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Hi Tom

No metal expert here, but has anyone suggested they spray weld the low spots, machine the surface flat as lightly as possible?

Steve

That's an idea if needed. I plan to measure the existing clearances first. As the head shop indicates it'll only need a shave of 0.010" to make flat. It hopefully has this room.

Thanks,

Tom

One more thing.
I don't see where the block was similarly checked for flatness. Take a machinists straight edge and shine light under and measure gaps with feeler gauges.
If that .007" "low spot" has a corresponding one on the block, you'll could have leakage if just one side is decked.
It's a tough call, because head is close to spec but one spot is suspect and overall damage from years of mating dissimilar metals. I'd make sure my machinist has a lot of experience with flat heads.
This is going to be more common as these motors age. The damned if you do, and damned if you don't scenario. It's expensive to cold spray something of this size all over to build up and once metal is removed, it's gone. Eventually, with no new parts available, cast will deteriorate to a point of unfit for service so it remains a scavenger exercise.
With the right care and anticorrosion agents in the coolant,
it should function for another 70+ years.

Head gaskets for flathead engines are made with a compressible center core or modern ones with compressible material. As these gaskets are not precision machined items they can often vary in thickness greater than .010" anyway. As to finding a good head being a scavenging search we have supplied many many good used and brand new cylinder heads for these models.

There is no need to go to the extreme of spray metallizing to return the head to exact original thickness, cutting .010 will not cause the valves to hit the head it will only raise the compression ratio a tiny bit and result in better performance.

Most important, after the motor is fixed the head needs to be retorqued several times after running and driving.


James From
Kanter Auto Products

Quote:

Valid statement if the head has never been worked on but unless you are the original owner you can never be sure someone else has not done the same thing before.

IMO, it is always a good idea to do the clay test on any unknown head before considering removing any material. Before so you don't waste time and money if it is already too close to the valves and after in case the shop took off more than they had planned. As several have found the hard way, the extra time spent would have saved a lot of aggravation and money.

OK, Head is back from the shop. In total they had to remove 0.014" to get it flat. I did some preliminary testing and the valve clearance will be OK.

Question though, the pistons, at top dead center, clear the block by a small amount. Is this OK? I found this out during valve clearance testing as the head would slightly rock when placed on the block and the crank rotated (without head gasket). It appears that the gasket thickness will keep everything from touching when assembled, however, is this normal?

Thanks!

Tom in KC

....is this normal?

No.

Almost sounds like at some point the block surface may have been milled. If the head gasket is thick enough when compressed and does not overlap the hole where the piston could touch it and piston goes no higher to hit the head, then it probably would be serviceable. I would really wonder about compression ratio and if you could get rid of any pinging that would result from the higher compression. That might be a bigger problem.

Would be interesting to know how much. If you don't have a depth gage, lay feeler gages next to a piston and run your finger across the two to find the exposure.

OK, the pistons are clearing the block between 0.010" to 0.020". I'm planning to install the head today and plan to hand crank it a couple of times to verify that nothing is hitting. There weren't any previous issues with pinging, however with the head now shaved, I will have to keep an ear out.

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