2N 4-Ring piston question

[DGaber]

My 2N ran OK cold, then missed upon warmup. I suspected a sticky valve and/or compression issue. Compression is 90 in #1, 2, & 4 and nearly 0 in #3. Wet test brought #3 up to about 40. I have 35/20 psi oil pressure cold/hot, never smoked or used much oil. Tore it apart & found the sticky #3 intake valve. Also found that previous owner replaced #3 piston.

The original pistons are all 3 ring, and the newer one is a 4 ring. However, it only has rings on 1st (top), 2nd, and 4th (below pin) grooves. The bore still shows cross-hatching and ring end clearance is good. Is it possible that putting rings on all four might clear up compression problem?

 

[deerefan]

It won't hurt, I know that. The sticky valve could be the whole problem. I know of some hi performance engines that use only one or two rings. I would go with whatever the factory calls for.

 

[Soundguy]

I agree... I'd scrub the valve stem down and get her moving free and perhaps hand lap it a bit.

4 ring pistons were the norm.. and then ford went to 3 ring.. less wear.

soundguy