Carb Jetting/ Venturi Sizing on Renault 688
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Thread: Carb Jetting/ Venturi Sizing on Renault 688

  1. #1
    Tadpole
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    Default Carb Jetting/ Venturi Sizing on Renault 688

    Hi guys,

    I have a 1969 Simca 1000(called the 1118 here in the states) and a 1967 R10. I am fitting a Dellorto 40 DHLA to it and Im wondering if you guys might have an idea of where to start with the venturi/jetting. I have 28mm chokes in there now. Cheers from California!

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  2. #2
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    Very nice car but I cannot help with those carbs.

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    Fellow Frogger! Shoji's Avatar
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    Yes very nice. Is that R10 with the round eye lights?

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    Yes. I think thats the only version we got in the states? and thanks!

    Quote Originally Posted by Shoji View Post
    Yes very nice. Is that R10 with the round eye lights?

    Sent from my Moto G Play using aussiefrogs mobile app

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    1000+ Posts Frans's Avatar
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    Hi Godzilla, good looking car you have there!!

    I think that the 28 mm chokes will be too small. The only base to work on that I can give you is for twin SD Carbs on the 1400cc.
    There we use in general 32 chokes 110 - 120 main jets and 180 - 200 Air corrections.

    You will have to adapt to the single SD carb from there. Only thing that I am sure of is that the 28 chokes will be too small for feeding 2 cylinders when we are using 32 chokes to feed a single cylinder.

    Regards, Frans.
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    Very nice R10 - thanks for posting here! Good luck with the jetting - I have no idea I'm afraid.
    JohnW

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    COL
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    Get a copy of John Passini's Weber Carburettors.

    There are two books the orange one with the theory and the green one with the Tuning & Maintenance.

    I think the green one has the information in it that you require.
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    Regards Col

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    Thanks for the tips! I just ordered a used copy of the green book. I welded in an O2 bung as well for my wideband. It would intrest me to see how the jet and venturi sizing changes mixture in realtime. Ive been doing megasquirt/EFI stuff untill I bought this car. Ill let you know how it goes.

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    Hi
    Just a comment. You cannot just decide on a choke size for that application without some more consideration of what is the state of tune, cam, head work etc. The rev range required and the tractability needed. Basic things to consider first. The jetting follows but will need to be adjusted as needed to get it perfect. The O2 sensor will be your guide if you know which jet controls what !!

    I notice the discussions on here sometimes assume the owner wants a race car for the road. Good if that is what you want, but some people may like a quick sports car with less hassels and more fun. Your choice if you select wiseley. Just saying !!!
    Jaahn
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  10. #10
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    Quote Originally Posted by jaahn View Post
    Hi
    Just a comment. You cannot just decide on a choke size for that application without some more consideration of what is the state of tune, cam, head work etc. The rev range required and the tractability needed. Basic things to consider first. The jetting follows but will need to be adjusted as needed to get it perfect. The O2 sensor will be your guide if you know which jet controls what !!

    I notice the discussions on here sometimes assume the owner wants a race car for the road. Good if that is what you want, but some people may like a quick sports car with less hassels and more fun. Your choice if you select wiseley. Just saying !!!
    Jaahn
    I agree. I dont have any other modifications to the motor, so I am really trying to keep everything a bit conservative.
    Anyway, I have it tuned a bit. It is driveable and pulls well. Its starts right up when cold as well. I have not yet hooked up the O2, so it will be interesting to see how far off the mark I am currently. I have not done a hot, rush hour commute with it yet, so I will see how the motor does without the tins underneath. Anyone run the tins with a header for road driving here?
    I also sourced a turbo muffler that I fit on the meca header.

    Carb Jetting/ Venturi Sizing on Renault 688-img_1456.jpg
    Carb Jetting/ Venturi Sizing on Renault 688-img_1457.jpg

    Here is a video of the sound. the forum is currently not allowing me to link this:
    https://youtu.be/lXyN9gvEplI

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    Yes I have headers and use the trays. I cut part of a new hole to fit dual pipes and covered part of the old hole with a plate and a few small 5mm bolts with lock nuts. (I always use metric bolts so as to keep the tools I have to carry to a minimum). I could not use pop rivets as I need to remove the plate to get the tray off.

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    Hi, I never use the trays in the engine compartment and have never had any problems.
    I notice you have an exhaust hanger attached to the bumper bracket. I is usual to attach the exhaust bracket to the cross member so that the exhaust moves with the engine, so preventing cracking of the headers.
    It looks like you have a very nice car.

    Henry
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    One for and one against the trays. I'll just keep them around for when/if I have any overheating issues. Thanks for the kind words! The exhaust is isolated with a stainless woven flex joint before the muffler and with rubber donuts after. We'll see if it stays together.


    Quote Originally Posted by rubyalpine View Post
    Hi, I never use the trays in the engine compartment and have never had any problems.
    I notice you have an exhaust hanger attached to the bumper bracket. I is usual to attach the exhaust bracket to the cross member so that the exhaust moves with the engine, so preventing cracking of the headers.
    It looks like you have a very nice car.

    Henry

    Took the car out to the abandoned naval base on the island and tuned it a bit more. Tweaked the timing and the accel pump shot.
    Carb Jetting/ Venturi Sizing on Renault 688-img_0099.jpg

    Carb Jetting/ Venturi Sizing on Renault 688-img_0103.jpg
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    1000+ Posts renault8&10's Avatar
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    Looks very nice, and by the sound of it you already have the tune nailed. If it starts cold and no flat spots - that's a win in my book.

    I've also run a hot R10 with a 1.4 engine without trays and not had any cooling issues. I ran a VDO electronic gauge and the car used to sit at 80C all day even in summer with our 40C days. (that's over 100 in your scale!). My engine has had two incarnations, a single 45mm DCOE sidedraft weber with a mild cam; then twin 45DCOE's and a race cam with extractors. The cooling remained the same in both cases.

    KB
    KB


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    Also turning up to say what a nice dam car!

    Works: 1999 Volvo S40 T4, (has Choo Choo's)
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    I like your car. It has a nice stance with the lowered suspension.

    Why the indicators on the bumper? Is that a USA thing or your own liking?

    Frans.
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    Young enough to do it anyway.

  17. #17
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    Haha no I really dont like those. And the overriders on the front bumper. those are standard on US spec cars. Also the clear lenses on the sides of headlights are a US thing from what I understand.

    I would like to shave some bits from the front to make it a little less "busy"

    Quote Originally Posted by Frans View Post
    I like your car. It has a nice stance with the lowered suspension.

    Why the indicators on the bumper? Is that a USA thing or your own liking?

    Frans.

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    Quote Originally Posted by renault8&10 View Post
    Looks very nice, and by the sound of it you already have the tune nailed. If it starts cold and no flat spots - that's a win in my book.

    I've also run a hot R10 with a 1.4 engine without trays and not had any cooling issues. I ran a VDO electronic gauge and the car used to sit at 80C all day even in summer with our 40C days. (that's over 100 in your scale!). My engine has had two incarnations, a single 45mm DCOE sidedraft weber with a mild cam; then twin 45DCOE's and a race cam with extractors. The cooling remained the same in both cases. KB
    That cooling result makes me ponder a bit... I have the old two-row core, the four-blade fan and the small top hose, and mine definitely goes up to 90 degrees on a hot day, with a new gauge and matched sender so I suspect it is right. When I get around to the R10 1300 motor, I'd perhaps better upgrade. you won't be surprised that I have all the bits..... it might be that just fitting a high capacity water pump, now we can get them easily, would be enough of a jolt but changing the pump just makes the other stuff easy to fit anyway.
    JohnW

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    Quote Originally Posted by Godzilla View Post
    Haha no I really dont like those. And the overriders on the front bumper. those are standard on US spec cars. Also the clear lenses on the sides of headlights are a US thing from what I understand.

    I would like to shave some bits from the front to make it a little less "busy"
    Please don't remove anything. You have a unique R10!
    I had those wheels on a XY Falcon. Neat
    Agree with Frans. Sits very nice
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  20. #20
    1000+ Posts renault8&10's Avatar
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    Quote Originally Posted by JohnW View Post
    That cooling result makes me ponder a bit... I have the old two-row core, the four-blade fan and the small top hose, and mine definitely goes up to 90 degrees on a hot day, with a new gauge and matched sender so I suspect it is right. When I get around to the R10 1300 motor, I'd perhaps better upgrade. you won't be surprised that I have all the bits..... it might be that just fitting a high capacity water pump, now we can get them easily, would be enough of a jolt but changing the pump just makes the other stuff easy to fit anyway.
    I use an R8/10 pump on an R12 housing (with one of the ports blanked). There was nothing special about my radiator other than being re-cored with a triple core centre, with the standard top and bottom tanks. Next time I might try one of those eBay chinese alloy rads. The fan, panel, bottle etc all remained standard and in the standard position.

    KB
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    KB


  21. #21
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    Quote Originally Posted by Godzilla View Post
    Yes. I think thats the only version we got in the states? and thanks!
    I thought you also had the "square" eye version (which is really rectangular) with the 1300 engine?

    US design rules at the time dictated rules about different bumpers and indicators which affected a range of imported cars, not just renaults. For example, a lot of the european cars with large trapezodial headlights had to convert to twin round headlights - think mercs, BMW's and the like.
    KB


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