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Gti-r bearings in RWD block

Practical Engine Building

Relevant Module: Worked Examples > Nissan SR20VE > Step 3: Engine Machining

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Discussion and questions related to the course Practical Engine Building

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I have an SR20DET VCT motor in my S15 and am about to do the bottom end and wanted to have the machining completed to allow the use of gti-r bearings. In the machining video it seems as though the only work required is the pop groove to be machined in the bottom end where the bearing sits and not the main caps. The standard RWD bearings are 17mm wide and the gti-r bearings are 19mm and also have more holes for oil to feed the crank hence the oil groove. What is required to make the gti-r bearings fit as it seems this was skimmed over? Just the oil groove machining? Will conrods or their bearings be different?

The only modification required to accept the GTI-R main bearing is to have your machinist groove the journals in the block. This is a very common modification that any machinist who has dealt with SR20s should be already familiar with. You're stretching my memory on the rod bearings and I don't have nay in front of me to confirm. I believe that the difference between the GTI-R and normal SR20 is in the rods and specifically the locating tang in the rod is moved 1 mm in the GTI-R rod to accept the 19 mm bearing shell and locate it centrally in the rod journal. We're actually running conventional 17 mm bearings in our race engine with good reliability at 630 whp/8500 rpm so at least at that level I wouldn't say the wider bearing is essential. If you want to run the 19mm shells you could have the rods machined to accept them though.

I'm not familiar with the engines, so this may not be relevant.

There have been instances where builders have used wider bearing shells than the crank' journals - or more accurately, the radii - were ground for. This had the unfortunate affect of blocking the oil escaping the bearing that would normally be carrying the heat generated there away - the result would be the oil overheating, breaking down, and the failure of the bearing... or worse, total destruction of the engine.

Might be something to bear in mind?

In this instance the crankshafts journals are identical but if you don't use the correct rod (or modify accordingly) then the bearing shell is offset in the rod and could interfere with the fillet radius on the crank. I have however never tried to use the wider bearing without the correct rod so I'm not speaking from personal experience here. Always something to watch out for though.

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