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MCS Length?

General engine tech -- Drag Racing to Circle Track

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steve cowan
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Re: MCS Length?

Post by steve cowan » Fri Mar 15, 2019 7:18 pm

I have not had the unfilled port on the bench, I did not port them, Competition Grinding out of Tucson did those back in 2004 and I never have used them.
The opening is about 2.7, prp about 1.9 and 1/2" past the prp about 2.04 and about 2.66 right before the short turn...Theses numbers are not accounting for the corner radius. I will probably try probing them although I will have no idea what I am looking at. :)
The change just seem to abrupt in that short of a distance but I know everyone use to gasket match heads instead of port matching.
[/quote]

Gary,
air speed will be fast at the back of the pinch,you probably need to let us know more information,engine size,rpm,application etc.
your entry size is a 1205 gasket,i minus 5% for corner radius 2.7'' - 5% = 2.56''
you need to look at avg cross sectional area of the entire port in cc and port length.
depending on application some guys use the throat as the MCSA and some use the pinch as the MCSA,we have had these discussions before.
getting the avg CSA is the hardest thing to measure and achieve because of the left and right port configuration,measuring it is even harder to be accurate.
steve c

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Re: MCS Length?

Post by GARY C » Sat Mar 16, 2019 12:50 am

steve cowan wrote:
Fri Mar 15, 2019 7:18 pm
I have not had the unfilled port on the bench, I did not port them, Competition Grinding out of Tucson did those back in 2004 and I never have used them.
The opening is about 2.7, prp about 1.9 and 1/2" past the prp about 2.04 and about 2.66 right before the short turn...Theses numbers are not accounting for the corner radius. I will probably try probing them although I will have no idea what I am looking at. :)
The change just seem to abrupt in that short of a distance but I know everyone use to gasket match heads instead of port matching.
Gary,
air speed will be fast at the back of the pinch,you probably need to let us know more information,engine size,rpm,application etc.
your entry size is a 1205 gasket,i minus 5% for corner radius 2.7'' - 5% = 2.56''
you need to look at avg cross sectional area of the entire port in cc and port length.
depending on application some guys use the throat as the MCSA and some use the pinch as the MCSA,we have had these discussions before.
getting the avg CSA is the hardest thing to measure and achieve because of the left and right port configuration,measuring it is even harder to be accurate.
[/quote]

I get all that, what I am asking is if you increase your Pinch MCS from a 1/2" long to 1" long or 2" long would have to increase the size (height and width) and if so is there a formula to determine how much?

I think a little time on the bench will be the best and easiest way to determine what I am looking for.

BTW... I found out tonight that if you have a 200cc RHS/PRO TOPLINE/EQ head your throat and bowl are already to big, Bowls are 1.9 across and Throats are 1.81 to 1.83 across depending on the casting. These are all out of the box 2.02 valve heads.
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Re: MCS Length?

Post by steve cowan » Sat Mar 16, 2019 1:38 am

Gary,
No formula that I am aware of for what you are asking, my own personal stuff the pinch is the restriction because of application and rpm. The only thing I can say is set the pinch width and blend wide as you can, smooth transition is what you want, it will be self explanatory when you do it,
Where are you at with these heads? Valve job done, throats sized etc
Just curious
steve c

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Re: MCS Length?

Post by GARY C » Sat Mar 16, 2019 2:22 am

steve cowan wrote:
Sat Mar 16, 2019 1:38 am
Gary,
No formula that I am aware of for what you are asking, my own personal stuff the pinch is the restriction because of application and rpm. The only thing I can say is set the pinch width and blend wide as you can, smooth transition is what you want, it will be self explanatory when you do it,
Where are you at with these heads? Valve job done, throats sized etc
Just curious
Long story short, after measuring them and talking with someone more knowledgeable than me I thought the guy that ported them in 2004 made the bowl and throat to big but it turns out that these casting are this size to begin with as I mentioned in my last post.
This is the Pro Topline CNC chamber 200cc runner head 2.02 valve. I don't want the big gasket opening so I will fill with epoxy and use a trim to fit gasket as it will most likly be on a 350 with a 6000to 6500 rpm hyd flat cam set up with nitrous.

Pinch is about 1.937... Mid port about 2.36... Short turn about 2.66... Throat is 2.51ish
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Re: MCS Length?

Post by SchmidtMotorWorks » Sat Mar 16, 2019 4:33 am

GARY C wrote:
Sat Mar 16, 2019 2:22 am
Pinch is about 1.937... Mid port about 2.36... Short turn about 2.66... Throat is 2.51ish
What criteria tells you that any part of the port is to large or too small?

The optimum CSA at any point is determined by the curvature of the flow trajectory at that point.
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Re: MCS Length?

Post by GARY C » Sat Mar 16, 2019 4:54 am

SchmidtMotorWorks wrote:
Sat Mar 16, 2019 4:33 am
GARY C wrote:
Sat Mar 16, 2019 2:22 am
Pinch is about 1.937... Mid port about 2.36... Short turn about 2.66... Throat is 2.51ish
What criteria tells you that any part of the port is to large or too small?

The optimum CSA at any point is determined by the curvature of the flow trajectory at that point.
Data from the industry testing performance engines.
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Re: MCS Length?

Post by SchmidtMotorWorks » Sat Mar 16, 2019 4:57 am

GARY C wrote:
Sat Mar 16, 2019 4:54 am
SchmidtMotorWorks wrote:
Sat Mar 16, 2019 4:33 am
GARY C wrote:
Sat Mar 16, 2019 2:22 am
Pinch is about 1.937... Mid port about 2.36... Short turn about 2.66... Throat is 2.51ish
What criteria tells you that any part of the port is to large or too small?

The optimum CSA at any point is determined by the curvature of the flow trajectory at that point.
Data from the industry testing performance engines.
What data?

Focusing on area over trajectory is misguided.
The flow velocity across the area near turns is not uniform or consistent with other regions of the port.
Waves don't travel concentric to center of area.

The emphasis on area, is a case of everything looking like a nail to a hammer.
It is easy to measure, but not the key feature.
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Re: MCS Length?

Post by steve cowan » Sat Mar 16, 2019 5:06 am

Gary,
street car ?? small shot ?? i am interested in the application
any thoughts on valve timing events to suit nitrous oxide,
steve c

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Re: MCS Length?

Post by GARY C » Sat Mar 16, 2019 5:50 am

steve cowan wrote:
Sat Mar 16, 2019 5:06 am
Gary,
street car ?? small shot ?? i am interested in the application
any thoughts on valve timing events to suit nitrous oxide,
It will go in this car, resurrected from a field in California. The heads have a 1.7 exhaust valve to test the theory of a larger ex valve for nitrous. Below is a rough idea of the cam for a .037 nitrous pill, about 50 horse with a 1.7 valve, I will possibly test up to 175 shot depending on what it actually gains. It's a test I wanted to do 15 years ago but I built a race car instead and these parts have been sitting on the shelf, I have everything but the cam and intake valves.
The 357 I tested years ago with a big wide spread nitrous cam picked up 160 ft lbs and 190 horse on a 150 shot so it depends on what short block I run as to how much I will be willing to test.
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Re: MCS Length?

Post by Carnut1 » Sat Mar 16, 2019 6:22 am

I remember that article and that car. Very cool project!
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Re: MCS Length?

Post by GARY C » Sat Mar 16, 2019 6:39 am

Carnut1 wrote:
Sat Mar 16, 2019 6:22 am
I remember that article and that car. Very cool project!
It was a 2 part, I still have both, I found them in the attic of a cabinet shop in the late 80's. at the time I was driving a 79 T/A and trying to build almost the exact engine.
The car cleaned up pretty well.
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Re: MCS Length?

Post by RevTheory » Sat Mar 16, 2019 7:54 am

What's the average throat diameter on the intake, Gary?

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Re: MCS Length?

Post by SchmidtMotorWorks » Sat Mar 16, 2019 12:39 pm

GARY C wrote:
Sat Mar 16, 2019 5:50 am
It will go in this car, resurrected from a field in California.
By the looks of the wheels, that is has the WS6 suspension package.
If everything is kept tight, that is a pretty good handling car
and
the engine bay that is easier to work on than late model cars.
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Re: MCS Length?

Post by GARY C » Sat Mar 16, 2019 2:27 pm

RevTheory wrote:
Sat Mar 16, 2019 7:54 am
What's the average throat diameter on the intake, Gary?
1.81 across, total like 2.5
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Re: MCS Length?

Post by GARY C » Sat Mar 16, 2019 2:42 pm

SchmidtMotorWorks wrote:
Sat Mar 16, 2019 12:39 pm
GARY C wrote:
Sat Mar 16, 2019 5:50 am
It will go in this car, resurrected from a field in California.
By the looks of the wheels, that is has the WS6 suspension package.
If everything is kept tight, that is a pretty good handling car
and
the engine bay that is easier to work on than late model cars.
Yes WS6, the car only has around 32,000 miles on it, it still had the Goodyear NCT tires on it from the article and from the looks of the rear tires I think most of those miles came from tire smoke :)
It still has original space saver spare, jack and hard ware, t top bag.
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