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  • Carbs on Fiat engine

    For those who have enquired here are some pics of my setup. Should add that the carbs. are DelOrto DHLA 45's
    Attached Files
    Last edited by h_m_cumming; 04-10-17, 08:35 PM. Reason: addition

  • #2
    Re: Carbs on Fiat engine

    Looking great. You back on the road now Hugh?

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    • #3
      Re: Carbs on Fiat engine

      I wish. Took a 5thou skim off the head, valves all ground in and assembled, sorting out gaskets. Got to hone the bores and then start fitting pistons.
      I think the reason the piston broke up was because the second ring gap closed up and distorted the ring which broke the lands, despite the fact that I made the gaps larger than recommended, so this time I'm makeing them wider still, I think 22thou. top and 25 second, which are more like a racing engine gaps. Time will tell.
      And then there's all the housework on top!!!!!
      Last edited by h_m_cumming; 04-10-17, 09:21 PM. Reason: addition

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      • #4
        Re: Carbs on Fiat engine

        That is the setup I had on the Fiat engine that I had in my rally car. A great engine, not a huge amount of power but very drivable. I loved the sound it used to make at full chat… I did consider swapping the engine into the roadster when I broke up the rally car but decided that it would be too much work…

        Mk2 SWB Marina Roadster with a 2.0L Pinto built in 1986

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        • #5
          Re: Carbs on Fiat engine

          I did a fair amount of work on mine and eventually got just short of 150 horses, so happy with that.
          Attached Files

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          • #6
            Re: Carbs on Fiat engine

            Many thanks to Hugh for posting these set up pics above. I too have the Fiat engine in my roadster and I would like to upgrade it to twin carbs. Its a winter/spring project and having dug into the detail I see a stumbling block straightaway. The current single carb fitted is the original one from the original donor '83 Argenta. While it works and the engine runs and it is quick - at higher load it does become starving for air. I tested this theory by comparing driving with the bonnet down and with the bonnet propped open (and tied in place!). When the bonnet is down it gets sucked down against the air filter top.. Originally, I was going to live with it but modify the air filter itself to recieve a cold air feed via a cone filter elsewhere. However, I've decided if I am going to do anything - its better if I do it properly from the start.
            So, the current carb fitted is downdraft & if I put twin Webers on it I'd have to modify the bonnet which I am very reluctant to do. Hugh got around the problem by using a sidedraft inlet manifold and fitting the carbs that way - I think that is the best way to go forward.
            Problem number 1: sourcing a compatible side draft inlet manifold for a 2.0 twin cam... When I google it - I can only find one reference to one that was for sale in Australia in 2016! However, I have found a suggestion on a blog that a company called Mangoletski might make them to order... I found their site and indeed it looks like they can:

            However, I'll need to know the precise geometry and bore dimensions to be sure it will fit my engine and I'll also need a twin carb kit that will be compatible and then once I've done as much as I can in the assembly myself, I'll take it to a local tuning specialist with a rolling road set up for them to finish it off for me. I am just about touching the 'intermediate' diy mechanics level and some things I know are beyong my ability.

            However - there is a nagging feeling at the back of my head... A while ago, I think I read somewhere that the Marina rear differential is ok up to about 130hp. Perhaps I also read that the Marina van diff was more capable - but those will be extremely hard to come by these days.. If I am going to upgrade to twin webers with a good air feed my engine will certainly rise up from its standard 112hp... Might I be heading for a fall? Are any of your Roadsters with a Marina diff' coupled to more than 130hp ?

            Thanks for your input!
            Tony
            Attached Files

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            • #7
              Re: Carbs on Fiat engine

              Hi Tony
              Just a quick reply for now. I too have a fiat twin cam 1800. I have lots of experience and knowledge of the carb situation, both good and bad. Just to say I did have twin downdrafts that fitted nicely under the bonnet with no mods. I don't anymore as they were a pig to keep tuned.
              Have you seen these on eBay. Came off a twinky so are probably set up for your engine. He has the inlet manifold for sale separately as well. http://r.ebay.com/mFRDV9
              Jon
              Mk2 SWB Marina Roadster with a 1800 Fiat Twin Cam engine and 5 speed Abarth gearbox built in 1987
              - I have no idea what I am talking about........ but my advice is always free! -

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              • #8
                Re: Carbs on Fiat engine

                That's what you want, and the right manifold although I'd use misabs. From experiance the std. marina diff is OK, it's torque not hp., within reason, that it doesn't like. If your upping the power I would regap your rings as I've found to my cost.
                Last edited by h_m_cumming; 11-10-17, 03:23 PM. Reason: addition

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                • #9
                  Re: Carbs on Fiat engine

                  Aha! Now that's what you call a community! No less than an hour after my post - both Jon & Hugh are there to support the upgrade!
                  Thank you Jon for the link and the heads up - I am eyeing the two sales very closely - only snag looks like the dellorto's are manual choke?

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                  • #10
                    Re: Carbs on Fiat engine

                    I only use the choke to start when cold but shut it off within 10/15 secs.
                    Just looked at the Mangoletsi one, it wont suit your setup as it is not offset for the dist.
                    Last edited by h_m_cumming; 11-10-17, 06:04 PM.

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                    • #11
                      Re: Carbs on Fiat engine

                      I have the same carbs on my Alfa 2 litre twin cam and I don't have any choke operational. A few pumps on the pedal and it starts ok, then hold at a high tick over for a few seconds and away you go. Less effective of course in mid winter but I tend not to use it so much then.

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                      • #12
                        Re: Carbs on Fiat engine

                        Hi Tony
                        I said my last post was quick so here comes the long one.
                        My engine was bought from a fiat specialist in Street, Somerset back in 1989. It is a fully rebuilt 1800cc that was fully blueprinted but otherwise standard. It will rev easily to 7500 rpm. Back in the day the carb upgrade was to put the 2000 cc carb onto the 1800. This worked ok when warm but cold running was poor. It also had a bad flat spot. I decided to upgrade to the twin Weber idf downdraft setup that was factory fit on some models but with the swept inlet manifold as I have a block mounted distributor like you. Also, this setup fits under the roadster bonnet without any mods unlike the side draft option that Hugh has fitted. This was great when properly in tune but I found I was constantly tuning them. Also, Guy Croft suggested that unless you had done some tuning work such as head porting and hotter cams then the twin carb setup was not really adding anything and suggests a better carb upgrade to a standard engine is to a Weber dgv 32/36. This is what I have done and I am pleased with the results.
                        I have an observation of your setup that may help. Your ITG filter is designed to pull air in through the top rather than the sides unlike a K&N filter. Your engine at 6500 rpm under load will be sucking at about 250 cfm. This is ALOT of air. If the top of your filter is close to the bonnet then you will be creating a massive low pressure, air stagnation problem which is basically sucking the foam against the bonnet.
                        Firstly, I would try a K&N style filter with a cold air feed or you could do what I have done and upgrade to the Weber dgv. There is an intake snorkel available for this that would really help get cold air directly into the carb.
                        I hope this helps.
                        Jon
                        Mk2 SWB Marina Roadster with a 1800 Fiat Twin Cam engine and 5 speed Abarth gearbox built in 1987
                        - I have no idea what I am talking about........ but my advice is always free! -

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                        • #13
                          Re: Carbs on Fiat engine

                          I would heed Jon’s advice. I have heard the same for Pintos. The stock car guys can get close to 180BHP with the twin choke downdraft Webber carb. I used to have one of those cheap pancake filters on mine and recently swapped it for a homemade filter arrangement, mainly because I couldn’t fit a K&N under the bonnet without cutting a big hole in it. I’ve found that it is flowing a lot better than before and am getting better performance.
                          I do love the sound of the Fiat Twin cam on the Delorto side drafts though!
                          Mk2 SWB Marina Roadster with a 2.0L Pinto built in 1986

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                          • #14
                            Re: Carbs on Fiat engine

                            Originally posted by jon_cox View Post
                            Hi Tony
                            I have an observation of your setup that may help. Your ITG filter is designed to pull air in through the top rather than the sides unlike a K&N filter. Your engine at 6500 rpm under load will be sucking at about 250 cfm. This is ALOT of air. If the top of your filter is close to the bonnet then you will be creating a massive low pressure, air stagnation problem which is basically sucking the foam against the bonnet.
                            Firstly, I would try a K&N style filter with a cold air feed or you could do what I have done and upgrade to the Weber dgv. There is an intake snorkel available for this that would really help get cold air directly into the carb.
                            I hope this helps.
                            Jon
                            Thanks Jon, the itg filter does suck the bonnet onto it - a distinctive circular mark is there to remind me every time I'd lift the bonnet.. However it also pulls air in through its sides and I think that is where it is actually supplying - albeit limited - air. I'm interested in the potential of downdraft - but given the restricted space makes me hesitant. I see the Weber dgv 32/36 is a manual choke, less attractive - but that's simply because the current set up is automatic and I'm used to it now. I'm still keen to get the new intake manifold and fit sidedraft carbs like Hugh has done - I can understand why he likes the sound - this engine makes a terrific sound when accelerating. The available space is my major hesitancy & although I currently don't want to - if I were to sell her in the future, I think that even if I try the Weber dgv 32/36 - if I have the unfitted side manifold - then that would be a good spare part to go with her... Is there much of a difference between the 2000cc and the 1800cc performance wise? If Guy Croft says that the Weber dgv 32/36 is a better carb upgrade than fitting twin carbs (without other tuning work) - then I'll really have to think about that; after all he is THE man when it comes to tuning these engines. I have his 'Modifying and tuning Fiat/Lancia TC engines' book; it came with the car.
                            My brother has a compression tester and I'll be borrowing it in a few weeks time to do a health check before I do anything else. Its sorn in the garage atm and I planned not to be back on the road until March after most of the road salting had finished. I drove up and through Glen Coe last November and the salt corrosion created a real mess underneath!

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                            • #15
                              Re: Carbs on Fiat engine

                              Have you looked at http://danstengineering.co.uk/ he may well be able to make a manifold up for you to your requirements, he specialises in manifolds for fitment of bike carbs onto car engines. I bought a manifold and carbs off him to put on my Zetec and they work very well could be angouther option to look into.

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