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Minimum Cross Sectional Area: Question

General engine tech -- Drag Racing to Circle Track

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mt-engines
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Re: Minimum Cross Sectional Area: Question

Post by mt-engines » Wed Feb 12, 2020 3:16 pm

skinny z wrote:
Wed Feb 12, 2020 2:25 pm
67RS502 wrote:
Wed Feb 12, 2020 1:33 pm
With the 224/224 cam it is a very similar to my 383.
My heads are on the very large side for it, but still made decent power, and ran well.
It made 483hp/490tq.
Chevy II with 373s a 10" verter and a 200-4r it ran 10.90s
daily driver mellow, good power at 4000.
mph was the same shifting at 6500-6800 with big heads.
Not sure what your goals are, with a decent head it should be very similar to my combo performance wise.
I'm not 100% sorted out at this point although it's been said this kind of combination has been done for decades. Still, I like the research side so I keep experimenting.
That your similar to 224/224 carries up to 6500+ I suppose says something about your heads. From what I'm finding is that I can expect to run out of breath before 6000. Which is fine by me. That said, I'm also finding that I could wind it up a little tighter. A decision I'll make once I've gone over the heads to make sure I haven't messed them up in the last couple of years.
If your carb cant flow enough air, it will choke out.
If your tune goes fat up top, it will run out
If the ports are too fast, it will choke out

Simple things like spacers and bigger carbs can help. Bring it to a chassis dyno, you wouldnt believe how much power can be made there. Air filter , air bleeds, float level adjustments. Then throw some jet back in it and tske it to the track.

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Re: Minimum Cross Sectional Area: Question

Post by 67RS502 » Wed Feb 12, 2020 5:10 pm

skinny z wrote:
Wed Feb 12, 2020 2:25 pm
67RS502 wrote:
Wed Feb 12, 2020 1:33 pm
With the 224/224 cam it is a very similar to my 383.
My heads are on the very large side for it, but still made decent power, and ran well.
It made 483hp/490tq.
Chevy II with 373s a 10" verter and a 200-4r it ran 10.90s
daily driver mellow, good power at 4000.
mph was the same shifting at 6500-6800 with big heads.
Not sure what your goals are, with a decent head it should be very similar to my combo performance wise.
I'm not 100% sorted out at this point although it's been said this kind of combination has been done for decades. Still, I like the research side so I keep experimenting.
That your similar to 224/224 carries up to 6500+ I suppose says something about your heads. From what I'm finding is that I can expect to run out of breath before 6000. Which is fine by me. That said, I'm also finding that I could wind it up a little tighter. A decision I'll make once I've gone over the heads to make sure I haven't messed them up in the last couple of years.
Just wanted to list my combo to show you what those Comp lobes can do with my garage build.
Yes it revs high because the heads are on the large side, its an old motor, I believe the csa is around 2.4.
but its a cam swap and single plane away from an easy 50-75hp gain.
Just work your heads, or pic up a better set!
67 camaro
girly rollers on pumpgas:
420 - 641hp BretBauerCam, 1.39, 9.79 @ 137.5
383 - 490hp 224/224, 1.56, 10.77 @ 124.6
502 - 626hp 252/263, 049s 1.44, 10.08 @ 132.7
62 Nova cruiser
383/200-4R/12-bolt w 373s
224/224 HR cam
1.57 10.97 @ 121.2

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Re: Minimum Cross Sectional Area: Question

Post by skinny z » Wed Feb 12, 2020 9:18 pm

mt-engines wrote:
Wed Feb 12, 2020 3:16 pm
If your carb cant flow enough air, it will choke out.
If your tune goes fat up top, it will run out
If the ports are too fast, it will choke out

Simple things like spacers and bigger carbs can help. Bring it to a chassis dyno, you wouldnt believe how much power can be made there. Air filter , air bleeds, float level adjustments. Then throw some jet back in it and tske it to the track.
I've got the carb covered.
Tune up is what I've been focusing on for the last decade or so (that isn't to say I'm the best at it though).
As for the ports...that's the whole point of this thread. Trying to figure that out.
I like the chassis dyno but I generally get there with my tune sorted out. Or close anyway. What I'd like with this build, seeing as how I'm going about it, is to put it on the engine dyno. Tuning there is something else. Tuning at the track is an "I've been there and done that" kind of deal. Taking a fresh lump with known results is what's driving this one.

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Re: Minimum Cross Sectional Area: Question

Post by skinny z » Wed Feb 12, 2020 9:33 pm

67RS502 wrote:
Wed Feb 12, 2020 5:10 pm
Just wanted to list my combo to show you what those Comp lobes can do with my garage build.
Yes it revs high because the heads are on the large side, its an old motor, I believe the csa is around 2.4.
but its a cam swap and single plane away from an easy 50-75hp gain.
Just work your heads, or pic up a better set!
It's much appreciated. We (as in a group of guys who build and race street cars) have always had a certain formula. Sort of be as fast as you can but still be able to drive everywhere even across the country sort of deal. That was great 15 years ago. And I was fairly competitive. Now I get crushed by a showroom stock purchase.
I'm not prepared to compete on that level right now. But I can be fairly quick (given the platform). This engine is a step away from that formula and more drag orientated.
That's why I appreciate your posting specs and results. A bogey of sorts.
Anyway, I've got smallish heads, which will remain as they are provided they're not FUBARED when I do a tear down this summer. A new forged shortblock in the works and the final step being the cam choice.
Which is where I'm going with my threads. I'd really like to get on the dyno.
I know 383 "Vortec" has been done a million times. But I don't necessarily have to follow the beaten path if there's something to be gained with some research.

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Re: Minimum Cross Sectional Area: Question

Post by David Vizard » Fri Feb 14, 2020 2:26 am

skinny z wrote:
Mon Feb 10, 2020 9:28 pm
Now I see where the misinterpretation is.
If you raise the CR and expect a cam spec to follow what we've all come to expect, you have to raise the target peak RPM also. As I said before, keeping the RPM target the same and raising the CR doesn't make sense. So then, neither do the results.
The same holds true with peak port flow. If you're at the limit, then cam and compression aren't going to have the same effect.
I've inquired about this with the developers but I think that explains it.
Skinny z

If you can't fill the cylinders you had better squeeze the heck out of what you've got!
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Re: Minimum Cross Sectional Area: Question

Post by David Vizard » Fri Feb 14, 2020 2:31 am

gmrocket wrote:
Sun Feb 09, 2020 7:08 pm
In the real world do you really think if you added more than half a point of compression, you would REDUCE the .050" numbers?

Effectively, put in a smaller cam? That's what I'm asking because you said the program suggested a much shorter cam

Sure don't sound right to me
Hi rocket man -

If the CR called for goes up and the RPM for peak power stays the same a shorter cam will be needed to make peak power at that rpm.
DV
David Vizard Small Group Performance Seminars - held about every 2 months. My shop or yours. Contact for seminar deails - davidvizardseminar@gmail.com for details.

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Re: Minimum Cross Sectional Area: Question

Post by gmrocket » Fri Feb 14, 2020 7:28 am

David Vizard wrote:
Fri Feb 14, 2020 2:31 am
gmrocket wrote:
Sun Feb 09, 2020 7:08 pm
In the real world do you really think if you added more than half a point of compression, you would REDUCE the .050" numbers?

Effectively, put in a smaller cam? That's what I'm asking because you said the program suggested a much shorter cam

Sure don't sound right to me
Hi rocket man -

If the CR called for goes up and the RPM for peak power at the same a shorter cam will be needed to make peak power at that rpm.
DV
So with over half a point more compression, even if you add 1 more degree to the .050" number, peak power won't increase at 5500?

The .050" number has to be reduced to increase power?

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Re: Minimum Cross Sectional Area: Question

Post by Stan Weiss » Fri Feb 14, 2020 4:56 pm

gmrocket wrote:
Fri Feb 14, 2020 7:28 am
David Vizard wrote:
Fri Feb 14, 2020 2:31 am
gmrocket wrote:
Sun Feb 09, 2020 7:08 pm
In the real world do you really think if you added more than half a point of compression, you would REDUCE the .050" numbers?

Effectively, put in a smaller cam? That's what I'm asking because you said the program suggested a much shorter cam

Sure don't sound right to me
Hi rocket man -

If the CR called for goes up and the RPM for peak power at the same a shorter cam will be needed to make peak power at that rpm.
DV
So with over half a point more compression, even if you add 1 more degree to the .050" number, peak power won't increase at 5500?

The .050" number has to be reduced to increase power?
Torque Master is not a complete engine simulation program. There are a limited number of inputs.

If just CR is increased (and peak HP RPM has remained constant) the duration shown is reduced but the est HP still has increased.

For the program to want / show the same duration with the higher CR as it did with the lower CR the peak HP RPM would needed to be raised.

Stan
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Do you use engine simulation software that uses cylinder head flow files?
We have a package of more than 3025 DFW or FLW Files

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Re: Minimum Cross Sectional Area: Question

Post by skinny z » Fri Feb 14, 2020 5:12 pm

David Vizard wrote:
Fri Feb 14, 2020 2:26 am
skinny z wrote:
Mon Feb 10, 2020 9:28 pm
Now I see where the misinterpretation is.
If you raise the CR and expect a cam spec to follow what we've all come to expect, you have to raise the target peak RPM also. As I said before, keeping the RPM target the same and raising the CR doesn't make sense. So then, neither do the results.
The same holds true with peak port flow. If you're at the limit, then cam and compression aren't going to have the same effect.
I've inquired about this with the developers but I think that explains it.
Skinny z

If you can't fill the cylinders you had better squeeze the heck out of what you've got!
DV
That certainly seems to be the case. Once I got a better grasp of the relationships between the various selectable inputs in TM, it was easy to maneuver around the program and observe how one plays into the other.
Thanks.

Kevin

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Re: Minimum Cross Sectional Area: Question

Post by skinny z » Fri Feb 14, 2020 5:20 pm

Stan Weiss wrote:
Fri Feb 14, 2020 4:56 pm
Torque Master is not a complete engine simulation program. There are a limited number of inputs.

If just CR is increased (and peak HP RPM has remained constant) the duration shown is reduced but the est HP still has increased.

For the program to want / show the same duration with the higher CR as it did with the lower CR the peak HP RPM would needed to be raised.

Stan
This is exactly how I'm learning the program works. And for my intents and purposes, it's giving me what I'm looking for with the engine parameters that I have. It's also interesting to see how one plays out against another. That's how the CR vs duration conversation came up in the first place.

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Re: Minimum Cross Sectional Area: Question

Post by Orr89rocz » Fri Feb 14, 2020 7:45 pm


Torque Master is not a complete engine simulation program. There are a limited number of inputs.

If just CR is increased (and peak HP RPM has remained constant) the duration shown is reduced but the est HP still has increased.

For the program to want / show the same duration with the higher CR as it did with the lower CR the peak HP RPM would needed to be raised.

Stan
I see the program works that way but in real life, does that work that way? I honestly havent heard that before. Does the same cam peak differently with just a change in compression ratio?

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Re: Minimum Cross Sectional Area: Question

Post by randy331 » Fri Feb 14, 2020 7:54 pm

Orr89rocz wrote:
Fri Feb 14, 2020 7:45 pm
I see the program works that way but in real life, does that work that way?
No it doesn't. I did a back to back raise the comp test. Same day on the dyno I pulled the heads and angle milled them enough to raise comp about 1 full point, put the heads back on and re pulled it. There was no noticeable change in where it made peak tq/hp at and there wasn't the power gain most think would happen with that increase in comp.

Randy

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Re: Minimum Cross Sectional Area: Question

Post by Stan Weiss » Sat Feb 15, 2020 2:02 am

skinny z wrote:
Fri Feb 14, 2020 5:20 pm
Stan Weiss wrote:
Fri Feb 14, 2020 4:56 pm
Torque Master is not a complete engine simulation program. There are a limited number of inputs.

If just CR is increased (and peak HP RPM has remained constant) the duration shown is reduced but the est HP still has increased.

For the program to want / show the same duration with the higher CR as it did with the lower CR the peak HP RPM would needed to be raised.

Stan
This is exactly how I'm learning the program works. And for my intents and purposes, it's giving me what I'm looking for with the engine parameters that I have. It's also interesting to see how one plays out against another. That's how the CR vs duration conversation came up in the first place.
Kevin,
What was the results from the other software that you used for recommended cam duration verses CR?

Stan
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Offering Performance Software Since 1987
Do you use engine simulation software that uses cylinder head flow files?
We have a package of more than 3025 DFW or FLW Files

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Re: Minimum Cross Sectional Area: Question

Post by GARY C » Sat Feb 15, 2020 5:23 am

randy331 wrote:
Fri Feb 14, 2020 7:54 pm
Orr89rocz wrote:
Fri Feb 14, 2020 7:45 pm
I see the program works that way but in real life, does that work that way?
No it doesn't. I did a back to back raise the comp test. Same day on the dyno I pulled the heads and angle milled them enough to raise comp about 1 full point, put the heads back on and re pulled it. There was no noticeable change in where it made peak tq/hp at and there wasn't the power gain most think would happen with that increase in comp.

Randy
So this one test makes it conclusive?

SAM, BES, Wells and other Engine Builders have done similar test and concluded that angle milling a head as an after thought was not a good idea if one wanted to take advantage of an angle milled head.
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Re: Minimum Cross Sectional Area: Question

Post by steve316 » Sat Feb 15, 2020 7:58 am

GaryC what is the comparison of angle mill to raise compression or as a after thought?

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