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Gaining thrust clearance

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Starting this topic to discuss different ways to gain thrust clearance in the event that your thrust clearance is a little tight or if you desire more clearance .. I have seen a few things online about polishing the thrust washers themselves to gain clearance and wanted HPA’s opinion on that specifically … would you see a direct benefit to polishing them to a mirror finish using very fine abrasives and compounds ? If sanding/polishing a thrust washer is a common practice to gain clearance how would you go about doing it to floating bearing such as in a SR20/2JZ ?

hello i use a surface grinder with a magnetic base to do mine now but i used to use an old cap and 1200 grit wet and dry on a glass plate to sand down the thrusts, i recommend lots of water or cooling fluid to make the job easy,

Regards Ross

My thoughts - and I may be wrong in some of them, so take under advisement.

First thing would be to establish exactly what the clearance is and if I actually needed to increase it.

Second thing woulds be to check if thrust bearings are available off-the-shelf in the correct size for the clearance required, and a shortish search suggests not, or if they can be custom made - this may be the easiest and/or cheapest option.

If those options aren't available, the usual option is to have a TRUSTED machinist grind the required material off the crank' cheeks where the thrust runs.

If preferred, though, one could certainly remove material from THE BACK of the thrust bearing, IF it/they are separate parts from the main bearing and not 'one-piece' designs - if one-piece it's grinding or custom. A 'mirror finish' isn't required, but it MUST be flat and of uniform thickness for the bearing face to be evenly loaded, with a uniform oil film, when in use. I would probably prefer to use a precision surface grinder, but a piece of plate glass, a fair amount of care, and frequent checking with a 1/10th thou' mic', or DTI, to avoid taking too much of anywhere, 'should' work well.

It is VERY unusual to need more clearance as the usual problem is having too much, so to iterate, are you sure you need it?

My thoughts , Gord when you say to remove the material from the “back” of the washer you are referring to the side that meets the block and not the crank ? Or are you referring to the rear washer and remove material from the side that meets the crank that carry’s the load ? … I’m building a SR20DET and the factory spec is .004-.010 and I’m currently sitting at .003 … I’d like to be around .006 … if it’s better to not tamper with the washer at all to make sure it’s tru and flat then would it be better to take the material off the front washer that doesn’t carry the load being that it’s less important than the rear washer ? I feel pretty confident that I could block sand the washer relatively flat… unfortunately I don’t have a machine shop local that can grind the thrust journal on the crank so my only option seems to be to sand and polish the washer … I did read that the RA on a thrust journal requires much finer surface than that if a normal rod or main journal and the spec of RA was a minimum or finer … would there be any benefits to going 3000grit with a buff to slick it shiny ?

Again, under advisement - there are some with extensive experience who can confirm if you need to increase the clearance for this engine.

I'm a little surprised it is actually under, as usually it will increase slightly in service - you must be keeping the oil very clean.

The side that contacts the block - the side that the crank runs against (well, the oil film) normally has a very thin coatingto improve the bearing characteristics, which shouldn't be removed.

The RA is the finishing grind on the crank, the block and rear of the bearings isn't as critical so long as they're flat/smooth.

With care, you certainly should be able to remove the material required from the back of the thrust bearing, and as suggested I'd check the material removal was even by using a high sensitivity measuring device, such a 10 thou' micrometer - this may be a bit anal, though, as you should be OK on the front with a thou' tolerance - comments welcome on that, peoples - as it's actually rather lightly loaded.

Of the two thrust bearings, I would recommend removing the material from the front, as the rear is subject to the rather high forces from clutch depression or torque converter thrust.

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