Question for U20 Engine Builders

[nolastyankee]

Calling U20 engine builders - 2 questions I can not seem to find answers to in the forum or on line.

I pressed in the rear jackshaft bearing yesterday for U20 00239 and have perfect alignment on the oil passage to #5 main bearing cap and the vertical oil feed for the cylinder head. However there is a 3rd oil hole in the jackshaft bearing that goes to nothing. I'm not seeing another oil passage in the block or the oiling diagram - is this right? The oil drain behind the bearing is also clear.

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One pic shows pointers to holes in question - passage under the chop stick is blocked, other hole showing test probe from cylinder head feed. Other pic has pointers removed.


Next question - I used a flashlight to check for machining debris inside the block and found what appears to be a huge piece of slag. Looks like a long lost time capsule from the Nismo casting department but wanted to check to see if this looks familiar to anyone as something that may have been damaged.

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[JT68]

Edited: On the block I checked, both of the two holes near together both overlap the head galley. The other (third) hole lines up with the main bearing oil hole.

If you are concerned about it you could ream the bearing hole that supplies the head up to about 3/16". There is no chance of "over oiling" the head since the supply would still be metered by the smaller hole supplied by the main galley.

The main bearing feed is a bored passage from main galley in line with the threaded hole for the distributor oil line.

One word of caution, the jackshaft bearing fit is fussy and should be checked/line reamed by a machinist. It is a tight fit, but too tight and it will seize. Fortunately, the V8 guys are familiar with the process since it is identical to that configuration, so most shops can do it. (If its a loose fit, they botched it)


Not uncommon on the slag, sometimes pieces like that come free! Kinda rough on a water pump!

[nolastyankee]

To close this out for future builders, I tore apart another block in storage to see what the rear jackshaft bearing looks like and found that it only has 2 oiling passages in the bearing vs the current bearing with 3. (2 hole bearing is a split bearing vs 1 piece Dura Bond I am using)

Since the current bearing is universal for U20 and 1600 (perhaps others) I am going to assume that the 3rd hole in the bearing is for a different application. The oiling diagram in the Datsun manual confirm 2 passageways - 1 from #5 bearing cap, other to cylinder head.

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[notoptoy]

Thanks for following up, that will help with head scratching in the future!

[JT68]

As long as both passages get an oil hole, it doesn't matter which type you use. The 3-hole type have been run for decades. (Most likely just a dual fit bearing for R,H,U). Both passages MUST align with a hole.