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  1. #1

    Default What is the correct secondary diaphragm for 4180 carb?

    According to the Holley master parts list, the correct secondary diaphragm for my 4180 carb is #35R-235A. When I search for this part number, Holley says it's the same as #135-4 which is used on the standard 4160 carbs. I have a #135-4 and it is too short. Even with the longest spring there is not enough preload to close the secondaries.

    Comparing the 4180 carb side-by-side with a 4160 it looks like the diapragm rod needs to be nearly 1/4" longer due to the thicker throttle body on the 4180. I haven't been able to find anyone who sells a 4180 secondary diaphragm outside of a kit, and I don't want to buy a whole kit just for the diaphragm.

    Assuming the kits have the correct diaphragm, someone must still be making them. Does anyone have a source or alternate part number that I can check?

  2. #2

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    I don't see one listed by itself at the Holley web site at all. I did find a Walker # for the 4180's vacuum secondary diaphragm though, of 64-197. It shows it's stem length, from the diaphragm's flat steel to the very end of the stem is 2.288". Yes, there would be an approximate 1/4" difference because the Holley 135-4 says it's only 2.054" on the web site.

    Walker Holley carburetor parts PDF catalog: http://www.walkerproducts.com/wp-con...del/holley.pdf
    (PDF pages 34, 35, and 42)


    https://buy.walkerproducts.com/carbu...omponents.html

    If you click on 64-197, it says it's $5.92...
    Last edited by Walking-Tall; 10-16-2016 at 10:17 PM.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  3. #3

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    I spent hours searching around and it is very confusing because people measure them two different ways, either to the end of the stem or to the center of the hole (which makes more sense). Unfortunately, the Walker part you listed is the same as the 135-4 (Holley measures to the center of the hole).

    These are the measurements I've been able to dig up for Holley diaphragms;

    135-2 ~ 64-170 = 1.875" center hole, 2.047" to end
    135-3 ~ 64-236 = 1.969" center hole, 2.135" to end
    135-4 ~ 64-197 = 2.054" center hole, 2.288" to end

    There is, or at least WAS, a 135-11 diaphragm but I haven't been able to dig up any information on it.

  4. #4

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    Yeah, Holley shows the -11, and doesn't say anything technical about it.

    What's up with your diaphragm? Did it tear?

    I know you said, understandably, about not wanting to have to buy a kit for one, but, there's this...
    http://www.ebay.com/itm/Holley-4180-...oAAOSw2s1U1rA7
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  5. #5

    Default

    Quote Originally Posted by Walking-Tall View Post
    What's up with your diaphragm? Did it tear?
    I never had the right one. Someone tried rebuilding this 4180 with a 4160 kit and, yes, they did tear the [wrong] diaphragm very badly.

    The only parts I needed off of this carb are the throttle body and secondary diaphragm. I'm actually building a hybrid carb using a 4180 throttle body on a "reverse-idle" 4160. The "idle" screws on the reverse-idle carbs control both the curb idle AND transfer slots. Normally, they don't work that well because you have to compromise between best transition and best idle. But, when you stick a 4180 throttle body on it you can set the curb idle independent of the transfer slots. No more drilling out idle feed restrictions, silky smooth transition can be had with the turn of a screw.

  6. #6

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    Hmmm, now I'm even more confused. The parts list for the 6619 "reverse-idle" carb that I'm building shows that it too uses the 35R-235A diaphragm. It also shares the same part number for the lever on the throttle shaft (63R-354A) as the list-50003 carb that I robbed the throttle body from. The mounting hole spacing for the diaphragm housing screws are identical between the two main carb bodies. The throttle shaft on the 4180 does sit considerably further down in the throttle body so something has to be different to make up the difference. The only thing else that could be different is the diaphragm housing. The two I have are the same but considering how my 4180 was butchered with 4160 parts it is possible that I don't have the correct 4180 housing.

    Does anyone out there have both a 4180 and a 4160 [that have not been molested] and can compare them side-by-side to see where the differences are?

  7. #7

    Default

    Quote Originally Posted by mrriggs View Post
    I never had the right one. Someone tried rebuilding this 4180 with a 4160 kit and, yes, they did tear the [wrong] diaphragm very badly.

    The only parts I needed off of this carb are the throttle body and secondary diaphragm. I'm actually building a hybrid carb using a 4180 throttle body on a "reverse-idle" 4160. The "idle" screws on the reverse-idle carbs control both the curb idle AND transfer slots. Normally, they don't work that well because you have to compromise between best transition and best idle. But, when you stick a 4180 throttle body on it you can set the curb idle independent of the transfer slots. No more drilling out idle feed restrictions, silky smooth transition can be had with the turn of a screw.
    Good idea, in essence creating adjust-ability, or variability of idle feed restrictions and idle air bleeds. Both of the rich/lean idle circuit maximums would still be dictated by the sizes of the internal idle feed restrictions (that are usually in the less than desirable upper location between the main and idle wells in a "reverse-idle" metering block, and I would relocate those down to the old-school location if possible, and/or remove the uppers and size lowers good and large, or do nothing else after uppers removal, so that the idle mixture screw settings in the 4180 base plate become the dictating area flow restriction for curb idle discharge) and the idle air bleeds though, unless those four restrictions are eliminated, leaving just their open channels, so that all air:fuel delivered to the primary curb idle discharge ports and transfer slots becomes the sole job of the 4180 mixture screws for curb idle discharge and the "reverse-idle" metering block's mixture screws for the transfer slots. So, I would say, yeah, no more precision drilling out of idle feed restrictions. I think you could probably eliminate the idle feed restrictions from the "reverse-idle" metering block and the primary idle air bleed restrictions from the carburetor's main body in this circumstance. Good luck with it, and I'd love to hear about how you make out with this hybrid. It should work real good.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  8. #8

    Default

    If you're able to do or get some fabricating done, the diaphragm stem could be extended and then a hole drilled where it's needed...
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  9. #9

    Default

    Quote Originally Posted by Walking-Tall View Post
    Both of the rich/lean idle circuit maximums would still be dictated by the sizes of the internal idle feed restrictions ..
    Yes they are but I'm nowhere close to exceeding what the feeds can deliver. Seems to run well with the air screws 1-1/2 turns out and the curb screws 2 turns out. I just got it on the road so I'm still playing with it.

    Before I swapped to the 4180 throttle body, I had to have the air screws at 1/4 turn out just to get it to idle which left it feeling very fat and lazy on transition.

    If you're able to do or get some fabricating done, the diaphragm stem could be extended and then a hole drilled where it's needed...


    This may be what I end up doing.

  10. #10

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    Awesome. Amazing how an engine acts so much better when these things get nicely dialed in, eh?

    Yup...
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  11. #11

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    Here's a very good and directly to the point conversation (and a link out to a NACA paper) regarding proper, best carburetor idle feed restriction "old school" lower location.

    http://racingfuelsystems.myfunforum....about1338.html
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  12. #12

    Default

    Quote Originally Posted by mrriggs View Post
    According to the Holley master parts list, the correct secondary diaphragm for my 4180 carb is #35R-235A. When I search for this part number, Holley says it's the same as #135-4 which is used on the standard 4160 carbs. I have a #135-4 and it is too short. Even with the longest spring there is not enough preload to close the secondaries.

    Comparing the 4180 carb side-by-side with a 4160 it looks like the diapragm rod needs to be nearly 1/4" longer due to the thicker throttle body on the 4180. I haven't been able to find anyone who sells a 4180 secondary diaphragm outside of a kit, and I don't want to buy a whole kit just for the diaphragm.

    Assuming the kits have the correct diaphragm, someone must still be making them. Does anyone have a source or alternate part number that I can check?
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  13. #13

    Default

    I couldn't dig up the specs for the 135-11 diaphragm so I took a chance and ordered one. It's definitely not long enough. In fact, it's exactly the same as the 135-3.

    It's odd that Holley would sell the same part under two different part numbers. What I received appears to be a genuine Holley factory sealed blister pack so I'm assuming that this part is legit. Maybe it was just labeled wrong at the factory and actually is a 135-3? Maybe the listed specs for the 135-3 were actually the specs for the 135-11? Or maybe they ARE the same part and that's why Holley discontinued the 135-11?

    Oh well, it doesn't really matter because it's not gonna work anyway. I think the 135-2 is my best option. It's short enough to accommodate a "bolt on" extension.

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