Low Compression Y Block

[abelincoln]

Our '56 312 has been pushing oil out the draft tube for some time. Compression checks at about 100 psi on all cylinders except cylinders no.s 2,3, and 6 which are about 80 lbs. I thinking its time to pull for new rings or a bore job. Any thoughts?

Thanks

Abe

[Guest simplyconnected]

You don't say how many miles are on this engine. I made the mistake of doing a head job without changing rings; BIG mistake. They need to be done together. Most of your compression loss is due to leaky valves, and old valve seals suck oil down the guides.

Old rings can't take the new-found high compression from a fresh head job; the rings quickly fail.

Spend a few bucks and overhaul this great 312. It's worth it. If your cylinder walls are bell-shaped, have them bored, and buy new pistons and rings. While everything is apart, I weigh the pistons, making sure they are all the same. I also put the flywheel (flex plate)/crankshaft/damper pulley together and balance them that way (because that's how it runs). Don't forget a GOOD roller-timing chain w/new gears. The factory service manual allows for 1/2" slop, but that's too much in my book because slop affects ignition timing.

With new bearings, rings, chain, and reconditioned heads, your engine will run really sweet for a very long time. If you want a little more kick, mill the heads .020". Your Y-block will still run on regular gas.

Come Spring, I will be overhauling two 292's.

Dave Dare