With the head off and on the bench, on blocks so I can see underneath, when I put petrol into the inlet and exhaust ports is there a problem if I see any seepage / leaks?

Best is no.1 inlet which has a slight dampness at one point around the seat, worst is no.3 exhaust which has seepage all way around the seat and drops of petrol form after a minute or so.

All valves show some seepage, inlets are generally better than exhausts.

Engine is a 1300 x-flow (for the 750MC series)

thanks
Rich

I would be suprised if petrol didn't seep past TBH. If you take the valves out and inspect the seats and valves for wear and either relap the valves in or take the head to a machine shop to have the seats recut if neccessary.

Cheers

mark

Yes! the valves should be gas tight, (which is thinner than petrol, :-) ), so looks like a strip down and at the very least a grind in job. If the seats are too bad you will need to get the them recut, but just a little. If the valves are too pitted, chuck them and get some new ones. Also while it's in bits check the valve guides for wear, if they are badly worn I think you have to have the head bored and shimmed, as from memory the guides are not removable on the Xflow, (may be wrong on that). HTH Ray

It is possible to bore out the "valve guides" on a crossflow and fit aftermarket guides . The valve seats will need recutting afterwards to ensure they are concentric with the guides . You may be lucky as already suggested and get away with a light lapping in. I tend to use engineers blue to check the seats , any parts that don't seal show up. Petrol down the ports will only leak through if the valve is not seating

Engine was rebuilt over the winter and the valves were refaced to the head then. I've only done 3 meetings so far this year.

Rich

IMO you would expect to see some seepage, as the valves are only under spring pressure. When you subject them to hundreds (thousands?) of psi from the combustion process they will probably not leak, although as mentioned, it is a good idea to lap them while you've got the head off anyway.

Best test is to turn the head on its side and fill the ports with kerosene, then point an airline jet at the combustion chamber side -- you don't need to go too close to valve but work you way round the rim of each valve seat in turn --- a few very tiny bubbles is ok but if you get a stream of bubbles its a fail.

I wouldn't be worried about a little seepage. As already said, they are only being held in place by spring pressure. When the car is actually running they'll be a few hundred PSI in the cylinder helping them stay closed....