Valves to piston gap

[SteveH]

Dave, Yup, it does say don't cut the valve seats and only lap them in. However, if the seat has been disturbed you'd have to cut it back to get it right again. In an ideal world, I'd have a new one each time
I've not had any issues with lifters after machining, however, my head doesn't look like it's had much taken off in the past. If it was a problem you could grind the top of the valve stem to cure it.

[Mark Halligan]

Dave,

I've just measured and these dimensions as best as I could and they seem OK, just.
I spose I'll found out when I get it running.
If there is a problem with these dimensions, how will it manifest itself, as a big bang or something else .

Mark.

[SteveH]

I'd guess the problem could be valves that don't close properly. The lower seat height would mean the head of the valve stem would be closer to the cam. The lifter has to fit within this space. If it gets too small the valve will stay open or the lifter will just fail to work. I hope mines OK now

[Mark Halligan]

So if in doubt would it be best to grind 0.5mm or so off of the valve stem or dismantle the tappets and take the same amount off of the little piston in the tappet?

Mark.

[SteveH]

Either way would have the same effect If your going to have the lifters out, replace them with solid jobbies. These will be better if you're going for mega power...and I'm sure you are Mark

[Jamo]

Whats the advantages / disadvantages of the standard angle vs the 3 angle??

[4WheelDrifter]

The three angle valve seat may not transmit as much heat due to a smaller contact area. That could be bad for the exhaust valves, as I believe most of the heat in the valve is lost through that area.
Just my own thoughts btw.

[ross25480]

Head job

Doug was your head ok in the end as mine looks identical to yours by way of amount of material that has been removed.

[Doug_RS2]

eh - ok - i used the head for a long time and it was fine.

[volcano rs]

Whats the advantages / disadvantages of the standard angle vs the 3 angle??

more air enters the cylinders more easily and it dosen't have to jump over sharp edges

[S2_Rennfahr]

1.7mm valve to piston clearance with CatCams 20v NM, with 11.2mm lift.