885 Head - Welding Scallop to Match ETA Block?

[chriso]

I know I've been asking a ton of questions lately, but trying to match info on Stroker builds from multiple sources is pretty difficult, as there's what appears to be 15 different ways to build a 2.7i stroker...

Today, I found a website that claims the best compression and solution for a 2.7i is to match the 885i head to the original (non S) ETA block, and weld the scallops to match the ETA pistons instead of using the domed I pistons.

So, on to the question:

Has anyone heard of welding the scalloped portion of an 885 head to match a Non-S ETA block to increase compression compared to any other option for a 2.7i?


Source: http://stle30.com/forums/index.php?topic=87.new

I'm very intrigued by this, and I'm interested in trying it, but I'm not sure where to go to have the head welded properly.

[digger]

If I understand correctly, they are saying to weld the angled squish band region on the 885 head to make it flush with the face of the head to match an eta flat top style piston.

Sounds ok in theory but that’s a lot of heat going into the head and all sorts of issue such as head gasket issues, issues with seats falling out, rocker shaft and cam alignment can result from the distortion, residual stress and change in mechanical properties of the alloy, though if done properly you get 885 flow from a smaller CC head with matching squish pattern.

Personally I would either use a 731 head as it has the right chamber from the beginning and get it ported by someone competent, it will outflow the 885 with a slightly smaller port cross sectional area when it is done well. Or i would also do the eta crank, eta rod, b25 piston, 885 head and 2mm off the block or better yet is the 2.8L option 84 crank, eta rod, b25 piston, 885 head before i would consider the proposal above.

In actual fact Paul Burke who is a 12V guru particularly on M10/M30 says that he has converted a 731 head to the an 885 angled squish style so the opposite to what is being proposed in that link.

[chriso]

So, Paul Burke converted a 731 to match a m20b25 block?

Theoretically, shouldn't a proper weld/fill be as strong/stronger than the original mold?

Is there a shop familiar with M20 heads that people would recommend contacting?


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[digger]

that's what Paul told me, presumably to use the small port. he did it to match the b25 piston dish-dome shape rather than the block as the block interface is essentially identical.

its not about how strong the filler material is its about controlling distortion, and making sure the cast alloy doesnt go soft and or crack, i know someone who could do it and a hell of a lot more but i think he would recommend against it as there are easier ways to skin a cat

[Madhatter]

If you fit larger +2mm valves from an 885 head into a 731 head, you start to run into shrouding issues, so you pretty much have to start taking to the squish band anyway. Starts looking a lot more like an 885 chamber shape when done.