Dunstall MK 4 Camshaft

Deckard · Feb 13, 2012

I've purchased this cam and believe it's a Dunstall . It has some interesting markings, Zephyr stamped above PD/04. It came out of a '71 810 part out on ebay. I'm wondering what the lash settings are. Same as stock Commando? Does anyone have the original literature for it?

Matt Spencer · Feb 13, 2012

According to this , it might be 8 & 10 . As they all do . http://files.me.com/davefriesen/1ii7ja

Deckard · Feb 13, 2012

I do have pretty much the same Dunstall Tuning Guide, but that refers only to the MK3 and it specifies .006 & .008.
Racing cam is .008 & .010. I have to conclude that the MK 4 is going to utilize the .006 & .008 unless someone has documentation to the contrary. That's my quest :roll:

RennieK · Feb 14, 2012

Dyno dave has some info:
http://atlanticgreen.com/camsurvey.htm

Matt Spencer · Feb 14, 2012

Fanks for the INFO , Rennie .

Intresting comparisons , down below . From the ramp profiles , id go for the 10 or more clearance if youve fancy springs.

The olde 3 in radius lifter trick is mentioned too . Can you see what originally was used on your Dunstall Cam ? ?
Presumeably his , with the 810 barrel .

The Old 2S was quieter running .016 ( 3S clearances ) than the stock 'S' at 6 & 8, looking at the ramps , it makes sense .

Was some cam that wanted 12 in & ex , if the grey matters functioning . 2S you just heard the valve action / actuation.
S you got the clanking type moise . :?

Cant see the ' 3S ' on there . :

RennieK · Feb 14, 2012

The 810 kits came with flat lifters. The lifters were radioused for the race cams which have noticeably wider (longer) noses on the lobes compared to regular cam lobes. The race cams were marked PD R2 or PD R3 etc. The race cams were pressure fed to the lobes through the flap valve location.

Hobot · Feb 14, 2012

Do you know what point they let the oil out the lobes?
2S/Combat cam lash int.-.008 and ext. -.010" for reference.

RennieK · Feb 15, 2012

You can see a race cam on page 17 of Matt's tuning manual link that shows the oilway on the lobes.

lcrken · Feb 15, 2012

hobot said:
Do you know what point they let the oil out the lobes?
2S/Combat cam lash int.-.008 and ext. -.010" for reference.

Here's another pic of Dunstall cams, this one from a 1974 catalog. The chamfered oil hole is clearly visible on the Mk 4 cam lobe.

Ken

Deckard · Feb 15, 2012

Amusing. I have a '71 Dunstall catalog and a '74. The MK 4 is listed in the '71, , p/n 3029, $76. In the '74 catalog MK 5, p/n 3029, $110. Same p/n 3029. The catalogs don't actually have dates, just the price sheets that I have with them.
Boston Cycles, RIP

RennieK · Feb 15, 2012

Of note in these photos is the lack of scrolling on the race cams to accommodate the needle bearings. Something to consider for those thinking of converting to needle bearings with stock cams.

Dunstall MK 4 Camshaft

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