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Thread: Advice on a 1298 pre-crossflow please

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    Wink Advice on a 1298 pre-crossflow please

    Hi
    I've joined up here as I'm thinking about building a 1298cc pre-crossflow engine.I've been mucking about with cars for decades but have never done a full engine rebuild and I figure its about time.The info on here is amazing so that would be a great help.
    I have a 1964 Lotus 7 which has the 1500 prexflow "cosworth" engine in it. As I'm just looking for a project build, I thought that building something a bit different from the 1500 would be a good idea., so it sort of makes "sense" to build another pre crossflow that could be swapped into/swapped out of the Lotus just for fun. Ideally I would like an engine that is really rev-happy and makes about 90-100 bhp. I think I read somewhere that the 1298 pre-x flow can be built up into really rev happy engine and that the bottom end is pretty strong in standard form.
    The thing is, I've also read that the 1300 pre-x motor was a bit of a rarity and was only used in early mk2 cortinas for a short while. As such, if I bought one, what is the parts availability for these rarer engines going to be like? or do most bits from the other pre-xflows fit? If the cylinders need a bore, would it be a total pain to find a new set to fit?
    Has anyone on here any experience with building a nice wizzy 1298 pre-xflow and could they give me any pointers as to spec? I'd really like to do this as a project but am I starting in the wrong place? Perhaps I should start with a crossflow instead. Would a xflow mate straight upto my gearbox? Would I need to think about any differences other than carbs being on the other side (for which i'd need a bonnet with a cut out on the other side)
    Any and all thoughts,advice, abuse,etc,etc gratefully received
    cheers
    Will

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    Re: Advice on a 1298 pre-crossflow please

    To answer one of my questions,I've just read that both pre x and x flow engines are modular, displacement being achieved by the throw of the crank. Therefore, pistons/overbores are not a problem.

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    Re: Advice on a 1298 pre-crossflow please

    x/flow would bolt straight up as its only a development of your pre x.

    a normal 1500 can be made quite rev happy, lets not forget its got the same stroke as a twin cam and they are not rev shy.
    unless doing it for class regulations in racing to me it makes no sense to build a 1300 cc engine.
    if 90-100 bhp is your goal an almost standard 1600 x/flow will give that

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    Advice on a 1298 pre-crossflow please

    And a tuned 1500 pre xf or 1600/1700 xf will make for a far nicer car to drive than a high stressed 1300.


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    Re: Advice on a 1298 pre-crossflow please

    Always use a 5 bearing block ! Rev happy ? Try the 1500 crank in a 1600 block with long rods, you will love it !

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    Re: Advice on a 1298 pre-crossflow please

    Many thanks for the replies chaps. Ok, so perhaps far more sensible to start with either a 1500 pre or a 1600 x flow.
    I'm not building for racing or anything and I dont want to go nuts on power as the car has the original Standard 10 axle which is the weak link (Standard 10s had 35 bhp).
    I just want to: (i) build an engine as a project and (ii) end up with an engine that has different characteristics than my existing motor. Hence the original idea to have something really rev happy that you have to work at it to keep it on cam as I like engines like that.
    Anyway, I am researching and learning all the time.
    Can anyone recommend an alternative to Peter Wallage's rebuild book? They seem to be very expensive if available.
    Many thanks
    Will

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    Re: Advice on a 1298 pre-crossflow please

    if you want something revy without any torque (and thus not stress the back axle) fit a bcf3 cam in a 1300 x/f

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    Re: Advice on a 1298 pre-crossflow please

    Thanks Graham. My initial thought was to rely on revs rather than torque for exactly that reason. I see with that cam that you need to check piston/ valve clearance carefully and may need pocketed pistons. Also, I see that cam makes power between 2,500 to 7k. Would you suggest beefing up the bottom end at all? Any other recommendations/necessities for that spec: double valve springs, uprated rockers,push rods,etc.
    Many thanks indeed.
    Will

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    Re: Advice on a 1298 pre-crossflow please

    you would need to check valve/piston clearance if going x/f route, 7,000 rpm would not worry a standard x/f bottom end assuming its in good shape, although an uprated set of rod bolts would be a good idea, push rods and rocker arms wil be fine, steel posts a good idea heavy duty valve springs will be a must but singles should be ok

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    Re: Advice on a 1298 pre-crossflow please

    We have scrapped many 1300 engines years ago, both pre and x flow as no one wanted them.

    Some 1500 blocks would easily bore to 85mm giving you 1650cc. Surely that would be a much better option than a 1300 engine unless you were restricted to that cc in a championship.

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    Re: Advice on a 1298 pre-crossflow please

    Hi. Youre right in that starting with the bigger block makes logical sense. I'm not really chasing the power,I'd be quite happy with 100bhp. Its more the character of the engine that I'm after. I love driving where all the power is in quite a narrow band and you have to really work hard to stay on cam. I do like the idea of the really wizzy, rev happy 1300 that you have to really thrash to get the power out of it. Daft but there we go cheers.Will

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    Re: Advice on a 1298 pre-crossflow please

    1300 crank in 1500 block works also, long rods and short pistons, bcf3 cam, some work on the head and … your screamer will be born !

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    Re: Advice on a 1298 pre-crossflow please

    Quote Originally Posted by racing escort View Post
    1300 crank in 1500 block works also, long rods and short pistons, bcf3 cam, some work on the head and … your screamer will be born !

    That sort of combination is something that I should think about. The bcf3 cam looks a good option for the sort of thing I'm after : characteristics look good and as I now know from Graham, the bottom end should handle the 7k fine.
    As an example of the sort of thing I'd like to end up with, here' a pic of my 911. Its 2 litre, does nothing below about 5k but then goes nuts upto 7,300. It puts out 160 bhp and by keeping it flying on cam I can keep up with cars with a fair chunk more bhp. I guess it would irritate the hell out of some people and its not the easiest in traffic but by god its fun!
    Thank to all for the replies.

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    Re: Advice on a 1298 pre-crossflow please

    look for the 120E block, it's a 1500 cc from a cortina, 5 bearings on the crank, the sump will need cutting and welding but it can be done … go for forged pistons and high CR, a head from a 1600GT and some porting will be enough to have big fun

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    Re: Advice on a 1298 pre-crossflow please

    the sump will need cutting and welding but it can be done
    No need to mod the sump on a Lotus 7 as there isn't a crossmember in the way..
    If you want to go down your original route I do have a 1300 Pre-xflow head that is surplus to requirements..also be aware that the later x-flow blocks (711m) are approx. 10mm wider across the engine mountings so will probably need a different mounting bracket on the exhaust side...Caterham item probably fits..
    Cheers, Brian.

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    Re: Advice on a 1298 pre-crossflow please

    I've never heard of a 1500 crank in a 1600 block, what rods are used?

    I have a crank and block that could be an interesting project!

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    Re: Advice on a 1298 pre-crossflow please

    The stroke of the 1500 crank is 5 mm less then 1600 one, you will need the long rods (burtonpower) and std pistons or short pistons and special ordered long rods … I don't know of a plug and play combination ...

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