Grinding XN cams
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  1. #1
    Gone Fishin' Ray Bell's Avatar
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    Grinding XN cams

    Met up with a long time Peugeot devotee the other day, Neil Irvine... he currently runs a 406 diesel and has a 505 SR wagon about to come back onstream. I think there's also a 505 GR in the family... and in the shed is a sadly deteriorating 404 with a 2-litre engine.

    In telling me about this engine, he mentioned that he had a cam done by Bert Jones in Sydney and that when he was discussing this with the people there they mentioned that 'most forget there's an angle between the inlet and exhaust followers' and don't take it into account.

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    I wonder how realistic this statement is? Probably quite so... it's long been well known that it's difficult to get a cam that works (David has some good references on his website, however...).

    Anyway, I raise this point just to get a discussion going.

    Neil further said that he had to set up his cam on a different angle for some reason, but when he got it in and gave the pistons a minor flycut the improvement was amazing.

    Without any real changes otherwise, he says he had more power up in the revs (which you'd have to expect) and, surprisingly, more down low as well... right through the range it was improved, and fuel consumption improved along with it!

    Now, I wouldn't mind a cam like that... he's going to check up the Bert Jones references for me when he gets a chance.

    What is the difference in angle between the inlet and exhaust followers? Anyone know?

  2. #2
    1000+ Posts PeterT's Avatar
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    He's probably refering to the lobe centrelines, typically around 108 degrees. Changing this angle moves the relationship between inlet and exhaust lobes, and thus the over lap, effective compression (inlet closing time) etc. Of course it's fixed on a single cam, but can be varied easily on a twin cam. I've had few cams done by Bert and they've always been amazing. He was always big on the finer details, and somehow always sold me a smaller grind than the one I thought I wanted. He was also big on crank angle, the relationship between rod length and stroke. It's a shame he's retired and someone hasn't gone on with the business.

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  3. #3
    1000+ Posts CHRI'S16's Avatar
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    <span><span class=ResizableText0><span><span</span> <span class=ResizableText0>class=ResizableText0></span>
    <span class=ResizableText0>
    Originally</span></span> posted by PeterT: <strong> It's a shame he's retired and someone hasn't gone on with the <span <span class=ResizableText0>class=ResizableText0>business .
    </span></span> <span class=ResizableText0></span></span> Peter is this the same fellow who worked for early SBR team when they did formula Brabhams? or a i thinking of someone else?... still its getting more difficult to find REAL tweekers and tuners who will play with heads and bottom ends. Xq</span>

    <small>[ 18 January 2003, 10:18 AM: Message edited by: xqisid ]</small>
    ... ptui!

  4. #4
    Gone Fishin' Ray Bell's Avatar
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    PeterT:
    He's probably refering to the lobe centrelines, typically around 108 degrees.....
    No, he's not... he's talking about the relationship if the followers to the cam in the block.

    You know how the pushrods come up in staggered positions, inlet relative to exhaust? Well, look at the block and you see the same thing, the inlet followers are some distance away (and hence some angle away...) from the exhausts.

    If you grind a cam in the conventional manner, using TDC for just the inlets, for example, the exhaust timing will be way out.

  5. #5
    Budding Architect ???? pugrambo's Avatar
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    Ray Bell
    [QB]

    Without any real changes otherwise, he says he had more power up in the revs (which you'd have to expect) and, surprisingly, more down low as well... right through the range it was improved, and fuel consumption improved along with it!

    Now, I wouldn't mind a cam like that... he's going to check up the Bert Jones references for me when he gets a chance.

    QB]
    9 times out of 10 when you have a better cam in a car and leave the original carb in place you gain power and fuel economy
    it is only when you start playing with bigger carbs and jets that the fuel usage goes up
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  6. #6
    Guru davemcbean's Avatar
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    Ray,

    The Bert Jones cam for the 504 is reknowned as the one to get. Bert no longer has the prototype. It went to Ian Robinson, then he gave it to Peter Portelli.

    I wanted this cam but Peter Portelli wouldn't do one for me unless I let him build a whole engine for me (get real!). The next best thing is the Wade cams 102 and 112, so I got a 112 at the advice from Wade (slightly less overlap and slightly more lift than the 102). I found the 112 improved performance throughout the rev range, whilst also improving economy, when I was using it with a Weber 32/36 DGAV with standard Cortina 2 litre jets. My economy only dropped when I was silly enough to bore out the second venturi and fit big jets with tiny airbleeds. I'm using the same bored out carb at the moment on my spare engine but are using more reasonable jet and air bleed sizes and the economy seems fine.

    Dave
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  7. #7
    Gone Fishin' Ray Bell's Avatar
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    Okay, let's look at the prospects of getting the Bert Jones cam...

    We know where there's one (in Neil Irvine's engine) and we can possibly obtain that from him... or diagram it by using a dial gauge on the top of the pushrod end of a rocker and a degree wheel on the flywheel.

    What about doing that and then getting Ivan Tighe to make up a master... or check among his masters and see if he has something the same... and work from there?

    Along the way we can eliminate the need to 'adjust' the cam timing, by getting it ground in the right place, and we can make sure we give all the right specs to Ivan so he can advance/retard the cam the right amount when he goes to grind the exhausts.

    Or do you know anywhere there's a more accessible Bert Jones cam?

    Also, Dave, have you previously heard of having to reset the cam timing with this cam?

  8. #8
    Guru davemcbean's Avatar
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    Ray Bell:
    Okay, let's look at the prospects of getting the Bert Jones cam...

    We know where there's one (in Neil Irvine's engine) and we can possibly obtain that from him... or diagram it by using a dial gauge on the top of the pushrod end of a rocker and a degree wheel on the flywheel.

    What about doing that and then getting Ivan Tighe to make up a master... or check among his masters and see if he has something the same... and work from there?

    Along the way we can eliminate the need to 'adjust' the cam timing, by getting it ground in the right place, and we can make sure we give all the right specs to Ivan so he can advance/retard the cam the right amount when he goes to grind the exhausts.

    Or do you know anywhere there's a more accessible Bert Jones cam?

    Also, Dave, have you previously heard of having to reset the cam timing with this cam?
    Sounds like a good idea.

    The only other person I know of with a Bert Jones cam is Dennis Edwards in Fertree Gully Victoria. I think the cam is in his 2 litre 203.

    I've never heard of any cam timing problems with it.

    Dave
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    1976 504 Ti
    1984 205 GT twin carb
    1991 205 SI 1.6GTI motor
    1994 106 Xsi
    1996 Mondeo V6
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    1997 Civic Cxi (great allrounder- revy, flexible, nimble, comfortable , economical, simple and durable )

  9. #9
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    I have mentioned the point about the angle of the pushrods to Wade's and they claim to have allowed for it.
    The 112 is a good choice as it has a very high lift for a stage 1 cam. Due to the small rocker ratio of the XN, XC motors you can easily end up with a hot cam having less lift than the standard one.

    Doug Norman has a 504 with a Bert Jones cam, the motor is unlikely to be pulled down in the near future though.

    Graham Wallis

  10. #10
    Gone Fishin' Ray Bell's Avatar
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    Thanks... I might talk to Neil about it when I get a chance.

    It won't happen in a hurry though, so if there are any others about just let us know...

  11. #11
    1000+ Posts alan moore's Avatar
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    If you could get a cam to Dean Tighe, it could be run up on the "cam doctor" and the grind would be plotted on the computer, showing the lobe centreline etc. and whether they have anything like it in the range of over 1000 grinds in stock.
    Alan.
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  12. #12
    Gone Fishin' Ray Bell's Avatar
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    Yes, that was the thought I had... whether we plot it without taking from the engine (which is complete, and in a car that might or might not be rebuilt) or manage to get it out.

    I'm quite sure Tighe's would have the profile, and I would have spoken to Dean about it.

    It's just a matter of getting our hands on the cam really.

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