Twin carb 504 replace with earlier setup
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  1. #1
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    Default Twin carb 504 replace with earlier setup

    I have a 77 504 with the dreaded twin carb setup. What's needed to replace this setup with the earlier single carb set up? I am told that it's easier to keep in tune and to maintain. Would I need new manifolds and/or linkages as well? What might the costs be, and are there any technical problems in this conversion?

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  2. #2
    1000+ Posts Wildebeest's Avatar
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    Default Twin carb 504 replace..

    Quote Originally Posted by BarryC
    I have a 77 504 with the dreaded twin carb setup. What's needed to replace this setup with the earlier single carb set up? I am told that it's easier to keep in tune and to maintain. Would I need new manifolds and/or linkages as well? What might the costs be, and are there any technical problems in this conversion?
    Barry,
    This is a very satisfying conversion for a 504 owner to carry out.
    The main and obvious bits required will be a carb. The Weber 32/36 DGAV from a 2litre Cortina is the popular choice. For a manifold, the 3 port head manifold, Solex type. Buy a new inlet manifold to head gasket.
    The choice of air filter is all yours. The easy way is the "sports" type, good for keeping out small birds and stones and providing an asthmatic intake sound. Your RWC man may frown on this. To keep some originality I would and have, gone for the late 504, early 505 dry element type. The cap that sits on top of the carb can be fettled to suit.
    Shop around for the bits at auto swaps or wreckers, it shouldn't be too ex.

    The original accelerator cable drum or one from an auto carb will fit onto the Weber throttle shaft, pack out with washer/s if it fouls the Weber linkages. The Peugeot accel. outer cable might utilise the existing bracket otherwise some fabrication will be needed. If its an auto it will need same for the kick down cable. If the Weber has a manual choke, bonus! Otherwise you could adapt the ugly heated auto choke. I always bin this and go "sans strangler"
    or fit a choke conversion. try and get a cable operated one, the electric type will cost more than your whole conversion ! A good idea at this stage would be to fit a new accelerator cable. Don't shorten it until the final assembly!

    Get hold of a gasket kit including float needle assembly and a fibre insulating spacer for between the carb and manifold. Clean the carb before dismantling with carby cleaner or thinners. Carefully dismantle,"OBSERVE", clean out jets and passages. The jetting etc for the Cortina will be as near as sh#t is to swearing suitable for the 504. The only jets accessible from outside the carb are the idle jets. After cleaning reassemble the jets, before refitting pull the idle jets slightly out of their holders. This will allow them to seat in the carb body. I always carry out a modifiication to the fuel hose fitting. These have been known to drop out causing fires. Pull this fitting from the carb and replace with a 1/8 BSP to 6mm tail fuel fitting. A 1/8 BSP tapered thread tap will fit the hole vacated by the original spout. Finish the hole with a !/8 BSP intermediate tap. Screw in the fitting with some thread tape, voila!

    Remove all the old carb and manifold also the EGR valve and plumbing. Do a tidy job of blanking off the old 'oles so as not to offend your RWC man.
    Some rearranging of heater hoses will be necessary. The ones no longer needed can be capped at the water pump or manifold with caps from auto accessory shops
    Fitting the manifold and carb should be straight forward.
    Tuning the finished job should be as per most carbs. You'll be pleased with your work.

    PS I read somewhere that the 504 twin or tandem carb setup was fitted to cope with American emmission laws of the day. Obviously they didn't give a toss what happened as the "newness" wore off.
    Last edited by Wildebeest; 12th December 2004 at 01:46 PM. Reason: Add text

  3. #3
    Budding Architect ???? pugrambo's Avatar
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    if you can get one get an early 504 air cleaner

    you can then cut the rubber boot to suit the weber and then make a plate to hold it in place

    the other bonus with this is it is an oil bath setup which is prefered to keep the crap out of the engine and it has a nice snorkel arrangement that forces air into it

    i did exactly this on a 604 once and i am still on the hunt for another one so i can do the same again

    i have also converted a few 504's over the years to the weber and they make the car easier to live with rather than the twin card setup

    just make sure when you get a weber that it has the fuel bowl facing towards the front of the car when it is mounted otherwise you are going to run into trouble

    2L cortina/escort
    chrylser centura 2L but these are getting rare in wrecking yards now
    ford falcon but it will need rejetting

    electric chokes are fine but they don't shut off till you touch the pedal so as the car is sitting idling and it warms up the revs pick up

    i prefer a water choke or manual myself even though i have an electric one on the 604 albeit disconnected

    the car still starts in winter but it needs to be sat in to hold revs up a little till it warms up enough for it to idle

    not a big problem unless you are in an absolute hurry
    3 x '78 604 SL

    1 x 2018 3008

    1 x 2000 Citroen XM,

    1 x '98 306 GTi6 sadly sold

    1 x secret project

    1 x '98 406 STDT troop carrier and i don't care if it stinks, i don't sniff it's arse Death by wank tank

    1 x '99 406SV 5spd wagon, time to burn more fuel

    1 x 1994 605 SV3.0

  4. #4
    1000+ Posts Wildebeest's Avatar
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    Default Twin carb 504 replace..

    Quote Originally Posted by pugrambo
    if you can get one get an early 504 air cleaner

    you can then cut the rubber boot to suit the weber and then make a plate to hold it in place

    the other bonus with this is it is an oil bath setup which is prefered to keep the crap out of the engine and it has a nice snorkel arrangement that forces air into it

    i did exactly this on a 604 once and i am still on the hunt for another one so i can do the same again

    i have also converted a few 504's over the years to the weber and they make the car easier to live with rather than the twin card setup

    just make sure when you get a weber that it has the fuel bowl facing towards the front of the car when it is mounted otherwise you are going to run into trouble

    2L cortina/escort
    chrylser centura 2L but these are getting rare in wrecking yards now
    ford falcon but it will need rejetting

    electric chokes are fine but they don't shut off till you touch the pedal so as the car is sitting idling and it warms up the revs pick up

    i prefer a water choke or manual myself even though i have an electric one on the 604 albeit disconnected

    the car still starts in winter but it needs to be sat in to hold revs up a little till it warms up enough for it to idle

    not a big problem unless you are in an absolute hurry
    Your final comment is a bit of contradiction in terms. 504 and hurry mmm?

    Your sideways carb comment reminded me of one our salesmen who got me to look at a Pajero that had been converted to Weber. The problem, it had an enormous flat spot and would "nod its head" when accelerating. Problem, the Weber had been fitted back to front! Of course they didn't want to spend money on it. Sound familiar!

  5. #5
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    I run 2 sets of triples. eg 6 carbys on my early 911, cause thats the way Dr Porsche designed it. I will admit finding a good carby mechanic is not easy, but when you do, you realise why that set up was used.
    If it came out of the factory with 2 carbys, there must be a reason. You don't think just 1 carby won't fall out of tune?
    I had mine rebuilt, and I tell you what, it made a vast improvement. I had jets which had been soldered over, others that had been drilled out, a float which had collapsed etc etc. When my carby man rebuit them he left nothing to chance eg you get a jet marked '50' - don't assume it is still such as someone may have filled & redrilled to a smaller or larger diameter. Measure all jets to make sure they are what is stated - even when new jets are used - some spare part departments do make mistakes. As for going 'out of tune' my seat of the pants experience tells me that 4,000kms down the track, they are just fine.

  6. #6
    1000+ Posts edgedweller's Avatar
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    T'was never the case for the twin carb 504's, whose reputation for inducing alcoholism and insanity is legend. Definitely to do with counting the parts in the spare parts bin, while trying to give a bit of extra ooomphh to the Sludgebox 04. Just going back to the standard, twin throat solex was a relief, having gone down the path you suggested and getting it right with the notorious Rover 2000 TC, that set up on a Pug was more than I could stand.

    Cheers ed ge

  7. #7
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    Quote Originally Posted by 911s
    I run 2 sets of triples. eg 6 carbys on my early 911, cause thats the way Dr Porsche designed it. I will admit finding a good carby mechanic is not easy, but when you do, you realise why that set up was used.
    If it came out of the factory with 2 carbys, there must be a reason. You don't think just 1 carby won't fall out of tune?
    I had mine rebuilt, and I tell you what, it made a vast improvement. I had jets which had been soldered over, others that had been drilled out, a float which had collapsed etc etc. When my carby man rebuit them he left nothing to chance eg you get a jet marked '50' - don't assume it is still such as someone may have filled & redrilled to a smaller or larger diameter. Measure all jets to make sure they are what is stated - even when new jets are used - some spare part departments do make mistakes. As for going 'out of tune' my seat of the pants experience tells me that 4,000kms down the track, they are just fine.
    Yes, nothing at all wrong with the twin carb setup, the problem was in the rest of the system, sticking EGR valve for example.
    Carbs don't go out of tune, SUs excepted. The only problem you may find is that the primary carby has a worn spindle preventing correct idle speed.
    If you convert to a single twin choke the early 504 is the best thing to use, I've yet to see a Weber work well in this application, these carbies are usually designed for a completely different application and more often than not put on the wrong way around.
    The primary barrel must be on the outside so it goes through the correct inlet channel in the manifold, this may mean the carby is back to front in terms of the float chamber needing to be on the front.
    Graham

  8. #8
    1000+ Posts Wildebeest's Avatar
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    Default Twin carb replace..

    Quote Originally Posted by GRAHAM WALLIS
    Yes, nothing at all wrong with the twin carb setup, the problem was in the rest of the system, sticking EGR valve for example.
    Carbs don't go out of tune, SUs excepted. The only problem you may find is that the primary carby has a worn spindle preventing correct idle speed.
    If you convert to a single twin choke the early 504 is the best thing to use, I've yet to see a Weber work well in this application, these carbies are usually designed for a completely different application and more often than not put on the wrong way around.
    The primary barrel must be on the outside so it goes through the correct inlet channel in the manifold, this may mean the carby is back to front in terms of the float chamber needing to be on the front.
    Graham
    Graham,
    I "dips me lid" in deference to your correct carby mounting theory. The Solex on the 3 port 504 manifold has its primary throat on the outside, having a more direct passage theoretically to the centre port in the head. The secondary carb throat feeds the larger ports in the head The carb mounting flange on the manifold bears this out.

    On the later 504/505 "square port" manifold, it is more open with no individual passages. The Solex fitting on these models also have the primary throat on the outside. Checking the carb mounting flange on this manifold will show the smaller primary hole on the inside contrary to the Solex carb.
    With this manifold/head layout the Weber conversion does work ok.
    With the 3 port manifold it may be more suited to an original Solex fitting.

    Theory can be a strange thing, engineers will insist that a job be done by the book and when their backs are turned the workers will do it their way usually with success.
    With the Weber conversions that I've done on both 3 port and square port they have been OK. Performance and economy as good as or better than the Solex. The big bonus is in their simplicity and easy to tune and they can be mounted with float bowl to the front.
    The conversion I did on my own '79 504 cost less than the replacement of the choke heater hoses!

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