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Valve pockets

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Tomas_Norway

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I am rebuliding and upgrading the engine of my BN-7.

I plan to use a Dennis Welch DWR-8 cam and original rockers in a DW alu head. DW informs that the block needs valve pockets for this cam. Does anyone have info on how deep theese pockets should be machined?
 
Denis Welch should know, you should contact them for the specifics in what's involved for determining their specification.

In the old days, you'd take a surplus valve (1 each intake and exhaust) and weld 3 or 4 cutting blades to them, and use a head with the valves removed as a pilot. You put the "cutters" up through the underside, as a valve would be installed, place the head on the block (it's heavy enough to not require bolting down) and turn the cutters with a drill motor. With the cutters resting on the top of the as yet uncut block, you could mark the stem for the amount of depth required. Repeat for all six cylinders.

I'm not sure how it's done today, but it would be good for all of us if you'd post how you do it.

Edit: it should be pointed out, that you can't cut too deep, or you'll expose the top (piston) ring, and then the block will be scrap (salvagable with a new sleeve).

Check the assembled engine with clay on top of the pistons (to leave an impression from the valve), rotate through the firing of all six (6) cylinders, and measure the depression in the clay. For a margin of safety, do this without the head gasket between the block and head, but take that thickness into account.
 
Hi Tomas,
If you aren't using domed pistons, you <span style="font-style: italic">should</span> be able to only relieve the exhaust valves. My cam has .430" lift (with higher ratio rockers) and that is what I did. Since I don't do that kind of thing all the time, I had my machine shop figure out the depth and do the work. There is an old thread HERE where MotorHead67 was thinking of installing the same DWR8 cam. Depending on factors like skimmed heads, his figures should be close to what you need.

Read Dave Russell's posts in that thread, basically, you need .060" of additional clearance between full lift of the valve and the engine block.

Here is a photo of my block with the pockets cut out to get an idea of where you need to go.
104981-pocketported.jpg
 
Tomas,

I hope your upgrading the corresponding components as well. I've found that DW is not the only or best source for all big Healey 6-cylinder upgrades. Heavy duty valve springs and timing chain can be found here as they are interchangeable with the MGC. https://www.kirks-auto.com/MGC/MGC_HeavyDutyValvesSprings.html

Dougie
 
I've got a full DW valve train set up; valves, guides, light cam followers, tubular push rods, vernier cam sprocket, steel rocker pillars...a few other bits! The engine is so mechanically quiet that you realy need to use the rev counter.
 
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