How To:Basic Cylinder Head Porting for Beginners

Mark:
I would say just stick to some basic bowl blending,contouring the guide bosses,and intake and exhaust port gasket matching and that motor will wake up.My Buddy's 390 didn't even have that much,as he was new to porting and reluctant to go overboard,and it worked really well.
Also,don't forget to gently work on straightening out that short turn radius a bit.

Scott


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Remember when NASCAR used vinyl tops? There was an episode of Mythbusters where they covered a car with golf balls or something, don't remember the outcome.

 

Thats a '69 oval port 325hp part number,right?
Those guys have a pretty decent port shape to begin with,but I find a lot of the BBC factory machine work to be VERY rough from the factory in the area under the valve seats,making bowl blending time VERY well spent.
I wouldn't make major changes to port size or shape,just a light touch up for gasket matching.
Straighten out the short turn a bit,and they should work pretty nice.
You can increase valve size if you like,but if you're sticking with a 396-402 size engine,the stock valve sizes with a small to moderate hydraulic cam work nice for promoting low rpm torque...at least I have found so.
Let us know how it turns out!

Scott


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It has been done. HRM did a great article back in the mid 80s about it.

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Mike:
Your input is exactly the kind of stuff guys would contribute,I'm just kind of opening the door for those with a higher level of expertise than my low buck,backyard stuff
Thanks Brother!

Scott


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Petty did that to cover his tracks when an acid dipping job went wrong and the roof buckled and warped.The vinyl was camouflage...lol

Scott


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I've been told that there is no gain in opening the bottom side of the exhaust port on the Ford small block heads, true or false?

I know on the 351 Cleveland 4V heads are open to much in this area from the factory.

 

Scott thank you, I found an edelbrock intake last fall and was thinking about putting in a mild cam , already have headers . With the porting I should feel quite a difference I'm hoping.
Mark

 

Mark,
Which intake did you pick up?

Scott


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Mark T, et-al -

Basically correct, in most instances, espicially American engines...do not lower the port floor.
And this works for both the intake and the exhaust.

If you must remove material from the floor of a port to match the gasket, by all means, do so.
BUT....do not continue this material removal past a nice blending, say maybe 1/2" or so, not much more.
On the exhaust side...I would not even lower the floor at all, despite the gasket size/shape. This will actually create a "dam" to make it more difficult for the chance of any backflow (reversion) of burnt gasses back into the combustion chamber.

I've verified this on many different heads over the years. It's a lot of work for either no gain OR an actual drop in flow.
And as I noted before, DO NOT lower the floor where the floor drops away toward the valve seat (short turn radius) on either the intake or the exhaust ports.

Mike

 

So your saying, don't bother port matching the lower side of exhaust ports? only the top and 2 sides? Is that correct?
This would confirm what I've been told by a local cylinder head guy.

 

That's why when my last electric die grinder died I didn't replace it....

 

They can be pretty rangy,can't they Steve?
I would use a pneumatic just for their low cost,compact size,and precise control of speed over a useable rpm,but I always hate to have that compressor running all the time.Drives me nuts.
I suppose if I had one in a separate room,isolated with sound deadener it would be a pretty good setup though.
Something to think about for sure.

Scott


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Mark T wrote -
"So your saying, don't bother port matching the lower side of exhaust ports? only the top and 2 sides? Is that correct?
This would confirm what I've been told by a local cylinder head guy."

Correct.
In the unlikely event that it's a huge difference...1/4", then take some of that mismatch out, but there's no need to remove it all.
And like I said, if you do have to remove some, do a blend operation of only about 1/2" long into the port.


Crazy Steve -
Back in one of my original posts, I mentioned the setup I use. It's a variable speed, foot controlled, electric motor. The motor itself is hanging from a rafter on a spring with a cable to the hand tool.
Using "double cut" carbide cutters, I rarely go over half speed and normally am in about the 1/4 rpm range. With a sharp cutter, you don't need a lot of rpm. It only leads to F-ups..!

The setup I have now has ported (int., exh. and chambers) of at least 35 sets of heads. I did have to replace the hand tool part one time...one of the bearings went south..!
And about 6 of them, I hogged out a LOT of iron...while doing experimentation on what to do on a particular brand of head to make the intakes flow well, (no aluminum versions available !)

Mike

 

When port matching, especially the exhaust side, I will try to move the gasket up as far as possible. That way, there is little to none to be removed from the port floor. I have even gone as far as notching the bolt holes in the gasket to do so.

 

You have to be very careful not to end up moving it far enough to get a misalignment and/or actually weaken the casting to the point of making it vulnerable to cracking by grinding too thin where the gasket has been moved.
Some of the castings can be scary thin in places...

Scott


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I run a pressure regulator on my air grinder line 60 to 80 PSI works well for the carbide cutters. It's much easier to control and you can work at full throttle, not feathering the paddle.

 

That's a good way to go too,just dial it down for painting,up a bit for porting,and crank that sucker for the impact gun!

Scott


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Thanks everyone, I'm learning alot!

 

what a fun day here in hambland!

 

Scott, I found a used edelbrock performer 390,sorry for the late reply I work second shift

 

No problem Mark!
The Performer probably won't be a huge boost in performance over the stocker,but it should take about 60lbs off the front of your car.
Those FE intakes are absolutely HUGE!
If you can hold out for a good deal on a Performer RPM,I would go that route,but your Performer will do a nice job in an application that's not too radical in the cam department.It should run pretty well with a port-match and nothing else.

What do you have for a carb?
We ran the stock Holley on my Buddy's 390GT and it ran nice.

Scott


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I have a Holley 1850 that was on it or an edelbrock 600 cfm . Either one will need rebuild as they haven't been run in 15+ years. It does not need to be a race motor it is in my ot 68 f 250 c6 with shift kit and 3.73 gears

 

Perfect!
The Performer and a 600cfm carb will work well in a truck for real sharp throttle response and plenty of snap down low where you need it.
That should be a pretty nice truck once you get it back together!

Scott


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Thank you for the compliment and the tech

 

gas pumper -

While I haven't used air as a source of power, I have used various rpm motors over the years.

Sorry...I prefer being able to vary the rpm at any time without messing with things...so "pedal" (not paddle !) it is.

Mike

 

There are at least two popular domestic heads that I have personally had on the flow bench that require extensive re-working of the intake port floor and short-side to attain big numbers.
For the FE guy, if you are putting it in a F350 and using it for towing, I would take the Performer 390 over the Performer RPM. If you look at the info in Jay Browns book, the Performer 390 carries considerably more torque from 2500-through to around 3400 rpm on the mild 428 example. After that, the RPM buries it.

 

Well come on George, which ones?

 

906/915 Mopar and early sixties FE low riser. I guess thats actually 3, sorta.

 

Would that also apply to most of the standard FE heads?