Clearancing Bearings
07-15-2005, 01:42 PM
#5
Senior Member
Join Date: Aug 2004
Location: San Diego
Posts: 186
Use 13rew bearings they have different clearances and have the largest clearance. You can order from Mazdatrix they stock the ones which have the largest clearance http://www.mazdatrix.com/b4.htm and they are alot cheaper than MFR Race Bearings. MFR Race Bearings are like $89 and stock 13brew's $33 and method I use for clearancing bearings is steel wool #00 and #0000 hand clearance and it takes a long time but it comes out really well.
07-16-2005, 12:07 AM
#6
Senior Member
Join Date: Dec 2003
Posts: 203
[quote name='13BTNOS' date='Jul 15 2005, 10:42 AM']Use 13rew bearings they have different clearances and have the largest clearance. You can order from Mazdatrix they stock the ones which have the largest clearance http://www.mazdatrix.com/b4.htm and they are alot cheaper than MFR Race Bearings. MFR Race Bearings are like $89 and stock 13brew's $33 and method I use for clearancing bearings is steel wool #00 and #0000 hand clearance and it takes a long time but it comes out really well.
[/quote]
I use a teardrop rubber sanding block and a metal lathe.
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I use a teardrop rubber sanding block and a metal lathe.
07-16-2005, 08:35 AM
#7
Fabricator
Join Date: Jan 2004
Location: Central Ohio (Hebron) Zephyrhills Fla.
Posts: 1,322
[quote name='C. Ludwig' date='Jul 13 2005, 05:49 AM']49 views and no one wants to comment? Lynn, Ito?
[/quote]
On new race rotor bearings I spin them up in the lathe and sand them a bit with 600 wet or dry silicone carbide paper and lots of oil. I take the very edges down to copper. I also remove the alignment tab.
I have no idea what the actual clearance is. I have never measured it. I do know where the bearings will get a shine in an overrev. (we now have good rev limiters).
On new race main bearings, I do the same thing. But scrape the flywheel end back to copper over 1/8" and then sand with 600. The front bearing I just sand.
The alignment tabs are required for oil passage indexing.
I run the cranks on the lathe and sand with oil and 400 wet or dry paper. I break the very sharp edges from the rotor bearing throws. I tear drop the oil outlets and polish the journals with a buffing pad and rouge on a 7" disc grinder. The shaft should look like chrome when done.
I open the oil hole in the bearings to remove missmatches with the oil passage in the stationary gear.
The only bearings I have lost since 1980 were in pro-built engines that I had not done myself. Those were a result (we found after the fact) of some cheap *** bean counters Mazda changing MFRs to save a few pennys or a million yen or whatever they use. Thank you Mazda. You saved a penny and the racing world lost several million in engines around the world.
*** holes.
The race bearings used to be cut from tubing stock. Now they are puzzle lock like stock bearings. But they work fine now so no problems in years.
This level of screwing with bearings is more a habit than a requirement. With a rev limiter set at 9,600 RPM there is little need to scrape a main bearing.
With a solid 100 PSI of foam free oil at not over 180 degrees, there is little need to polish the crank.
Keep in mind that we run as close to 9,600 RPM as is possible for 40 minutes. Oil temps are a big problem. Also this is a NA 12A at 245 HP.
Turbo engines crossing Nevada in record time on a hot day need more work to stay alive. The once a week blast to the redline in a street car needs no such attention. (but it won't hurt it either).
Lynn E. Hanover
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On new race rotor bearings I spin them up in the lathe and sand them a bit with 600 wet or dry silicone carbide paper and lots of oil. I take the very edges down to copper. I also remove the alignment tab.
I have no idea what the actual clearance is. I have never measured it. I do know where the bearings will get a shine in an overrev. (we now have good rev limiters).
On new race main bearings, I do the same thing. But scrape the flywheel end back to copper over 1/8" and then sand with 600. The front bearing I just sand.
The alignment tabs are required for oil passage indexing.
I run the cranks on the lathe and sand with oil and 400 wet or dry paper. I break the very sharp edges from the rotor bearing throws. I tear drop the oil outlets and polish the journals with a buffing pad and rouge on a 7" disc grinder. The shaft should look like chrome when done.
I open the oil hole in the bearings to remove missmatches with the oil passage in the stationary gear.
The only bearings I have lost since 1980 were in pro-built engines that I had not done myself. Those were a result (we found after the fact) of some cheap *** bean counters Mazda changing MFRs to save a few pennys or a million yen or whatever they use. Thank you Mazda. You saved a penny and the racing world lost several million in engines around the world.
*** holes.
The race bearings used to be cut from tubing stock. Now they are puzzle lock like stock bearings. But they work fine now so no problems in years.
This level of screwing with bearings is more a habit than a requirement. With a rev limiter set at 9,600 RPM there is little need to scrape a main bearing.
With a solid 100 PSI of foam free oil at not over 180 degrees, there is little need to polish the crank.
Keep in mind that we run as close to 9,600 RPM as is possible for 40 minutes. Oil temps are a big problem. Also this is a NA 12A at 245 HP.
Turbo engines crossing Nevada in record time on a hot day need more work to stay alive. The once a week blast to the redline in a street car needs no such attention. (but it won't hurt it either).
Lynn E. Hanover
07-17-2005, 10:56 AM
#8
Senior Member
Join Date: Feb 2003
Location: Calgary
Posts: 564
I don't want this to turn to a shitfest, but it goes back to basic machine and engine building basics, never ever take sandpaper or abrasives to a bearing, the abrasive partilces end up embedded in the pores of the bearings, because thats how soft metal bearings are designed to work, if you sand your bearings, your are installing a "loaded" bearing into the motor no matter how many times you rinsed it. Thus the bearing has no ability left to absorb extra foreign material, and will in fact tend to give some back up to the oil harming the shaft journal.I know some people are come back with well I did it yada yada yada, it doesnt mean its right..
There are two proper ways to cut bearings, one is cutting with a lathe , the other is scraping a bearing to size. Both remove material without embedding foriegn material into the bearing. The last alternative is to polish or cut the shaft journal down, I polish the journal to match the bearings quite often, I also use the bearing scraper method, but those tools are hard to find nowadays, the ones I have are over 40 years old, I have never seen another set.
The other good alternatives are as 13btnos said buying sized bearings, which is also a good plan and the easiest for those without access to the right tools..
When installing the bearings, you get much better overall clearances and less bearing crush, if you heat the rotor to 400 and freeze the bearings.. I wouldnt omit the the tab either, I keep the tab and also coat the outside of the bearing with loctite retaining compound. On higher rpm motors another trick I picked up across the pond was machining another tab rcess across from the stock one to keep the bearing locked down, effective apparently to 10,000 rpm +...Maxt
There are two proper ways to cut bearings, one is cutting with a lathe , the other is scraping a bearing to size. Both remove material without embedding foriegn material into the bearing. The last alternative is to polish or cut the shaft journal down, I polish the journal to match the bearings quite often, I also use the bearing scraper method, but those tools are hard to find nowadays, the ones I have are over 40 years old, I have never seen another set.
The other good alternatives are as 13btnos said buying sized bearings, which is also a good plan and the easiest for those without access to the right tools..
When installing the bearings, you get much better overall clearances and less bearing crush, if you heat the rotor to 400 and freeze the bearings.. I wouldnt omit the the tab either, I keep the tab and also coat the outside of the bearing with loctite retaining compound. On higher rpm motors another trick I picked up across the pond was machining another tab rcess across from the stock one to keep the bearing locked down, effective apparently to 10,000 rpm +...Maxt
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