Guys,

I got my engine back from the machine shop and it appears they have lost one of the two steel sleeves that help to align the head, gasket and block. Anyone know where I might pick on up in the Atlanta area? Are they really necessary, or just expedient?

Thanks Craig

Craig: I'm no expert, but a backyard mechanic for some 40 years. I don't think the alignment collars are necessary, but I'd find one and use it if I were you. The head bolts and the head holes have a bit of side tolerance free play. I "think" the collars will keep the head and block in near perfect alignment until you get all bolts torqued.

I'm currently putting a top end on now and did a test fit this evening. The alignment collars were most useful.

I don't know where to find them, but I'd start with the machine shop that misplaced them. Most likely, they'll be able to replace the one theirs placed. Good luck, Brad.

Your local Nissan dealer might have them. They probably have a better microfiche image also. #4 shows as highly available and cheap.

Datsun 240Z/260Z Cylinder Block & Fitting L24, L26 (To Nov.-'74)

DOWEL :: Nissan Parts, NISMO and Nissan Accessories - Courtesyparts.com

It is made to get a good alignment between head & block.

If you don't use them, head bolts will insure this purpose. You will increase stack up on your build. Engine will work but cam sprocket might not be perfectly aligned, combustion chambers will not be exactly in front of pistons, etc.

Would 1mm / 0.040" matter? No idea but it is a 1$ piece to source, I would not mess with such parts & risk engine premature wear/failure.

Thanks everybody, I'll get a replacement.