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Eccentric Shaft End Play no less than 0.005?

Old 02-19-18, 03:08 PM
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Eccentric Shaft End Play no less than 0.005?

I am rebuilding my first engine and am unable to reduce the end play below 0.0045 inches. I have an S4 N/A block that I've reused everything from, except for the irons. I've felt pretty confident in getting the block together but am really stuck as to where this extra slop is coming from.

So far, I started with a Y spacer that measured out to be 3.165" and that sat at 0.0045 inches of end play. I have sanded it and shaved off some material to get to 3.13" which is getting to be smaller than any OEM spacer available (I think). For some reason I still get 0.004" end play with reducing the spacer by 0.025"

Also switched out the front and rear stationary gears to those that were in the original block. Hasn't made a difference either. I've been assembling and disassembling the front stack tons of times, and I am rather sure I am getting the orientation of everything right. Inner washer has the chamfer toward the engine block, and I haven't smashed either torrington bearing (did that once at first), have the 6 bolts for both gears torqued down, and also included the washer for the counterweight.

I'm feeling pretty stumped here. Am I missing something?
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Old 02-19-18, 07:50 PM
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are your roller bearings used? is the center thrust plate in good to new condition? either of those 2 being worn will cause excessive slop.
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Old 02-19-18, 08:09 PM
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I have two brand new thrust/torrington bearings, and the thrust plate and accompanied washers are smooth and flat. They have visible markings, but no wear.
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Old 02-20-18, 05:26 PM
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Lapped irons will also affect end play. It is possible to end up with a motor that is too short if they are excessively lapped.
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Old 02-20-18, 06:17 PM
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Hmmm. I've bought the replacement irons from a buddy years ago. Don't remember anything about them being lapped, but that doesnt mean it never happened. Is there a way to measure and see if they were lapped? I suppose the overall iron thickness is in the FSM?

I do believe the irons I used had shiny rotor surfaces. At least there was no indication to me that they had been lapped in the past.
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Old 02-21-18, 08:30 AM
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I can usually tell from the finish but to be certain you can measure the depth of the coolant seal grooves compared to a known good iron.
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Old 02-21-18, 09:06 AM
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Re: eccentric shaft endplay, Mazda spec is 0.04 to 0.07mm. I've torn down a few new OEM 13B-REW crate engines recently for portwork and other upgrades, and both were on the tight side of spec from our rotary friends in Japan.

I'm not a fan of sanding spacers in search of correct fitment, I like to use the proper OEM spacer. I think you mean your spacer is 0.3165 inch thick? Based on your measurements, you started with a D--- have you tried an A? That should get you within spec

The depth of brand new coolant seal o-ring grooves is approx 1.6 mm. Use that as your baseline.

Hope this helps


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Old 02-23-18, 04:12 PM
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As an experiment, I tried putting together the front stack with no spacer at all, being careful that the thrust bearings were somewhat in place. Still got 0.005" end play.

So, to me that means its not a problem with the spacer. What else could this be? There is no noticable step wear or bending on any of the front stack components.

Would a seal or something caught between a housing and iron cause this? Would a motor thats too short or too long cause excessive end play?

Wouldn't a lapped motor be too short, thus having little to no end play at all?
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Old 02-25-18, 09:54 AM
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Originally Posted by IRPerformance View Post
Lapped irons will also affect end play.
Please explain this in detail. I would like to savor you realizing how wrong you are.

End play is defined without any engine housings at all, just the eccentric shaft, front stack, and front stationary gear.

The only way that side housing lapping might affect things is if the engine is so short that the rear rotor journal bottoms out on the rear stationary gear. But this has zero effect on endplay, just clearances.

Last edited by peejay; 02-25-18 at 09:57 AM.
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Old 02-26-18, 11:10 AM
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Ok folks, so here it is! Wallow in my idiocy if you like, but I do pray tell that I called two reputable parts suppliers, and neither said anything about the part I missed either.

I honestly couldn't care less because it was so easy to fix. Hopefully this will be my stupid mistake on my first rebuild.

I forgot to put the copper washer on the bolt. Did that, and I had no endplay whatsoever with my original spacer. Had to go all the way up to a T to get the 0.0025"

Case closed!
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Old 04-24-18, 07:01 PM
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what engine was this end play for? i ask because i thought i recalled the FD engine didn't have the "COPPER" washer on the main eccentric shaft/pulley bolt.
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Old 05-02-18, 08:00 AM
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Originally Posted by FD7KiD View Post
what engine was this end play for? i ask because i thought i recalled the FD engine didn't have the "COPPER" washer on the main eccentric shaft/pulley bolt.
The second sentence of his original post indicated he was working with an S4 NA motor.
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