Valve Height Data Anyone?

[malcolm]

I've got a cylinder head back from the machine shop and I'm not happy with it.

It's has new exhaust valve seats and at one end the exhaust valve face is proud of the cylinder head by maybe 0.5mm, and the exhaust valve at the other end is recessed into the head by 0.5mm.

I'll take it back and have them try again. Does anyone have data for the correct height to set exhaust valves? It's a 1397cc R5 C2J engine.

 

[malcolm]

Here's the trouble - the exhaust valve seats have been cut 2mm into the head at one end going down to 1.5mm into the block at the other.

I've taken a valve out of another head and it looks like they should be cut about 0.5mm into the head. Given the exhaust valve opens only 8mm shrouding the first 2mm doesn't seem clever.

I've looked in the MOT-C and Haynes manuals but can't find a figure for these.

 

[Steve Hennessey]

I had a look in Haynes yesterday as well but nothing. It's a shoddy piece of work they have carried out, never seen anything like it in my life - should have put new seats in and done it properly first time.

 

[malcolm]

Popped back to the engine place and they insisted they had measured the old seats up and put the new ones in the same spot.

So I did a trial fit of the cylinder head and rockers and compared the valve clearances between inlet and exhaust, and true enough the gaps are quite consistent inlet to exhaust (max 0.2mm difference) so the exhaust valves are indeed roughly where they were. Wish I had taken photos.

No idea what's going on now. Doesn't look right but maybe they were really like that originally. Tempted to just build the engine and be done with it, but it's not a sensible way to install valve seats. There's some aluminium machined away so fitting new seats at a more sensible height will only leave a gap.

Phoned Paul up (Mr Reno) and he reckoned the heads were specific to the 1400 (and maybe the 1300) so replacements are not available. Reckon my best bet is to take the corner off to improve flow a little.

 

[malcolm]

Fixed it Steve! I've rounded off the area maybe 1/4 inch around the valves so the step to the vale seat is about 0.5mm (similar to the other heads I have).

I reckon someone in the past re-cut the exhaust valve seats. Disappointing that the engine place didn't notice something was odd and could only work to 0.5mm tolerance. Won't use them again.

 

[Steve Hennessey]

That looks better!! If an engineering shop cannot cannot do a proper job then yes, give them a wide berth.

Now, if you want to be really fussy once the valves are in, use a burette and measure the capacity of the chambers