Karl,
Right now we can find usable block for little money. The bores themselves are very robust and normal use cause relativly little wear. Bores can be damaged, but miles don't seem to be that big of a factor unlike other materials which tend to just "wear out".

So considering the cost of overboring and tacit legality of simply taking perfectly good block and as standard process to overboring it, this was not made legal. This is viewed purely as a increase for the class to allow overbores. Really the last thing I want to to have 944 guys feel that they NEED to overbore to be compeitive.

For now at least we have enough cheap blocks to be ok. Now none of these used block may be perfect, but they seem to work pretty well. The intent is to keep costs down and so if the bores are not "perfect" they should still make a good motor. So this way if a guy needs motor any old junk yard one should suffice rather that a "perfect" one. BTW if the differene between "perfect" and "OK" is 2 hp that is something we can live with.

Now I will say it not easy to regulate parts bin blueprinting or even your "repair" as it can be hard to find in tech. Your coating process is not legal by the letter of the rules. Why? It is not stock. It is not a factory approved process to restore the bores to stock and now you have a different material that piston runs on. This could impact motor performance.

Now we both know that any performance gain would come from bore size rather than material, but it remains that given the rules there is no way this is legal. However it is also pretty clear that short of taking a material sample of walls, I doubt it could ever be detected either.

So where does that leave you... I guess "tech shed" legal as you said.


Now the current rule on blocks is going to be the same for the forsee able future. However I am well aware that supplies of old, but usable stock parts can and will diminish over time. I have no clue when, but at some point we may not be able to get used blocks. So what to do then? Well bite the bullet and allow some form of overbore or repair soemthing to make use of lightly damged existing blocks. Sure it will cost more, but it will be the right thing if it is the only way to keep the cars going.

However that time is NOT NOW. The same idea applies on other parts too and that is why rules are never fixed forever. They can of course be locked in for a few years.

Definetly do not want rules creep. No shortage of finding blocks at this point.

Anybody know what the size difference is between a 0,1 and 2 pistons?

Which ones are bigger? the 0 or #2?

And wouldn't looking for the perfect bore be the same as looking for a performance advantage?

Spend that $$$ on driving instruction or test days. There is more time lost between the gas pedal and the steering wheel than any you will find in the machine shop. IMO

The size difference between 0, 1 and 2 is very small 0 is the smallest and 2 is the largest, but all of these are well under an overbore by an order of magnitiude.

Porsche used tolerance groups to make the mfg process easier/cheaper by allow each part to have greater tolerance (this reducing cost) and then matching them to use in the right blocks to gain a tighter operating clearance.

Joe,

I understand. I'd like to be a data point to help you guys come up with a ruleset that works into the future.

Remember, I am here because I don't like the "unspecness" of Spec Miata.



p.s. I also hate the idea of "Tech Shed Legal" and have fought it in SM for years. It's been a tough fight that does not need to happen in this class.

well finally pulled the pistons out everything ok except bent rod on #4 and burnt piston. bearings looked fine on all othe rods though. when i bought the car it looked like it had a gnew head probably broke a belt and bent a valve . live and learn. car ran well just leaked a little oil around the rear balance shaft seal. right now John at APART ABOVE are discussing options and parts. thanks for all your replies