Distributor Diaphrams

[HondaBoy]

ok, just so you know i've had the vacuum removal process done for a while now. i was wondering if the vacuum advance and retard are of any use now? i have the advance diaphram hooked up and doesnt cause any problems or anything, but was just wondering would it even make a difference if i take the vacuum off it? its connected to what was the secondary opener vacuum port on the carb so its on active when the throttal is pushed most of the way down. anyone have something to add on this? also need to hook up a vacuum gauge so i can see where things are while im driving.

[A20A1]

what?

the secondary vacuum is not intake manifold vacuum.

It's venturi vacuum

which means you're going backwards with the advance diaphragms operation.

it's supposed to run on intake manifold vacuum that way as throttle is opened you drop intake vacuum and the spring in the diaphragm can do it's thing.


if you hook it up to venturi vacuum, the spring has nothing holding it back untill the throttle is opened and there is enough venturi vacuum to resist the spring inside the diaphragm.

Please check your ignition timing following the books proceedure, removing vacuum from the diaphragm and checking the timing, then connecting the diaphragm to the "intake manifold vacuum" and seeing if the timing changes are in spec.

#25 needs the thermovalve and #2 used direct manifold vacuum.

if you don't need #25 for cold start then just cap it off or leave it open on the diaphragm.

[A20A1]

get a vauum gauge... well two if you can afford it.

watch the difference between intake manifold vacuum and venturi vacuum at the secondary port.

[HondaBoy]

ah, so really i dont need to have any vacuum hooked up the the distributor anymore right?

[BITESIZE]

Your gas mileage will suck ass with the vacuum diaghram.

[HondaBoy]

you mean, gas mileage will suck ass with it connected? i'm always looking for ways to save a bit. so pretty much just plug that shit up and dont use it? i was wondering if the egr valve if connected to the secondary puller vacuum port would do anything or what. i've just wondered that for a while, but its not connected.

[A20A1]

well you'll be sucking farts everytime you apply throttle. forget the egr for now.

[HondaBoy]

i took the venturi vacuum off the advance port and capped the vacuum port on the carb off. runs good.

[HondaBoy]

ok, so i wanted to get this strait. # 14 is supposed to be connected to the distributor advance as pictured in the link. but, my # 14 doesnt pull vacuum. and when the car is warmed up, i should have it be retarding the timing more so than advancing? i've never had a real strait answer with where to connect my distributor advance and retard diaphrams after doing the vacuum removal. more or less, i just want a vacuum port. i know the carb pretty well so front or back are a good discription when telling where the correct one is. i wanted to correct it the way it should be. i've read over and over the how to over the years and asked a few times but still nobody has a real answer. please help me out with a real answer. i'll probably get to this tomorrow if anyone actually knows what i need.
https://www.3geez.com/forum/showthread.php?t=11067

[A20A1]

#14 is the power valve that runs off or intake manifold vacuum, it shares the same vacuum tap that the diaphragm did... thats the only reason the DIS and #14 are on the same line.

[HondaBoy]

ah, well that still isnt an answer that helps me, but thanks anyway. i'll just ask my teacher since he can probably give me a good strait answer on what would be best to do. actually both my shop and body shop teachers are quite knowledgable with carbs so it wont hurt.

[A20A1]

#14 does not pull vacuum... #14 is a internal diaphragm inside the carb. It uses intake manifold vacuum.

There is only one place that the carb and the distributor connect to... follow the lines and you will find the intake manifold vacuum port.

The only thing that pulls vacuum is the port on the intake manifold that line #14 is connected to and since #14 is connected to the manifold, The distributor can use the same vacuum line to get vacuum, not from #14 but from the manifold.

[A20A1]

Just look at the diagram.... pretend #14 isn't there and you don't have a powervalve.... follow #2 to the intake manifold...

Any of the RED arrows are vacuum ports on the intake manifold... but I would use the vacuum port at the rear of the manifold next to the brake booster.

[2oodoor]

you mean, gas mileage will suck ass with it connected? i'm always looking for ways to save a bit. so pretty much just plug that shit up and dont use it? i was wondering if the egr valve if connected to the secondary puller vacuum port would do anything or what. i've just wondered that for a while, but its not connected.

I agree, I have not been able to find a direct answer to the same question. Why would having the vacuum advance working make your gas mileage "suck ass" . Every other make car I've worked with , the vacuum advance saves gas. What I am to gather is this diaphragm is a vacuum retard? I always used to set up cars with vacuum applied to dist advance at part throttle or just off idle, or ventried vacuum. Otherwords, vacuum is not applied to dist advance at idle. So I assume this engine does not work like that. My weber conversion is set up with manifold vacuum applied at idle, which goes against my previous experiences. I really rather have it connected to the port on the back of the carb. But which one is right. (using #2 vacuum port on dist, closest to the dist housing)
Also, speaking of webers, My fast idle screw does not hardley contact the fast idle cam, even screwed all the way in to compress spring. Best I know it is factory setup, but for mazda, still that should not matter, unless wrong screw was used to begin with.

[A20A1]

Did bitesize say diaphragm or diagram... the diagram makes the carb run without any extra air intake, so it'll run richer. I assume a little work on either the venturi or even the booster to get more air in and lessen the restricton you could lean things out more.

[HondaBoy]

that made things much more clear there. thanks mike for taking the time to work with me on this question. being you are the carb god and all

[HondaBoy]

well, connected distributor retard diaphram to #2 where you showed it in the pic. seems to work ayt. guess i'll keep an eye on my fuel mileage, but i'ma wanna be gettin on it all the time. you know how that goes. but yeah, thanks again. i need to get some new vacuum caps, hoses and some fitting. for now, its running great. reset timing after putting vacuum on the retard diaphram, seems to work well. i'll just have to give it a few days or so.

[2oodoor]

Glad you got your car a little better Honda Boy, I am still re reading the whole thread. Maybe I missed something, wouldnt be the first time.....

I am still, dazed and confused just a small amount. Talking to myself wondering why does the engine speed up with vac line put on the retard diaphragm. I will look the dist centrifrical advance how to. and then , dazed and confused , will go out and buy a chevy CRANE adjustable advance to see if some fab work will make it fit the Honda dist.
My car just will not stay the same every day, and it wants to diesel sometimes after I get it where it seems perfect., then I think, , maybe it was the cheap gas I just put in it. The baby is gonna need octane cuz the head has been shaved a good bit. Probably. Im getting 29mpg now average after two weeks city and interstate driving and tuning around with it, daily driver. It seems like its outta time (valve) some days.. just no guts.. but then my linkage disk where I cut it off the OEM carb is turned where it is not even getting close to opening secondaries right now, It will adjust correctley, there is plenty of adjustment,
I just want to leave it there for now to see how the 300K bottom end holds up for a few weeks. No that is BS, I just have not had a good day to reset it all back,

[nskforlife]

i have a question, is the egr valve the plug connected to the air box right before the plastic piece of tubing that runs to the pass. side fender?? Its No. 15
if so, could my car run without it, cause only the ground wires still intact on that plug, i didn't think anything of it so i let it be, what is this plug/wire, what does it do, and do i need to replace it???

[A18A]

i love this thread!! i must read through it properly when im fully awake

[A20A1]

No #15 is the hot air door diaphragm

The plug on the intake tubing is the intake temp sensor.

[HondaBoy]

as it shows in this picture, i have done the same. the distributor vacuum retard is now connected just like that, #2 follows from the distributor to the rear of the intake manifold. when the engine is fully warm, it runs best. most times of the years its warm, but right now its fairly cool and runs rough somewhat until warmed up.

[HondaBoy]

after doing this i now am getting about 27 mpg, mostly easy driving and highway. never have got close to that until connecting the distributor retard diaphram. so yeah, it is useful i now know. well more than i thought.