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Originally Posted by avanti-176
I have gmpp aluminum "fast Burn" heads on my 390 stroker sbc, this passage is taken gmpp's site........
Interesting that they only use the sodium filled stems on the exhaust. I have not broken one yet, and they really rev.
Dan
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I think the exhaust are usually all that get the sodium treatment, since they only flow hot gases they benefit most. I think that the 427 ones were just the exhausts, although I'm not positive. They were used on the FT exhausts and the exhaust was the only valve that VW used them on. The FT and the VW also had bigger diameter valve stems, which would reduce flow, but the 427 ones had standard stem diameter. That may have also lead to some of the failures. I don't recall seeing either the VW or the FT valves ever "popping" as would happen with the 427 ones.