48 replies to this topic

[Johnny D]

A picture is worth a thousand words.

Just saying.

J~

[RWP80000]

Ron Alan, on 15 Oct 2014 - 2:26 PM, said:

I like what Rob wrote. I like what Glenn wrote...either works IMO. I also feel the current wording is completely clear...though apparently that is just me 

And what do we do with the Spec Miata engine builders that massage the material at the edge of the plunge cut and the parent material. Or are we better off investigating for a plunge cut tool that functions as the OEM Mazda too and many other head manufactures world wide that plunge cut ( some call it throat cut) with zero massaging the material at the edge of the plunge cut and the parent material.

 

First for those wanting to see a of a multiple flute tool for machining the chamber and bowls, here is a picture of 1970's OEM production cyl head chamber unshrouding cutter combined with the bowl(throat) shaping tool. tool has 8 total flutes ( six different cut angles).  Three cut angles per set of four flute cutter carbide insert sets.  

 OWNER-PC - 2014-10-18 15.10.33.jpg   28.79KB   6 downloads

 OWNER-PC - 2014-10-18 15.09.52.jpg   26.41KB   4 downloads

This was for maching V8 cast Iron heads.( Oldsmobile) and has absolutly now bearing on the machining of SM aluminum small valve heads.

 

Picture of a current Cyl Hd machine tool cutter holder of which the cutters are commonly referred to as 3D Fast Cut system available through Goodson Supply.  These cutters are typically interchangeable across manufacturers.

 

 OWNER-PC - 20141018_150105.jpg   150.15KB   4 downloads

 

Due to space limitations, I will add additional images with a new post reply to show cutters and tool holder for performing specific Spec Miata head machining of plunge cut and seat angles in greater detail. 

 

Rich Powers

 

[Johnny D]

I suggested pictures for the rules.

Here's a legal head which indicate the important features. (insert picture here)

Here's and illegal head, indicate why, (insert picture here)

 

There was a comment about tech making different judgement calls.

It's a lot harder to make a bad call with photo/pictures showing legal/illegal, IMO.

J~

[RWP80000]

Here are individual images of current head machine tooling which is being used on the SM heads. The first is what is used to do a "Plunge cut".  This tool is just barely able to reach the full 12mm depth before bottoming.

 OWNER-PC - 2014-10-18 14.58.23.jpg   30.1KB   7 downloads

 

The second shows a cutter for machining the 45 deg seat.  The portion which is 45 deg is in the middle and is .045 inch wide.  The other two angles on the cutter are the outside one which is the 30 deg angle allowed for narrowing the seat width and the inside longer angle is the 70 deg angle that cuts the seat below the 45 deg angle and is specified as not being allowed to drop below the ferrous material of the valve seat into the aluminum at its maximum depth of cut.

 OWNER-PC - IMG_2803.JPG   26.81KB   6 downloads

 

Not being experienced in using the more advanced processes of this post, I hope when posted people are able to see the details that I could when viewed on my phone (before being uploaded here).

 

I never did understand the rules wording that said you could not remove flashing.  This just goes against any normal shop practices and one which would result in local machine shop customers being given non compliant parts back without ever knowing it and without the local community machine shop even being aware they were doing something improper.  Now I also do not think they would make an effort to trim/blend the short side radius with a tool as part of their process.  I do think they might rub a piece of crocus cloth over things though.

 

Regardless, I see a lot of confusion as to exactly what is being talked about.  The plunge cut on the long side radius or bowl cut will dig in deeper and deeper as you go for the max 12 mm depth and in fact most do not utilize the max of what is allowable.  The result of the deep cut is to create the flat cut on the bottom of the plunge cut and shape of the throat in this area does not create much of a burr or flash.  However on the short side radius as the plunge cut is made, only a very small amount of material is removed and as a result of the way the floor of the port bends away from the vertical plunge cut it is much more likely for the tool to shear off a fine ribbon of material that rolls away from the cutter and hangs as flash after the plunge cut tool is removed.  Given this it is only nomal to clean up this type of machining flash.  This in now way justifies any blending or transitioning of the base runner material into the plunge cut.  I think that you could allow any flashing or burrs to be removed as long as it did not exceed a small width of say .010 to .020.  That would allow any hanging "chads" to fall and not allow for any performance enhancing blending to occur while being totally consistent with standard  machining practices.

 

The other thing is that I think many are thinking the the SCCA rules plunge cut is meant to accomplish exactly what Mazda was doing in production.  The plunge cut rule is nothing like what the production head maching process represents and was in my opinion done in the way it was so that if someone was to pursue the head machining modifications for purposes of equalizing heads it would be obvious it had be done and there would be little room for massaging of the heads through the machining process for other advantages.  If I remember correctly there was to be a specific 90deg sharp cut transition required of the cutter with no tolerance language which in reality cannot be supported as it is impossible to transition between the vertical cut and the flat cut with out some tolerance given or allowed.  It is impossible to make a tool that cuts perfectly sharp much less stays that sharp in use.  There has to be some specified radius no matter how small that is.  This is the kind of absolutes in the wording that come back to bite us in the end.

 

As far as my position on this issue I do think that the liberties taken needed to be and that SCCA had no other choice based on the wording of the rules. I also do not think those liberties are responsible for the performance of the front pack. I also think that the rules should be written to cover all but the most aggressive of flash removal.  If anyone thinks this action is all that is holding them back then it would be a very cheap performance gain for any and all as it takes very little knowledge or equipment to "deflash" a head to whatever limits eventually are defined.  I don't care which way they go as I will make sure we are in compliance with either a newly built head or by verification we are in compliance with the rules as published.  Either way the head is coming off before our next race.

[RWP80000]

"Sure hope that SCCA provides clear picture documentation of both the non-compliant as well as the one(s) that were deemed compliant so there is no mystery as to what is deemed acceptable and what is not.  Given that this has become an area prone to improper interpretation possibly even by SCCA Scrutineers, it would be very helpful to the SM community at large to see visual documentation of the specific infractions.  Also, having such a large sample size inspected provides a broad spectrum of potential casting/throat machining possibilities to clear up  for grey areas people are likely to encounter when inspecting parts or performing/providing instructions to local machine shops." 

 

Rich Powers

 

I am also in support of pictures as seen in my post #217 of the "All things Runoffs 2014" thread pasted above.

[Steve Scheifler]

Rich, excellent stuff! I would like to help everyone better visualize the entire plunge-cut issue but have been unable to photo/video the actual process (did get one offer last night but impractical to fly there this weekend).

But adding to what has been posted already I have what I hope are a few helpful pictures. I pulled apart a VVT head this afternoon and cleaned up one chamber so we could get a better look at a purely stock one with plenty of miles on it. The four close-ups are of the same cylinder and I've kept the orientation about the same in each, with short-side up.

This first one shows both intakes on #4. The blue arrows show where the steel valve seat ends and the aluminum head material begins. The red arrows show where the factory plunge cut for installing the seats also took a little metal out of the "long" side of the port, also called the bowl or pocket .



The next three are all of the left side valve opening from the first picture but at slightly different angles to show where the plunge cut removes metal as you move around towards the "short-side radius".







I believe that where most heads ran afoul of the rules on visual inspection was in the area where the plunge cut tapers to a thin line as you get to the short-side and then the edge of that vertical cut all along the short-side. In the last picture above the blue arrow again shows where the steel seat ends and the aluminum "shelf" on which is sits begins. The red arrow points to the bottom of the narrow vertical plunge cut in the middle of the short-side. As you can see here it looks very sharply defined with no beveling, rounding, blending visible from this angle, and in the other pictures there are no tool marks in the "corners" other than the cutter.

Tech also spent a lot of time feeling that vertical edge along short-side section and we are told failed at least one because it was too smooth or not "sharp"" enough. As I feel this stock head which I cleaned with engine degreaser and a light scotch brite as I normally do, I would describe the short-side edge as "unambiguous" but not "sharp" even though it looks quite sharp in a 2-dimensional image. I believe this is where the builders are most concerned about removing any "flashing" left by the cut. Is that correct Rich?

Unfortunately, without access to the Runoffs heads we are mostly in the dark about exactly how they differed, but some apparently had very conspicuous grinding marks at the transition to the short-side similar to what this poorly focused image below indicates, as well as significant smoothing/rounding of that edge along the short-side.



This last pic is not the same head but is a similar one mounted in the machine for re-cutting the plunge per the rules. This one has just been finished and you can see that there is still relatively little metal removed in the bowl area, well below the allowed limit. (more is not necessarily better and you need a flow bench to know for certain).

[FTodaro]

Steve once again thanks for your work and effort. We now know exactly what we are looking at and what to check. Now we just have to see the new rule and see if we can interpret and more importantly apply the rule to what we see in our heads. 

 

I am no engineer, but with the small amount of surface area that we are dealing with, its hard to imagine  how a de burr or even a blending has that much of an impact on performance. 

 

Now we need to get a look at the rule then get your pictures back out and do a show and tell.

[RWP80000]

"Tech also spent a lot of time feeling that vertical edge along short-side section and we are told failed at least one because it was too smooth or not "sharp"" enough. As I feel this stock head which I cleaned with engine degreaser and a light scotch brite as I normally do, I would describe the short-side edge as "unambiguous" but not "sharp" even though it looks quite sharp in a 2-dimensional image. I believe this is where the builders are most concerned about removing any "flashing" left by the cut. Is that correct Rich?"

 

Steve,

Excellent photos! And yes,I think you have it correct in your statement.  I have examined a head very closely in the area of the short side radius and find that a small pocket mirror inserted into the intake bowl from the combustion chamber side along with a small light makes examination very easy for signs of tool marks as opposed to trying to access any smoothing by "feeling" the sharpness of the transition.

 

I am also in complete agreement that more plunge cut is not necessarily better and that is where the professional builders who have the equipment/time and resources add their value by developing an optimized package withing the rules.

[Tom Sager]

Steve, Thanks for the very informative and helpful pictures and explanation.  Appreciated.  I think most reasonable people would conclude that it should be permitted to clean up to a very small extent a legal plunge as a part of competent machining.  How to define that will be the tricky part and where that line is drawn will impact how many heads may not be able to go forward legally.  

 

I for one felt that the engine prep rules crafted in I believe 2010 was good work by those that contributed and wouldn't want to see NASA or SCCA stray any farther from those than necessary to clarify what can and can't be done.  

[Steve Scheifler]

I am also in complete agreement that more plunge cut is not necessarily better and that is where the professional builders who have the equipment/time and resources add their value by developing an optimized package withing the rules.

Unfortunately, that was never the intent of the re-plunge rule. The purpose was to provide a relatively simple way to compensate for production variances, decreasing the benefit of going through a pile of heads to find the gems which would reduce the reliance on expensive pro engines. But predictably, people immediately started experimenting with them on a flow bench and found the optimum way to apply the new rules, regaining some of the advantage and putting the pro builders back in charge since that is beyond the average machine shop. Fair enough of course, that's racing, but then they got greedy and sloppy. Had they stuck with simply softening the edges around the top and more artfully blended the transition it might never have been protested and continued passing normal tech as it has before. But in an arms race amongst people making a living off the results, someone always gets greedy. And when you have to rely on others to do your dirty work, there is always a risk that someone gets lazy.

Plunge cuts into the bowl in the 1.6 where large and inconsistent and that is was prompted the rule. From the few VVT examples I've seen close up I'm not sure the rule was even necessary for them.

[Jim Drago]

I saw this on FB today.. may have some pictures/ explanation

http://www.allenskil...cut-details.pdf

[Bench Racer]

The facebook article is very explanatory, interesting enging builder stuff.
A plunge cut bowl question would be, in picture 13 and 14, it views as tho the plunge cut is parallel with the inside diameter of the valve seat and there is a shelf at the in this case 9mm deep that per say would interupt the flow. Is my view crrect in what the pictures shows? Also the port paths and bowls are galss beaded. SCCA rule: My take is glass beading would be illegal per SCCA rule .4.

Just saying, or asking.

[john mueller]

I saw this on FB today.. may have some pictures/ explanation

http://www.allenskil...cut-details.pdf

 

 

The facebook article is very explanatory, interesting enging builder stuff.
A plunge cut bowl question would be, in picture 13 and 14, it views as tho the plunge cut is parallel with the inside diameter of the valve seat and there is a shelf at the in this case 9mm deep that per say would interupt the flow. Is my view crrect in what the pictures shows? Also the port paths and bowls are galss beaded. SCCA rule: My take is glass beading would be illegal per SCCA rule .4.

Just saying, or asking.

 

That article is from NASA's SpeedNews written by the SoCal SM Director Brett Becker.

[RWP80000]

 

Posted Today, 12:25 PM

The facebook article is very explanatory, interesting enging builder stuff.
A plunge cut bowl question would be, in picture 13 and 14, it views as tho the plunge cut is parallel with the inside diameter of the valve seat and there is a shelf at the in this case 9mm deep that per say would interupt the flow. Is my view crrect in what the pictures shows? Also the port paths and bowls are galss beaded. SCCA rule: My take is glass beading would be illegal per SCCA rule .4.

Just saying, or asking. 

Bench Racer,

 

I also noticed the glass beading which raised concerns that this could be illegal.  I say "could be" in that if it was only used to remove carbon from the combustion chamber and if it was never used in the ports or bowl area below the valve seat it would not be removing any material relative to the port flow. I think the pictures in the article show it was not confined to the combustion chamber.

 

This very issue shows why it is so hard for a DIY racers (who do not have all of the shop equipment necessary to perform all engine rebuilding functions) are at such a disadvantage in having work done that is 100% compliant and may never even know when they are not.  Local machine shops all have their own way of cleaning parts and unfortunately it is very difficult to thoroughly clean carbon from aluminum without very high end cleaning equipment which many small operations do not have.  Glass beading is a very common solution for those that do not.  I for one would never want a head to be glass beaded as the potential for the glass media to be trapped (as between guide and casting) and eventually dislodged to pass through the engine who knows when.  ( Soda blasting which is water soluble is the best alternative) but by the tech rules could be deemed in violation.

 

As for the plunge cut being parallel to the valve seat, Yes it is, and should be, as the plunge cut tool is allowed to cut the vertical inside diameter of the valve seat (which for the 1.8L has a 1.178 in  maximum diameter).  The plunge cut in this article is being cut concentric to the valve guide as the machine tool being used pilots in the valve guide of the seat/throat being machined.

 

As for a shelf being created, that is also true and why some builders do not cut down to the full (12mm) distance that the rules allow. As to that shelf interrupting flow, it needs to be viewed from the direction of flow in the port.  In the case of the intake, the flow is coming down through the port toward the valve seat and this shelf is not necessarily obstructing the flow.  It may cause some turbulence which could disrupt total flow or the increased volume in the port could affect the velocity resulting in an impact on cylinder charge volume.  I am sure someone knows!  On the exhaust side, it is a different story as you are extracting the spent combustion gas out through the port and it definitely presents an obstruction.

 

Rich Powers

[htron435]

Whatever is eventually decided, SCCA and NASA absolutely MUST be in agreement with this decision.  We NEED to have one set of engine rules.

[Jamz14]

I saw this on FB today.. may have some pictures/ explanation

http://www.allenskil...cut-details.pdf

JIm, Mckenzie happens to be my head builder that I keep referencing that says you can make the plunge cuts without deburring or blending. He even noted that no blending is allowed. This is how I know my head is complaint with plunge cuts taken to the limit. Those cuts are extremely sharp and square.

 

In your opinion, is it possible to achieve the plunge without noticable blending?

[Johnny D]

Whatever is eventually decided, SCCA and NASA absolutely MUST be in agreement with this decision.  We NEED to have one set of engine rules.

 

Do you think SCCA is going to go along with this thinking ??

 

I intend for the HP war to come to an end in NASA come 2015.

 

 Just asking

J~

[Bench Racer]

Rich, I'm no engine builder..................... My comments within your post below are items I read in the McKenzie Cylinder Head article and or viewed in the video.
 

Posted Today, 12:25 PM


The facebook article is very explanatory, interesting enging builder stuff.
A plunge cut bowl question would be, in picture 13 and 14, it views as tho the plunge cut is parallel with the inside diameter of the valve seat and there is a shelf at the in this case 9mm deep that per say would interupt the flow. Is my view crrect in what the pictures shows? Also the port paths and bowls are galss beaded. SCCA rule: My take is glass beading would be illegal per SCCA rule .4.

Just saying, or asking. 

Bench Racer,
 
I also noticed the glass beading which raised concerns that this could be illegal.  I say "could be" in that if it was only used to remove carbon from the combustion chamber and if it was never used in the ports or bowl area below the valve seat it would not be removing any material relative to the port flow. I think the pictures in the article show it was not confined to the combustion chamber. Rule .2.  "The original casting must not be modified in any way or polished unless specified below." I beleive we would agree if one bead blasted one half the gasket side of the head we would view a toally differen surface condition/modified than the surface condition of the unblasted part of the head. Mine is not to debate improvement or no improvement, my words are strictly referenced to the written rule. < With that said and if correct, bead blasting/modifying the conbustion chamber would also deem a head illegal.

 

This very issue shows why it is so hard for a DIY racers (who do not have all of the shop equipment necessary to perform all engine rebuilding functions) are at such a disadvantage in having work done that is 100% compliant and may never even know when they are not.  Local machine shops all have their own way of cleaning parts and unfortunately it is very difficult to thoroughly clean carbon from aluminum without very high end cleaning equipment which many small operations do not have.  Glass beading is a very common solution for those that do not.  I for one would never want a head to be glass beaded as the potential for the glass media to be trapped (as between guide and casting) and eventually dislodged to pass through the engine who knows when.  ( Soda blasting which is water soluble is the best alternative) but by the tech rules could be deemed in violation. Understand your words ^, shade tree builders SHALL be aware and understand the rules, have the required equipment or stay ou of the head building business.
 
As for the plunge cut being parallel to the valve seat, Yes it is, and should be, as the plunge cut tool is allowed to cut the vertical inside diameter of the valve seat (which for the 1.8L has a 1.178 in  maximum diameter).  The plunge cut in this article is being cut concentric to the valve guide as the machine tool being used pilots in the valve guide of the seat/throat being machined. < Understand.
 
As for a shelf being created, that is also true and why some builders do not cut down to the full (12mm) distance that the rules allow. As to that shelf interrupting flow, it needs to be viewed from the direction of flow in the port.  In the case of the intake, the flow is coming down through the port toward the valve seat and this shelf is not necessarily obstructing the flow.  It may cause some turbulence which could disrupt total flow or the increased volume in the port could affect the velocity resulting in an impact on cylinder charge volume.  I am sure someone knows!  On the exhaust side, it is a different story as you are extracting the spent combustion gas out through the port and it definitely presents an obstruction. < Understand. Presume there is a reason OEM heads have a smooth plunge cut transition in both the intake and exhaust bowls. Left a message for my son who is the USA OEM manager for a diameter tool manufactuer for many auto manfactures heads/blocks asking about for his knowledge of flow via the intake runner having what we see as a smooth plunge cut or a counter bored plunge cut. Son returned call, he presumes the c'bore would disrupt the intakerunner flow.   I'm sure anyone reading/engine builder and Steve who has used a flow bench may able to inform on this flow issue if they have c'bored a bowl or two. Maybe the info is known in an article someplace or one would need to machine a runner/bowl in plastic and flow smoke and watch both the c'bore plunge cut and the more normal smooth plunge cut.

 

EDIT:

Read an article from Austincc.edu and add the following from article. Not smart enough to transfer the picture.

 

<>(A)>In this production intake port, air starts into the port flowing smoothly. When it encounters the factory casting flaw on the floor of the port, smooth flow breaks into tumbling and turbulence. This causes restriction to the overall airflow in the port.( The turbulence in the airflow becomes more severe as air passes the sharp edges of the short side radius in this drawing. Smoothing the radius and removing (certain) casting bumps and flaws (not all of them) reduces turbulence and increases flow./>

 

 

David Dewhurst
 
Rich Powers

[Jim Drago]

JIm, Mckenzie happens to be my head builder that I keep referencing that says you can make the plunge cuts without deburring or blending. He even noted that no blending is allowed. This is how I know my head is complaint with plunge cuts taken to the limit. Those cuts are extremely sharp and square.

 

In your opinion, is it possible to achieve the plunge without noticable blending?

pm sent

[RWP80000]

 

Bench Racer

Rich, I'm no engine builder..................... My comments within your post below are items I read in the McKenzie Cylinder Head article and or viewed in the video.

 

 

David, I know where your coming from and don't disagree and respect where you are coming from. I am also trying to stay away from the quantitative aspect of this rules discussion for the most part as I will leave that to those with the most at stake.  

 

In the Mckenzie article the top right photo shows a head that appears to me to have been full bead blasted in preparation for the valve machining operation.  My concern is that it is a very common practice to use bead blasting to clean carbon from aluminum and most machine shop customers loose control over their parts once they are handed over for processing.

 

I perfectly understand that the SCCA rules are trying to convey that there is to be no actions taken that could be used to result in enhanced performance from the process.  They even say no chemical process should be used.  Does that mean that ultrasonic cleaning (which uses a chemical solution)  automatically renders a head illegal?  We have to be careful to not overly wall ourselves in with rules that cannot be enforced or that overly restrict what goes on using standard machine shop operations.  Yes, we should not allow people to use these processes to enhance the flow performance but if someone wants to bead blast their head's cambers and gasket surface strictly for purposes of cleaning the parts I see no reason to consider that head illegal. 

 

I think we got into this mess primarily because of the "absolute" type of rule wording relative to not removing "any" flash from the plunge cut.  This absolute instead introduced vagueness.  It is not in the nature of any good machinist to leave flash hanging and as a result what probably started as simple light flash clean up resulted in the rules "creep" we now have as SCCA TECH never paid close attention to this area and builders never bothered to seek rule relief since things were "getting by".  In place, there should be a standard machining/parting line clean up tolerance of some specified minimum/maximum value (as the case may be) that (unless otherwise specified in the rules) is allowed for all machining operations.