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For engine builders: How much do you clearance on your race engines?

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Old 10-24-02, 11:57 PM
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For engine builders: How much do you clearance on your race engines?

What non-stock Mazda clearances do you use when building race engines (high RPM, high hp, endurance, etc)?



Heres some stuff I found in the MazdaComp Tech pages.

For Apex Seals
ALLOWABLE RANGE FOR APEX SEAL TO SIDE HOUSING CLEARANCE IS:
12A ENGINES = 0.09 - 0.10 mm (0.0035" - 0.0039")
13B ENGINES = 0.12 - 0.125 mm (0.0047" - 0.0049")

NOTE: For endurance engines, we recommend additional seal to housing clearance - to a maximum of 0.15 mm (0.006").
For Main Bearing
THE CLEARANCE OF DIMENSIONS A & B FOR ENGINES OPERATING UP TO 8500 RPM SHOULD BE 0.076 - 0.089 MM (0.0030" - 0.0035"). CLEARANCE FOR ENGINES OPERATING ABOVE 8500 RPM SHOULD BE 0. 1 01 MM (0.0040"), PARTICULARLY AT THE REAR JOURNAL BECAUSE OF ECCENTRIC SHAFT FLEX CAUSED BY THE COUNTERWEIGHTS.
Old 10-25-02, 01:32 AM
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yes those are just a couple though. There is a lot of other blue printing that should be done. Some of which are the side seals, you got the apex seal, front and rear bearings also adjustable with the shaft, the sides of the rotors including the lands and the rotor faces. Some of these blueprinting process are best left for a good machinest. Other can be dont in a simple step with 400 grit sand paper.

CJG
Old 10-25-02, 01:38 AM
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I have all of the Stock Specs in my 87 FSM (dunno what changed over the years) which gives clearances, but they're just for standard operation.

I have a Word Doc of Racing Clearances that I'm making and don't have much right now. I'll release what I haven't been told to keep secret if I can ever get it somewhat finished.
Old 10-28-02, 01:35 AM
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So no one who has seen this thread has any idea...
Old 10-29-02, 08:00 PM
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Old 10-29-02, 08:14 PM
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nodes a post ***** :P
Old 10-29-02, 09:57 PM
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yeah, and I can't believe that NO ONE has anything to say about this thread.
You people are pathetic.

The only person to say anything didn't say much, but at least he bothered.
PATHETIC!
Old 10-30-02, 08:12 AM
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Take it easy. How do you expect to get any help if you attack the people you want to help you.

I need to know about this too guys. I asked for a recomendation on a book similar too "How to modify your RX7" but more on the 13Bs. I want to know how to build the perfect Rotary, but I don't have the time, money, or facilities to find out buy testing.
I am currently using the manual for tear down. When I am done I will need to know the best way to put it together for my needs.
Old 10-30-02, 08:42 AM
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The racers are the only people that get down to this depth on a regular basis. In other words it takes someone who has built a lot of motors to be able to provide these numbers. This is a secretive area for a lot of people believe it or not.
Finding someone to give you a breakdown of all their clearance modifications may be a little bit of a wait.
Since builders like Pineapple actually sell race engines to the public they know someone could and has checked their clearances at some point. This does not mean that every trade secret they have is in their sales engines though. So they may be willing to give you some numbers. David Atkins would probably tell you as well. Just be sure to have a pen in hand and be ready to write fast!
My next motor is being cryogenically treated and all of my specs are changing due to that lack of thermal expansion and contraction. If you read my posts you will see that I have shared a lot of how-to's but I limit some areas I go into.
I would never leave out something critical while guiding through a process. But questions about how I built specialty machinery is beyond discussion.
The time it takes and cost of trial and error leaves some of these people pretty tight-lipped. Just go around some of these guys when they have a motor pulled apart and start looking at their porting, etc. and you will get an idea of just how secretive they are

Bottom line I would suggest one of the shops that sell race motors since no one is telling you here. If you are going to get your rotors shaved and you send them to Pineapple or somebody, that will increase your odds of getting plenty on clearance info for all your other areas as well.
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