HPI stamped on head - what does it mean?

I have an RH4 head on my '73 850 that has HPI stamped over the left exhaust rocker cover. I'm wondering what it signifies?
I am aware of High Performance International, and that the owner George did do performance upgrades, including I believe custom camshafts and big bore kits. I don't need to strip my engine for any reason (runs very nice thank you), but I am curious as to what mods might have been made.
I realize that any answers will be pure speculation regarding my particular engine, but perhaps a little history on what George did back in the 80's might be of interest. There's surprisingly little mentioned about HPI within the annals of this forum.
How many others have this stamp too?
Appreciate any info.

I had read about their work, that's the first company that popped into mind for me as well.

My 850 had the same stamp on the head. It turned out to have a heavily planed head and a very lumpy cam in it, plus came with a Dunstall exahust system.
That was 1984, i have since sold the head and cam to a guy with a race bike and the exhaust is now also standard.

Well, judging by the cooling fin spacing, I could easily believe this head has been skimmed. Although I would really need to compare it to a standard 850 to be sure.

If I was to set up a degree wheel and dial gauge on the rockers, does anyone know what the actuation ratio is between the valve end of the rocker and cam itself?

I have seen reported 1 :1 on the exhaust and 1:1.13 on the inlet.

Never measured it myself.

I have measured 1:1.12 on my Atlas.

Slick

texasSlick said:

I have measured 1:1.12 on my Atlas.

Slick

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Hi Slick,
Is that on just the inlet, or do you think that applies to both valves?
Thanks.

BruceB said:

Hi Slick,
Is that on just the inlet, or do you think that applies to both valves?
Thanks.

Click to expand...

I do not remember which rocker I measured, or if I measured both.

Sorry

Slick

Commando rocker ratio is 1.13 for both intake and exhaust rockers.