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Manx DOHC box

This is a discussion on Manx DOHC box within the Technical forums, part of the Caferacer.net Forums category; Anyone out there know if you can mount a long stroke DOHC Manx cam box on a SOHC Manx head? Front vertical fins need to ...

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  1. #1
    Senior Member Cyorg's Avatar
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    Manx DOHC box

    Anyone out there know if you can mount a long stroke DOHC Manx cam box on a SOHC Manx head? Front vertical fins need to be trimmed for starters….
    "Non urinat in ventum"

  2. #2
    Senior Member jalsteve's Avatar
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    Get the right head!

    Are the valve angles in the head the same sohc vs dohc?

    Are the holding down bolts on the same PCD?
    Lite the blue touch paper and stand well back!

  3. #3
    Senior Member Cyorg's Avatar
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    I believe the valve angles are the same and yes the hold down bolts are on the same PDC. Getting the correct head would be the simple (budget permitting) and logical thing to do, but I have a SOHC head and a somewhat limited budget. There may be someone out there willing to swap heads, but I hate acquiring expensive things like that sight unseen and I live in the colonies where these types of bits are almost non existent. I've spent a fair amount of time scouring the net looking for Norton OHC info and I've been able to find some interesting stuff, but it seems a lot of the information is simply stored in peoples heads. If all I have to do is trim a couple of the vertical fins (which need repair anyway) and perhaps fabricate a new vertical shaft or a few spacers then it starts to make sense… to me anyway, but at this point I'm still trying to figuring out what I don't know.
    Maybe I'm looking in the wrong place, but I can't even find any parts books on post war Inters or a Manx. I found some pre war stuff...
    "Non urinat in ventum"

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    Senior Member jalsteve's Avatar
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    Longstoke dohc stuff is hard to find, it always was even in period due to a relatively short production run. The formula 3 guys (coopers and the like) preferred the longstroke engine so most were snapped up and blown up, crankcases and gearboxes usually got torn apart. Tuners like Steve Lancefield had his own cases made in heat treated alloy for strength. I would look into the historic formula 3 scene as a source of parts.

    The cambox needs to come down low enough so that the pushers sit on the valves, the valves don't need to be centralised. The 350 short stroke has the valves central to the pushers but the 500 they valves are very much toward the edge (the valves on the 500 are further apart but the cambox casting is the same). You also need to check the two bevel housing (Oldham coupling) apertures in the cambox and crankcase, they must align. If these do not then you have a problem. I will check the data I have for valve angles.

    It sounds feasible but I would hunt for the correct parts, not just because it's correct but because I wouldn't want to bugger up an original sohc head.

    Sometimes you just need to let the moths out of the wallet, building cammy Nortons isn't cheap.

    PS I am building a short stroke manx engine at the moment, I will post some photos.
    Last edited by jalsteve; 11-03-2015 at 12:14 PM.
    Lite the blue touch paper and stand well back!

  6. #5
    Senior Member Cyorg's Avatar
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    [QUOTE=jalsteve;340061

    Sometimes you just need to let the moths out of the wallet, building cammy Nortons isn't cheap.[/QUOTE]

    You figured out I was Scottish?

    Good to know about the pushers. Thanks. I was looking at them the other day and wondering why the hell the wear pattern was so far on the outside and not centralized.
    If I put spacers between the " cylinder head holding down sleeve nut" and the cam box, I can get it so the valve stem comes in contact with the pusher at approximately the same location as the wear pattern. The cam box still comes in contact with the tallest vertical fin on the right hand side, but it looks as though removing a few thou off the fin with a file would do it...depending on how much things expand and in what direction. Maybe thicker spacers are the answer. They used "sleeve nut distance pieces" on the CS1 and CJ, but don't show them being used on the prewar 30 and 40 in the book that I have. My kingdom for a parts book/diagrams that shows both the garden gate and featherbed long strokes.

    I definitely get what you are saying about buggering up a head. It's one of the main reasons I'm trying to dig up info on the subject and would likely hang myself if I fucked it up. If all I end up having to do is shave a small amount off one fin, I'll feel ok going ahead with it. Given that I have to straighten and repair a few other fins and along with the fact that someone removed some fin material to the right of the intake port to clear god knows what… I'll be able to convince myself that it is acceptable and it's probable that I'm not the first to do it.
    "Non urinat in ventum"

  7. #6
    Senior Member jalsteve's Avatar
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    Longstroke Manx dimensions

    Bore 79.6mm
    Stroke 100mm
    Combustion chamber Hemispherical
    Inlet valve 1.915 inch dia
    Exhaust valve 1.735 inch dia
    Valve angle 77 degrees included angle.
    Inlet cam M59
    Exhaust cam M59
    Tappet Dia 0.75 inch Contact radius 1.0 inch
    Valve timing IVO 60 IVC 67 EVO 85 EVC 45 (0.004inch clearance)
    Con-rod length 7.5 inch

    Remember the valves will have lash caps, valve clearance is determined but one of or a combination of lash cap thickness, pusher cap thickness or pusher length.
    Lite the blue touch paper and stand well back!

  8. #7
    Senior Member TrialsRider's Avatar
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    We like Manx anything in any condition just as long as it's clean -> Pictures please !

    Quote Originally Posted by Cyorg View Post
    Anyone out there know if you can mount a long stroke DOHC Manx cam box on a SOHC Manx head? Front vertical fins need to be trimmed for starters….
    Burt Munro could have probably done it in his garage with crude hand tools.
    Last edited by TrialsRider; 11-03-2015 at 02:24 PM.

  9. #8
    Senior Member Cyorg's Avatar
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    Quote Originally Posted by jalsteve View Post
    Longstroke Manx dimensions

    Bore 79.6mm
    Stroke 100mm
    Combustion chamber Hemispherical
    Inlet valve 1.915 inch dia
    Exhaust valve 1.735 inch dia
    Valve angle 77 degrees included angle.
    Inlet cam M59
    Exhaust cam M59
    Tappet Dia 0.75 inch Contact radius 1.0 inch
    Valve timing IVO 60 IVC 67 EVO 85 EVC 45 (0.004inch clearance)
    Con-rod length 7.5 inch

    Remember the valves will have lash caps, valve clearance is determined but one of or a combination of lash cap thickness, pusher cap thickness or pusher length.
    Yes.. remembered the lash caps, but don't have any at the moment. Should be simple to find (I think) seems to be lots of bits available for SOHC.
    Working on getting a new barrel from Bennet. I have a featherbed long stroke barrel, but the Garden Gate variety has much less liner sticking out the bottom. He just needs to get the top spigot cut down on the new barrel from 1/4 to 1/8 so it fits the head I have. This confuses me somewhat, as I'm assuming the head I have (with 1/8 recess) is garden gate vintage, so why would there be barrels of the same vintage with 1/4 spigots. I'll get around to asking him that…
    I have a 7.5 Manx rod and an appropriate new Alpha B/E assy, just don't have Manx flywheels. I have an Inter set… at least I believe they are Inter even though they arrived encased in magnesium. I believe they will work and I don't plan on beating this thing, so the Scottish perspective (try to use what I have) may prevail. Then again maybe not...
    "Non urinat in ventum"

  10. #9
    Senior Member Cyorg's Avatar
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    Quote Originally Posted by TrialsRider View Post
    We like Manx anything in any condition just as long as it's clean -> Pictures please !
    I'll get to that at some point. I'm in the process of changing from a HP laptop to a MacBook and either I'm digitally challenged or it's easier to upload photos with a MS OS.
    The MacBook is forcing me to use one of those sites like photo bucket and I can't stand all of the ad bullshit.
    "Non urinat in ventum"

  11. #10
    Senior Member TrialsRider's Avatar
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    Photobucket isn't so bad once you get used to it.
    As soon as you get logged in, navigate to your library. That will prevent it from sorting all of your recent uploads by date and prevent it from running the stupid flash advertisement that says it won't slow you down, but does.
    Only use the photo links under the heading "Direct" and manually add the [img] and [/img] hypertext to the copied string.

    If your MacBook has a retina display, you'll be seeing detail in the photos that nobody else does. (unless they have a Mac with a retina display)

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