96 replies to this topic

[anassa]

There was some visible wear, i just put everything back together nice and tight, but when i was putting it back I just got some questions again.

Squareback when you put everything like the first posts on port capping did you also cap the the 3rd pic (1st post) where i circled the red cap? or did you leave that open?


Then for CRXfantic, or anyone that knows, i noticed on your devaced carb a piece was different, and i was wondering if it made a difference. Its the green circled piece, on mine you can see there is two ports and also on the middle back there is a little screw thing to adjust it or something.

Yours - green drawn part is how mine looks like. on the bottom right, the yellow is from before.. so ignore that.




Mine - circled in green, you can kinda see what I'm talking about.





I just want to make sure. Also you can tell that i cleaned the mani, i also tried to clean the carb up.

Edited by anassa, 04 July 2008 - 02:53 AM.

[DarkHand]

That's the AC booster diaphragm. When you turn on the AC, a solenoid gets voltage allowing vacuum to hit that diaphragm, which pulls up on the linkage and raises the idle speed. No need to cap it.

[anassa]

Finally I am done.


It idles a bit high ~ 1300, but it holds, no biggy, it runs right?


Some pics of how it looked when it was done:











Hope this thread will continue to be a help to anyone who intends to do a devac.


Oh and if anyone still has knowledge of certain things that made their devac easier please do share.

Edited by anassa, 20 July 2008 - 06:02 PM.

[Punjab]

on the back of the mani there is 4 pluggs that had lines off them dose it matter if you cap them or leave them open

[DarkHand]

on the back of the mani there is 4 pluggs that had lines off them dose it matter if you cap them or leave them open

If they're the big ports, you have to cap them. They lead right into the intake and are huge vacuum leaks If they're the little ports coming off the plastic thermovalves, they can be uncappeed.

[Punjab]

Yah the plastic thermovalves i was going to pull them out and replace them with alum. block off bolts

[DarkHand]

Yah the plastic thermovalves i was going to pull them out and replace them with alum. block off bolts

I was trying to do that too, but I looked everywhere and couldn't find a bolt with the right size threads. I even asked some custom fastener companies and no one could get them unless they were made custom and in batches of 1000. The thermovalves actually have a tapered thread for sealing purposes; DIN 906 pipe plugs are tapered the same way and would be perfect if anyone on the planet stocked them with M16 x 1.0 threads. Straight-cut threads should work with thread sealant though.

So instead of bolts I filled the holes in on a spare intake with lots of JB Putty. Haven't tested it yet, even though the stuff is very strong I'm worried about the putty failing one day and getting pulled into the engine.

[Captain Regular]

I've been thinking about doing this. My vacuum system has been victimized by the previous owner, and there are lines that have been rerouted and others that have been plugged with ball bearings, finding them has been a real pain. I already want to do a carb rebuild, and I'm thinking "While I have it off, I might want to clean this vacuum system up, too." But... What exactly does the devac DO? I read through this whole thread, and there seem to have been issues that were largely MASKED by the vacuum system (I think my vacuum system is CAUSING some of mine) but otherwise seems to simplify the whole engine. In a "normal" devac, what sort of impact can I see on MPG and power? Are there downsides to doing this, and what are they? I know one wrote that it HURT his MPG, but it seems he had other issues that caused that.

[DarkHand]

What exactly does the devac DO? I read through this whole thread, and there seem to have been issues that were largely MASKED by the vacuum system (I think my vacuum system is CAUSING some of mine) but otherwise seems to simplify the whole engine.

You're exactly right. The main benefits are a ridiculously simplified engine bay, and the elimination of many points of failure.

In a "normal" devac, what sort of impact can I see on MPG and power? Are there downsides to doing this, and what are they? I know one wrote that it HURT his MPG, but it seems he had other issues that caused that.

MPG typically goes down a little due to the fact that the carb runs more rich. The emissions equipment watches for some different conditions that make the carb run more lean or rich depending on the situation, and that goes away. The changes are bad for performance, but good for emissions. The devac keeps the carb in its natural state of 'rich', which is what brings down MPG a little.

The two biggest downsides are that you absolutely cannot pass emissions inspection in states like California or anywhere that does a visual inspection. Sniffer-only tests can be passed, but it's harder. Pull out all the stops and tricks that are out there when you go in.

The other is that the car can be a little harder to cold start. The choke isn't working exactly as it's meant to along with the vacuum throttle control. Some people have trouble, but starting a carbed car is never as easy as a fuel injected car.

As long as you live in an area where it's legal to do so, it's definitely a good idea on a car with a problematic carb!

[ydennek]

what did you do about that red hose sticking out?



What did you do with the Air Suction Pipe #16? I put the black box back on the end, is there a better option?


Did you tape up all the extra wire plugs/connectors , the ones that went into the emissions control boxes, what did you do with them?

Edited by ydennek, 02 October 2008 - 04:47 PM.

[Captain Regular]

You're exactly right. The main benefits are a ridiculously simplified engine bay, and the elimination of many points of failure.




MPG typically goes down a little due to the fact that the carb runs more rich. The emissions equipment watches for some different conditions that make the carb run more lean or rich depending on the situation, and that goes away. The changes are bad for performance, but good for emissions. The devac keeps the carb in its natural state of 'rich', which is what brings down MPG a little.

The two biggest downsides are that you absolutely cannot pass emissions inspection in states like California or anywhere that does a visual inspection. Sniffer-only tests can be passed, but it's harder. Pull out all the stops and tricks that are out there when you go in.

The other is that the car can be a little harder to cold start. The choke isn't working exactly as it's meant to along with the vacuum throttle control. Some people have trouble, but starting a carbed car is never as easy as a fuel injected car.

As long as you live in an area where it's legal to do so, it's definitely a good idea on a car with a problematic carb!

I'm not sure how "problematic" I'd call my carb. Well, I guess it's pretty bad. It runs rich NOW, I think whoever hacked the hell out of the vacuum lines before tried to devac it. I live in Florida, and we have NO inspections at all, so the devac wouldn't be a problem. I don't even know how functional (if at all) my vacuum system is in its current state, and I figured it would be easier to take it all out than to try and pinpoint however many problems it has.
If it runs richer normally, couldn't I simply adjust the fuel mix to be a little leaner?

[DarkHand]

I'm not sure how "problematic" I'd call my carb. Well, I guess it's pretty bad. It runs rich NOW, I think whoever hacked the hell out of the vacuum lines before tried to devac it. I live in Florida, and we have NO inspections at all, so the devac wouldn't be a problem. I don't even know how functional (if at all) my vacuum system is in its current state, and I figured it would be easier to take it all out than to try and pinpoint however many problems it has.
If it runs richer normally, couldn't I simply adjust the fuel mix to be a little leaner?

Sounds like a devac candidate to me then!

You can try adjusting the mixture screw, but don't forget that it only affects the idle mixture. The carb will run differently afterwards, so hold off on major adjustments until then. You may or may not need to rebuild the carb, but it's so much easier after a devac.

[squareback]

what did you do about that red hose sticking out?



What did you do with the Air Suction Pipe #16? I put the black box back on the end, is there a better option?


Did you tape up all the extra wire plugs/connectors , the ones that went into the emissions control boxes, what did you do with them?

The first red hose can be eliminated, but leave the end open. #16 connects to the exhaust manifold and should be disconnected there and removed. The leftover connectors can be taped up if you like, but I think most people let them hang. No matter.

[ydennek]

The first red hose can be eliminated, but leave the end open. #16 connects to the exhaust manifold and should be disconnected there and removed. The leftover connectors can be taped up if you like, but I think most people let them hang. No matter.

Thank you so much for responding. When i remove Air Suction Pipe(16) should i pug the hole on the exhaust manifold and if so what should i plug it with?

[Captain Regular]

Sounds like a devac candidate to me then!

You can try adjusting the mixture screw, but don't forget that it only affects the idle mixture. The carb will run differently afterwards, so hold off on major adjustments until then. You may or may not need to rebuild the carb, but it's so much easier after a devac.

Wait wait wait. It only affects the idle mixture? So if I spend 95% of my time MOVING on the interstate, rather than running the engine at idle, will THAT fuel economy be affected? My MIXTURE doesn't change as I apply throttle, does it? I'm absolutely confused. This is the first carbed car I've had. It seems simpler in theory, but not in mechanics, but I'm still not USED to it. I was under the impression that the fuel/air mixture ratio is FIXED and only adjustable by that screw, and applying throttle increases fuel AND air flow in the same proportions. I'm in Florida, it's always fairly warm, so I'm not super concerned about cold starting, but...well, it would be NICE to start easier, but as long as it starts RELIABLY... I'll be good. Mostly, I want to INCREASE my MPG on this car. I'm barely getting 30 now, and I KNOW it's better than that. And it's all in the carb, I'm sure of it. And I'm fairly certain I'm running rich, and if the devac and carb rebuild I'd like to do don't take care of that, but a devac renders it richer than normal anyway, I SHOULD just be able to manually adjust the mixture to compensate, right? Or am I missing some fundamental of carburetor operation here?