heads - shaping edges

[SGKent]

Have a set of T4 bus heads from Len that am finally getting ready to install. At the transition from the flat area to the chamber there is a fairly sharp edge. It isn't quite sharp enough to cut you if you just touch it, but it is pretty sharp. Generally one doesn't want sharp areas that can act as a hot spot for ignition. I tried calling and e-mailing Len to ask this but can't reach him. Does anyone know if that edge is by design, or if I should dress it with a small dremel carbide to soften it maybe .020"? Or just drag a backwards facing pocket knife blade over it to knock the edge down?

Thanks -
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[GARRICK.CLARK]

Just knock the edge off it with a bit of emery cloth

[jpaull]

I would use a fine grit cartridge roll(just a tiny bit), then a polishing buff.

[SGKent]

thanks all, a good friend got back to me too, he agrees that while it may not be an issue, sharp edges are best gone inside the combustion chamber.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[Ohio Tom]

I always remove all sharps from combustion chambers.

You are correct in that it can lead to glowing re-hot and causing detonation.

[SGKent]

thanks - I hit them about .020" - .030" wide at a 45 degree angle +/- with a concave shaped small carbide dremel to round them, then sanded them with 800 grit and hit them with compressed air to clean since they are new heads with no oils or grease on them. Feels substantially better without removing much metal. My instinct on these things is usually pretty good, but I honestly didn't know if there was some new reason they were left sharp. I was always taught sharp things in a combustion chamber were potential sources of ignition.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[modok]

The only reason to be sharp would be.....
Sometimes, right around the intake valve the sharp transition can help re-atomize some liquid fuel that may be drizzling.....and in that area it is cool enough the sharp edge is ok.

But any sharp edge that is in a potentially hot area....fix it.

[Floating VW]

I can see I'm already too late, but I was going to go against the grain and say leave it sharp. Or at most do what jpaull suggested and don't make it any duller than what a buffing pad would do.

My logic goes along with what modok said, a sharp edge on that part of the combustion chamber helps induce turbulence during the compression stroke, which in turn helps the air/fuel charge burn more quickly and evenly and reduces the chance of detonation. And since it's on the quench pads, I'm thinking it shouldn't get too hot, unless you're running on the ragged edge of high compression/low octane/lean air-fuel.

I left mine as sharp as possible after hitting the chambers with a buffer, with no detonation running 8.0 to 1 static (7.6 to 1 dynamic) compression and 87 octane fuel.
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"It's time you started treating people as individuals, rather than mathematically predictable members of an aggregate set, regardless of how well that works."

[Alstrup]

Correct. Just break the edge, no more.
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https://www.thesamba.com/vw/forum/viewtopic.php?t=435993