How To:Basic Cylinder Head Porting for Beginners

Thanks Dave,
On a real mild 302 with stock valve sizes,alum intake,600cfm Holley and good ignition,and a Crane [email protected]"/.484"/110 LSA cam,the seat of the pants increase in torque,and horsepower was VERY noticeable.The engine just ran "better" all over,and picked up about 500-600rpms before it wanted the next gear.
I would guess you could pick up between 25-50hp depending how mild or insane your combination is.
Stock heads are going to choke a big solid cam,but once you open the heads up the power will really wake up.

Scott


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Hey!Good to see
You back!


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YES!!!!!!!!

We did real quick bowl blend and gasket match on a buddy's o/t 67 GTA 390 and it turned out to have all our Chevy buddies scratching their heads wondering why the old "boat anchor" was so quick away from a stoplight!

FE's respond REALLY well to a bit of porting!

Scott


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I would like to thank George for raising this point,which is something I included in my lead-in photo but neglected to address in the text:

Either use a pneumatic grinder due to its lower speed,or use an electric grinder with variable speeds,or as I have,a box to control speed of the tool.
If need to in a pinch,you can rig one up from a rheostat and a box from your local Hardware store (always support the Mom n Pop operations!)

As George noted,if a long shank cutter catches the casting the wrong way it can kick back with enough force to bend the tool.
It may sound funny when you talk about a guy with a grinder shaking and wobbling all over the place like some cartoon dog,but take it from me:IT IS TERRIFYING.

The first and LAST time it ever happened to me I was doing a set of oval port big block Chevy heads for my good friend Tony C's 427 powered Chevelle.....
....When the cutter caught and ricocheted,it did so with so much violence that the grinder almost came back and tagged me in the nuts!
Worse still,it was shaking so violently that I had to use all my strength just to hang onto the tool,and could not adjust my grip to shut the power off!!!
I was finally able to shut it off by yanking the cord right out of the wall,but if that cutter had come free of the chuck before I could shut it down,I guarantee it had the potential to kill someone.

So,thanks FalconGeorge for the reminder about speed issues,and always play safe guys!

Scott


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No problem Brother!
Pm me for some updates on some Hydro info!

Scott


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That's cool, that is the combo I have now! I'm going to rework a set of D0oe Windsor heads to replace the D9s I have now using this info. Also going to replace my stock manifold with headers (probably short tube so it doesn't interfere with the z bar for my clutch) I'm really anxious to try this out.


-LUKEY-

 

Its only happened to me once when I was in my twenties, and man, THAT was enough!The scariest part is getting the balls to brace yourself and hold that shaking mad bastard with one hand so you can shut the power off. If it happened now, I honestly dont know if I'm strong enough now.

gets the adrenaline pumping, let me tell you.

 

Thanks this is the stuff I like to read and learn from, I have a set of big block head I am going to try to clean up

 

You're not kiddin Brother!

Scott


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One other thing I will add, you should get long shank cutters right from the get-go. A beginner working the bowl with a short cutter has a very good chance of tagging the valve seat with the collet. A 6" shank will keep the collet well back from the valve seat. Oh well, you were gonna do bigger valves anyway, right??

 

Which big block heads have you got?
I learned a really cool ultra-low buck BBC speed secret from a motor built by John Lingenfelter about twenty years ago that involves an oddball porting technique on an even more oddball cylinder head....if you have the stock,small port "peanut port" BBC heads do NOT junk them!!!!

If you're interested,all it involves is loading some bigger valves into those heads,some bowl work,and gasket matching the first inch or so of the intake port to the larger,passenger car size oval port intake gaskets.
If you are after a BBC that makes absolutely explosive torque on a Happy Meal budget,this one will do it!

Scott


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Very good point George.The grinder will bang up those valve seats in a hurry when you get tunnel vision on that nice profile you're putting on the guide boss!

Scott


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Voice of experience there... I got all those standard mistakes out of the way early on...

 

Thanks for the information, really makes me want to try it...


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Do yourself a favor and get some clear faceshields or at least good safety glasses. those needle sharp iron chips produced by carbide burrs are no fun in your eyes and will guarantee an emergency trip to the eye doc. for removal. ask me how I know! also, and for the same reason wear leather gloves unless you like picking really painful slivers out of your skin. just sayin!

 

Critical tool that is missing here, a small pair of dividers. If I was at home, I'd post a pic of mine. As a general rule, you want the pocket (and the csa, for that matter) to be around 89% of the valve diameter. So you multiply the valve diameter by .89' divide by 2, subtract half the valve stem diameter, and set the dividers to that dimension. Then you stick a valve in the guide upside down, and use the dividers as a go/no-go gauge between the valve stem and the sides of the pocket.
There are situations where you may want to cut the pocket on a bias, for instance, when porting a sbc port for low/moderate lift application, you may want to bias the pocket towards the long wall, to encourage the air to move across the back of the the valve towards the centre of the bore to generate some swirl, but this is not really entry-level stuff, so as a rule, you will be keeping the pocket centred on the guide at first. The dividers can also be used elsewhere in the port to maintain consistency, and you can use them to quickly check internal dimensions from port to port. They are not expensive, and you will (or should at least, unless you are making a hash out of it) use them dozens of times on your first set of heads.

 

If I was going to go more in-depth with this,I would have covered templates,measurement,and cc-ing,but this was just a very quick and dirty overview of the bare minimum effort required to get some real,tangible gains with minimal effort or access to experienced porters,dedicated tools or equipment,or flow benches.

Just trying to keep it simple for guys wanting to make a first attempt George.

Scott


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I do highly recommend the dividers, even for a beginner, mine cost me less than $10, and I wouldn't even turn my grinder on without them sitting on the bench ready to go. Bias cutting the pockets may be a little much, but I wanted to give an example to illustrate possible exceptions to keeping the pocket centered.

 

Feel free to start an "Advanced Porting" thread any time you want George,this one is for beginners.

Scott


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There's a how to cut it -
And then there's a where to cut it -
And then there's a why to cut it -

 

Ok,that's strange....George made a few really good recommendations for titles on the subjects of porting and fluid dynamics,so that those interested in learning a little more could dig deeper into the subject,but we seem to have lost a page in the thread...?

George,if you wouldn't mind posting some of those recommendations again,I'm sure they could be of benefit to a lot of the guys reading this thread.

Thanks,

Scott


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Yeah !!! What he said. Please
I read the posts yesterday, came back today to copy the info and - POOF! Gone

 

First, I'm old and over the years I have tried a lot of things and unless you just want the experience there are cheaper ways to get more flow. Modern cylinder heads that are designed and CNC'd will flow more air than an engine can pump.

A set of stock GM Vortec 220CC heads will flow more than a 383 SBC can use and they cost about $900 a pair ready to bolt on.

I also found that just because it looks good doesn't mean it will perform better.

Get a little heavy handed with a grinder and it goes from "oh wow" to "oh shit" in a heartbeat.

 

I agree that modern stuff is a good deal,and also that excessive grinding can do as much harm as good in many cases.
However,with something as restrictive as a stock 289/302 Ford head,you'd have to do something pretty drastic to do any harm beyond what the shitty baseline numbers are on these heads.
Those ports are so small that they act as a built in rev limiter.

The point of this thread was merely to give a few tips and a bit of guidance to guys on a very limited budget,wanting to stick with their stock heads,but increase performance a bit,and learn a bit about porting along the way.

We could all just bolt on a set of Dart heads and call it a day,but that kinda takes the fun outta this whole Hot Rodding thing,doesn't it?


Scott


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Exactly my point......only I sways seem to get a whole lot more word-y about things.....Haha...!

Scott


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At my labor rate I could do a lot of porting for $900.

 

My big Ol ass could be parked at the work bench for quite a few hours for that rate too...

Scott


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Scott - great tech article!!! Thanks, great pics.

I wouldn't touch the combustion chamber - you will lose compression unless you change your pistons. I do know that people expand the wall a little on the Chevy camel hump 2.02 heads because that large intake valve is so close, I would save that for the advanced porting thread.

Thanks for taking the time to post this.




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With some common sense porting ,a cam swap , a used intake and headers will wake up any motor .With a weekends worth of work and $500 you can gain a lot on a junkyard motor .

 

That's when it's fun to have a guy that spent $3000-$4000 on a ZZwhatever crate motor crawling all over your car wondering "how does this old crap run so good!?!?"

Scott


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