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  1. #51
    Legendary Lancista fay66's Avatar
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    Re: Carb Upgrade - S3 Fulvia

    Quote Originally Posted by alfaromeo View Post
    Hi Brian,

    Glad to hear the 32 mm Dell'Ortos are working well. When you mention that you suspect some rich running condition, just out of curiosity, would you be able to hook up a fuel pressure gauge and see what the pressure is currently?

    I have a adjustable fuel pressure regulator and typically set it at 2.7 lbs for the Dell'Ortos, 3 lbs appears to be a upper limit. I believe the standard Solex setup actually ran at a slightly higher pressure from the factory.

    Jay
    Hi Jay,
    I'm sorry I don't have the equipment and I'm not sure I'd know what to do if I did:-((. but I'm not sure it would be relevant anyway, early Fulvia's didn't have a regulator fitted but I fitted a "filter King" about 7 years ago as I was fed up with the amount of debris, be it from the fuel or the tank creating running problems.
    That Filter Kings pressure has never been altered from it's supplied setting whatever that was, and I certainly didn't have any pressure/Carb problems while climbing through the Pyrenees or the Alps.

    Regards
    Brian

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    Re: Carb Upgrade - S3 Fulvia

    Quote Originally Posted by RallyRobin View Post
    It seems Dellorto UK has done this setup successfully before (DHLB32 on a 1.3S engine) and Matt was able to set me up with 28mm chokes and recommended jets to get started with. Very quick response from them - very helpful.
    I know this is an old thread, but how did you go with this Robin? I've found myself in a similar position to you and am wondering how it all turned out for you with the 're-jetted and re-venturied' DHLB 32's in the 1.3 Fulvia.

    If Robin is no longer with the forum, does anyone else happen to know how his 1.3 responded to those carbs?

    Cheers...Justin

  3. #53
    Legendary Lancista Marnix's Avatar
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    Re: Carb Upgrade - S3 Fulvia

    A very old thread indeed. Didn't see it before.

    I have no doubt the 1,3S engine CAN run on DHLB32 carbs, but the performance won't be great I guess (I am guessing, never tried it). For the 1,3S engine, need DHLB35 carbs, with the appropriate 1,3S jetting.
    They were never provided by the Lancia factory (on production cars), but available as after-market from Dellorto.
    You can install DHLA 40 or 45 (with the wider barrel spacing) with either an inlet manifold that ends out in wider spacing, or an adapter piece that starts from the original inlet manifold and extends to wider spacing.

    There was some remark in the thread about the DHLB35 having no provision for fuel return line. That's actually incorrect. There were two types of fuel banjos available (for the FRONT carb in this case, not the rear carb as with solex) one for cars without fuel return line and another for cars with fuel return line.
    Lancia Fulvia 2C 1964
    Lancia Fulvia Coupe Rallye 1,3 1968
    Porsche 924 1979
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    Re: Carb Upgrade - S3 Fulvia

    Thanks for that Marnix. I've learned a lot about carbs from your posts over the years, especially your article "Syncing The Suckers" that's in the download section. I'm so glad you took the time and effort to write that because it got me out of big trouble once and led to me having a much better understanding of the Solex PHH's and carbs in general.

    I'm also glad you've weighed in on this issue too.

    I should add at this point that I've got a Fulvia Berlina S2 (818.302 engine). The data I've received from Dellorto lists the venturi used in the DHLB 35 for my model as being 29mm along with the Berlina GTE, Rallye 1.3 Coupe and Zagato Sport 1.3. It lists the S2 Coupe, the Zagato Sport 1.3S and the 1.3S Coupe as using the 31mm venturi.

    My situation is that I've found a set of Fulvia version DHLB 32's for about half the price of a set of DHLB 35's (which the seller also has. Both sets are in similar condition). The price of the DHLB 32's is a bit high, a bit painful, but bearable. However, the price of the DHLB's is VERY high, VERY painful and VERY hard to justify especially for my style of driving (no racing/ track work). Hence the re-examination of whether the DHLB 32's could be made to work sufficiently.

    So on paper, this is the comparison assuming the DHLB 35 jets and venturi (both main and auxiliary) have been loaded into the DHLB 32 (they fit; I've checked with Dellorto UK)



    • On both, the air would enter the same size opening (around 40mm) and continue down a 40 mm barrel until passing through a 29mm venturi.



    • On the DHLB 35, the air would then open up into a 35mm throttle valve (6mm wider than the venturi) but on the DHLB 32 it would open up into a 32mm valve (only 3mm wider than the venturi, a difference of 3mm).



    • Straight after this, the air/fuel mix would exit the carbs and on both it would then enter the 35mm rubber flange/ spacer and down into the inlet manifold then combustion chamber.


    So, the airflow would go:

    -------------In-----Vent--Throt--Flange
    DHLB 32- 40mm>29mm>32mm>35mm
    DHLB 35- 40mm>29mm>35mm>35mm

    From a physics point of view, I'm trying to get my head around how much of an effect this slight difference is going to have (and why).

    As Ed Levin has previously said, there needs to be a sufficient expansion (widening of space) off the back end of the venturis to cause the vapourising of the fuel. He mentions there's an industry 'ideal venturi to barrel size' formula of 1.25:1. If that is the case, the ideal venturi size for the DHLB 32 is 25.6mm. In the data from Dellorto, it lists the venturi used for the DHLB 32's for the 1.2 Fulvias as being 26mm, so that formula sounds about right. Dellorto UK also mentioned the venturi should be about 6mm smaller than the throttle size that they open up into to fully facilitate fuel vapourization. Again, we land on 26mm. So if I had a 29mm venturi opening into a 32mm throttle barrel instead of a 35mm throttle barrel, how much will that 3mm smaller expansion space effect vapourization?

    After a lot of research and thinking, I still don't really know, which is why I was hoping there was someone out there who had tried it.
    I've had a good look around on all the forums and can't find a report from anyone who's done it. 'RallyRobin' was the closest one I found, but it looks like he's no longer registered with this forum.

    However, I tracked down Matt from Dellorto UK who 'RallyRobin' referred to in his post (he's since left Dellorto UK but they put me in touch with him). He didn't remember that specific case but recommended using a 26mm venturi instead of the 29mm to ensure there's enough of an expansion off the back end of the venturis to facilitate vapourization. He says that when you do this, you get increased low down performance but a loss of top end.

    So in that scenario the airflow would be:

    -------------In-----Vent--Throt--Flange
    DHLB 32- 40mm>26mm>32mm>35mm>

    There were also some recommendations from Dellorto UK for jet sizes to compensate for the smaller throttle barrel and venturi size.

    I'd still prefer to hear directly from someone who has tried it before making a decision, but a well informed guess may have to suffice. However, with the cost of the carbs in question it's going to have to be as well informed as possible.


    The Weber DCOE/ Dellorto DHLA 40/45 option ticks a lot of the right boxes (can buy them new, can buy parts, well known to tuners etc) but then there's the reports of people not being able to close their bonnets after installation. I see most places that sell the manifold and adaptor now place a warning in their ad that this can happen. Also, once you add up the cost of the DCOE/ DHLA 40/ 45's and the custom manifold/ adaptor, you're getting close to the price of a set of DHLB 35's (which bolt straight on), albeit second hand and probably in need of work.

    But like you've previously said Marnix, there's a looming parts availability crisis for the DHLB 35's which is only going to get worse as time goes by (until the day comes we can just 3D metal-print them out at home)

    My primary reason for wanting to change away from the Solex PHH C35's is the issue surrounding wear around the throttle shaft. The ability to access the jets from the top and having somewhere to easily attach vacuum gauges would also be nice, but not my primary concern. I had a Fulvia friend who recently experienced 'ovalized' throttle bores caused by wear around the spindle which in turn caused the butterflies to scrape against the bore walls and it's got me paranoid.

    My version of the PHH C35's have shaft bushes (brass I think) but they're still prone to wear. They're not worn/ leaking now but that could change at any time.

    From an engineering point of view, that throttle shaft really cries out for a proper bearing and I'm only really going to be able to fully relax once there's one there; not just for my sake but also for that of future custodians of the car.

    So, for the way I use my car (no racing/ track work), I can't really justify the cost of the DHLB 35's or the DCOE 40's + custom manifold/ adaptor, but I could justify the lower cost of the DHLB 32's if they could be made to work 'good enough' without too much of a sacrifice in performance. If it looks like it's just not a viable option, I'll start looking at alternatives like revisiting your idea Marnix of doing something with micro ball bearings on the Solex PHH C35's.

    Any thoughts anyone?

  5. #55
    Senior Lancista Taddraughn's Avatar
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    Re: Carb Upgrade - S3 Fulvia

    You can take care of the spindle issue with some bearings like the ones in the below ebay link. Even if you need a machine shop to perform the modification of the carb housings for you, I can't imagine they would charge very much to align the bodies properly and mill a couple holes to press bearings into.

    https://www.ebay.com/itm/260988909848

    bmarler has done the bearing modification so you may want to ask him about the specifics of it if you go that route.

  6. #56
    Legendary Lancista Marnix's Avatar
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    Re: Carb Upgrade - S3 Fulvia

    That's a long post. I will take some time later to reply to several issues being brought up.

    Let me start by getting a few common misunderstandings out of the way:


    - the Dellorto do not offer an improvement in engine performance. Actually, if you compare the jetting (with a few small changes due to slightly different internal carb setup) the Dellorto setup for the 1.2, 1.3 and 1.3S are about "copy-cat" of the Solex configuration (for example 26mm venturi for the Solex C.32 and the Dellorto DHLB32; 29mm solex - Dellorto for the 302 engine; 31 mm for the Solex - Dellorto for the 303 engine). The jetting is slightly different, but not that much, and gives about the same engine performance / characteristics. The reason to put in Dellortos instead of Solex carbs is NOT to have better perfomance, but reliability. I should maybe explain the different strategy: Solex was producing carbs CHEAP. They are not designed to last "for life". If worn, just throw the old ones away and put in new ones (it is the sixties, the throw away area; they are cheap anyway, and Lancias are (were) expensive cars, so the owners didn't mind much paying for a new set (not many working hours either). Dellorto made their carbs "bullet-proof", to last for life: their engineering is superb compared to Solex. If I would be Lancia, and have to buy lets say 100000 carb sets, would I buy the cheap from Solex or the expensive from Dellorto? Actually, my personal experience is my 302 engine runs better (smoother) on the Solexes than on the Dellortos (that is, Solexes rebuild to new, not worn ones).
    - a common mistake is to compare venturies by their diameter; actually, it is the SURFACE that counts (but to make it easy they are always specified in diameter). So a 29mm venturi is a lot larger than a 26mm venturi despite being only 3mm larger in diameter.
    - Ed is right in saying that the relation venturi diameter versus throttle opening behind the venturi is important. I didn't try it, but you could maybe go for a compromise, and put in a 28mm venturi (larger than the 1.2 26mm, and smaller than the 28mm of the 1.3)
    the DHLB35 was exclusively made by Dellorto for the Fulvia; the DHLB32 was made for a number of different cars (the Fulvia 1.2 but also Fiat), and comes in different versions. The non-Fulvia DHLB32 are NOT really suitable for the Fulvia (there are a number of significant differences, and it would be quite hard to make them suitable for the Fulvia. I am not sure why the DHLB32 you found are cheaper than the DHLB35, if bothe would be the version for Fulvia (and not the DHLB32 for non-Fulvia). My experience is that it is even harder to find FULVIA DHLB32 than DHLB35, and that they cost about the same. Most DHLB carbs need some refurbishing, but the good news is, them being bullet-proff, most can be easily brought back to near-new state.
    - there is a number of known problems with te Solex carbs. Spindle wear is one of them. About all these issues can be cured if done professionally. I bring back Solex carbs to new, along the way dealing with some of the weaknesses of the Solex carbs. It pbrings them up to Dellortto standards... unfortunately, also to Dellorto proce range.
    - apart from "sucking-the-sucker" in downloads, there is another part I wrote about carb theory (only one part available yet). It is really a simplified explanation to give people some basic understanding. It may be worth reading the section in it about choke (venturi) size effects. I fact, venturi size is a compromise really. small size gives good low RPM performance, at the cost of high RPM power. Big size gives greater high RPM power, at the cost of low RPM performance. While the text gives a simplification, it gives some basic insight in why this would be so.
    Lancia Fulvia 2C 1964
    Lancia Fulvia Coupe Rallye 1,3 1968
    Porsche 924 1979
    Alfa Romeo 33 1.4IE 1993

  7. #57
    Legendary Lancista fay66's Avatar
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    Re: Carb Upgrade - S3 Fulvia

    Hi Marnix,
    I note the talk is of DHLB 32's,
    The Dellorto's fitted to my 2c are DHLA 32's, what is the difference? as when I purchased mine over 10 years ago they were new and came already jetted for my 2c.
    I agree with your comments that my 2c is no faster fitted with the Dellorto's, but she certainly runs a lot smoother, but one great advantage is how long they stay in tune, compared to the solexes.
    BRIAN

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    Re: Carb Upgrade - S3 Fulvia

    Quote Originally Posted by Taddraughn View Post
    You can take care of the spindle issue with some bearings like the ones in the below ebay link. Even if you need a machine shop to perform the modification of the carb housings for you, I can't imagine they would charge very much to align the bodies properly and mill a couple holes to press bearings into.

    https://www.ebay.com/itm/260988909848

    bmarler has done the bearing modification so you may want to ask him about the specifics of it if you go that route.

    Thanks for that Taddraughn, I may very well do that if the DHLB 32 option turns out not to be feasible.

    The problem I can see with putting a 12mm O.D bearing on the shafts of the PHH C35's is that once that collar around the shaft has been reamed out to accept the bearing there's not going to be much meat left on it. The bush in the diagram has an OD of 10mm (I think) and an I.D of 8mm so that means the hole is also about 10mm in diameter. We'd need to ream that out another 2mm, so that collar will lose another 1mm in thickness all the way around. I'm not sure what the thickness of that collar is though.

    Click image for larger version. 

Name:	Screen Shot 2019-06-12 at 11.36.44 am.png 
Views:	4 
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ID:	14840

    I'll take your recommendation and contact bmarler and see what his experiences were with having this done.

    Thanks for the tip and the link to the bearing!

  9. #59
    Legendary Lancista Marnix's Avatar
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    Re: Carb Upgrade - S3 Fulvia

    bmarler has been doing the same as I have been doing. He contacted me and we discussed the modifications outside the forum, as it was a bit too specialized. He is a nice guy, so you can contact him for sure about his experience.
    Lancia Fulvia 2C 1964
    Lancia Fulvia Coupe Rallye 1,3 1968
    Porsche 924 1979
    Alfa Romeo 33 1.4IE 1993

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    Re: Carb Upgrade - S3 Fulvia

    Quote Originally Posted by Marnix View Post
    That's a long post. I will take some time later to reply to several issues being brought up.

    Let me start by getting a few common misunderstandings out of the way:


    - the Dellorto do not offer an improvement in engine performance. Actually, if you compare the jetting (with a few small changes due to slightly different internal carb setup) the Dellorto setup for the 1.2, 1.3 and 1.3S are about "copy-cat" of the Solex configuration (for example 26mm venturi for the Solex C.32 and the Dellorto DHLB32; 29mm solex - Dellorto for the 302 engine; 31 mm for the Solex - Dellorto for the 303 engine). The jetting is slightly different, but not that much, and gives about the same engine performance / characteristics. The reason to put in Dellortos instead of Solex carbs is NOT to have better perfomance, but reliability. I should maybe explain the different strategy: Solex was producing carbs CHEAP. They are not designed to last "for life". If worn, just throw the old ones away and put in new ones (it is the sixties, the throw away area; they are cheap anyway, and Lancias are (were) expensive cars, so the owners didn't mind much paying for a new set (not many working hours either). Dellorto made their carbs "bullet-proof", to last for life: their engineering is superb compared to Solex. If I would be Lancia, and have to buy lets say 100000 carb sets, would I buy the cheap from Solex or the expensive from Dellorto? Actually, my personal experience is my 302 engine runs better (smoother) on the Solexes than on the Dellortos (that is, Solexes rebuild to new, not worn ones).
    - a common mistake is to compare venturies by their diameter; actually, it is the SURFACE that counts (but to make it easy they are always specified in diameter). So a 29mm venturi is a lot larger than a 26mm venturi despite being only 3mm larger in diameter.
    - Ed is right in saying that the relation venturi diameter versus throttle opening behind the venturi is important. I didn't try it, but you could maybe go for a compromise, and put in a 28mm venturi (larger than the 1.2 26mm, and smaller than the 28mm of the 1.3)
    the DHLB35 was exclusively made by Dellorto for the Fulvia; the DHLB32 was made for a number of different cars (the Fulvia 1.2 but also Fiat), and comes in different versions. The non-Fulvia DHLB32 are NOT really suitable for the Fulvia (there are a number of significant differences, and it would be quite hard to make them suitable for the Fulvia. I am not sure why the DHLB32 you found are cheaper than the DHLB35, if bothe would be the version for Fulvia (and not the DHLB32 for non-Fulvia). My experience is that it is even harder to find FULVIA DHLB32 than DHLB35, and that they cost about the same. Most DHLB carbs need some refurbishing, but the good news is, them being bullet-proff, most can be easily brought back to near-new state.
    - there is a number of known problems with te Solex carbs. Spindle wear is one of them. About all these issues can be cured if done professionally. I bring back Solex carbs to new, along the way dealing with some of the weaknesses of the Solex carbs. It pbrings them up to Dellortto standards... unfortunately, also to Dellorto proce range.
    - apart from "sucking-the-sucker" in downloads, there is another part I wrote about carb theory (only one part available yet). It is really a simplified explanation to give people some basic understanding. It may be worth reading the section in it about choke (venturi) size effects. I fact, venturi size is a compromise really. small size gives good low RPM performance, at the cost of high RPM power. Big size gives greater high RPM power, at the cost of low RPM performance. While the text gives a simplification, it gives some basic insight in why this would be so.
    Thanks for that reply Marnix.

    I'm not sure why the DHLB 32's are being offered cheaper than the DHLB 35's. They were actually amongst a box of of other stuff that he'd kind of forgotten he had. He only remembered after we'd been talking about the DHLB 35's a while. He just said "Oh, and I've got these too, but you're probably not interested". He seems to be of the impression that the DHLB 35's he's got are worth their weight in gold but that the DHLB 32's aren't really worth much.

    The first thing I did was jump on this forum where I came across your posts about the Fiat DHLB 32's not being interchangeable with the Fulvia ones, so I took your advice and checked for the vacuum pipe that sticks up at 45 degrees on the Fiat units but is absent on the Fulvia ones. They looked like a matched pair so I already suspected they were the Fulvia ones (as you say, the Fiat ones were used as singles), and sure enough the holes for those vacuum advance pipes is blanked off on the casting (no hole, just a dimple in the casting where the hole would go if it was a Fiat variant).

    Fulvia
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    Fiat
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    Plus, they've got the tags etc and look identical in terms of tarnish colour and wear. They're definitely twins.

    About your suggestion of trying a 28mm venturi, the Dellorto UK guys have been giving this topic some thought too and came back with the same suggestion. Their final verdict was to play around with 26mm, 27mm and 28mm.

    About your observation on the size of the venturi (not I.D) and the surface of it being important; I'm not quite sure what you mean:

    "- a common mistake is to compare venturies by their diameter; actually, it is the SURFACE that counts (but to make it easy they are always specified in diameter). So a 29mm venturi is a lot larger than a 26mm venturi despite being only 3mm larger in diameter."

    You may have to walk me through that one. I'm eager to know what you mean though; I'm just having trouble seeing it in my head. It's probably staring me right in the face though...

    I'll have a look at your other article in downloads about the fundamentals of carbs tonight; I'm looking to reading that.

    I also came across another post by you explaining that butterflies scraping against barrel walls in my series of carbs (PHH C35) isn't so much due to wear around the shafts as it is due to sideways (horizontal) play in the shaft. You also mentioned that you rarely see wear around the throttle shafts in my series of carb because there's a Teflon bush in there that doesn't tend to wear down.

    If that's the case, maybe I'm worrying unnecessarily about the wear around the throttle shaft and should instead focus on eliminating sideways (horizontal) play in the shaft (I think you say it's because the way the centre spring pulls and it can be rectified with shim washers).

    Even if that's the case, I'll still keep trying to get to the bottom of whether DHLB 32's can (theoretically at least) be used on a 1.3 with satisfactory results (We've already come this far; can't stop now!).
    Last edited by halejustin; 18th June 2019 at 11:25 PM.

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