There is an easy explanation for the metric and SAE versions of the non-smog
alloy heads for the 1600. All of the pre 1967.5 heads were SAE and non-smog.
These were a mix of iron and aluminum. In the 1967.5 production, the heads
were altered. There were bosses cast for the impending air injectors, but they
were not drilled and the hardware was changed to Metric threads.
Per Nissan, the change happened with the 67.5 cars starting at engine R-40000
and U 20-00001. Since so many of these cars have been bastardized, it is not
uncommon to have mixed parts. When I bought my 1500, it came with a 3 main
1600 block and a metric smog head. The carbs, distributor and other
accessories were the originals. Must have been fun cobbling that thing
From: datsunmike [mailto:firstname.lastname@example.org]
Sent: Tuesday, November 11, 2003 12:20 PM
To: Raper, Sidney; Fred Schroeder; email@example.com
Subject: Nuts & Bolts, I Got Screwed
All the body bolts, screws and nuts are SAE. Cars built from 67.5 forward
use metric for drivetrain nuts and bolts although I can't confirm the exact
date of the conversion. I've seen metric and SAE pre-smog aluminum heads.
Except for the head bolts which are all SAE for all roadsters.