How smooth does the face of a block really need to be

[sujitroy]

I've been at the block face of a Stag's engine with a Roloc. (The block has been sitting in my garage for may years.)
I have noticed around the water channels some imperfections on the surface. The rest of the block face is relatively OK.

Can I get away with not having the block face decked?

Sujit

[Motorsport Micky]

That's NOT what your post heading asks.

The deck surface needs to be parallel and square to the centre line of the crankshaft with the block deck surfaces at 90 deg to each other. The machining needs to be carried out on a miller with a good finish but still showing some large cutter or flycutting marks which will be indiscernible to the touch or fingernail but will provide a "grab" to the gasket underneath. The imperfections on the waterways MAY be ok depending upon whether the imperfections cross any gasket lines, they only have to seal under water pressure of 20lb, your judgement. See the post regarding applying Wellseal to head gasket surfaces, this is a good reason to use Wellseal.

Micky

[flying farmer]

Pay particular attention to the back of the block between the rear head studs where there is only a narrow strip of metal between the bore and the waterway. The block face often sinks at this point.

At least half the engines I have rebuilt have needed the block faces skimming because of this. There is a picture in the technical section under the tips for rebuilding the Stag engine thread.

The block of which that picture was taken had suffered multiple head gasket failures in previous owners hands, it is still running well now the problem has been sorted.

Otherwise, as Mickey says, sealing the waterways using a touch of sealant is not a problem, but the fire ring area of the head gasket needs to be perfect.

Neil