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#1
Johnny D

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http://www.scca.com/...ck-aug-club.pdf

There's this.
J~

WHAT DO YOU THINK?
SPEC MIATA
The CRB requests member input on whether or not the use of .25 mm(.010 in) over size pistons in all SM engines should be
permitted. The Spec Miata advisory committee asks that members take into account the following in addressing this question:
• The cost of new crate motors is approaching $3500. Many used blocks are too worn to be suitable candidates for
proper SM engines. The SMAC has decided to explore the possibility of allowing 0.25 mm (0.010 inch) over bores.
The intent is solely to contain costs. While sleeving blocks is allowed, few machine shops do it well and the costs to
do it properly are substantial.
• Over bore pistons and rings are readily available from Mazda and the cost is the same or less than standard. The
basic engine rules would not change in regard to OEM parts since only Mazda parts would be permitted.
• The performance gain is negligible. For a 1999 Miata making 128 HP, the gain from the over bore pistons would be
no more than 0.77 HP based on the added displacement.
• The purpose of permitting this over bore is not to create a performance enhancement nor as a parity adjustment
measure. However, the advisory committee is mindful that this may become the perceived "standard" and that many
competitors will feel that they "must" build to the new over bore allowance. To prevent this, cars using the over bore
allowance would be assessed a 15-20 pound weight penalty. That will assure that there will be no performance
advantage to using the over bore. But, a competitor with a running core motor will be able to build it without spending
$3500 for a crate motor and will not sacrifice any performance or build quality due to worn out bores.
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#2
dstevens

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Most amateur racing allows of bores to 30 thou. 10 thou isn't that much. Prior to having my current block measured I checked new MSM block pricing and sleeve pricing. New block just under a grand, sleeving from a good shop between 150=200 per hole depending. Over bore using torque plates, tank, magnaflux and hone about 300. Mazda pistons and rings as stated in the rules, 140 rings, about 200 pistons (compared to OE spec third party of about 110 for pistons and rings)

I thought it was silly not to allow over bore in the first place. And while they are at it they should spec an acceptable OS on crank.

#3
Danny Steyn

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IMHO I doubt that 0.010in overbore will even make the quoted 0.77HP difference. add that to a 15-20 lb weight penalty and it seems like a sensible approach to me although I have no idea how diffucult it is to source decent bottom ends

Danny
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#4
Steve D

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... although I have no idea how diffucult it is to source decent bottom ends

Based on the Adept Studios photos I keep seeing on Facebook, there's no shortage in South Florida!!

Steve DeVinney
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Series Champ - Won a points based series in a Spec Miata We have a Winnah! - Won their 1st race... Congratulations! Bona fide - A bonafide Spec Miata driver

#5
Sphinx

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Most amateur racing allows of bores to 30 thou. 10 thou isn't that much. Prior to having my current block measured I checked new MSM block pricing and sleeve pricing. New block just under a grand, sleeving from a good shop between 150=200 per hole depending. Over bore using torque plates, tank, magnaflux and hone about 300. Mazda pistons and rings as stated in the rules, 140 rings, about 200 pistons (compared to OE spec third party of about 110 for pistons and rings)

I thought it was silly not to allow over bore in the first place. And while they are at it they should spec an acceptable OS on crank.


You're assuming a DIY disassembly and reassembly. What's it run to have a shop do it? And how about all the stuff that should be replaced "while you're in there"?

#6
chris haldeman

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I would totally support allowing an overbore. I however diagree with the adding of weight because of the almost unmeasurable gain in power. There would be no way to tech or know who had an over bore and who didn't. The added weight is not needed. Just simply allow an overbore and be done
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#7
Ron Alan

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It would seem to be a simple way to keep costs down for the budget/do it yourself racer. I think the ability to repair/salvage the crank should also be considered. One spun bearing and its $500 for a new crank? Not a mechanic so if this is something that is to easy to cheat up I'm sure someone will chime in.

And agree with Chris above 100%...to difficult to monitor, just let it be done!

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#8
dstevens

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Based on the Adept Studios photos I keep seeing on Facebook, there's no shortage in South Florida!!


LOL

He'll be here all week, be sure to tip your bartenders and waitresses and try the veal....

#9
dstevens

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You're assuming a DIY disassembly and reassembly. What's it run to have a shop do it? And how about all the stuff that should be replaced "while you're in there"?



On a short block it's bearings, perhaps the oil jets. Always do gaskets and seals when it comes down that far. You'd have to get Mazda parts as most of the machine shops will use OEM. For example my guy uses ITM and JD Rock if you use his parts. It's a couple hun plus parts to assemble. For a clean, reconditioned short block with labor and Mazda parts is about a grand if you pay someone. Around these parts, anyway. And that's assuming good crank and rod cores. The local re-conditioner has 1.6 long blocks for about 1600, but likely OE spec parts, bored and an OS crank. A new crate at 3500 is still a pretty good deal but I think the overbore is more for the shade tree/ DIY crowd. I'm just about to button up the short block. It's documented in the link on the .sig.

#10
Danny Steyn

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Based on the Adept Studios photos I keep seeing on Facebook, there's no shortage in South Florida!!


Not to sideltrack this thread too much, but thanks for noticing Steve :) . When I am not wheeling a car around a track I can be seen in the dingiest dumps trying to source fine bottom ends..... This was one of the better ones I sourced at a local yard last year!

Posted Image

Here is the video depicting my search.....


http://www.youtube.com/watch?v=da_rPBVXIPo

Danny
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2 x SCCA Runoffs Champ | 1 x NASA National Champ | 6 x June Sprints Champ | 10 x ARRC Champ

1 x SCCA Super Sweep | 2 x Triple Crown | 4 x Hoosier Super Tour Points Champ | 6 x Majors Points Champ | 5 x SEDiv Driver of the Year

 

 

June Sprints winner  - June Sprints winner Series Champ - Won a points based series in a Spec Miata ARRC Champion - Won the ARRC Race in a Spec Miata We have a Winnah! - Won their 1st race... Congratulations! Bona fide - A bonafide Spec Miata driver NASA Champs Winner - NASA Champs Winner June Sprints winner  - June Sprints winner ARRC Champion - Won the ARRC Race in a Spec Miata ARRC Champion - Won the ARRC Race in a Spec Miata Majors Winner - BFG Supertour Winner -

#11
Jim Creighton

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Before I say what I was going to say, I must say that I never went a machine shop/ welding shop and found anything like that. Danny, I guess I'll need to lighten up on you and the OPM gang. Maybe you'll take me with you to wipe your brow as you operate.

But, back to real life. Every division has a very simple to use bore gauge which was purchased with the SM compliance money. It is easy to use and quite accurate. It is very easy to determine the actual bore. And all it takes is removing a spark plug and placing the motor a TDC or BDC. Takes less than minute. Since it is non invasive, it could be a part of post race compliance.

If you don't place a weight penalty on the over bore, then all the builders will build to max allowed. As a long time production car engine builder, we were allowed .047 over. Those who were conservative built new motors to .040, the rest built to .047.

And in a class such as SM where any advantage is an advantage, it has to be considered. I haven't figured the exact percentage, but 20 pounds sounds close.

#12
Jerry Cabe

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Based on the Adept Studios photos I keep seeing on Facebook, there's no shortage in South Florida!!


+10 :D

Jerry Cabe
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#13
Jerry Cabe

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On a short block it's bearings, perhaps the oil jets. Always do gaskets and seals when it comes down that far. You'd have to get Mazda parts as most of the machine shops will use OEM. For example my guy uses ITM and JD Rock if you use his parts. It's a couple hun plus parts to assemble. For a clean, reconditioned short block with labor and Mazda parts is about a grand if you pay someone. Around these parts, anyway. And that's assuming good crank and rod cores. The local re-conditioner has 1.6 long blocks for about 1600, but likely OE spec parts, bored and an OS crank. A new crate at 3500 is still a pretty good deal but I think the overbore is more for the shade tree/ DIY crowd. I'm just about to button up the short block. It's documented in the link on the .sig.


I'm not sure about the 1.8, but the 1.6 L is significantly cheaper. New crate engine from MazdaSpeed with tax, and delivered to me in Ohio, was about $2500. Comparing that price against what it would cost to rebuild my old engine, it just made sense to go with the crate - and now I stll have a dog engine for enduros. The 1.8 engine will have a different decision point for rebuilding vs crate.

Jerry Cabe
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Make it Rain - Made Paypal donation of $100+ Bona fide - A bonafide Spec Miata driver

#14
Jerry Cabe

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But, back to real life. Every division has a very simple to use bore gauge which was purchased with the SM compliance money. It is easy to use and quite accurate. It is very easy to determine the actual bore. And all it takes is removing a spark plug and placing the motor a TDC or BDC. Takes less than minute. Since it is non invasive, it could be a part of post race compliance.

If you don't place a weight penalty on the over bore, then all the builders will build to max allowed. As a long time production car engine builder, we were allowed .047 over. Those who were conservative built new motors to .040, the rest built to .047.

And in a class such as SM where any advantage is an advantage, it has to be considered. I haven't figured the exact percentage, but 20 pounds sounds close.


Jim,

Just because the SCCA spent the SM compliance Fund on tools and inspection equipment for each division (I'm glad we got something for the money), does not mean that they are being used. I go to almost all the events in the Great Lakes Division, and with the exception of putting the top three across the scales, post-race is non-existent. I have only seen the Whistler attempted to be used at one event in the past three years (not properly either).

As usual, people are kidding themselves if they believe the overbore will not become the "must have", and for many in the never checked Regional racing, it will become the "no, mine is stock". Will anyone be able to tell the performance difference, probably not for most drivers.

Jerry Cabe
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Make it Rain - Made Paypal donation of $100+ Bona fide - A bonafide Spec Miata driver

#15
William Keeling

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Every division has a very simple to use bore gauge which was purchased with the SM compliance money. It is easy to use and quite accurate. It is very easy to determine the actual bore. And all it takes is removing a spark plug and placing the motor a TDC or BDC. Takes less than minute. Since it is non invasive, it could be a part of post race compliance.


Not what I have seen -- not accurate at all; just ask the SWDIV driver who had to take it his head off to show that the tool was wrong.

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#16
Steve D

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I'll expose my ignorance here, but the weight penalty seems to be just that - a penalty.

All other things being equal, displacement and the resulting power produced is not a 1:1 equation, is it? If the displacement increases by 0.65% (if my maths are correct), the power gain would be ~0.5% just based on volumetric increase? What about the offset of larger (just barely heavier?) pistons?

I'd hate for this allowance to be made in an effort to help the budget guys, then have them legitimately complain about a 20 lb (~0.08%) weight penalty.

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#17
Mike Collins

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Jerry you are showing your age. Mazdacomp now charges almost 3500 for a crate motor. Guess you missed the memo.
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#18
dstevens

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Jerry you are showing your age. Mazdacomp now charges almost 3500 for a crate motor. Guess you missed the memo.


I just went and looked it up at MSM for reply to Jerry. A 1.6 longnose, B61P-02-300 is US$3100. And it's backordered. Still not a bad deal. As a comparison, stock GM 350 crate $1500, stock CR125 shifter kart engine $2500, KZ2 shifter kart engine, $4500.

#19
Johnny D

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I guess mine blew up just in time, Sept $2700.

I have a feeling a certain person here will start selling pro built one with some miles on the engine for $3K to 3.5K if this rule is passed. Which will work out well for everyone.

My vote, do it, no weight penalty
J~
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#20
Alberto

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My initial reaction is > fudge No.

My reasons:

1. I can get a 1.6 for $500 off craigslist or a JDM importer (Atarco for example).
2. I have seen absolutely no evidence of lack of 1.6 motors or parts. Prove it if you can.
3. $3,500 for a crate motor ain't bad and I'm sure the quality is excellent. In my brief time in SM, I've seen and read of more than a few "PRO" motors blow up w/ not much use.
4. I suspect that building the motor would cost about as much as a crate motor. I remember reading ad nauseum on the old site about how building a motor was much more expensive than buying a crate.


If they want to make engine rules changes, they should switch to a spec sealed engine package like other spec series IMO. IT is a builder's class. SM is a Spec class.
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