deshrouding valves

[Yves]

Here is my question : I have dart pro 1 aluminum 215's that I use on a 400 block with 4.165 bores. How much can I deshroud the valves without getting into a danger zone and how many cc's will the chamber grow ?

Thanks

[Dart Vader]

I consulted one of our techs about this, here's a rundown on what he told me:
Dye the head around the chambers and bolt the heads to the block. Then scribe the bore size onto the head. Don't make the chamber cross-section bigger than the bore of the block. The chamber CCs will be unknown once unshrouded so you'll have to measure after you are done and mill the head to the desired volume.

If you are not a highly experienced head porter it would probably be most beneficial to take it to someone who performs this modification regularly, since it's a tricky one.

Good luck, and let us know if you need anything else!

[Awesome Bill]

You should use a chamber un shrouding tool, just scribe the bore in the head from the bottom of the cylinder and send us the heads. We will do both intake and exhaust to the scribe for $250.00, clean and reassemble the heads for proper clearance and spring pressure.

[Yves]

It's a little difficult since I live in Europe. Sending over is going to cost. However I do have a pretty competent machine shop over here. I was thinking of having the deshrouding done by the same machine that grinds the valve seats but with a cutter of some sort.
Anyway the scribe tip is a good one. Will keep that in mind.

Any idea on how thick the walls of the chamber are on average ?

[Awesome Bill]

You have plenty even @ 4.200 bore. That area is solid. that is what we do also, just get a chamber relieving cutter from Sunnen or whomever your head shop uses. I have many different ones with different angles to make a perfect rolled cut.

[Yves]

Thanks Bill