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Thread: What mods needed to run 3.5 on lpg

  1. #11
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    If it is the same as the 3.9 then on the passenger side of the block below the exhaust manifold towards the front/middle the compression ratio and engine number is stamped on a machined flat bit.

    However on mine it is obstructed by the exhaust manifold however you should be able to see enough to figure it out.

  2. #12
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    Quote Originally Posted by Utemad View Post
    If it is the same as the 3.9 then on the passenger side of the block below the exhaust manifold towards the front/middle the compression ratio and engine number is stamped on a machined flat bit.

    However on mine it is obstructed by the exhaust manifold however you should be able to see enough to figure it out.
    Yep. On the 3.5L it's there too. Right above or below the engine number if i remember correctly.

    Does anyone know the proper ignition advance for gas on a 3.5L, without compromising for petrol?

  3. #13
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    Quote Originally Posted by Bulldog View Post
    Does anyone know the proper ignition advance for gas on a 3.5L, without compromising for petrol?
    I just had LPG fitted to my 3.9 and the guy said he times for 10 deg BTDC. It runs fine on ULP and LPG. I'll fiddle with it and maybe time it for PULP and LPG after the first check up.

  4. #14
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    Quote Originally Posted by pete View Post
    Is there any way I can tell what engine I have, ie compression ratio ect and so forth and what are the best ones? As far as I know my 3.5 is the standard stage1 engine with a holley on it.
    Thanks Pete
    G`day Pete

    Where the dip stick is on the flat surface

    The #s closest the cylinders or top #s is the compression ratio .

    The first 3 in the engine # or prefix will tell what the engine is where it`s from ( vehicle ) and the ratio ?

    If you can`t see the stamped ratio post the prefix and i`ll tell you if i have them .

    Earlier 3.5s will run lpg ok but not as long as later 3.5s and early or late the prefix will tell .

    The early had smaller valves and different materials than later .

    Cheers

  5. #15
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    Quote Originally Posted by Bulldog View Post
    Yep. On the 3.5L it's there too. Right above or below the engine number if i remember correctly.

    Does anyone know the proper ignition advance for gas on a 3.5L, without compromising for petrol?
    Bulldog, did you time your engine correctly (as per other post), I hope you did'nt put the dissy in with the crank at 6 degrees, Regards Frank.

  6. #16
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    Quote Originally Posted by Utemad View Post
    I just had LPG fitted to my 3.9 and the guy said he times for 10 deg BTDC. It runs fine on ULP and LPG. I'll fiddle with it and maybe time it for PULP and LPG after the first check up.
    10 degree's is a good compromise, i was running 12 on my rangie but backed it off if i was using petrol alot.
    MY08 TDV6 SE D3- permagrin ooh yeah
    2004 Jayco Freedom tin tent
    1998 Triumph Daytona T595
    1974 VW Kombi bus
    1958 Holden FC special sedan

  7. #17
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    Quote Originally Posted by loanrangie View Post
    10 degree's is a good compromise, i was running 12 on my rangie but backed it off if i was using petrol alot.
    When I first got my Disco it was running 12 deg BTDC (according to the timing mark) and it ran ok on ULP. Maybe I should just bump it up to 12 and see how it goes.

    What is the ideal timing for LPG?
    I have read that LPG requires more initial but less overall advance. I guess you can't achieve that without a twin map module.

  8. #18
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    Quote Originally Posted by Utemad View Post
    When I first got my Disco it was running 12 deg BTDC (according to the timing mark) and it ran ok on ULP. Maybe I should just bump it up to 12 and see how it goes.

    What is the ideal timing for LPG?
    I have read that LPG requires more initial but less overall advance. I guess you can't achieve that without a twin map module.
    About 12- 14 for lpg, advance it 1 deg at a time and then rev it till it pops and then back it off, a test run under load will let you know if its happy or not.
    MY08 TDV6 SE D3- permagrin ooh yeah
    2004 Jayco Freedom tin tent
    1998 Triumph Daytona T595
    1974 VW Kombi bus
    1958 Holden FC special sedan

  9. #19
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    With a Rover V8 you may be wise not to take too much notice of the actual timing mark and tune it by ear.
    The reason I say this is because Rover timing marks are often completely innacurate and this situation gets even worse with an old engine that has a stuffed timing chain.
    I run mine at about 12 degrees and it seems fine on both LPG and Petrol this may not be the same for all engines though.
    With LPG you are much better off with Electronic ignition (don't skimp on the leads either) as it will be less labour intensive than the standard points system I used the Electronic system from a 1994-1999 Discovery that I bought from Triumph Rover Spares in Adelaide and its the best thing I did.

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