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-   -   Seized built engine while cranking for oilpressure (https://www.miataturbo.net/engine-performance-56/seized-built-engine-while-cranking-oilpressure-101886/)

LeoNA Jan 13, 2020 03:59 PM

Usually the crank housing bore has material removed from the cap and block, but the amount is small (.001") which is a non-issue in regards to the oil pump. They must have over cut the caps which requires align boring, then honing and they tried to do it all by honing. Align boring is selective and honing is not. Its all a pain in the ass to do it correctly. When I install studs I measure the housing bores and if their only out a few tenths I run it. If their out more I just swish it with the hone. There are tricks to do it correctly but its a dying art.


Originally Posted by Twibs415 (Post 1559487)
same thing happened to me. A new to me machine shop did my line hone and raised the crank centerline. That’s a no no on direct driven oil pumps. Engine never even ran it cranked and seized almost instantly.

I’d be looking into tossing the main bearings and filing and dowels on the new pump and measuring the crank to gear clearances when installed.


Japanraider Jan 17, 2020 11:23 AM

https://photos.app.goo.gl/9wP1W3G7zywxQrej9

Frofro97 Jan 17, 2020 11:46 AM


Originally Posted by Japanraider (Post 1559884)

kinda looks like it ate metal chunks, was there stuff on the oil pickup tube filter?

Japanraider Jan 17, 2020 12:02 PM

there where no metal chunks in front of the gears. not in the drained oil neather in the pickup tube.

curly Jan 17, 2020 12:07 PM

Any chance you put thicker gears in a thinner housing? Or was this purchased as a complete unit?

Japanraider Jan 17, 2020 12:10 PM

it was a complete unit. didnt pull it apart before assembly.

LeoNA Jan 17, 2020 12:34 PM

With a new pump you can turn the gear rotors by hand to make sure the there is enough side clearance. I lube them up with a few drops of assembly lube which not only gives it some initial lube but also helps it pull oil quicker by improving sealing. If the engine was assembled within a months of start up I would not crank for oil pressure there should be plenty of residual assembly lube. If your concerned about minimizing the initial no oil pressure time on the first start up you can use thinner oil for startup 5-30 or warm the oil before filling. I always add the oil just before the startup.

LeoNA Jan 17, 2020 01:10 PM

I just pulled the information sheets that came with the last pump that I installed and it does list the side clearance in the inspection report. Also it lists that pump is pre-lubricated. Did the gear rotors have oil on them? Did it ever make oil pressure? The pictures look as if it ran dry for an extended period.

Japanraider Jan 17, 2020 01:29 PM

The pump was prelubed and made pressure for 5 second before it seized

ICE-.- Mar 24, 2020 11:16 AM

Any info on how this turned out, kind of heart breaking to start that way, does the crank turn freely with the oil pump off?


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