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  1. #1
    Join Date
    Jan 2015
    Location
    Paignton Devon
    Posts
    214

    Relative fuel consumption

    I have a rover v8 3.9 14cux injection engine which is almost ready to go into the car, hopefully in January after running it up on the test stand, I'm told I could expect maybe 30 mpg on a long run?, However, I've just bought a Holley 390 carb, offenhauser manifold and cobra air filter, now, they 'look' right whereas the injection doesn't , but what sort of fuel consumption could I expect if I fitted them? The engine is standard apart from having a cyclone cam from real steel, I assume the mpg will go down, I can live with a reasonable amount but if it dropped drastically to say mid to low teens that might shelve the idea. Opinions and experiences welcome
    Cheers
    Roger

  2. #2
    Join Date
    Dec 2008
    Location
    Newcastle upon Tyne
    Posts
    1,675
    Roger,

    I have a very similar set up and am not bothered about "looking right", I built it as a kit car NOT a replica (vexed terminology) of an AC Cobra. I also have a Viper Cyclone camshaft in a 3.9 EFi with a hot wire 14 CUX but have increased the CR to 10:1 and performed some mild flowing & port matching work on the cylinder heads.

    With this configuration the best figure I have achieved was 25.6 MPG on a long run on motorways and dual carriageways in convoy with some very sedate drivers. On "normal" runs, B roads and spirited driving, I get around the 18MPG and on track days I get 11 - 12 MPG.

    If you prefer the look of a Holley I would go for it, if you are not happy with the look of YOUR car it will always rankle and they are not built, or meant, to be fuel efficient!


    Hope this helps.

    Regards,
    Ian
    Pilgrim Sumo Mk3; IVA Apr. 2014; RV8 3.9 EFi ; Cosworth T5; Granada Donor

  3. #3
    Join Date
    Jan 2015
    Location
    Paignton Devon
    Posts
    214
    Thanks Ian, good to hear from someone with relevant experience, I too am not an open the bonnet and " ooh look at the size of that" sort of person, but I got the carb etc at a price I couldn't refuse so it gives me the option of using either, whichever I use I'll keep the other so it could be changed at any time

    Roger

  4. #4
    Join Date
    Jun 2012
    Location
    northumberland
    Age
    49
    Posts
    146
    Hi Roger,
    Horses for courses when it comes to cobra replica's engine's and carburetion set ups, some prefer injection and others carbs, a well set up carb and engine on a rover will match an injection set up and obviously is more period looking. A 390 Holly a decent carb and if it's the offenhauser 360 manifold you have, then it's a very good combination for a 3.9.A tip f you fit this trim the valley gasget seals the rubber ones where they tuck in to the block and heads as they stand too proud and can crack the inlet manifold when torquing it down.
    You can nearly always sort a carb out at the roadside if need be rather than a poxy £2quid sensor leaving you stranded.
    Good luck in whatever you choose and don't be stuck to ask for advice.

  5. #5
    Join Date
    Aug 2009
    Location
    Birmingham
    Posts
    531
    Have the look and the fuel injection FiTech

    I have one fitted, very impressed with outcome. UK supplier.

  6. #6
    Join Date
    Jun 2012
    Location
    northumberland
    Age
    49
    Posts
    146
    I have seen them Daryn they look authentic a bit, and if you want fuel injection at least you ain't got a massive plenum sitting there.it still looks old school, glad you like the set up.

  7. #7
    Join Date
    Jul 2007
    Location
    Burton upon Trent
    Age
    47
    Posts
    1,049
    I built mine with EFI and was happy with performance, however, I changed to Edelbrock carb and manifold because... the looks/sounds are better, plus constant electrical gremlins are harder to fix than mechanical at the side of the road, but then, I am an old school mechanic.
    MPG is not really an issue with me, given the amount of miles we do. The pressure of the big toe determines a lot too
    C an
    O nly
    B e
    R eal
    A drenalin
    Sumo, 4.2 RV8..... Edelbrock

  8. #8
    Join Date
    Aug 2009
    Location
    Birmingham
    Posts
    531
    Quote Originally Posted by southern roadcraft View Post
    I have seen them Daryn they look authentic a bit, and if you want fuel injection at least you ain't got a massive plenum sitting there.it still looks old school, glad you like the set up.

    Here is my FiTech installation, straight out of the box and bolted on. Did no tuning what so ever and revs like a beast. I have a very very lumpy cam that only produces 6inHg and the FiTech EFI smoothed the tick over out and gave great throttle response.

  9. #9
    Join Date
    May 2004
    Location
    Perth
    Posts
    4,540
    To increase fuel consumption, fit a hood!

    On my annual four hundred mile round trip to Silverstone I have always traveled without the hood fitted, and over the ten years I have normally averaged just under 20 mpg at a steady 70 mph on the motorway. This year, because of the weather, I had the hood fitted for both legs of the journey and averaged just under 30 mpg which actually made me think the gauge was stuck!

    (Ford 302 with Holley Street Avenger)
    Last edited by Clive; 15-12-17 at 03:28 PM.
    Cheers, Clive

    (If I'm not here, I'm either in my new workshop or on the golf course!)

  10. #10
    Join Date
    Jan 2015
    Location
    Paignton Devon
    Posts
    214
    Cheers for the replies, I like the look of that fitech outfit but it's not in my budget at the moment, Because I've spent time sorting out the wiring and fitting the injection stuff I've got, I think what I'll do is get that running and use it to run in the cam, that will at least prove the engine before it goes in (and also give me a sense of achievement !) I can then take that off fit and setup the carb etc for fitting in the car, that way I will know that both systems work and they can be changed fairly easily, might even turn it into a long term back to back road test !

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