We are currently running on the new domain and server: www.Speed-Talk.com

IMPORTANT: Update your bookmarks to https://www.speed-talk.com/forum/
(Right-click the URL and select "Bookmark this link")

Minimum Cross Sectional Area: Question

General engine tech -- Drag Racing to Circle Track

Moderator: Team

Post Reply
SpeierRacingHeads
Vendor
Posts: 385
Joined: Sun May 13, 2012 1:28 pm
Location:

Re: Minimum Cross Sectional Area: Question

Post by SpeierRacingHeads » Tue Feb 11, 2020 11:33 am

skinny z wrote:
Tue Feb 11, 2020 11:28 am
SpeierRacingHeads wrote:
Tue Feb 11, 2020 10:40 am
IMO, the key isn't a cylinder head or a manifold, it's the camshaft.
A Super Stock 358 with a 1.6in² pinch peaks at 7400.
An interesting fact and right on topic. For the record, what kind of CR does a Super Stock engine have? The 1.6in² would reflect the "stock" nature of the heads correct?
I'd to be interested to see how this program would respond to the input of an SS engine. I'll have to research the details. (Love the Stockers by the way. Well worth the price of admission.)
10-1 for most 350/300 combos. Some of the LT are 11-1..

Here is my 172cc port. Look at the SSR...

Image
Speier Racing Heads
Chad Speier
785-623-0963

skinny z
HotPass
HotPass
Posts: 285
Joined: Tue Mar 11, 2008 8:42 am
Location: Canada

Re: Minimum Cross Sectional Area: Question

Post by skinny z » Tue Feb 11, 2020 11:55 am

SpeierRacingHeads wrote:
Tue Feb 11, 2020 11:33 am


10-1 for most 350/300 combos. Some of the LT are 11-1..

Here is my 172cc port. Look at the SSR...

Image
I was going to add that the SS port must be fairly trick given the 1.6" pinch. Guess I was right.
That CR is surprisingly low (to me anyway). And I'm gaining an understanding of how TM might work in that regard. One of the things it does is assign what some of us might think as an absurdly high duration given the CR. I can see where this is going.
Thanks.

steve cowan
HotPass
HotPass
Posts: 1007
Joined: Wed Jul 27, 2011 5:22 am
Location: brisbane AUSTRALIA

Re: Minimum Cross Sectional Area: Question

Post by steve cowan » Tue Feb 11, 2020 12:46 pm

SpeierRacingHeads wrote:
Tue Feb 11, 2020 11:33 am
skinny z wrote:
Tue Feb 11, 2020 11:28 am
SpeierRacingHeads wrote:
Tue Feb 11, 2020 10:40 am
IMO, the key isn't a cylinder head or a manifold, it's the camshaft.
A Super Stock 358 with a 1.6in² pinch peaks at 7400.
An interesting fact and right on topic. For the record, what kind of CR does a Super Stock engine have? The 1.6in² would reflect the "stock" nature of the heads correct?
I'd to be interested to see how this program would respond to the input of an SS engine. I'll have to research the details. (Love the Stockers by the way. Well worth the price of admission.)
10-1 for most 350/300 combos. Some of the LT are 11-1..

Here is my 172cc port. Look at the SSR...

Image
Is that picture a stock port location or is it raised like the other epoxy ports you have shown before??
steve c

Orr89rocz
HotPass
HotPass
Posts: 1907
Joined: Sun Sep 28, 2008 9:25 pm
Location:

Re: Minimum Cross Sectional Area: Question

Post by Orr89rocz » Tue Feb 11, 2020 1:05 pm

Thats begs the question and perhaps it was already discussed, does area matter as much as shape?

1.8 csa in a 15 deg ls style head vs 1.8 csa in a 23 deg sbc lets say. Straighter shot to the valve, less SSR angle, should tolerate higher airspeed. So more flow, more power but does it make more rpm?

SpeierRacingHeads
Vendor
Posts: 385
Joined: Sun May 13, 2012 1:28 pm
Location:

Re: Minimum Cross Sectional Area: Question

Post by SpeierRacingHeads » Tue Feb 11, 2020 1:35 pm

steve cowan wrote:
Tue Feb 11, 2020 12:46 pm
SpeierRacingHeads wrote:
Tue Feb 11, 2020 11:33 am
skinny z wrote:
Tue Feb 11, 2020 11:28 am


An interesting fact and right on topic. For the record, what kind of CR does a Super Stock engine have? The 1.6in² would reflect the "stock" nature of the heads correct?
I'd to be interested to see how this program would respond to the input of an SS engine. I'll have to research the details. (Love the Stockers by the way. Well worth the price of admission.)
10-1 for most 350/300 combos. Some of the LT are 11-1..

Here is my 172cc port. Look at the SSR...

Image
Is that picture a stock port location or is it raised like the other epoxy ports you have shown before??
For sure raised. It's a scanned copy so I can CNC them and hand tweak.
Speier Racing Heads
Chad Speier
785-623-0963

68corvette
HotPass
HotPass
Posts: 205
Joined: Sat Jan 08, 2005 5:33 pm
Location: Finland / Hyvinkaa

Re: Minimum Cross Sectional Area: Question

Post by 68corvette » Tue Feb 11, 2020 1:39 pm

Orr89rocz wrote:
Tue Feb 11, 2020 1:05 pm
Thats begs the question and perhaps it was already discussed, does area matter as much as shape?

1.8 csa in a 15 deg ls style head vs 1.8 csa in a 23 deg sbc lets say. Straighter shot to the valve, less SSR angle, should tolerate higher airspeed. So more flow, more power but does it make more rpm?
According to this article the case is the reverse:
https://www.google.com/url?sa=t&source= ... 1446090670

Orr89rocz
HotPass
HotPass
Posts: 1907
Joined: Sun Sep 28, 2008 9:25 pm
Location:

Re: Minimum Cross Sectional Area: Question

Post by Orr89rocz » Tue Feb 11, 2020 1:59 pm

68corvette wrote:
Tue Feb 11, 2020 1:39 pm
Orr89rocz wrote:
Tue Feb 11, 2020 1:05 pm
Thats begs the question and perhaps it was already discussed, does area matter as much as shape?

1.8 csa in a 15 deg ls style head vs 1.8 csa in a 23 deg sbc lets say. Straighter shot to the valve, less SSR angle, should tolerate higher airspeed. So more flow, more power but does it make more rpm?
According to this article the case is the reverse:
https://www.google.com/url?sa=t&source= ... 1446090670
Hmm i didnt read that to state it was the reverse. It seems to agree, more straight port and less short side turn angle is ideal. Edit: let me study figure 12 more

SpeierRacingHeads
Vendor
Posts: 385
Joined: Sun May 13, 2012 1:28 pm
Location:

Re: Minimum Cross Sectional Area: Question

Post by SpeierRacingHeads » Tue Feb 11, 2020 5:07 pm

I kind of like the biased approach..

Image
Speier Racing Heads
Chad Speier
785-623-0963

steve cowan
HotPass
HotPass
Posts: 1007
Joined: Wed Jul 27, 2011 5:22 am
Location: brisbane AUSTRALIA

Re: Minimum Cross Sectional Area: Question

Post by steve cowan » Wed Feb 12, 2020 1:03 am

SpeierRacingHeads wrote:
Tue Feb 11, 2020 10:40 am
IMO, the key isn't a cylinder head or a manifold, it's the camshaft.

A Super Stock 358 with a 1.6in² pinch peaks at 7400.
I find this statement interesting especially from a head porter,
Surely application specific, I can't see running a super stock camshaft for a 170 cc head with as cast port location, SSR etc.
Forget all the low drag short block stuff, I am talking about induction tract, intake manifold, intake port, combustion chamber, exhaust port etc, what am I missing here??
steve c

SpeierRacingHeads
Vendor
Posts: 385
Joined: Sun May 13, 2012 1:28 pm
Location:

Re: Minimum Cross Sectional Area: Question

Post by SpeierRacingHeads » Wed Feb 12, 2020 11:31 am

steve cowan wrote:
Wed Feb 12, 2020 1:03 am
SpeierRacingHeads wrote:
Tue Feb 11, 2020 10:40 am
IMO, the key isn't a cylinder head or a manifold, it's the camshaft.

A Super Stock 358 with a 1.6in² pinch peaks at 7400.
I find this statement interesting especially from a head porter,
Surely application specific, I can't see running a super stock camshaft for a 170 cc head with as cast port location, SSR etc.
Forget all the low drag short block stuff, I am talking about induction tract, intake manifold, intake port, combustion chamber, exhaust port etc, what am I missing here??
I think the key to a cylinder head having the secondary choke upstream is the speed at the floor at the apex. And the back half of the port built to handle the speed. The SS combo's show how important the camshaft is.

I've applied this thinking in a lot of combos and if the head is built right, you can get by with less area needed and let the cam do it's job.
Speier Racing Heads
Chad Speier
785-623-0963

skinny z
HotPass
HotPass
Posts: 285
Joined: Tue Mar 11, 2008 8:42 am
Location: Canada

Re: Minimum Cross Sectional Area: Question

Post by skinny z » Wed Feb 12, 2020 11:42 am

So, it's obvious that the standard formula for MCA regarding CID and RPM doesn't hold true for all applications. Which makes perfect sense. But does it hold true for a conventional port? More specifically, my mildly ported RHS Vortecs have an estimated MCA of 1.8 sq in. Calculators estimate that the max RPM and 383 CID would be somewhere around 5500. I think this may have been asked and answered already but these SS heads have me rethinking my RPM potential.

SpeierRacingHeads
Vendor
Posts: 385
Joined: Sun May 13, 2012 1:28 pm
Location:

Re: Minimum Cross Sectional Area: Question

Post by SpeierRacingHeads » Wed Feb 12, 2020 12:26 pm

skinny z wrote:
Wed Feb 12, 2020 11:42 am
So, it's obvious that the standard formula for MCA regarding CID and RPM doesn't hold true for all applications. Which makes perfect sense. But does it hold true for a conventional port? More specifically, my mildly ported RHS Vortecs have an estimated MCA of 1.8 sq in. Calculators estimate that the max RPM and 383 CID would be somewhere around 5500. I think this may have been asked and answered already but these SS heads have me rethinking my RPM potential.
Some porters port off target velocity and some off of required area. Target velocity makes smaller ports.
Speier Racing Heads
Chad Speier
785-623-0963

User avatar
67RS502
Expert
Expert
Posts: 764
Joined: Wed Apr 20, 2005 12:57 pm
Location: Houston Tx.
Contact:

Re: Minimum Cross Sectional Area: Question

Post by 67RS502 » Wed Feb 12, 2020 1:33 pm

skinny z wrote:
Sun Feb 09, 2020 12:40 pm
gmrocket wrote:
Sat Feb 08, 2020 9:25 pm
I don't think you've said what type of cam you want to run? maybe I missed it...hyd flat? anyway, with your comp a bit on the low side you might be best to keep your seat timing on the shorter side and go with a more aggressive lobe to get you into the bigger .050" numbers.

it will build more cyl pressure, TQ , on the low end and the bigger .050" will help make more pwr on the top end of the rpm range and will not fall off as quick.
This is a hydraulic roller.
I'm certainly starting to go in that direction. The heads are obviously the limiting factor (and they aren't going to change) so I find I'm RPM limited with the CID. Not so much so that so it'll stop it from making decent power but the peak HP RPM is going to be lower than i had started off going for initially.
So yeah, nothing special now I guess as I had wanted to work this in another direction but it appears it's going to be a fairly traditional "Vortec 383" spec. Or at least modified Vortec 383.
The aggressive lobe is subjective though. An Xtreme Energy from COMP is easy to handle while I found their XFI profile to be little harder on parts. The latter being 274/224 w/ .575" and 1.6 RR. It looks though that the current cam spec is going to be in around 283/231 with .550" lift. That's tame in relative terms and I'll be looking for other lobe profile lists (like Mike Jones' offerings) to compare.
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.
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

skinny z
HotPass
HotPass
Posts: 285
Joined: Tue Mar 11, 2008 8:42 am
Location: Canada

Re: Minimum Cross Sectional Area: Question

Post by skinny z » 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.

mt-engines
Member
Member
Posts: 59
Joined: Fri Sep 27, 2019 12:35 pm
Location:

Re: Minimum Cross Sectional Area: Question

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

SpeierRacingHeads wrote:
Wed Feb 12, 2020 12:26 pm
skinny z wrote:
Wed Feb 12, 2020 11:42 am
So, it's obvious that the standard formula for MCA regarding CID and RPM doesn't hold true for all applications. Which makes perfect sense. But does it hold true for a conventional port? More specifically, my mildly ported RHS Vortecs have an estimated MCA of 1.8 sq in. Calculators estimate that the max RPM and 383 CID would be somewhere around 5500. I think this may have been asked and answered already but these SS heads have me rethinking my RPM potential.
Some porters port off target velocity and some off of required area. Target velocity makes smaller ports.
Casting limitations is what can throw a curveball for either, being able to get the desired short turn can be a compromise to the rest of the port. Also clutch or converter car can habe an effect on how i may size the ports. I am more conservative with clutch cars sizing.

Post Reply