1961 CB72 Project

G-Man · Post by **G-Man** » Sat Aug 15, 2015 12:26 am

R100
My motivation is to remove any sharp edges or corners which could cause pre-ignition. The slight lowering of the compression ratio is a side effect of removing the metal.

G

R100 wrote:Beautiful work G-Man.
I think you are right about the compression. It will probably come back closer to where you want it with that slight dishing of the valves.

R100 · Post by **R100** » Sat Aug 15, 2015 2:54 pm

G-Man wrote:R100
My motivation is to remove any sharp edges or corners which could cause pre-ignition. The slight lowering of the compression ratio is a side effect of removing the metal.
G

Good point.
No need for any extra glow plugs in these cylinders.
I think I will at least smooth the edges of those slots in the valves.

LOUD MOUSE · Post by **LOUD MOUSE** » Sat Aug 15, 2015 4:00 pm

Engine builders including HONDA have used the slotted valves for longer than some of us have been alive.
Extra work if you like but I defy you to tell me the difference other than valves which CAN/MAY warp when someone takes the middle strength away and lowers the compression.
Praise you may get but the end cost may not be worth the time/things you are doing to that head. Best Of Luck In The Long Run................lm

R100 wrote:
G-Man wrote:R100
My motivation is to remove any sharp edges or corners which could cause pre-ignition. The slight lowering of the compression ratio is a side effect of removing the metal.
G
Good point.
No need for any extra glow plugs in these cylinders.
I think I will at least smooth the edges of those slots in the valves.

G-Man · Post by **G-Man** » Sat Aug 15, 2015 11:35 pm

Sound advice, LM. I just enjoy playing in my workshop and get carried away sometimes...... :-)

G

LOUD MOUSE wrote:Engine builders including HONDA have used the slotted valves for longer than some of us have been alive.
Extra work if you like but I defy you to tell me the difference other than valves which CAN/MAY warp when someone takes the middle strength away and lowers the compression.
Praise you may get but the end cost may not be worth the time/things you are doing to that head. Best Of Luck In The Long Run................lm

R100 wrote:
G-Man wrote:R100
My motivation is to remove any sharp edges or corners which could cause pre-ignition. The slight lowering of the compression ratio is a side effect of removing the metal.
G
Good point.
No need for any extra glow plugs in these cylinders.
I think I will at least smooth the edges of those slots in the valves.

LOUD MOUSE · Post by **LOUD MOUSE** » Sun Aug 16, 2015 5:35 am

It's sort of like you are the Pied Piper of machining parts and to say that removing the slots will prevent pre-ignation in these engines hasn't been proved but now one person believes it and is going to change his valves.
If these engines have pre-ignation it will have more to do with "engine tune" than a hot (They Usually Are) valve.
BTW the valve will not be a Glow Plug. .........................lm

G-Man wrote:Sound advice, LM. I just enjoy playing in my workshop and get carried away sometimes...... :-)

G

LOUD MOUSE wrote:Engine builders including HONDA have used the slotted valves for longer than some of us have been alive.
Extra work if you like but I defy you to tell me the difference other than valves which CAN/MAY warp when someone takes the middle strength away and lowers the compression.
Praise you may get but the end cost may not be worth the time/things you are doing to that head. Best Of Luck In The Long Run................lm

R100 wrote:
G-Man wrote:R100
My motivation is to remove any sharp edges or corners which could cause pre-ignition. The slight lowering of the compression ratio is a side effect of removing the metal.
G
Good point.
No need for any extra glow plugs in these cylinders.
I think I will at least smooth the edges of those slots in the valves.

G-Man · Post by **G-Man** » Tue Aug 18, 2015 7:56 am

I've got to start collecting and re-working some parts for those 'spare' early dampers. Thankfully, apart from being a little bit longer / shorter, the damper internals don't seem to have changed over the years of production.

Where things did change was the method of holding in the internals. The screw changed from a steel part with peg-spanner holes to a nasty aluminum version with slots (with these) to a steel slotted version (better) ...

And then on to the 'built for production' crimped version.

For me, it is quite handy to find these later ones as they are sealed better and less likely to be tampered with. Once you get the crimped end off the innards become donor parts for those more desirable early versions, with a little modification.

I have the luxury of my old lathe here but it would be quite possible to use a dremel grinder to cut the end off. There are no springs inside so it won't fly across the workshop. Just a little oil to mop up...

The guts can be a little tight so I have a simple fixture for pulling them out in a controlled way.

G

modelman · Post by **modelman** » Tue Aug 18, 2015 11:57 am

G-Man, is that the 'Prestige' platers in Swinton you use??

If so, its only 10 miles from me & iv'e been using Brians services for around 25 years & we must have passed each other very close as I also collected my stuff from him last week!!

If your'e nearby again, let me know & I'll pop across to say hello & we can go for a coffee & a sticky-bun!!