During the overhaul of a generator package, we came across an issue that could’ve been costly to our client.
As standard, we removed & dismantled the cylinder heads, including the valve seats.
However, the process for the seat removal (to heat each head to 220°C, then remove the valve seat & install the new one before the head can cool) doesn’t allow time to measure the valve seat bores.
With aluminium heads, the new seats require a higher interference fit than cast iron heads, & we ‘ve seen the results of valve seats dropping in the past!
We tested the new valve seats by allowing the heads to cool, & re-heating them back to 200°C.
When running, the cylinder head faces should see temps around 450°C.
The valve seats were then checked for movement & during this process, we found there was too much, so the valve seats were removed for oversized seats to get the correct interference fit.
The OEM doesn’t offer oversized valve seats, so they recommend new cylinder heads at a cost of around £1.5k each.
The alternative?
We’re having them made by a trusted specialist, at a fraction of the cost, allowing us to complete the overhaul with minimal delay and cost.
