Some Advice Needed For Mi16 Head Machining?

[rallysteve 22]

I have two different mi16 heads (both for the alloy block engines). One of them was removed from the complete engine with bottom end problems I bought ages ago. However this seems in the best condition. I have removed all of the valves etc from it and am now thinking about machining for it. I was planning on having the valve seats re-cut and a skim on in just to make sure its all true. However after looking in the rebuild manual it states the head height should be 132mm +/- 0.15mm and maximum machining possible is 0.2mm however my head is at somewhere between 131.4 and 131.5mm (hard to tell exactly as i only have some digital calipers) Is it going to be possible to skim this head a bit further? The other head I have measures about 131.6mm but has slightly worse pitting where corrosion has begun and doesnt generally seem as clean as the other.

 

The block this head is for has been decked by about 1.5mm i believe so I am worried about running too close with valve clearance etc.

 

Also thinking about the valves. As far as im aware the seats are all standard and valves are of a standard size, when i take the head to be machined and have the seats re-cut am i looking to have three angle cuts?

 

Can anyone advise at all?

 

Thanks Steve

[petert 588]

You can skim the surface until the cutter almost touches the intake seats. Obviously you don't want to machine them flat! As for valve to piston clearance, that's just something you as the engine builder need to verify. When it goes bang there is only one person responsible. Corrosion is not an issue. Anyone who can TIG weld can easily patch up the holes then machine it flat.

[rallysteve 22]

Thanks Peter,

 

I understand that i will have to check the valve to piston clearance carefully before i fully assemble. I just wanted to make sure I wasnt wasting my money having a head machined to then find it it useless.

 

Cheers Steve

[Tom Fenton 1,542]

Worst case scenario you could have the pockets in the pistons enlarged slightly.

[rallysteve 22]

Good Point, thanks Tom.

 

Will get it skimmed slightly just to clean it up and make sure its true.

 

What do I ask for when I take it in to have the valve seats re-cut? I have heard of people having the valves 'back-cut' what does this mean / offer as advantages?

 

Cheers Steve