535 replies to this topic

[Alex Bolanos]

I have heard more than once (and I believe it) that the current plunge cut rule (which does not allow a plunge cut to be massaged) helps to make more heads more similar in performance and would reduce the need to find the plum casting, the pick of the litter.  So even if NASA and SCCA don't want any rules creep, what would be the objection to keeping the current plunge cut rule which defines the depth, diameter, position and finish of that cut?  

 

Going back to stock heads (no plunge cut allowed) would seem to favor those that have the wherewithal to inspect and test a bunch of heads or pay top dollar for the few plums that builders set aside for their "special customers".   

 

 

THIS ^^  Who wants to have to own a junkyard with a flow bench to run up front in SM?  <3 Dragho

[Neddy]

Does a head that has been plunge cut aftermarket (without any blending) look any different to a "as cast" OEM head that has had a similar amount of material removed?

 

If they can't be 110% reliably differentiated, there cannot be a question about removing the current plunge cut rule...can there? 

[Ron Alan]

it's funny...  There were a sizable number of emails and calls sent in to the CRB and Mazda  saying PLEASE DO NOT DEEM STR SMOOTHING LEGAL!   Those folks must stay away from this site or just not post for fear of being flamed.

 

Perspective is important.

 

Good night.  Kiss your wife and hug the kids cuz that's what's important, not this silly stuff.

Many have said it...but as we were also told what is said here doesn't matter so many of us wrote! And I'm sure many have chosen to keep quiet like how you vote! I never talk politics to my sister but I always vote to cancel hers out

 

But my hand is up here...no STR mods. Sadly,  if rumors play out and plunge cuts are also disallowed...god help the class. As Tom, Steve, and Frank to name a few have posted today...it makes no sense to remove the plunge cut portion of the rule. This punishes those who played by the rules in good faith and did what was allowed. AND DID NOT REMOVE MATERIAL OR BLEND AS IT SAID YOU CANT DO THIS! 

 

Granted...the innocent will still be hit if only the STR mods are out...but hopefully they will have some recourse or discounts if they go back to the shop that built the head. But if in fact we all(most of us with new heads in the last 5 years)have to start over I'm a lucky one that has 2 stock 99 heads to flow    As for my 95...larger plate please

[Ron Alan]

Does a head that has been plunge cut aftermarket (without any blending) look any different to a "as cast" OEM head that has had a similar amount of material removed?

 

If they can't be 110% reliably differentiated, there cannot be a question about removing the current plunge cut rule...can there? 

Yes...it looks and measures different for the most part

[Karl]

Ron, no it does NOT.  I can guarantee that nobody would have been able to tell to which head I had installed new seats and plunge cut to make look like OE.

[Karl]

PREFACE: Ignorant is not a bad word.

 

John,

 

The people that don't want the STR modified probably come from the following list.

-Too little prep to ever be at the front of the pack

-Too principled to believe that rewarding "cheaters" can ever be a good thing

-Ignorant about what STR modification can do (for flow and for parity in the class)

 

We have a democratic republic because the founding fathers knew that the masses were and would probably always be ignorant of the whole picture.  

[Karl]

Steve S,

 

I'm with you on the flywheel, but until we get over the hump (again a bit of ignorance creeping in) that a modified flywheel is dangerous, we get nowhere.  REMINDER: we had 1600s running safe 14.5 lb flywheels ten years ago AND currently the 1600 FW rule stipulates that the 1600 FW be heavier than the 1800 second gen unit.  We can do better, and to follow the little steps way of doing things, we can remove the outer ring as a first step.  It was part of getting to 14.5 anyway. 

[Karl]

Bench Racer (David right?)

 

You should read all the posts.  There is good stuff here.  I would like you to tell us why throwing heads away that bring more parity to a class (that continues to message the rules for parity) is a good thing.  I struggle here because I don't consider you ignorant about head work and the reasons for it.  Help me???

[Karl]

Danny and the others who question modifying the VVT RP and weight,

 

Using your video (that was fun and brought back some great memories) and Drago's dyno data, it should be clear to all that your car had more top end, as you said.  You smacked the black car a few times at the top of forth.

 

I proposed a bigger RP for the VVT to bring it in line with your car, BUT you can't do that without ALSO adding weight to the VVT.  2mm more hole and 50 lbs more on the floor should come close to equalizing the acceleration curves.  Do nothing and you open the door to bring two cars and test to see which works best at each track.  I have no problem with anyone having multiple platforms, but when they are able to use different platforms based on track to win championships, then I see that as a problem.  

 

I'd love to see you and the OPM guys do what you can to a 1600 to make it run those lap times at RA.  

[Karl]

"Plunge cut, what is it and why the debate?"

 

It is what ALL head builders (OE and aftermarket, which can be further broken down) NEED to do after they install the valve seats.  

 

For the OEs it's a cost equation.  Cost to produce really consistent castings v cost to machine them better.

 

For our head builders it's about getting the most power possible, and that is not a bad thing.  In fact, I would argue that with transparency, it's the best way to get us where we want to be, on even footing.

 

For the cost of a new motor from Mazda, you can make your used motor even better than the crate.  We went down the crate path.  I got 110HP and my buddy got 113.  That's what you guys who are telling John to not allow STR modifications want?????

 

The plunge cut itself gets you nothing, in fact, making the valve seat diameter bigger is taking power away.  The best plunge cut will ONLY remove as much of the NEW seat material as required to smoothly transition to the previously machined plunge cut.

 

Plunge cutting a head that has not had new valve seats installed is not necessary and probably counter productive.  

 

Blending the STR on the other hand is easy and cheap (broken record) and if you go too far, you will give up the gains the first little bit of smoothing gave you.  You don't need any measuring tools here guys.  Allow the 1600 and NA 1800 builders to go 12 mm into the ports and the NB builders to go 9 mm into the ports.

 

If you do any more than remove a little from the STR and take ANYTHING away from the LTR you will be going backward.  "He went crazy with the ports...." elicits fear for most reading, but finish that up with "....and now he can't keep up!" probably brings a chuckle.

 

Ignorance is the enemy, so let's keep talking and see if we can't overcome it. 

[Parity]

For the OE it's fairy simple. The cost to produce a plunge cut during the initial production is fairly negligible while the cost to control core shifts and profile tolerances on an automotive casting can be quote high. Mazda could easily reactivate the existing tooling and spec the permitted plunge cut as part of the manufacturing process. I'd be glad to bid on that job.

 

 

 

For the OEs it's a cost equation.  Cost to produce really consistent castings v cost to machine them better.

 

 

[Keith Andrews]

Danny cuts to the chase.  As a practical matter, only the front-runners and a few honorable and/or naive mid-packers will replace their heads (or even inspect them to see if they are compliant).

 

That's why I suggested a revision of the rule to allow de minimis work around the edge; i.e., enough to save some heads, but not enough to create a discernible advantage... with the proviso that it be objectively measurable. Then, face it: Even with such a change, there will still be plenty of illegal heads in use behind the front-runners, and maybe among the front-runners at some events. It's too hard to police compliance in this area, so we have to accept the fact, revise the rule and move on. It's not a perfect solution, but it's good enough. No matter how this specific issue is addressed, it will elicit action by only the small number of drivers who have a shot at a podium at the very biggest events. Too much focus on it raises the risk that bigger issues will be neglected.

 

We should focus on routinely teching at the Majors and the best-attended regionals for the cheapest, most effective and readily-detectible cheats; compression, for example. A list should be made up and one or two of the significant items checked at each event. This will cause some delay and inconvenience for both the drivers and the staff, but enhanced credibility for the process makes up for it.

 

I couldn't agree more.

[Steve Scheifler]

Karl, I don't doubt what you are saying but would certainly like more support, across all the engine variants, for your claim about the limits of what can be gained by working within the prescribed plunge depth. Assuming that when you say doing more than basic smoothing is "going backwards" refers only to that very limited depth, and assuming that the same gains are easily achieved by anyone who can follow instructions, then I could see supporting such a rule.

Please expand on your statements about doing just the plunge without also doing the seats.

[ner88]

Regardless of the results, I, like most back markers, mid-packers or race for the enjoyment of it guys, will continue to run what we have!

[Karl]

ner, 

 

You are exactly the guy I would like to see supported.  When something breaks, you should be able to count on the rest of us to help you get back on track with a faster car with limited expense.  I assume you would be happy with a faster car if yours broke and you had to invest something to get it going again. 

 

Watch Danny's video.  Three cars at the front?  You know how much more fun it is when it's ten??? 

[LarryKing]

 

Three cars at the front? You know how much more fun it is when it's ten???

 

You seen dat too? 

 

Kinda same deal at Runoffs also.

[Karl]

<<Please expand on your statements about doing just the plunge without also doing the seats. >>

 

If someone could tell me how to post a picture I will.

[Caveman-kwebb99]

You seen dat too? 

 

Kinda same deal at Runoffs also.

 

Many stayed away, if the rules were not up in the air, many more racers would have attended what it one of the best events of the year!  would have been 8-10 at the front.

[Karl]

 Capture.PNG   8.66KB   5 downloadsOkay, we are getting there.  

 

the top rectangle is the valve seat

green line represents the "bottom" of the straight portion of the OE plunge cut

the black curved lines below the green line represents the OE curved portion of the OE plunge cut

the red circle shows the sharp transition that so many are talking about in the STR

the OE sharp portion is in black.  Actually all black is OE

the blue arrow represents where the OE plunge cut "blends" into the LTR

the purple shows what I was able to do with a specially made cutting tool and the subsequent less sharp STR

the grey lines off to the side show how much deeper you would have to go in this case to improve the STR's "reverse" curve 

 

My cutting tool had a slightly larger radius (I actually designed it as a complex radius) than OE which allowed me to go deeper and smooth things out.

 

I hope the rest of you who have access to a little round file but no expensive head machine or CAD tool designing program will agree that smoothing out the area in red with your file is easy and CHEAP and can be done when you rebuild your head anyway.

 

Please forgive the purple line going into the port under the red circle.  I wanted to show how the cutter "spun" in the port and how my radius was a bit bigger than OE.

[Karl]

Note:  This wasn't all about cheating, though I'm sure it looks that way.  If I drew a bunch of OE ports for you, you would see how this procedure will equalize flow WITHIN one head.  Some of those heads were a mess.  

 

p.s. I think quite a few of you have a "catch the cheaters and send them home in a box attitude".  Possible to adopt a "tell us what the cheaters are doing so we can decide if we should make those modifications part of the rules" attitude instead? 

 

p.p.s. We would not be taking about any of this IF Mazda could produce each car with, how many moving parts?, in exactly the same way.