the 220CC for peak HP. Their results seem consistent with some of Vizards published results if you scale the runner size for displacement.
Glad you found it because I searched and couldn't lol

I thought that one was a pretty interesting comparison.

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Old 10-14-2020, 01:47 AM
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Originally Posted by amcmike View Post
Yes, I remember that one. Found it again: It was a 408 and they tested 165cc, 195cc, and 220cc AFRs. The 195cc produced the best peak torque AND peak hp (10+HP over the 220s). And on the 2500rpm start of the pull, the 195CCs matched the 165CCs for torque. Now, it was a mild camshaft so probably with more cam lift, might have seen an advantage on the 220CC for peak HP. Their results seem consistent with some of Vizards published results if you scale the runner size for displacement.
Did they test at different acceleration rates, or just 300 rpm/sec. Would have been a prime opportunity to test at 300, 900 and 1500, then I am betting the results would gave been more varied

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The PY Online Forums is the largest online gathering of Pontiac enthusiasts anywhere in the world. Founded in 1991, it was also the first online forum for people to gather and talk about their Pontiacs. Since then, it has become the mecca of Pontiac technical data and knowledge that no other place can surpass.

 




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