Flat Top Pistons in a '74 1F? (1 Viewer)

Jun 15, 2020
Hi everyone! I'm new to the forum and the FJ40 world and I've reached a roadblock in my '74 restoration.

I’m working on a 74 FJ40 with a 1F engine, serial number 556166. It ran and drove well, but I did a compression check to find that cylinder 6 had low compression. When I removed the head I realized the piston was cracked. However the cylinder walls aren’t scored.

I would like to replace that piston only because the others had fine compression. My dilemma is that the engine has flat top pistons instead of domed pistons like a ’74 should have. It also appears to have been rebuilt in the past because the pistons are stamped 0.50 mm over which is 20 thousands over. I know SOR offers the 20 over flat top piston, but not the 20 over rings.
I’m trying to decide what the best course of action is for my engine. Is there a source for flat top 20 over rings, or can I use the rings meant for a ’74, which are available in a 20 over size.


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