- Posts: 3
- Joined: July 26th, 2018, 6:19 pm
Is this rumor true? Possible? Worth it? Apparently there is enough "meat" on the 41.8 seats to accommodate the extra 1.7mm width.
If possible and/or common, does anyone have any photos of how the new seat looks? Perhaps a diagram that shows this?
Thanks for any info. Gary in Oregon/
- Posts: 146
- Joined: September 22nd, 2013, 7:21 pm
Regardless of sufficient meat on the existing valve seat (of which I don't know if there is) valve seat configuration, valve throat size and combustion chamber shape dominate the effectiveness of a (larger) valve. It's no use installing a larger valve without improving these.
Plenty of info/pictures and even diagrams to be found on this forum. Even better: invest in the GC workshop manual 2013 version. Worth every penny if you want to endeavour serious and reliable engine improvement.
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- Joined: June 18th, 2006, 9:31 am
- Location: Lincoln, UK
No you can't fit 43.5mm to the seat for a '42mm' valve - attempting to do this will leave the 43.5mm valve overlapping the seat insert even if you cut it at 45 deg to its extreme diameter - and then the cast-iron insert will fracture at the sharp outer edge. You must leave at least 0.5mm material outboard of the contact face with cast-iron seat inserts.
Moreover the throat diameter of the insert is way too small for a 43.5mm inlet valve and would have to be bored out.
I see this mistake often made.
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