Intake port short side radius check gauge

[femtnmax]

This idea came from the Ford GT40 SAE Papers and the Speedtalk forum.
According to both, and thoroughly verified by Ford in their 427 development program to win the LeMans races, a 1/2 inch radius is the minimum allowable for flow to remain attached to the port surface, and minimize flow seperation.  The flow can then make use of the Coanda effect where fluid flow will follow a convex shape when directed tangent to the surface.
The idea is to check the floor of the intake or exhaust port to determine if the short side radius is too abrupt, which is typicallly the case.   Ideally the port flow should be equal everywhere in the port, and stay attached to the port walls.  This is of course impossible, but the closer the flow gets to this the better, including the short side radius where the flow turns about 90 degrees then heads past the valve seat into the cylinder.
The wire gauge is made from thin wire, I'm using #14 wire for house lighting.  It's a little too stiff, but close enough for the photos.  You want the wire to form easily to the shape of the port, but be stiff enough to keep the shape so it can be transfered to paper or templates.  I form the wire shape right down the middle of the port.
On the 'formed' wire, I mark the valve seat and intake gasket surface, put the wire on paper and trace its shape, marking the two locations just mentioned.  Then measure from the two locations to the head gasket surface to complete the diagram on the paper.
I then use a Sacajawea dollar to compare the short side turn traced on the paper to an acceptable minimum.  The dollar has a 1.045 diameter; thus a touch more than 1/2 inch radius.  A quarter has a smaller radius but is fairly close.
The 360 head in the pics, casting #596 has a real nice short side radius, as you can see the dollar has a  much smaller radius, so no modification is necessary.   On the other hand, a typical Ford 390 C8AE casting has a sharp bend that needs to have the radius increased.   The aluminum template in the photo is for a Ford 390 intake port.

[nivvy]

what are you saying..... ford heads suck 

[femtnmax]

what are you saying..... ford heads suck 

True, the Ford's flow is going to seperate at a much lower velocity than the 360 mopar

[71chally416]

Up to a point the more you lay back the short side the more it flows upstairs and the less down low and the more it delays breakover (when the port stalls and flows no more air) On a stock Chrysler head that's usually before .500" lift. It's always a trade off when you cut there. It will help, help, help, then fall off a cliff and the port is ruined. That's what seperates good head porters from hacks. They good ones have did their homework and ruined a few heads along the way to find out what works and what doesn't on the flowbench, and it's a bit different for every type head you port. Sounds like you're on the right track. 

[femtnmax]

Sounds like you're on the right track. 

I've ruined one set of heads already   
I don't have access to a flow bench, wish I did, but most players in this field keep their cards close.  I can't really afford to pay for porting, plus you'd just be handed a finished product and I wouldn't learn anything.
So I'm studying all sources available.    I'm just applying the basics, so won't get that extra flow thats out there.  But for my street use it will be ok.
I really want to take Mondello's porting school.  My wife thinks its great, so half the battles won.  Maybe this fall if money's there.

[71chally416]

You're really shooting in the dark without a flow bench. I can't tell you how many hours I've spent on the one in the shop. You at least have a grasp of where the flow is. Here's my latest obsession. A set of "Poly" heads for a big block. The only set in exsistence carved from solid billet aluminum.

 

[71chally416]

Here's a 340 T/A head I did years ago. Note the guide boss. Lot's of flow to be gained reducing it as much as possible.

[moper]

Keep on Speedtalk. They are a phenominal group in the advanced section. You want to also include volume and airspeeds in that. You can slow down the column by enlargin the cross section too, making it easier to turn the air without seperating the mixture. It is definately NOT a cut and dried 1/2" and you're done. I use the .016 mechanic's wire to do the same thing because it's easier to form with fingertips. I also use it for figuring length of a port and cross section for various calculations. If you have not bought Pipemax from Larry Maeux, you should do so. You sound like you're at the level where seeing the relationships between size, volume, and shape will really help.

71 - What the hell is htat head from again? Taht just looks cool...

[71chally416]

71 - What the hell is htat head from again? That just looks cool...

Well it was for my 630 KB motor before I sold it. The idea is to get the exhaust valves away from each other so it doesn't torch through the chamber between 3&5 & 4&6 cylinders like it did on the B1-TS heads when you run a big load of nitrous. Here's the chamber side.
 
 

[femtnmax]

Keep on Speedtalk. You want to also include volume and airspeeds in that.  You sound like you're at the level where seeing the relationships between size, volume, and shape will really help.

I have filled a spiral notebook with detailed notes from speedtalk over the last several years.   When you work out of town and live in motel rooms for 12 months stretch, need something to focus on away from work.
I make port molds before, during and after.   I like tin-sil 70-25, cut em up and graph calculate the areas.  DAvid Vizard's book Small block chevy cylinder heads has great info for street porting.  The basics can be applied to any head.  Just don't get carried away making chips, instead measure often.   I won't get every cfm, but things like narrowing guide bosses, etc are proven to help, so thats what I stick to.

[moper]

That's beyond my normal shopping lists.... But what about Predators? You still have the closeness of 3/5 and 2/4 with the EIIE arrangement. With the std 18436572 firing order, you still have 3 and 5 getting hot. Wouldnt the EIEIEIEI idea be better? Just tossing around ideas. As I said, you're beyond me with that project....lol

[71chally416]

The problem with that is I'd have to toss all my cams into the trash. Not cheap for custom ground billet rollers.    Don't know where the project is going in the future. I also have a set of ProStock hemi heads too that I picked up afterwards that will support the motor I want to build. Something over 800 cubes.

[femtnmax]

Its not anal, its research.  Incorrect port Xsection area ratios also cause port flow stall, the worse the ratio the lower the rpm where the stall occurs.  The further the choke point (too small an area) from the throat, the more likely the flow is to stall at a lower rpm.  Its well documented in Speedtalk; where racers correct the port areas and the stall is moved to a higher rpm out of the engines chosen rpm range.   Like you say, a flow bench is really what is needed.
All I'm trying to do is put the rpm where stall really takes over well above my rpm range, so I can make use of higher cfm dwell time, rather than having flow starting to drop off at only 0.5 lift for example. 
If I wasn't trying to build an entire car  (lots of $$$$$), I'd run the heads down to Utah to a well respected speedtalk members flowbench.  Thanks for all your inputs.

[71chally416]

You can have the nicest heads ported to perfection but if your short side radius isn't correctly formed the port might still stall like a stock head does. Head porters are usually very secretive about that part of the port and you have to take anything they say with a grain of salt. They aren't likely to just give away the secrets to what they they spent 100's of hours researching to make a living doing. More likely they'll send you chasing your tail doing the wrong thing so you'll be disappointed with the results so they can do some heads for you in the future.  That's the truth. The smartest man I've ever met with race motors tells the biggest tails to people that pick his brain, and the few people he has gone out of his way to help never listen to his advice.