About two years ago I built up a Rajo head engine for a club members speedster. Yesterday it wasn't running well so he did a compression test and all four cylinders register over 60 pound, yet coolant started coming out of #4 plug.
How can this be???
Any idea what we can expect when we pull the head?

Head gasket problem? A small crack will let coolant seep and still keep pretty good compression. Just how much coolant is coming out?

And what exactly do you mean by "... coolant started coming out of #4 plug"? Was the plug still installed but with coolant seen on it? Maybe the coolant came from someplace else, landed on the plug, and shorted it out?

When he removed #4 plug for the compression test he notice a small amount of coolant. Overnite it half drained the radiator, about to the level of the head gasket.

"About to the level of the head gasket" sounds promising. Let's hope it's the head gasket!

Likely a leak in the head gasket at the rear of the engine where the water passage transitions from the block to the head.

This is not the first time this has occurred, each time we check the flatness of the block and the head and they appear ok. So he just replaces the gasket.
This time he is taking the head to a machine shop to check flatness.
Has anyone experience with a solid copper gasket on these four valve heads?

Tony,Has your friend tried an aviation type gasket sealer.It never hardens & works great.

Tony
I'm doing a run of solid copper head gaskets. Mostly flathead, but will be making a couple of OHV ones. As these are being done using CNC water jet, making a F head version wouldn't be too difficult if you are interested
The flathead ones are costing about $60.00 each. Might be a little extra to make one F head for the programming

I think you just hit the nail on the head, 4 valve Rajo, the reproduction gaskets have been a problem, someone was making them with out a complete fire ring around the valve side of the bore.

I just ordered a spray can of "Hylomar". It is the best sealant for a solid copper head gasket, bar none!!

Les,

Whenever I hear of solid copper head gaskets, I always wonder if maybe photoengraving their faces, to produce a narrow ridge around the combustion chamber openings and coolant passages would be of any benefit in creating a better seal. I'm imagining a ridge, maybe just .002 higher than the surrounding faces. Probably would add cost with minor benefit, however a thought just the same.

Jerry
Well all the stuff is available. The "etchant" at electronic shop. The "resist" is as simple as laser ink printed onto plastic sheet and then iron it onto the metal
Actually you could probably just draw it on with "sharpie " ink

Tony, I have a 4 valve Rajo. What the head gasket guys will tell you is that solid copper is not a good option unless it's the only option.

Double check that the leak isn't from the block - the rear bolt that is hidden under the rocker tower can let coolant up into the intake and then down into the cylinder.

Also - definitely want to change the oil if there's been any coolant on the piston as it will have leaked down into the oil pan.

I had head gasket issues with my 4 valve. In the end I had Olson's Gasket make me a composite material gasket, but with a full fire ring all the way around the combustion chamber. Since installing that one I have zero issues. You'll have to contact them directly, but that's definitely the way to go.

(Message edited by Wreckrod9 on October 16, 2016)

The hylomar is just as effective also les. If you do a run of overheads I'd like to get one