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Main Girdles!!


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If you look at the way a lot of Chevy/Ford blocks are designed, Where the main caps are bolted on is the lowest part of the block. The main caps hang way below the oil pan surface. The Datsun blocks are like the Mopar blocks,where the block oil pan surface is below the main cap surface, and the main web extends down at a 45 degree angle. A much stronger design. Granted the girdle ties the caps together. Also the short I4 forged, counterweighted crank doesn't deflect as much and doesn't ask the block for help keeping it in place.


The old aircooled VW's didn't have a counterweighted crank, and if you spun them over 4400 rpms a lot, it would eventualy warp the case at the center main.At high RPM's It relied on the magnesiun case to keep it from flexing in the middle, and it wasn't up to the task. A counterweighted crank fixed it. The point is, with a good crank and balanced assy, the block can be made out of magnesium and live. Datsun did a very good job in the design department. I guess that why we're all here.

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The L-series engine may have a deep-skirt block, but many Datsun engines are like the Chevy small block where the block doesn't extend below the crank centerline. They still don't need a girdle, probably for the reasons you listed: High quality fully-counterweighted cranks, precision factory balance, and relatively stiff crankshaft.


Short throw? The L20B has a longer stroke than the Chevrolet 327 V8. But on the other hand, the L-series has a deep skirt.


The short skirt design saves a lot of weight. The deep skirt design can be stronger. Deep-skirt is making a comeback. It appears that strength is more important and even influences NVH, with newer blocks having less noise and vibration.


Agreed, those Datsun engineers knew what they were doing.

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Oops, when I said short, I was referring to The length of the crank (Rigidity) not the stroke. I've always thought the L series motors were pretty long legged, compared to the bore sizes.


If I was to ever fab up a girdle for an L motor, it would be more or less a steel plate between the block and oil pan, with spacers welded where the main studs (not bolts) came through. That way it would not only tie the caps together, but also to the block. I cant really see the need though. Maybe alcohol injected, turbo charged, and nitrous oxide all at once, somewhere north of 600 hp, then things would start moving down there. Too rich for my blood.

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The L doesn't really need a girdle. They were extremely over-engineered. The KA is a grandson of the L series and an L head will even bolt onto a KA block.


In the picture below, if you were asked to pick which main bearing was from the KA, and you picked the left side one.... you'd be wrong. Yes the skinny one on the right is from a KA24E which makes about 50% more hp than the L20B.





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Wonder if they make girdles for L, A, J, KA, SR, CA and VGs?

I guess sarcasm is hard to type :rolleyes: . Sorry guys. While I do enjoy the debate, I agree that there is no need for a girdle on a Nissan product. The link I posted just struck me as funny. It's a sarcastic response to the Chinese junk being offered by other venders on ebay -- a buyer beware warning. If you read the whole ad I'm sure you caught that. The girdle is foam and the bolts are Play-Doh. In the case of the Olds engines the mains aren't even as sturdy as the Chevys and Fords. They actually have "windowed mains" in the '70s vintage engines to save weight/cost. This made a girdle necessary at increased power levels.

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