Need Help- Porting Heads for beginners

Okay gotcha Steve! What’s your suggestion with the valve guide boss, just round off the sharp edge?

back to what you were talking about earlier with the pictures you were illustrating, I made this picture up to understand the exhaust valve cylinder wall with the circles portraying the cylinder bore, and the arrows pointing to the exhaust cylinder wall, correct?

And I made a video but I can’t seem to upload it on here of what I believe to be the area you want me to remove material, is this correct? I’ll just add screen shots

 

Hi all, lets start from scratch here since some folks may have just tuned in so to speak.

Also because this string of info started near 2 years ago now I went back and reread what I posted here.

I could have explained some things in a better way and in some of the things I posted I did not proof read and left a word or two out that left a questionable meaning to what I was trying to get across here.

The very first thing you want to do before you even go into a given port even with just a sanding roll, no less a Burr is to access what you have to start with, let me repeat that, you must ascess what you are starting with!

This will allow you to formulate a plan of attack and work on the areas of the port likely to provide the most flow gain for you work effort.

Locating and working on these areas first will also mean that your far less likely to fall into the pit of loosing air flow and reworking the areas where you do not want port enlightenment to take place.

A golden rule for porting is to always produce a greater percentage of flow gain the the percentage of enlightenment you add to the overall port.

Another way to say this is you always want to produce a greater level of CFM gain then CC increase in the overall size of the port, be it Intake or exhaust!

Tools you will need are inside snap gauges as in my photo and a cheap digital caliper.

Here's the first step in making a valve bowl template.
I use .200" thick plexiglass, or a old valve, can use even just .060" thick plastic from a hobby shop or basswood if you like.

Take note of how the 1.60"" template is fully done, as its areas where the flat side meet the Round has been made a softer transition, unlike the photo of the 1.66" template.

This is nessarry so do not leave it out when you make your templates!

My handles are long 6/32" machine screws on my plexiglass ones.

Lets start off as if we are accessing a head with a 2,00" Intake valve , so we need to make a template for doing such.

With our inside snap gauges and caliper we find that the the biggest minimum diameter of the valve bowl ( restriction point) is about 1.60" or about 80% of that 2.00" valve.

Keep in mind here tha a minimum throat size for a give valve size to start to produce the highest PEAK LIFT flow numbers that it can, is a 85% minimum .

Notice that in my example here we are starting off at 5 % down from that minimum.

In my photos you will see what the finished template should look like and how to make it .

Back in section 6 of this string on Tuesday I posted a picture of a 1.60 x 1.50" template down in the minimum diameter section of a head, now I will also post a photo of that same template further into the port at what I and many other porters call the window area.

Take note in this photo of how well the template fits into this window area!

The flattened side if the template is on the common wall between both Intake ports and one end of the template is sitting as it should on the crown of the short turn .

The shape and size of this port is very close to being geometrically perfect, and as you enlarge the throat if you need to in the heads you are working on, then you need to maintain this same geometry!!.

Also I have posted the 3 steps in making a valve bowl template.


That's all for today folks , tomorrow I will post more and get into making the needed short turn template and also provide a better explanation by means of another diagram of why we are working things out in this way.

 

Steve is posting some real great info. This is also why I like to start with an unmolested small-valve head. Nothing is missing that you can’t put back,and I can remove what is needed.

 

Steve, I appreciate this so much, your knowledge is so helpful!

I’m going to start on those templates this week

but I have questions, the valve bowl template is used just to enlarge the throat, correct? Also, can you talk about where you start to take material off in a measurement form when using this template, so maybe you start to enlarge the throat let’s say 1/4 inch below the valve seat and you stop 1/8 inch above the valve guide boss. I just wanted to know a start and stopping point in that regard. But maybe you’ll explain this in your next post anyway but I wanted to ask.

 

Hi all!

Here's how to make a short turn template and some
What how to use it.
In regards to using it the complete right way and describing such I am still thinking about the best way to go about saying such so that it's fully clear.
So give me until tomorrow morning to get that posted.

As you can see from photo 1 it's simply made already for you by making a valve bowl throat template i discribed how to do in my last post if your using a big enough item of material.

This a quadrant of the circumference of the size you use for your throat template .

My photo 2 is a geometric drawing of how a Intake port is designed for the most part .

Note how the throat diameter is 1.60" and the short turn is 1/2 that diameter, so it's a circle with a radius of .800" with a arc of .800" also when you chop it into quarters.

Although I will not talk in detail about the roof arc just yet , but just note that it's .800" plus 1.60" for a total of 2.400" .

My photo 3 shows how this .800" template is used to judge the arc / radius of the short turn.

My next photo shows the usage of a drawing Compass to better show you all how these dimensions relate to each other.

Now if you find that you want to go up to a bigger throat diameter, here's how things need to change.
For one thing, and it's a big thing the short turn needs to be taller and we want to in regards to a iron head stay away from using epoxy to make that short turn taller.

Note here that by making it taller we are making it a bigger arc/ radius!

So now what can we do to make this a bigger arc/ radius?
Well we lay back the short turn by grinding it to follow the arc of a bigger template.

Also what we are doing by laying back the short turn is moving the crown/ high point of the short turn back towards the port flange.

In my next photo ( number 5 ) of the short turn with a bottle cap on it that is bigger then my example of .800" you can clearly see how much meat we do not have to work with.

In photo 6 you see a short turn template of .900" which would be needed if you where reworking the throat up to 1.800" from my starting example of a 1.60” throat.

I hope you can see from this photo how the short turn needs to ground to get this new bigger arc in place, as posted above your laying back the short turn, or softening it as some Folks say , but to me that term leaves out the major importance that it needs to be a specific radius / arc.

A great way to get familiar with what I have presented here is to measure up your heads intake and exh bowl Id and then draw up what it looks like geometrically even before you step into making and templates .

My last photo is a bit of a exaggeration to show more clearly what the changes look like when as in this example of mine you where go from a 1.60" throat up to a 1.800" throat .

This info should give you enough to chew on until tomorrow.

 

Good weekend morning all!
Here is more needed detail into what I have posted about already.

But before I do that I need to cover how important it is in your assessment of stock valve bowls to make a template out of a old intake or exh valve.

your stock as cast assessment must be done by sizing down a stock valve to your stock throats minimum diameter.
This will allow you to drop the resized valve into the guide to better judge what is going on in regards to the geometry of your stock valve bowl, be it intake or exh!
Here’s a drawing I made up of what I will say is a average stock short turn in any cast iron head, not just Buick.

being able to slide a valve bowl template that you have made into the guide while getting it to just sink passed the bowls minimum ID means that you are judging what’s going on while the template is following the heads valve inclination angle which is super important!

Here is something very important in regards to what I have seen of the stock short turn in BB Buick heads as compared to my drawing here, that being the radius of the short turn back on up to the crown just after the bottom cut in these heads has a flat or straight run to it before the arc/ radius actually starts off.

This has a big effect in terms of air velocity going over the short turn.

The effect of this straight section will slow down air flow over the short turn just as laying back the short turn will , this allows a bit more high lift air flow to take place for a given amount of throat area , on the other side of the coin it will cut into air flow numbers that could be had at lower lift ranges.

also very important if you choose to go up to bigger throat percentages is the width of the short turn.

This area I am talking about is the floor width from just before the crown of the short turn all the way around to whatever the as cast or bottom cut is in the valve bowl.

One of the purposes of the flat 94% side of the valve bowl template you make is to check this floor expansion rate.

it’s other purpose is that the short turn on its way up to the crown from the seat area needs to go from being round into being like more of a D shape which is what this flat side of the valve bowl template is.
For today I am going to leave off hear and ask anyone following this to post back with any questions, in fact if your really having a hard time , then just PM me and I will pass along my phone number for you to just call me.

Please keep in mind that the overall shape of the short turn is by far the single most important thing to get right in terms of any porting work done to your heads even if your just doing valve bowl work, that’s why once again it’s so very important to assess what you are starting off with!!!

 

Steve does polishing the combustion chamber face around the valves to a smooth mirror like finish have any gains? Does it promote a cleaner burn? I watched a guy on YouTube do that to a nissan or some other offshore brand head.

 

It can be a double edge sword type of deal.

yes a polished chamber can help to reduce carbon build up which can bring about pinging at times, but a bit of a ruff surface will help to break up streams of wet flow running over the chamber out from the valve seat which can aid in better burning of all the fuel and air that makes its way into the chamber.
To be on the safe side I would only polish the chamber walls around the exh valve.

unless you have some big pimples in your chambers or very ruff casting surfaces I would only polish out where I posted above.

You DO however want to roll over any sharp machined edges like those of unused spark plug threads and the meeting of the chamber and the deck surfaces.
You just need to be sure that if you roll over the chamber lip I just talked about that you do not undermine the fire ring of the head gasket.

 

Ok thanks Steve, I'll probably just leave the chambers as is accept for taking the edge off like you mentioned. I will have the heads cut just a bit to make them nice and smooth for mating purposes. From my understanding I just need to "touch" that edge slightly correct? Is it best to use a burr or a cartridge roll to do that?

 

Use a sanding roll, it will take a tad longer but your far safer since a slip will not do harm. You only need to roll over the lip by .010”.

 

Yeh I hear you, I wouldn't want to slip with the burr and gouge my freshly machined heads.

 

This is great information Steve, just to clarify the old valve you make into a template for the minimum diameter of the throat, where does the machine screw and pvc template come into play? make that one when you go into bigger throat size? for instance, im going to enlarge my throat to 88% of my valve size is that when i should make that machine screw/pvc template or just make another old valve template?

 

Yes , for bigger then stock throat sizes make templates not of used valves , but if you want to save yourself some work and get good head start then as in my picture here once again you can have a shop do what I do and use a cutter for installing seats if they have one a little smaller then your throat percentage your going up to.

this started life as a 1.60” throat and now it’s 1.775” and I am going up to 1.80”.

note that whatever your final size will be you need to make templates to do the needed work in size steps if your grinding out more then .030” to get to your final size.
This will keep your from making mistakes since your a novice so to speak.

also a very important part of the rework of the bowl is that you do not want the full new throat size to continue on down to the roof.

this is the other use for the 94% flat size on the valve bowl template.
Here is a shot of a 1.700” template on the roof against the common wall of a valve bowl with a up sized 1.830” throat.

 

I got it Steve, when you used the cutter, how far are you taking it down, it only looks like 1/2 inch? Youre not going down further because you want to keep the shape of the bowl? Whats your procedure on using the cutter, secure the head and use a drill press?

 

Let me back up a little here and this I will cover is very very important, so reread it until it’s at the forefront of your mind!

You start off with a stock size throat template to ascertain how and where changes take place especially in the valve bowl.

1st off all factory cast iron heads of the many different brands I have worked on all have a taper in the valve bowl from the last angle of the bottom cut down to the roof.

some valve bowls will pinch in and then flare back out either in there width left to right, there length rear of valve bowl to short turn or both to some amount.

whats important about noting this at first is our rule that you only have .180” of port wall thickness to work with and unless we have a sectioned / cut away of a head to investigate we want to cut no more than .060” out of that .180” for a iron head that will see a lot of heat up and cool down sessions, especially if that wall we are working on needs to support the clamping loads of a head bolt for instance.

In keeping this firmly in mind, if we have a valve bowl that has as I was talking before a top to bottom taper to it then if you find you could max out the throat at 91% mid way down / in then if you tried to maintain that 91% all the way down to the roof of the valve bowl you would stand a darn good chance of grinding thru a port wall.

This is 1 big reason as I posted up yesterday for the 94% width flat side of the throat template in the picture that shows it in use,

the second big reason is for a problem that can take place called air mass sheer, turbulence , or tumble as I call it .
When this takes place at high flow rates which goes hand in hand with high port velocity’s you loose control of the air.

There is a big difference between the air speed going around the roof and out into the chamber and the much faster air speed due to the tighter short turn radius trying to make its way over the short turn.

what then happens due to the total air mass running thru the bowl is that air passing over the floor can not make that turn and plows into the air already making its way out of the long side of the bowl.
This collision/ turbulence when it takes place at a certain air speed cuts into flow numbers big time !
This problem is far more likely to take place in heads that have a valve inclination angle of less then 16 degrees in combination with a low port angle which discribes most all factory iron heads that are not of the Hemi type, or of the raised port type.

Now getting back to the template and it’s usage , if you limit the roof width to only 94% yet the width of the floor can go much closer to the throat width you are using then that will limit the total air mass and hence maximum air speed and keep you out of trouble in terms of having a turbulence / tumble issue take place.

I know what your thinking , yes you could possibly get more air flow if the roof path was allowed to be made up to 98% of the template width, but for a novist porter to find this problem out would take a flow bench, and then once found you would have to know how to go about dealing with it and get rid of it.

Once again sorry this is so long, but once you get up to a 88% or greater valve to throat percentage, ( should you decide to due such ) then all the more critical becomes the need to get things 100% right on the money!

 

Okay, thank you for the word of caution, I will certainly do so. As a novist maybe I should just do the 85% throat size of the valve and I won’t try to use the cutter myself to open the valve throat.

 

Ive completely butchered my new stage 1 SE heads i guess,....because all this makes my head hurt ha

 

Now I'm just a ole dumb knuckle buster but with 455 cid with a high stall converter and a 4150 carb of generous size,..and the appropriate cam how much of this really matters,...?? Just thinking aloud here

We are worried about low speed response in such an application,..actually it's helpful to bleed some TQ off,...so how much of this applies to a 400+cid performance engine,..true performance engine where low speed rolling response isn't really an issue like putting a 245cc runner on a 302 to 370cid engine?

 

It’s never the thing to do in regards to as you say “ bleed off torque”
Doing such require’s one to drop cylinder pressure which results in a motor that is slower to gain rpm, and at some point run hotter.

The rate at which a motor gains rpm is a big factor in any Vehicles performance.

In terms of a flat out race motor you want to move that peak torque amount to a more useful rpm range by means of the cam spec’s, and then run the needed gearing and converter to get the motor right up into that narrow power band and keep it there for almost all of the remaining 1/8 th or 1/4 mile run.

The correct way to deal will excess torque in terms of a motor that is not intended for flat out racing is to run rear gears and or tire size combinations that allow the use of that level of torque without it just all going up in smoke.
This type of move assumes that dropping a street / limited strip motors overall gearing does not lug the motor down so far that it’s then prone to pinging.


Keep in mind that in a 4 cycle engine and spinning at 5000 rpm the column of air & fuel sitting at the back side of the intake valve and extending on back to the opening out into the plenum has only ,006 seconds to get into the chamber once the valve opens, so if you think that port velocity thru a given amount of port area can be taken lightly then your barking up the wrong tree here!

It’s been clearly noted that the Fords mid 60s Indy 4 OHC v8 motor with its near Boss Cleavland sized intake ports was a dog even after all the development time Ford engineering put into it!

Yup, the Ford V8 did rev higher then the Offy 4 cylinder Motors that where dominating Indy at the time , but the Offy motors where just as good a match for the new Ford nightmare!

In fact Dan Gurney sent one of these engines to Westlake engineering in England where they made the intake ports smaller and picked up power across the motors whole rpm band!

If your talking about a flat out race motor and your not averaging 400 FPS air speeds in the rpm band where the chosen Cam is to attain peak torque and HP numbers then you are sacrificing potential increased performance without question!

I am sorry if all of this info makes your head hurt, but I am just trying to to help folks doing whatever level of porting work to there heads get the most out of there efforts , to not screw things up and to better understand why to do things a certain way.

No one here is twisting your arm to read this and many times folks like you interweave under lying innuendo’s like you know more , which is all fine, but if you have added proven info then by all means feel free to contribute and post it up!

 

Alright Steve, I finally found my digital caliper, and my pinch point seems to be the same place in all my valves, exhaust or intake. Maybe 1/4 below the valve seat, picture attached. Now I know you said you want that curve from the seat down into the bowl for better efficiency, so is it okay to enlarge there or should I go further down and take the next pinch point?