How To:Basic Cylinder Head Porting for Beginners

I got a question about the porting. first I have been wanting to do my old heads and I got the stuff to do it and this shows me just what I was looking for. A hot rodder friend of mine told me he prefers to keep is intake ports on the rough side after opening them up and exhaust as smooth as you can get them. The roughness on the intake helps for the fuel and air to mix. Does his advice have any merit?

 

I have been told that a rougher finish helps on the intake,and I have also been told that it's bullshit,and that it tends to pull fuel out of suspension in the mixture....

I don't know how much it can hurt to leave them rough,I mean,the castings are as rough as theyre ever gonna get from the factory,and most cars seem to run pretty good off the showroom floor,right?

I think it's largely a matter of preference,but there is a ton of science involved.

I bet George can throw $0.02 cents worth in on this.

Scott


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A lot of this stuff revolves around velocity.
You can gain net flow but loose the velocity and the work results in a net loss of performance even though they pass more air in and out.
Unless you are running forced induction and cam overlap then biggest is best for max effort.


There's an old tech by nunzio Romano on porting Pontiac heads.
I haven't seen it for many years. One of the things I do remember about it was that they placed several dozen center punch marks in the combustion chamber in a spiral galaxy like pattern - Promoted swirl of the charge.

 

Singh grooves..oft debated, possibly tested..

http://somender-singh.com/content/view/7/31/

I put them in a one lung motorcycle. Never dynoed, seat of the pants couldn't tell.



Sorry, drifting off topic.

 

Singh grooves, man, I aint following anyone down THAT rabbit hole....
Heres the dividers I was talking about, I was just thinking, its been probably 35 years since I bought these, they may be more than $10 now, but they are still WELL worth the money.

I deleted those references because I kinda thought I might be straying outside the intent of this thread, I'll repost them...

 

Well, to have a really valid opinion of my own on the subject, rather than just repeating other guys opinions, I'd have to have access to a wet flow bench...MAN , I FREAKIN WISH!!!
FWIW, I finish my stuff with an 80 grit roll, which basically means I dont know any more than anyone else, and I am just guessing. Theres a cd available from Speedtalk on boundary layer airflow, that would be a good one. I gotta put it on my birthday wish list.
The dimples in the chamber are a Jim McFarland deal. He actually had a good article on this subject somewhere on the internet, I printed it out, and put it in one of my binders. I'll see if its still there, and link to it if it is.
They arent really about inducing swirl, so much as disturbing the boundary layer in that area of the chamber, to prevent fuel sticking to the chamber wall. You would use them if you noticed a "clean" area in the chamber that wasn't "coloring" due to fuel wash, around the circumference of the intake valve towards the plug for instance, or over the top of the dome.

And this is rapidly turning into a thread on "advanced" porting...

 

Heres a link to the Jim McFarland article, good read.
http://www.n2performance.com/lecture9.shtml
Most guys dont really focus on looking at the chamber after running the engine, there are SUBSTANTIAL amounts of power to be had there in a serious engine. My approach has alway been as follows. First, I start out by trying to get my target compression ratio with the best possible chamber shape. Then I put a few passes on the motor and pull a head. I look for clean spots (no carbon) that indicate inactive combustion. Then I reshape the chamber/dome in that area, and go racing again, repeat until I get good color all the way across the piston top. Once I've done that, I re-cc everything, and take another light cut off the heads to get back to my original target compression ratio. If you make good guesses in the first place, and really think hard about what you are doing as you put it together the first time, you arent removing much material through this process, its more a matter of small tweaks.

This may seem to be off-topic for a porting thread, but its best to look at the chamber (this includes the top of the piston, as it has a big effect on airflow) as part of the intake port.

Edit: Link doesnt work, might not be available anymore. I printed this out 3-4 yrs ago.

 

Found a link that works. Some HAMBers may not want to use this, its off a Toyota Supra forum...
Better get it quick, before the mods see it...

http://mk3ukr-supra.net/Combustion%20pattern%20-%20by%20J.McFarland.pdf

 

Heres the Harold Bettes book I referenced earlier, this one is a must. Gotta warn guys, this isn't a "how to port a SBC head" book its theory/math heavy. Unless you are serious about understanding this stuff, you will probably find it pretty dry. Just giving a heads-up.

 

good pics and I am sure that following steps would feather out, blend any divets, spots in the chamber as those can lead to hot spots, or at least the pros would say....I think at the end of the day anyone with some mechanical skills, likely can do some port work that will wake up the motor a little, want to get full on, get or build a flowbench, start cc'ing stuff etc - I think your pictures and tech will help out a lot of people who want to wake things up a bit

 

George:
Thanks so much for posting this stuff;pretty much anything by McFarland is usually filled with some REALLY meaty tech.I love reading that guy's work.
Even if I don't agree with a certain point of view or theory,there is always value to be found in the fact that it gets you thinking,and allows you to dig deeper and find your own stance on the issue.

Also George,sorry if I seemed a little standoffish earlier;my intent wasn't to draw a line in the sand,but to get you to crack open the vaults and start a more advanced thread that my hillbilly ass really doesn't have the repertoire to cover.

I kinda like having it all together in the same thread though,because that way the reader can get progressively deeper into the tech as he's ready for it.

This one is shaping up to be a good one.

Scott


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Thanks Brother.
I was shocked how tough it was to get a decent photo of a stationary hunk of iron!:O
The ports always either seemed too dark,or too shiny and reflective.It really is tough to find a balance and get a decent photo.

Scott


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It IS REALLY hard to photograph ports.

 

I am like a kid with the first playboy taken from dad's stash when I read some of your replies I don't want to take my eyes off of it. I know porting can go to extreme but the basic port for the beginner (me) is all i need for now. I know top engine builders put a lot of money in the heads. A top fuel engine builder will spend 100k in just the heads according to one book I read. But I'm just doing a weekend cruz'er, and a little more HP or TQ for a few afternoons with a die grinder is what we are all about. thanks for your insight and quick response.

 

Hmm, one thing I didn't see here....WEAR EYE PROTECTION..!
And for you high speed grinder guys...ear protection.

I've been doing this stuff a long time and can tell you that eye protection is a MUST.

Also, with good carbide cutters (double cut)...you DO NOT need a high speed grinder.
I have an electric grinder, with a foot pedal to vary the spindle speed. The motor hangs from the rafter on a spring. It has a cable driven hand tool.
I very rarely ever even get to half speed except with very small dia. tools.

Also, be carefull about going back and forth across a wall/flat surface. As the cutter starts at one corner, you take it across to the other/opposite corner, the cutter spends more time in each corner thAn it does traversing the flat face of the wall/floor/roof.
Vary the angle of the cutter as you straighten and or flatten a surface. That is, don't always have the cutter straight in the surface. Cock it at about a 30 degree angle for a few movements or strokes, then the opposite direction, then back to straight.
This way helps to insure that the surface isn't low at the corners and high in the center....of each wall.

Go slow, better to spend a few more minutes per port that the "ah shit" comment, or...I'll just make the whole thing a little larger to make up for the F-up...!

The dividers are a good tool, as are home made sheetmetal templates for curves.

Mike

P.s. - Chamber work can go a LONG WAY toward making power. The comment about not cutting into the chamber is nuts.
But...as it says, you need to know what you want to do and how much metal removal is going to take place. While you may loose 1/2 a point in compression, some heads will not only have a better flame front travel, but the ports will actually flow better.
The combustion chamber is an extension of the port...!

 

Good call Mike;
I actually did kind of a shitty job touching on safety,as I got caught up in the lust for horsepower!

As stated earlier,the chips from the cutters are more like tiny needles or slivers,and they are absolutely EVIL.
They will get in your skin,in your clothes,I guarantee they will somehow find their way int the sweaty old crack of your ass,but no matter what,you do NOT want one of these little bastards to find an eyeball!If one does,you will wish you had never been born.

I would recommend some type of safety glasses with a neoprene seal to the face,to prevent chips from falling into the eye.

Also,when removing the glasses,make sure to tilt your head forward,with eyes closed,remove glasses,brush any chips or debris out of hair,and off of forehead and face,then sit up.
This will prevent getting any of these little bastards in your eyes,and keep you safe and ready for your next project!

Scott


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Thanks for this post, especially since they're SBF heads. I picked up a set of GT40s (not P) that I'm working on. They don't have thermactor bumps, but there's still a bump on the ceiling that I'm removing. You've given me confidence to remove the entire boss from the bowl.

 

Mike:
Those GT 40's respond really well to porting,as they are basically a newer production version of the C9 Windsor heads,with 1.84"/1.54" valves,and very similar port shapes and dimensions.
I have done a few sets of them and they really work nice on a 289 or 302 with a fairly snotty cam.
They are mostly overlooked for aluminum heads lately,and are just about the best bang for the buck out there right now if you ask me!

Scott


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Here is a Chevy example, not that I am biased

Green is my favorite color



not done yet, but really opened the bowls to about 90 percent of the seats on these heads, not really needed for a street motor, but these are going on a 11.5 to 1 motor


getting exhaust ports ready to be matched


opened up in most parts, still need some work in these pics, not done yet


more shots along the way










getting there, then a quick sandblast to really see where I am




shot of chambers, polishing compound is all over the place


all ridges, casting marks and roughness smoothed out in chambers, almost done


Another set, aluminum matched to a FelPro 1205 - most important is not getting too aggressive, take your time, remove material and blend, don't go too far!


Not the best pic and also non friendly hamb car photo bombed this pic


It is also important to know the cylinder heads you are working on, as in knowing oh on a Ford 302 head part number yadda yadda yadda they have extra material here or are thin here so be careful. You want to get everything as consistent as you can, important to keep the grinder moving.

In the area of these areas of the bowls, they were heavy with ridges, having done research we knew we could remove a good deal, but also blended it all in to remove bumps etc. Removing more material isn't always better. I also always do the intake manifold to match.




074 BBC heads, light gasket matching and smoothing of the casting


I didn't have a before picture, but this shows the same part number, some rough casting in ports, light ridges, didn't go crazy on these.

 

What a great thread. Thank you poweshftr.


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BostonCamaro:
That's some nice work Brother!Now things are beginning to get rolling!

And Cowboy:
Thanks very much.It feels good when I can give a little something back.
The HAMB has provided me with SO much support,information,connections for parts,etc.
I would be up the creek on my coupe project without the HAMB!

My next porting project is going to be a set of Chrysler Hemi '555' casting heads....it should be a good one!

Scott


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The rought vs. smooth debate is an easy one to proove/disproove (read that...Wet Flow Bench).

Just put a VERY small drop of water (or most anything) on a smooth surface. It just sits there, not moving, spreading out, nothing.
Put the same sized, same substance drop on a rough surface. Depending on where it lands, a high or low area. The drop will move around, not sit still.

The bad part is the throttle transition from a low throttle blade angle to a high angle.
At lower rpms and low throttle angle, that fuel will stick to the smooth walls, with a low velocity, there's nothing to pull it off of the wall. Now open the throttle hard, inject even more fuel (accelerator pump for the carbureted guys), and now with the extra fuel drops, the increased air speed, even more fuel enters the chamber because the fuel that was sticking to the walls has finally been pulled off of the walls by the new higher air flow speed.

All this just doesn't happen when the walls are a bit rougher (I use 60 grit rolls to finish), because the fuel is moving on the surface anyway, so less adhears to the walls, the fuel that does stick to the high spots doesn't stay in place because those drops and VERY small in the first place, and the little fuel that sticks to the low areas, is so small it's almost insignificant.

The Wet Flow bench designed flow bench prooved this all out. Just color the "fuel" so it can be seen entering the clear cylinder, how much and when. All this shows up very obviously.
BUT...all this goes out the window with injector nozzles that are way down by the valve head...the whole port can now be smooth.


Another area that needs carefull work is the short turn radius.
This is impossible to show in a picture without cutting the head apart.
This is an area that can make or break low lift flow. And "low lift flow" counts. Low lift would be considered .010" to about .300" lift. Consider a cam with .450" or .500" lift, that makes up roughly half of the lift actuation...!

You need to be very carefull about making a smooth, clean, single radius in this area. A "flame" type cutter or a larger ball cutter with teeth on the "backside" of the given diameter is required to make this area the best it can be.
Stock ports have varying shapes. I've seen from hard angles in many Chrysler heads to nice clean radii in later designed heads with everything in-between.
Do NOT lower the main floor area in any way, anywhere near the short turn area.

Be very carefull and use your finger tips to "feel" the shape (pretend it's undercover time in the bedroom and you are makeing that new person feel good...!). Not kidding here..! Feel the shape, spend some time moving your fingers around noticing all of the shapes in this area.
Remember, you want as single, as smooth a radius from the port floor (all the way across) and roll it into to the valve seat as possible.

Mike

 

On a street engine, I like what Joe Mondello was promoting: do not open the intake port to the bottom edge of the valve seat but leave enough material to produce a "venturi" effect that enhances low-lift flow. He also recommended polishing this 1/2" below the valve seat while leaving the port "stone" rough.
I like using various sizes of flap wheels for this polishing.
David Vizard has a lot of "beginner" advice for those wanting to improve performance on a shoestring budget. Don't know how available his books are today.
Regarding dimples or centre-punch depressions: how long do they remain carbon-free in the combustion chamber of a running engine? Same thing with the Singh grooves?

 

Powershifter, i plan on doing some basic porting on my 68 390 later this year, i think with your instructions it would benifit even if i just port matched and smoothed things out. are there any places in an FE head to stay away from or bumps (like you mentioned for the emissions) that are ok to remove. dont want to ruin them. thank you Mark

 

powrshtr, I have a 396 and it has stock 3931067 heads. please PM me I would like to see what you can show or teach me on this thanks man

 

Mike VV,

If having a rough surface is better, would it make sense to hit the ports quickly in the blasting cabinet with a rough grit?

 

Really, I am not much more than a back-yard hack myself. I dont have sufficient math/fluid dynamics knowledge to dance with the big boys. I've just been at it a long time, built my flow bench back in the late seventies, have been learning ever since.
Theres a lot more information out there now than there used to be, the guys that knew their shit were very tight-lipped throughout the seventies/eighties. I highly recommend that Harold Bettes book for you and 31vicky, I think you guys would find it a real treasure trove.

 

Mac -

I'd guess it depends on the end result. You don't want it too rough (peaks vs. valleys), this will inhibit overall flow. A bit smoother (about twice as smooth) as the stock as cast port (50's thru 80's iron heads) is a good visual.
But ending up with a nice even surface that equals about a 60/70 grit surface, sure. But would it be worth the extra work...?? Would sure look nice..

Note, that this is for the intake ports only...right..!?

For those of you that like shine....polish the exhaust to your hearts content.

The combustion chamber isn't so picky. All the different things that people have tried over the years....not worth the effort. If it were, youl'd see it in every raceing cylinder head out there..! Don't be fooled by gimmics...no matter where they may have come from.

Go and buy a NASCAR cylinder head from the carburetor days of a few years back. You can you know. Check out how really simple and free of gimmics they actually are. Those guys spends almost every waking hour trying to enhance flow.
Much the same as a Pro Stock cylinder head. But the NASCAR head is more realistic to a street head vs a Pro Stock head.

For what it's worth...the "ventury" effect is almost impossible to achieve just cleaning up stock ports. Most castings (I've seen) do not have enough metal just below the seat to do this evenly, all the way around the seat.
But when installing larger valves, it can be done, bit it's VERY time consuming to do correctly. And if you don't have enough material all the way around the opening, it's not worth trying to do.
In reality...the "ventury effect shape" is best left for those with a lot of hours with the grinder in his/her hand. Otherwise, it can and will most likely be very frustrating.
It's also a shape that is more suited for a moderately hot rodded engine, vs. a higher rpm engine. Faster moving fuel droplets don't like being forced around bumps like that espicially on the back wall of the bowl.

Mike

P.s. - "pwrshftr"...not trying to highjack your advice here..just lending another experienced hand...

 

Just to add to the smooth versus rough finish debate:

Why don't golf balls have smooth surfaces? Because aerodynamics have proven that the dimpled surface defeats wind resistance better than a smooth surface.

Can we apply this technology to ports? I don't know the answer, but it would be interesting to know.

 

yeah, I am no pro for sure, I am in the back yard hack category for sure... none of us here are building engines for John Force, I also leave the intake runners a little more on the course side of things and my experience has been that some well thought out mild porting can wake things up a bit, at one point I was doing the research and gathering items for a flow bench, but then I said to myself..am I building engines for John Force? nope, so didn't follow through on building a bench, maybe I will one day...