cd45 Posted October 24, 2007 Share Posted October 24, 2007 I went to the junk yard yesterday, and they had a disty for the Brat. I pulled it, after I made sure the vacuum advance worked. Brought it home and cleaned it up. Pulled the vac advance. I got home from work tonight, went out, and they are different disty's. The one I have is a Hitachi, the one I got is a Nippondenso. The local parts house has the cap for the nippon, but the rotor they list is the same as the Hitachi. I tried the one I had, and it is not the same. I plan to fo to town tomorrow with the parts to see if any of the parts houses have one. I hope. Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted October 25, 2007 Share Posted October 25, 2007 Hitachi = 4WD ND = 2WD They are interchangeable, but you need to swap to the same brand coil as well so the coil resistance range matches that of the distributors ignitor. If you don't you risk burnout of the ignitor or the coil. GD Quote Link to comment Share on other sites More sharing options...
cd45 Posted October 25, 2007 Author Share Posted October 25, 2007 I am running an MSD coil in it right now. Will that make a difference? Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted October 25, 2007 Share Posted October 25, 2007 I wouldn't run anything other than stock. There's nothing to be gained by an aftermarket coil anyway. They generally aren't as high quality as the originals, and most (including MSD and Mallory) are made in Mexico these days where the quality control stinks. The spark plug does one thing - it ignites the mixture. It's a boolean function - there really isn't a such thing as a "better" spark (talking practical terms - as they relate directly to stock EA series engines). As long as it's igniting the mixture close to 100% of the time that's all that's required of it. The stock ignition system is more than adequate for a non forced-induction engine. If you were running special fuel, or extremely high compression (IE: forced induction) then there might be a need for the spark to jump a higher density air gap, but short of that there is no good reason to "mod" the ignition system. I can think of much better ways to spend $40. GD Quote Link to comment Share on other sites More sharing options...
cd45 Posted October 25, 2007 Author Share Posted October 25, 2007 What would happen if I put the old coil back in, and then plugged the end of the vacuum advance? Would the car run right? Would my mileage suffer? I have no idea. Quote Link to comment Share on other sites More sharing options...
joostvdw Posted October 25, 2007 Share Posted October 25, 2007 What would happen if I put the old coil back in, and then plugged the end of the vacuum advance? Would the car run right? Would my mileage suffer? I have no idea. yes your mileage will suffer and it will run terrible, just do as GD said a couple posts up, that's the only proper way. Quote Link to comment Share on other sites More sharing options...
cd45 Posted October 25, 2007 Author Share Posted October 25, 2007 HELP! I cannot find another disty locally. The only one I found is the Nippondenso. I have the Hitachi. The advance will not interchange. If anyone has a good vacuum advance, with 2 mounting screws, I am very interested. I really want to drive the Brat. Let me know, we will work out a deal. Quote Link to comment Share on other sites More sharing options...
85T-REX Posted October 25, 2007 Share Posted October 25, 2007 What would happen if I put the old coil back in, and then plugged the end of the vacuum advance? Would the car run right? Would my mileage suffer? I have no idea. Actually your Brat would run okay. The vacuum advance only works when first opening the throttle. After that, and the rpm's are up, the centrifugal advance does the rest so you can plug the vac line and the most it will do is stumble a little when you take off. Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted October 25, 2007 Share Posted October 25, 2007 HELP! I cannot find another disty locally. The only one I found is the Nippondenso. I have the Hitachi. The advance will not interchange. If anyone has a good vacuum advance, with 2 mounting screws, I am very interested. I really want to drive the Brat. Let me know, we will work out a deal. A good distributor shop can rebuild you vacuum advance for about $20. These are the guys I use - they are local to me: http://www.philbingroup.com/ Actually your Brat would run okay. The vacuum advance only works when first opening the throttle. After that, and the rpm's are up, the centrifugal advance does the rest so you can plug the vac line and the most it will do is stumble a little when you take off. That is incorrect. Full advance will never be achieved without the vacuum can. Vacuum supply to the advance pot is "ported" and rises with increased throttle posistion and engine speed. Max advance is split between the vacuum and centrifugal units and will max out around 15 degrees without the vacuum, and around 25 with it. In practice the vacuum can not working will generally not be very noticeable at all. If everything else is in good condition there won't be an off-idle stumble. It just won't advance fully, mileage will take a hit, and max power on the freeway will be reduced by a small, but noticeable amount. The off-idle advance due to the vacuum pot amounts to only a degree or two - not enough to cause any kind of obvious stumble. I've run with plenty of bad vac cans, and you can't really tell. I would estimate that by this point 75% or more of the EA series engines on the road have an innoperable vacuum advance pot. 9 out of 10 of the ones I've tested were shot. GD Quote Link to comment Share on other sites More sharing options...
85T-REX Posted October 25, 2007 Share Posted October 25, 2007 That is incorrect. Full advance will never be achieved without the vacuum can. Vacuum supply to the advance pot is "ported" and rises with increased throttle posistion and engine speed. Max advance is split between the vacuum and centrifugal units and will max out around 15 degrees without the vacuum, and around 25 with it. GD Yes what I wrote is correct. The port is just above the upper half of the throttle plate. When the throttle is first opened, the vacuum is pulled through that port but as the throttle plate opens further, less and less vacuum is pulled through the port. At full throttle, there is 0 vaccuum so how could it still be working? It's all up to the centrifugal at the higher rpm's. I've tested it all with a timing light and that's how I know it's correct. Quote Link to comment Share on other sites More sharing options...
85T-REX Posted October 25, 2007 Share Posted October 25, 2007 Actually your Brat would run okay. The vacuum advance only works when first opening the throttle. After that, and the rpm's are up, the centrifugal advance does the rest so you can plug the vac line and the most it will do is stumble a little when you take off. cd45, Try this and you will see for yourself how it runs. Quote Link to comment Share on other sites More sharing options...
cd45 Posted October 25, 2007 Author Share Posted October 25, 2007 Thanks guys, I will try this when I get home. If any of you find a vacuum advance, I still want a good one. Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted October 25, 2007 Share Posted October 25, 2007 Yes what I wrote is correct. The port is just above the upper half of the throttle plate. When the throttle is first opened, the vacuum is pulled through that port but as the throttle plate opens further, less and less vacuum is pulled through the port. At full throttle, there is 0 vaccuum so how could it still be working? It's all up to the centrifugal at the higher rpm's. I've tested it all with a timing light and that's how I know it's correct. You are wrong. Hook up a vacuum gauge and see for yourself. "Ported" vacuum means the port is right below the venturi in the carb, thus reversing (basically) the manifold vacuum curve. What you describe is manifold vacuum. This is a common misconception and I've had this argument with others on here before. Take a look at my post count - I know of what I speak with regard to EA series distributors and carbs. Again - ported vacuum (called for by the EA distributor design) rises with engine speed and throttle position. More specifically, and to clarify the distinction, there is a difference between the vacuum produced by the engine, and the ported vacuum SUPPLY on the carb which is entirely artificial in nature. It's produced by the difference in pressure between the two ends of the venturi in the carb. So while you are correct that there is no ENGINE vacuum at full throttle, there is PORTED vacuum at full throttle. Just as there is tons of engine vacuum at closed throttle, and no ported vacuum. It's reversed, and it's designed that way on purpose. GD Quote Link to comment Share on other sites More sharing options...
85T-REX Posted October 25, 2007 Share Posted October 25, 2007 You are wrong. Hook up a vacuum gauge and see for yourself. "Ported" vacuum means the port is right below the venturi in the carb, thus reversing (basically) the manifold vacuum curve. What you describe is manifold vacuum. This is a common misconception and I've had this argument with others on here before. Take a look at my post count - I know of what I speak with regard to EA series distributors and carbs. Again - ported vacuum (called for by the EA distributor design) rises with engine speed and throttle position. More specifically, and to clarify the distinction, there is a difference between the vacuum produced by the engine, and the ported vacuum SUPPLY on the carb which is entirely artificial in nature. It's produced by the difference in pressure between the two ends of the venturi in the carb. So while you are correct that there is no ENGINE vacuum at full throttle, there is PORTED vacuum at full throttle. Just as there is tons of engine vacuum at closed throttle, and no ported vacuum. It's reversed, and it's designed that way on purpose. GD Has anyone tried this? I don't think post count has anything to do with it. I can't find any info that supports his argument. Not that it really matters, just curious. I'm only going by what I know and have done myself in order to help cd45. Quote Link to comment Share on other sites More sharing options...
robm Posted October 25, 2007 Share Posted October 25, 2007 Where the vacuum advance makes the most difference is at light load, part throttle cruising conditions. I have never played with a Subaru's vacuum advance, but on a Corolla I had, the highway mileage dropped from 40 MPG + to 25-28 MPG when the canister developed a leak. Driveability and power were not noticeably affected. There were a lot of other cars with Hitachi distributors on them, like Hondas and Datsuns. They all have slightly different vacuum advance characteristics, it might be possible to play with the vacuum advance by swapping on a canister from a different car. Worth a try, if you can score a few out of the junk yard for a good price. But I would recommend that you get a good one, intended for your car, first, so you know if you are improving anything or not. Quote Link to comment Share on other sites More sharing options...
4x4_Welder Posted October 26, 2007 Share Posted October 26, 2007 GD is right on this. For even more fun, see what happens when you run the vacuum advance off the manifold vacuum- Not very easy to get the idle right, but much harder to stall, more torque off the line, and less pinging at higher throttle angles. Of course, mileage does take a hit then also. Quote Link to comment Share on other sites More sharing options...
cd45 Posted October 26, 2007 Author Share Posted October 26, 2007 Thanks guys. Right now, I have the advance plugged, and the line to the manifold plugged. It still has a small stumble when you take off but, if you push the pedal smoothly and evenly, it runs fine. I am still looking for a vacuum advance to replace the bad one. If any of you find one, let me know. I know we can make a deal. Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted October 26, 2007 Share Posted October 26, 2007 Just call the guys I linked to. They can rebuild it for you by mail. Any used ones are likely not going to last as long anyway. GD Quote Link to comment Share on other sites More sharing options...
cd45 Posted October 27, 2007 Author Share Posted October 27, 2007 Thanks GD, I sent them an e-mail, just haven't heard back from them yet. Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted October 27, 2007 Share Posted October 27, 2007 Thanks GD, I sent them an e-mail, just haven't heard back from them yet. Better to call - they are a small outfit, and the place isn't real tidy so I doubt they check their email too often. They do great work, but the place is old, and in a bad neighborhood GD Quote Link to comment Share on other sites More sharing options...
daeron Posted October 27, 2007 Share Posted October 27, 2007 Better to call - they are a small outfit, and the place isn't real tidy so I doubt they check their email too often. They do great work, but the place is old, and in a bad neighborhood GD why does it seem like those are the BEST of the best places???? Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted October 27, 2007 Share Posted October 27, 2007 why does it seem like those are the BEST of the best places???? Seems that way doesn't it? These guys do a lot of electrical equipment restoration for shops all around the portland metro area. That's how I found out about them. I don't think they do a lot of "walk in" customer work so their location isn't really geared toward consumers.... no real storefront just a door next to a tavern. Hehe. But I highly reccomend them for their electrical and distributor work. A complete rebuild runs less than $100 for everything and it comes back shiny, with the vac can painted high-temp black. I've always been impressed. Old guys, and somewhat crotchety, but highly skilled. GD Quote Link to comment Share on other sites More sharing options...
daeron Posted October 27, 2007 Share Posted October 27, 2007 Seems that way doesn't it? These guys do a lot of electrical equipment restoration for shops all around the portland metro area. That's how I found out about them. I don't think they do a lot of "walk in" customer work so their location isn't really geared toward consumers.... no real storefront just a door next to a tavern. Hehe. But I highly reccomend them for their electrical and distributor work. A complete rebuild runs less than $100 for everything and it comes back shiny, with the vac can painted high-temp black. I've always been impressed. Old guys, and somewhat crotchety, but highly skilled. GD People and places like this REALLY embody almost all that is great about America. Quote Link to comment Share on other sites More sharing options...
85T-REX Posted November 26, 2007 Share Posted November 26, 2007 You are wrong. Hook up a vacuum gauge and see for yourself. "Ported" vacuum means the port is right below the venturi in the carb, thus reversing (basically) the manifold vacuum curve. What you describe is manifold vacuum. This is a common misconception and I've had this argument with others on here before. Take a look at my post count - I know of what I speak with regard to EA series distributors and carbs. Again - ported vacuum (called for by the EA distributor design) rises with engine speed and throttle position. More specifically, and to clarify the distinction, there is a difference between the vacuum produced by the engine, and the ported vacuum SUPPLY on the carb which is entirely artificial in nature. It's produced by the difference in pressure between the two ends of the venturi in the carb. So while you are correct that there is no ENGINE vacuum at full throttle, there is PORTED vacuum at full throttle. Just as there is tons of engine vacuum at closed throttle, and no ported vacuum. It's reversed, and it's designed that way on purpose. GD Well, it took me a while to find all the pieces to try this so I apologize for the late post. I hooked up a vacuum gauge to my Hitachi and this is what I found: No throttle - 0 vac. Cracked throttle - 20 vac. Full throttle - 0 vac. all the way up to 5500 rpm. This is exactly how ported vacuum is supposed to work. The venturi mentioned is for the fuel siphoning. The faster the air passes through the venturi, the more fuel is pulled into the throttle body. That's how a venturi works. I hope this clears up any confusion on this issue. Quote Link to comment Share on other sites More sharing options...
robm Posted November 27, 2007 Share Posted November 27, 2007 It would have been instructive to look at manifold vacuum under the same circumstances. I will guess manifold vacuum will be: closed throttle 20" vac. or more cracked throttle 20" vac. full throttle 0" all the way to 5500 RPM. Could you be so kind as to give it another shot under these conditions? And did you measure this with the car actually moving, or just sitting in the driveway? Quote Link to comment Share on other sites More sharing options...
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