#1  
Old 04-16-2021, 10:06 PM
RH68 RH68 is offline
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Default How much porting for around 230cfm?

My machinist has started porting my #13 heads. Stock, they flowed 205I/175E at .500. He did some work on the short turn and to the roof in front of the valve guide and has gotten up to around 215cfm at .500. He hasn’t touched the pushrod bulge area or runner area yet.

How much porting and where is it typically needed to get up to the 230cfm range? Engine is a 400 and the cam is a Crower 60243.

TIA!

  #2  
Old 04-17-2021, 12:20 AM
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You haven't mentioned whether the bowls were blended into the seat yet. I would think that would've been done first and provided the biggest gains before working the roof and the short turn. A gasket match to a R.A. IV intake gasket is often done as well.

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Old 04-17-2021, 07:17 AM
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Who is porting them?

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Old 04-17-2021, 07:40 AM
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That 215 cfm is a good start in the quest for 230 cfm, but what about the also very important flow numbers Below .500” lift, did the machinist report on those?

In peticular between .200” and .400” lift which is where the valve spends much more of its open time then it does at .500” lift, if that’s about the max lift your thinking of running?

Messing with the short turn in a 14 degree head like your casting number 13 can without knowing the Geometric principals it was designed with can greatly reduce intake flow numbers in that very important. .200” to .400” lift range, such that even with the added flow of 215 @ ,500” lift it will not make up for what could be a big total flow loss when you add up the stock and ported flow numbers between .200” and .400” to .450” lift and average them out.

Very important to making good or increased power are the intake flow numbers at .200” lift .
If the porting and valve job done does not keep the flow numbers at atleast 140 cfm or better then the motor will not perform as well as could be!

Here are my stock intake flow numbers from a # 13 head taken at 28”.

.100”. 77.2

.200”. 145.2

.300”. 176.6

.400”. 198.2

.450”. 201.7

.500”. 202.8

.500”. 204

.600”. 204.4

.650”. 207.3

The main restriction in these heads is the stock minimum size of the valve bowl which is 1.6” by 1.5”.

The stock area of the push rod bulged can pass over 255 cfm before it be comes a restriction at least during a flow bench test.
In practice with a manifold bolted on however it’s better to open it up to .980” and form it into as constant a radius as you can just like the stock shape was..

To achieve 230 cfm the that minimum valve bowl throat size of basically 1.60” will need to go up to 1.65” to 1.68” depending on how the rest of the valve bowl has been blended out / reworked.
This size gain is why most times just doing a common bowl blend in a 67 and up D port head does not provide much of a flow gain.

There is a very important relationship between the throat size and the overall short turn arc.

The stock 1.60” throat call’s geometrically a .800” short turn arc which the stock high comp D port heads like yours barely have, and this was intensional by the factory so that port air speed would be some 10% higher then a perfectly shaped port.

The bad side to this is that when increasing the throat size and in conjunction with the heads 14 degree valve inclination angle is that at a certain level of increased intake flow the shape/ basic arc of the short becomes critical in not loosing control of the air mass passing over the short turn.

When this takes place flow levels drop off like big time!

A 1.650” throat calls for a minimum short turn arc of .825” and a 1.68” throat calls for a .840” throat.

This all means that the short turn needs to be very carefully layed back and widened such that the overall height of it at its apex is still nearly stock , but this apex is just pushed back more towards the intake flange.

Templates can and should be made to guide this work!

What are the current rest of the intake flow numbers under .500” lift with your current peak of 215 cfm ?

Here are some flow numbers from a stock 6X-4 head that I am currently porting up to attain 230 cfm @ .500” .
The first column is stock flow and the 2nd is ported, also note that the valve job is still stock.

.100”. 76 78

.200”. 134.9. 142

.300”. 179.8. 185.5

.400”. 198.3. 214.2

.450”. Same 222

.500”. 207.5. 231.5



Was your exh flow test taken on a center exh port or on a end port, to me the flow level you reported on seems like a end port, if not then it seems a little high.
The peak flow numbers I usually see are in the low to mid 160s.

Anyway, I hope this all helps out!

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Last edited by steve25; 04-17-2021 at 07:55 AM.
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Old 04-17-2021, 07:56 AM
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The 240+ 6x heads I got from SD years ago still used the standard intake gasket.

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Old 04-17-2021, 01:00 PM
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Not knowing much about port shaping and turn radius's and the like, I opened up the valve throats per the Jim Hand book using shaped/cut valves and fitting them through the port openings - grinding them open until the machined valves would fit down through. No templates of any kind, just eyed things up.

I "boat tailed" the valve guides. Port matched to RA IV gaskets, equalized all the ports at the pushrod buldge with a little clean-up grinding and blending the RA IV ports in about 1".

Smoothed the rough castings with a sanding roll to clean up the ports.

Ferrea Valves. Good valve job.

Here are my flow numbers on the intake side:

100 94.5
.200 157
.300 201
.400 214
.450 224
.500 230
.550 234

  #7  
Old 04-17-2021, 01:17 PM
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Jim,
Thanks for this info. Nice numbers! I will pass this on to the machinist. He is going to do some more work on the heads next week.

Would it be possible to get the porting info from Jim Hand book from you? I have the newer version of the book by Rocky Rotella that doesn't include this info.

Is what Jim Hand shows in the book what Steve explained below about opening the bowl to a certain diameter and making the short turn radius equal to half that diameter? I have seen some other postings about using an old 1.66 exhaust valve as a template for the bowl.

Thanks!

Quote:
Originally Posted by PontiacJim1959 View Post
Not knowing much about port shaping and turn radius's and the like, I opened up the valve throats per the Jim Hand book using shaped/cut valves and fitting them through the port openings - grinding them open until the machined valves would fit down through. No templates of any kind, just eyed things up.

I "boat tailed" the valve guides. Port matched to RA IV gaskets, equalized all the ports at the pushrod buldge with a little clean-up grinding and blending the RA IV ports in about 1".

Smoothed the rough castings with a sanding roll to clean up the ports.

Ferrea Valves. Good valve job.

Here are my flow numbers on the intake side:

100 94.5
.200 157
.300 201
.400 214
.450 224
.500 230
.550 234

  #8  
Old 04-17-2021, 01:39 PM
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Nice results for a novist porter Jim!
What head castings are these?

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And he was not talking about 1/8 or 1/4 mile ETs!

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Two dry rotted 14 x 10 Micky Thompson slicks.

1) un-mailed in gift coupon from a 1972 box of corn flakes.
Two pairs of brown leather flip flops, never seen more then 2 mph.

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  #9  
Old 04-17-2021, 01:40 PM
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Steve,
Thanks for this info. This is very helpful. He showed me the flow numbers at the lower lifts as well and there was improvement there also, I just can't remember the exact numbers. I didn't have my phone on me or I would have taken a picture of the values. He flowed the stock ports, after doing the porting, and then after doing a valve job. The valve job only added about 1 cfm so at that point we met and discussed where to go next. He is going to work on the heads more next week and I will give him this info. The heads were rebuilt previously and had Ferrea valves and a previous valve job done at that time.

I found the following series of photos showing head porting for 240cfm. Would this be good info to pass on to him also? https://www.flickr.com/photos/937804...7677860709404/

Also, does this graphic show the relationship you were explaining between throat diameter and short turn radius and how to lay it back? https://www.flickr.com/photos/937804...7677860709404/

Last question - in another porting post I read that you need to flatten the short turn by bringing down the radius on the shared wall sides of the intake ports so that it is more of a rectangular shape instead of a U shape. Is this what you meant by widening the short turn?

Thanks!

Quote:
Originally Posted by steve25 View Post
That 215 cfm is a good start in the quest for 230 cfm, but what about the also very important flow numbers Below .500” lift, did the machinist report on those?

In peticular between .200” and .400” lift which is where the valve spends much more of its open time then it does at .500” lift, if that’s about the max lift your thinking of running?

Messing with the short turn in a 14 degree head like your casting number 13 can without knowing the Geometric principals it was designed with can greatly reduce intake flow numbers in that very important. .200” to .400” lift range, such that even with the added flow of 215 @ ,500” lift it will not make up for what could be a big total flow loss when you add up the stock and ported flow numbers between .200” and .400” to .450” lift and average them out.

Very important to making good or increased power are the intake flow numbers at .200” lift .
If the porting and valve job done does not keep the flow numbers at atleast 140 cfm or better then the motor will not perform as well as could be!

Here are my stock intake flow numbers from a # 13 head taken at 28”.

.100”. 77.2

.200”. 145.2

.300”. 176.6

.400”. 198.2

.450”. 201.7

.500”. 202.8

.500”. 204

.600”. 204.4

.650”. 207.3

The main restriction in these heads is the stock minimum size of the valve bowl which is 1.6” by 1.5”.

The stock area of the push rod bulged can pass over 255 cfm before it be comes a restriction at least during a flow bench test.
In practice with a manifold bolted on however it’s better to open it up to .980” and form it into as constant a radius as you can just like the stock shape was..

To achieve 230 cfm the that minimum valve bowl throat size of basically 1.60” will need to go up to 1.65” to 1.68” depending on how the rest of the valve bowl has been blended out / reworked.
This size gain is why most times just doing a common bowl blend in a 67 and up D port head does not provide much of a flow gain.

There is a very important relationship between the throat size and the overall short turn arc.

The stock 1.60” throat call’s geometrically a .800” short turn arc which the stock high comp D port heads like yours barely have, and this was intensional by the factory so that port air speed would be some 10% higher then a perfectly shaped port.

The bad side to this is that when increasing the throat size and in conjunction with the heads 14 degree valve inclination angle is that at a certain level of increased intake flow the shape/ basic arc of the short becomes critical in not loosing control of the air mass passing over the short turn.

When this takes place flow levels drop off like big time!

A 1.650” throat calls for a minimum short turn arc of .825” and a 1.68” throat calls for a .840” throat.

This all means that the short turn needs to be very carefully layed back and widened such that the overall height of it at its apex is still nearly stock , but this apex is just pushed back more towards the intake flange.

Templates can and should be made to guide this work!

What are the current rest of the intake flow numbers under .500” lift with your current peak of 215 cfm ?

Here are some flow numbers from a stock 6X-4 head that I am currently porting up to attain 230 cfm @ .500” .
The first column is stock flow and the 2nd is ported, also note that the valve job is still stock.

.100”. 76 78

.200”. 134.9. 142

.300”. 179.8. 185.5

.400”. 198.3. 214.2

.450”. Same 222

.500”. 207.5. 231.5



Was your exh flow test taken on a center exh port or on a end port, to me the flow level you reported on seems like a end port, if not then it seems a little high.
The peak flow numbers I usually see are in the low to mid 160s.

Anyway, I hope this all helps out!

  #10  
Old 04-17-2021, 01:42 PM
RH68 RH68 is offline
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Also, my cam has .479I/.494E lift with 1.50 rockers. I haven't decided yet whether I will use 1.50 or 1.65 ratio rockers.

  #11  
Old 04-18-2021, 06:47 PM
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Quote:
Originally Posted by steve25 View Post
Nice results for a novist porter Jim!
What head castings are these?
7K3 heads. Took me some time to get the work done and I've never gone to this extent. I usually just do a port match, clean up the passages, and round sharp edging.

I also did some slight chamber work per the Jim Hand book and I Cc'd the heads at 98 CC's. - 455CI, .060" over.

  #12  
Old 04-18-2021, 07:05 PM
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Quote:
Originally Posted by RH68 View Post
Jim,
Thanks for this info. Nice numbers! I will pass this on to the machinist. He is going to do some more work on the heads next week.

Would it be possible to get the porting info from Jim Hand book from you? I have the newer version of the book by Rocky Rotella that doesn't include this info.

Is what Jim Hand shows in the book what Steve explained below about opening the bowl to a certain diameter and making the short turn radius equal to half that diameter? I have seen some other postings about using an old 1.66 exhaust valve as a template for the bowl.

Thanks!

The Hand book provides the work he did to his heads. No one photo shows it all and the text covers what he did in steps. Your porter should know much of what is in the book.

However, the key is to open th throats in 3 steps. So 3 spare valves need to be cut down and used as a "go/no-go" gauge. You could rig up somthing, but I used some valves and ground them down to size.

The 3 sizes are 1.63" dia, 1.66" dia., and 1.69" diameter. The throats get opened up so as to slip the valves down into the throats. I spray painted white paint into the throats to see what you grinding. Then when completed, blended the throats smooth.

A better approach is to purchase the DVD video, "Performance Porting" by Pete McCarthy which shows you in the video how to do what Hand shows in his book - I assume Hand got his info from McCarthy. This helped me to understand what was being done with the 3 valve templates.

http://www.petemccarthybooks.com/#!/...ORTING_DVD/198

  #13  
Old 04-18-2021, 07:57 PM
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Jim,
Thanks for the info. I think the engine builder will understand what to do once I speak with him tomorrow. I spent a few hours last night reading through old posts on head porting and have a better understanding of what you guys are explaining.

One question about what you said about using the 3 valve sizes as gauges - are these all for just the throat itself so do you use decreasing diameters the further you push the valve down the guide into the throat from the valve seat? I saw some pictures in other threads of turned down valves placed into various areas of the rectangular part of the port.

Thanks!

Quote:
Originally Posted by PontiacJim1959 View Post
The Hand book provides the work he did to his heads. No one photo shows it all and the text covers what he did in steps. Your porter should know much of what is in the book.

However, the key is to open th throats in 3 steps. So 3 spare valves need to be cut down and used as a "go/no-go" gauge. You could rig up somthing, but I used some valves and ground them down to size.

The 3 sizes are 1.63" dia, 1.66" dia., and 1.69" diameter. The throats get opened up so as to slip the valves down into the throats. I spray painted white paint into the throats to see what you grinding. Then when completed, blended the throats smooth.

A better approach is to purchase the DVD video, "Performance Porting" by Pete McCarthy which shows you in the video how to do what Hand shows in his book - I assume Hand got his info from McCarthy. This helped me to understand what was being done with the 3 valve templates.

http://www.petemccarthybooks.com/#!/...ORTING_DVD/198

  #14  
Old 04-18-2021, 08:24 PM
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A local shop in PA that rebuilt the engine for me 20 years ago.

Quote:
Originally Posted by OCMDGTO View Post
Who is porting them?

  #15  
Old 04-19-2021, 04:20 AM
Will Will is offline
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Quote:
Originally Posted by RH68 View Post
...

I found the following series of photos showing head porting for 240cfm. Would this be good info to pass on to him also? https://www.flickr.com/photos/937804...7677860709404/

Also, does this graphic show the relationship you were explaining between throat diameter and short turn radius and how to lay it back? https://www.flickr.com/photos/937804...7677860709404/

Last question - in another porting post I read that you need to flatten the short turn by bringing down the radius on the shared wall sides of the intake ports so that it is more of a rectangular shape instead of a U shape. Is this what you meant by widening the short turn?

Thanks!
Wow, I had no idea those pictures were still out there! I haven't used that flickr account in years, pretty much completely forgot about it... LOL.

Those heads flowed right about 240 @.500 and 245 @ .550 with nice gains at all lift points. I don't think I have the flow sheets for them any more.

Note that that is with standard size intake gaskets. There's no reason to go to RAIV size unless you're "max" porting a set of iron heads. Even my 270 cfm #061s use standard port openings.

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Old 04-19-2021, 06:47 PM
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Quote:
Originally Posted by PontiacJim1959 View Post
Not knowing much about port shaping and turn radius's and the like, I opened up the valve throats per the Jim Hand book using shaped/cut valves and fitting them through the port openings - grinding them open until the machined valves would fit down through. No templates of any kind, just eyed things up.

I "boat tailed" the valve guides. Port matched to RA IV gaskets, equalized all the ports at the pushrod buldge with a little clean-up grinding and blending the RA IV ports in about 1".

Smoothed the rough castings with a sanding roll to clean up the ports.

Ferrea Valves. Good valve job.

Here are my flow numbers on the intake side:

100 94.5
.200 157
.300 201
.400 214
.450 224
.500 230
.550 234

I don't think I have ever seen that much flow at .100 of lift.

  #17  
Old 04-19-2021, 07:27 PM
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Quote:
Originally Posted by ponjohn View Post
I don't think I have ever seen that much flow at .100 of lift.
I can't comment on it as I wasn't there. I had a younger guy I work with whose dad has an engine machine shop and builds Nascar, dirt track, and other winning competition engines. He has all the latest equipment and I think the flow bench was a Superflow? He used a BB Chevy 4.25" flow cylinder as my 455 is .060" over. There is a column listed "Range" and the .100" lift number is shown as "Range 3" and 63% while all other numbers are listed as "Range 4." Have no idea what that means and that my explain the lift number?

His dad used to be the head porter for a nascar team. He was pretty impressed with the heads and said they should be capable of 500HP. I am not shooting for 500HP as I don't have the compression or cam. I think 400HP-425HP with good TQ numbers is more realistic and good enough for the street.

  #18  
Old 04-19-2021, 07:35 PM
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Yes, close to that level of flow( mid 80s ) can be had near like he posted, but the down side to that is if you go shooting for higher flow numbers at higher lift the port velocity is so high that turbulence/ flow seperation will hold you back from getting those bigger numbers!.
And then you need to know how to stabilize the flow to eliminate that condition.

What made that high a number at .100” was that the valve opening tool was a little off.
At lifts of .100” or less even Being only .002” off one way or the other can make for a 5 to 8 cfm difference very easily!

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Last edited by steve25; 04-19-2021 at 07:43 PM.
  #19  
Old 04-19-2021, 07:56 PM
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Quote:
Originally Posted by RH68 View Post
Jim,
Thanks for the info. I think the engine builder will understand what to do once I speak with him tomorrow. I spent a few hours last night reading through old posts on head porting and have a better understanding of what you guys are explaining.

One question about what you said about using the 3 valve sizes as gauges - are these all for just the throat itself so do you use decreasing diameters the further you push the valve down the guide into the throat from the valve seat? I saw some pictures in other threads of turned down valves placed into various areas of the rectangular part of the port.

Thanks!
The three intake valve sizes are used in opening up the throats. You start with the smallest, grind open the throat so the valve can pass down into the throat. Once good, you then go to the next size and open it up, then the third. You are using the 3 sizes to get the throats round/equal and not go too far, so you step up a little at a time. too much, and the new valve, 2.11", won't have enough valve seat for use and then you'll have to go oversize on the valve.

The video I suggested really shows how to fit the valve down into the throat. Then once completed, you can then clean up the throat and blend it into the larger opening. I didn't open up the area past the valve opening as some can do. I just smoothed it all up.

Here are a few pics if they help any.

Pic #1 is the 7K3 head as I pulled off my 400CI. I rebuilt it, bit also knew I had a leaky Q-jet upon occasion so you can see the soot in the combustion chamber. BUT, you can also see the flow pattern that hits the machined "ramp" of the combustion chamber to the left of the spark plug - it is clean of soot. Hand's book says to smooth this area and remove the "ramp" by grinding it back a little - which I did any may account for the extra 2 CC's the head now has if the original head only had 96 CC's, it now measures 98 CC's.

Pic 2 & 3 show the intake throat. Painted with white spray paint so you can see what you are grinding away on the walls. In pic 3 you can see how I ground the valve guide down and created a taper to it.

Pic 4 is the combustion chamber where I ground down the "ramp" on the intake valve side and then blended/smoothed it up. I did not open up the combustion chamber to match a head gasket as some will do. Left everything else alone.

Pic 5 is how they look finished and from the machine shop.

I did not do much work on the exhaust side other than grind a few bumps, port match, and smooth and clean them up with a sanding roll.

So nothing professional on my part and just hope I did a well enough job to make a difference and not go the opposite way and kill flow. LOL.
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Old 04-19-2021, 07:58 PM
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Quote:
Originally Posted by steve25 View Post
Yes, close to that level of flow( mid 80s ) can be had near like he posted, but the down side to that is if you go shooting for higher flow numbers at higher lift the port velocity is so high that turbulence/ flow seperation will hold you back from getting those bigger numbers!.
And then you need to know how to stabilize the flow to eliminate that condition.

What made that high a number at .100” was that the valve opening tool was a little off.
At lifts of .100” or less even Being only .002” off one way or the other can make for a 5 to 8 cfm difference very easily!

Just accept the numbers without assuming .002" one way or the other.

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