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Thread: replacement engine ideas for 91 classic

  1. #31
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    Quote Originally Posted by 350RRC View Post
    Go for a top hatted 3.9 or 4.6 and get a quality LPG system installed. A bloke at Crafers could assist here.


    cheers, DL

    Pardon my ignorance, but what exactly is a 'top hatted 3.9' ??? - another set of (better or longer-lasting or more expensive) fancy heads ? What are the advantages with (a) Petrol and (b) LPG

    Do 3.9's benefit from a cam modification? - something more suited to LPG perhaps. - A mechanic aquaintance explained it in terms of timing of valve opening and the (faster) rate of opening as well as time open/closed.

    Heading towards LPG if I decide to keep the EH....

    Thanks.

  2. #32
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    top hat bore liners, they stop the liners shifting. Have a search on here, plenty of info

  3. #33
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    Do 3.9's benefit from a cam modification? - something more suited to LPG perhaps. - A mechanic aquaintance explained it in terms of timing of valve opening and the (faster) rate of opening as well as time open/closed.

    IMHO there are few cams better than a standard 3.9 cam for an RV8.

    There are several posts on here where people have fitted a different cam and been disappointed with the result.
    While "hotter" cams can give benefits to light road cars , if done with other mods such as heads, extractors etc, they can make a 2 tonne unloaded 4WD gutless at the revs you use on the highway, and introduce a need to change down on every decent hill.
    More torque at low revs is what is needed in a 4WD and CCs are the best remedy.
    Regards Philip A

  4. #34
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    Thanks Vern, - the "Thanks" icon seems to have vanished...

    PhilipA, ditto. - makes some sense as the '89 I was using to pull a 1.5 ton sweeper/trailer had been fitted with a warmer cam...pulled great from stopped, but was gutless at 90+ km/h, whereas a D1 with the 4cyl diesel was painful for the first 60 metres...then quietly got faster and fasterandfaster to.... easily beyond 100km/h pulling the same boat-anchor.

    So, keep my 3.9 standard until the liners shift too much, then replace with shift-less 'Top-hats'. Makes sense to the wallet! (gunna be lightened with the LT-230-in / BW-out then the LPG conversion.

    Holiday in SA is sounding good

  5. #35
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    CC's ???

  6. #36
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    CC's ???
    As in Cubic centimeters
    As in 4600CCs (or 5000Ccs) vs 3950CCs.

    Regards Philip A

  7. #37
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    Ah.... cc

    - undercanstumble.

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