Need Help- Porting Heads for beginners

Discussion in 'Street/strip 400/430/455' started by Christopher Spouse Drew, Jul 25, 2018.

  1. Bigpig455

    Bigpig455 Fastest of the slow....

    Yeah, I just had to see what this manifold will do. Ultimately, I've got set of untouched manifold and heads for the 462 so it'll be PSMCDR eligible. On those heads, we're gonna concentrate on stem sizing, design and competion valve job.

    But again, I'll ask the pros: A lot pocket porting I've seen is pretty uniform across the port, and just flattens out the transition from the port roof to the bowl floor by flattening out the valve guide and support as much as possible. I didnt go that route on these, I tried to promote the port flow bias of the outer wall of the bowl (which is also the outer wall of the cyl) I didnt "Tear drop" the valve guide, although I did blunt it a little bit, if anything I tried to leave as much material on the inner walls/floor of the bowl to, I dunno, promote fuel shear, flow bias, velocity and swirl? I just wondered if anyone had ever taken that approach and how it worked for them?

    Here's a crappy picture that tries to illustrate what I mean..
     

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    Last edited: Jan 24, 2021
  2. Stevem

    Stevem Well-Known Member

    Here are some more cut in stone head air flow facts to keep in mind gang.

    For any given INTAKE valve size a large amount of flow up to a certain lift is totally controlled by the seat and valve angles used !

    The simple formula is valve size X .18.
    So for a example when using a 2.03” valve the flow all the way up to .364” lift is far more effected by how as I posted the seat angles and angled used on the backside of the valve.

    This then means only above .364” lift will the port shape and port size start to make a good level of difference!

    Why this effect takes place is because below as in this example .364” lift the velocity is the highest in the gap formed between the valve and the seat area in the top of the bowl.
    Once the valve is above .364” lift the air flow velocity begins to be higher in the port itself!

    This also means that the average home porter with no flow bench and no means to cut different valve seat angles , multi angles and different seat widths have very little means to improve there intake port flow a great amount within this .364” lift range without specific guidance from someone who has done such who has a flow bench!

    On the exh side of the head this formula is valve size X.35.
    So if you want to look at a average 1.60” valve size then flow numbers up to .560” can be very much more effected by seat and valve backside angles also!

    back on the intake side of the head above .364” lift as the port velocity is building with increasing lift it’s very very important to always keep in mind that high velocity air, just like high pressure water will always take the path of least resistance, as this will produce the greatest level of flow for the smallest area used, and the highest level of efficiency in regards to lift.

    Always paramount when porting especially on the exh side is to not loose any flow you already have, just gain flow.

    In terms of the Buick intake port bowls that have a big mass of iron on one side of the valve guide that can be cut and tapered back a good amount( .180” ) to better match the angle and shape of the other side of the valve guide once Boat tailed out by grinding.

    This difference from one side to the other was done intentionally by Buick since it helps with mid lift and higher swirl rates to assist in faster burn rates, but it does cut into mid and high lift flow numbers that could be otherwise had, even in a otherwise stock intake port.

    The reshaping work in this area must be undertaken carefully and in a specific way to get a specific overall shape.

    later today I will draw up some guides to help make better sense of what I have posted here and I will post them in the morning .

    in regards to more then 3 angle / competition valve job be very weary!
    The full radius valve job can for sure produce higher levels of air flow as seen on a bench, yet murder wet flow handling/ capability of the head which reduces burn rate and only severs to cut into hp, not increase it!

    If a shop can not provide back to back A/B dyno test results from having a full radius valve job done and not then don’t pay a penny for such!!
     
    Last edited: Jan 25, 2021
  3. Christopher Spouse Drew

    Christopher Spouse Drew Well-Known Member

    Thanks Steve for for your detailed response, I look forward to your next post to make my beginner ass understand better haha

    So I’m starting bowl work, and I’ve been watching porting videos and I took there advice and go some dykem, valve grinding compound and Lappers. It made a nice mark where the valve seat is and I’m told that every thing under the valve seat take the material down so it’s a straight shot to the valve seat. What’s your opinion on this? Is there more to it? Here some pictures. It’s very apparent on the exhaust side under the seat.
     

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    Last edited: Jan 25, 2021
  4. Stevem

    Stevem Well-Known Member

    Nothing could be a more wrong thing to do then going in with a grinder and cutting in a 90 degree from right under the seat into the bowl.

    There are some sections of the exh valve seat in all heads circumference where it has benefits in terms of bigger high lift flow numbers to have only 2 angles .
    This is needed at the short turn area in many exh ports and even intake ports that have far less overall short turn height then what’s needed in relation to the minimum diameter of the valve bowl throat that you are dealing with.

    here’s a cart of the efficient of having no angle , 1 then 2 then 3 and then 4 angles, it pretty self explanatory!
     

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    Last edited: Jan 25, 2021
  5. Christopher Spouse Drew

    Christopher Spouse Drew Well-Known Member

    Okay. I thought those videos were helpful but I guess they are teaching me the wrong technique.
    Here’s the video if you want to check it out.


    Im a visual person so your providing all this good information and I just can’t get the picture in my head.
     
  6. Stevem

    Stevem Well-Known Member

    In watching most of that video he is porting a Pontiac head of 1965 to early 1967 vintage from what it looks like .

    I am vastly familiar with Pontiac heads as getting them to perform better is what got me into this whole porting/ airflow testing thing for my own benefit some 35 years ago now.

    he is only going mostly straight down and in from below the bottom cut of the valve job, not the main seat.
    There are 2 reasons for being able to do that on this type of Pontiac head and not drop off any flow numbers.

    1) these early heads have a 21 degree valve inclination angle.
    2) all Pontiac non performance heads have only a 75% intake valve size to valve bowl minimum diameter.
    This was intensional by the factory to work best with the 30 degree intake seat that 98 % of all Pontiac heads have.

    if you have not forgot another basic rule of thumb that states that for any given size valve used to allow it to flow the best maxed out high lift flow numbers that it can, the valve to valve bowl percentage I mentioned before needs to be a minimum of 85% up to a max of 92%.

    The 75 % that this guy in the video started with is 10% under this 85 % minimum, so that’s what allowed him to grind near straight down and in from below the 60 degree bottom cut in that intake port bowl.
    This why watching videos of porting work being done on other brand heads then your own that your reworking can be a disaster!!

    The stock intake valve to valve bowl minimum diameter on the Buick big block heads that I have worked on starts off at a bigger percentage then the 75 % as seen in this video you posted.

    whenever you increase the valve bowl percentage in any brand head if you want to durive the maximum flow gain from such a rework job then other dimensions , curves and radiuses need to change also to get the overall geometry as dead on as can be within the confines of the port wall thickness you have to work with.
    These Pontiac heads in stock form flow some 190 intake cfm thru a 1.92” valve.
    I have ported then up to 250 cfm with the use of a 1.94” valve.
    But hears a concideration that could happen with any head.
    These heads are of a closed chamber design and as such once you do port work and get to the 235 cfm flow level no added flow will be seen with added work until the chamber is unshrouded by a good amount.
    Once unshrouded the peak flow number of 235@.600” lift change to flowing that 235@.500” lift .
    Without a flow bench at your disposal you would never find this out, that’s why porting with templates to a specific geometry is the way things should be done unless your going in to gently blend things in and remove casting anomalies and gasket match.

    And also folks keep in mind that in regards to gasket matching on the exh side the worst thing you could possibly do is to gasket match the floor !
     
    Last edited: Jan 25, 2021
  7. 1969RIVI

    1969RIVI Well-Known Member

    Here's the 68 430 heads I've been working on. I had the heads hot tanked and sonic tested and did the majority of the work months ago so there is a bit of surface rust in the ports. I think I'm on the right track (I hope o_O) with the bowls and valve guides. I think I need to blend the gasket matching a bit further back into the ports though? Sorry for the crappy pics.
     

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  8. Christopher Spouse Drew

    Christopher Spouse Drew Well-Known Member

    okay great information once again Steve, I wish we had Buick porting videos. What do you think about that grinding this bump down flush to the roof on the exhaust, bad idea? Why?
     

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  9. 1969RIVI

    1969RIVI Well-Known Member

    Hey Chris I'm just like you when it comes to stuff like this, I can read it 10 times and I'm still scratching my head. Show me once maybe twice and I'm good for life lol
     
  10. Christopher Spouse Drew

    Christopher Spouse Drew Well-Known Member

    Okay so 85%-92% of the valve which mine is stage 1 valves which are 2.1
    Yeah it’s tough to take these words, as detailed as Steve is, and put it into working on these heads but I’m committed to doing it myself.
     
    1969RIVI likes this.
  11. 1969RIVI

    1969RIVI Well-Known Member

    yep me too! I will eventually get a set of aluminum heads but it's just not in the budget yet. I'm balls deep in my engine build that I'm also doing myself.
     
  12. Stevem

    Stevem Well-Known Member

    It’s not just as little a amount of work as increasing the minimum diameter / percentage of the valve bowl throat because other dimensions of the port may need to change also to fully complement the new increase size of is this throat .

    As this throat dimension increases so does the possibile need of the height of the short turn and the height of the roof of the bowl, along with the circumference of the rest of the port right on on back to the intake flange.

    For example, if your running a 2.10” intake valve and your shooting for a 85% throat diameter then that needed size would be 1.785”

    Now you need to figure out the needed port circumference, you do that by Multiplying 1.785 by 3.14 and you then get 5.600”

    making geometric porting temples is the single best thing you can do!
    As a much needed starting point this will allow you to assess the stock geometry and sizes of your port to find out what your working with and what areas to attack first to get the best bang for your buck as they say.

    For example if the stock throat is 1.55” while using a 2.10” valve and you want to go up to a 91% throat size then that would be a dimension of 1.91”.

    enlarging a 1.55” throat up to 1.91” would mean grinding a total of .360” which then means that .180” would need to be ground off of each left side wall and the right side wall in the valve bowl, and maybe the rear of the bowl also as in my first photo here.

    The problem here in my example is that the average port wall thickness of any iron GM head IS only some .180 ” on average and this does not account for core shift or port wall meat lost to rust,so to get your needed 1.910” minimum throat diameter you would be grinding into water or air by the time you have reworked the port out to the flange!

    Here are some pictures of what happens to be a late model Pontiac head getting reworked into a larger throat size .

    The stock throat is 1.60” and I am just starting off the process of going up to 1.77” as can be seen by the lip left by the cutting process around the 1.60” x 1.50”‘template.

    This head uses a 2.11” valve so I am going from a 75.6% throat up to a 84% throat.
    In the picture note the template down in what is still a stock throat diameter that I have not cut / machined down into all the way,

    This template is 1.60” by 1.50” and fits like a glove in the stock throat.

    The next photo is that 1.60” x 1.50” template back lit in a port that’s is sized out to a 1.83” throat.
    The full rework of that port to the needed sizes and shapes has brought up the flow from a stock 208 cfm@28” to 270 cfm@28”.

    Thats all of the posting I will do for today gang as I am getting over having Covid and am still pretty beat!
    I suppose many of you want to know how to make this and other templates, by Wednesday morning I will have that info is Posted for you all.
     

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    Last edited: Jan 26, 2021
  13. Christopher Spouse Drew

    Christopher Spouse Drew Well-Known Member

    Steve, I hope you’re feeling better man! Go get some rest.

    but what you just posted made a lot of sense to me, I look forward to your template post later in the week.
     
  14. Stevem

    Stevem Well-Known Member

    Chris, you do not need to remove that boss out all the way since it's mainly sheilded by the valve guide.
    Just leave it as tall as it is and reshape it into a Tee Pee as best that you can, or if no thing else grind it down at a angle towards the cylinder wall side of the Exh port since that the way a bunch of flow out of the cylinder wants to make its way into the roof of the port.
     
  15. Christopher Spouse Drew

    Christopher Spouse Drew Well-Known Member

    okay so like in the picture I drew? And I’m working that shape around the 360 degrees of this boss?

    and your second suggestion is I angle this boss towards the the port wall that the exhaust shares with the intake when you say cylinder wall?
     

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    Last edited: Jan 26, 2021
  16. Stevem

    Stevem Well-Known Member

    Chris / folks I am getting stuck here working real late since I have not been at work for 9 days and need to catch up, but Chris, I will answer your question better by means of a drawing or two and a bit more detail.

    First though here is something to train your mind to think about in regards to exh flow and a parallel 2 valve head like these and tons of others are, which are also not a canted valve head.
    Here’s how you have to think!
    If you where to sit the head on a block and look up into a cylinder from the oil pan side you will notice that the exh valve is way offset to one side of the bore in regards to the greatest portion of cylinder area, and that the cylinder wall side of the exh valve is quite shrouded due to that wall.


    This means that since these are not a canted valve type head that most of the flow exiting the cylinder does so by making its way into the open exh valve from the intake valve side of the cylinder, especially at high lifts!

    a canted valve head is one where as the valve opens it is also doing so on a additional angle and unshrouding itself.

    what needs to be done to aid this effect is to grind the valve guide boss and that air injection boss ( and also modify a valve job ) such that once airflow enters the valve bowl it has freer access to the cylinder wall side of the guide , the boss and roof area because like I posted earlier this is the natural way the larger portion of the air mass wants to go and which again like I posted the path of least resistance and the path of greater efficiency.

    Here’s that drawing that should help you.

    note that when you grind to deepen the roof around the guide and the cylinder wall side of the valve bowl that you have no more then .180” of thickness to work with.
    To play it safe in these two areas I would not grind any more then .050” unless you have a junk head to section up and check out.

    The air injection boss should be ground like the valve guide but with more taper to it and a rounded over lead in nose if you can do such.
    The added depth you grind in on the roof once you get passed the side of boss and out to the main roof should then extend out across the width of the roof on out to the flange, but note that this added .050” of roof height in terms of width should taper / tilt back to the stock roof height on the intake valve side of the roof as in my 2nd drawing.

    Also note in my second drawing that only the added roof height should be carried out all the way to the flange, the added port width should start to get slowly back to the stock flange width once your grinding work reaches the crown of the short turn.
     

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    Last edited: Jan 26, 2021
  17. Stevem

    Stevem Well-Known Member

    By the way if you have a long enough Burr to reach to the boss from the exh flange, then just grind the whole thing out of there as it takes only 5 minutes more with a 20,000 rpm grinder.

    this also makes slopping the roof from left to right and raising it easy.
     
  18. 1969RIVI

    1969RIVI Well-Known Member

    Hey Steve not sure if you can tell by my pics I posted previously but am I on the right track with the bowls and guides on the heads I'm working on? Do I need to blend the runners back farther from the gasket matching? Not trying to hijack Chris's thread, just figure since him and I are both noobs at this and on the same path we can learn from one another's progress.
    Cheers, Bob
     
  19. Christopher Spouse Drew

    Christopher Spouse Drew Well-Known Member

    Okay Steve, I do have long carbide burrs, so take the guide boss and that air injection boss down to the roof? What do you think about the integrity of the valve guide now that you take that structure away?
     
  20. Stevem

    Stevem Well-Known Member

    No!!!! Do not reduce the length of the valve guide extension, only remove the air injection boss

    Removing the valve guide boss will cut into low lift flow,
     

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