franky240z Posted May 1, 2012 Share Posted May 1, 2012 I've a set of new webbers and i'm going to fit a new distributor, am I right in thinking i'd be better off with a mechanical advance? Whats the best option to go for? Quote Link to comment Share on other sites More sharing options...
duragg Posted May 2, 2012 Share Posted May 2, 2012 I think you would be best off by running the Triples with a known good distributor of ANY kind for a while prior to replacing the Dizzy. You want to reduce the number of variables until you have the Triples dialed in somewhat. I had my L24 dizzy recurved after I got my DCOE L28 up and running. Quote Link to comment Share on other sites More sharing options...
Leon Posted May 2, 2012 Share Posted May 2, 2012 What's a distributor? But in all seriousness, the stock distributor has mechanical advance. It's the advance curve that you're worried about. Search around and you'll find some good discussions on the topic. Quote Link to comment Share on other sites More sharing options...
240zip Posted May 2, 2012 Share Posted May 2, 2012 At a minimum, use a mechanical advance, I use an MSD. There's not enough vacuum on the triples to properly make a vacuum advance work. With the MSD you can change the advance curve. I have a Sun 504 distributor tester and it allowed me to test and set a custom curve. At bit of an overkill, but I had one in the shop so figured why not. I'm running the MSD with 6AL. Works well. I tried a vacuum collector and few other means of trying to get more vacuum, it just had this terrible early RPM bog. When I went with the MSD mechanical advance it cleared up. Much more lower-end response. This has been discussed before. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted May 2, 2012 Share Posted May 2, 2012 What's a distributor? Hey, that wheel is broken, it's missing a tooth.... Quote Link to comment Share on other sites More sharing options...
Leon Posted May 2, 2012 Share Posted May 2, 2012 At a minimum, use a mechanical advance, I use an MSD. There's not enough vacuum on the triples to properly make a vacuum advance work. With the MSD you can change the advance curve. I have a Sun 504 distributor tester and it allowed me to test and set a custom curve. At bit of an overkill, but I had one in the shop so figured why not. I'm running the MSD with 6AL. Works well. I tried a vacuum collector and few other means of trying to get more vacuum, it just had this terrible early RPM bog. When I went with the MSD mechanical advance it cleared up. Much more lower-end response. This has been discussed before. This definitely has been discussed before. However, triples make plenty of vacuum to used the vac advance. The problem is that there is no ported vacuum source to drawn from, so you'd end up getting way too much advance at idle. Vac advance is beneficial, on top of having a properly matched mechanical advance curve. However, in order to make it work right, you need a ported vacuum source and a vacuum log to strengthen and smooth out the signal. By that time, you might as well go crank-trigger. Only cost me $400. Hey, that wheel is broken, it's missing a tooth.... Dammit! I got ripped off! Quote Link to comment Share on other sites More sharing options...
srgunz Posted May 2, 2012 Share Posted May 2, 2012 Quote. "The problem is that there is no ported vacuum source to drawn from, so you'd end up getting way too much advance at idle." My triple manifold came with a distributor vac. port. Quote Link to comment Share on other sites More sharing options...
Leon Posted May 2, 2012 Share Posted May 2, 2012 Quote. "The problem is that there is no ported vacuum source to drawn from, so you'd end up getting way too much advance at idle." My triple manifold came with a distributor vac. port. No, it came with a manifold vacuum port, nowhere does it say that it's for the distributor. The distributor needs a ported vacuum source, not manifold. Quote Link to comment Share on other sites More sharing options...
srgunz Posted May 3, 2012 Share Posted May 3, 2012 Not according to the race shop that set the car up. Anyway it revs so fast to 7500, I am happy with it. Quote Link to comment Share on other sites More sharing options...
rejracer Posted May 3, 2012 Share Posted May 3, 2012 Not according to the race shop that set the car up. Anyway it revs so fast to 7500, I am happy with it. key words: "race shop". You use a ported vacuum source for the distributor so you get consistent timing which produces a smoother idle. It also allows for a tad bit more power at tip in as when you crack the throttle plates it adds timing. It's a street driveability thing. If this is a street car you want both mechanical and vacuum advance. Mechanical advance compensates for RPM fluctuations which prevents low rpm detonation while under a heavy (low vacuum) load. In reality there is no "mechanical advance", rather it's low rpm retard. Vacuum advance compensates for engine load, which greatly improves fuel economy, throttle response and smoothness. Match your advance curve to your engine setup. Open chamber heads require a more timing. If you have an open chamber head get the distributors with more mechanical advance if a closed chamber head and matching pistons get a distributor with less mechanical advance. Concerning the triples and vacuum, they really need a vacuum manifold to work properly. Once you get to the point of using triples, it's not really a street car imho. Sure lots of people use them on the street, but there are compromises to be made when going that route. For instance there is no ported vacuum source on them, as a result either smoothness is sacrificed when using manifold for vacuum advance or fuel economy suffers due to no vacuum advance. With that said, use what works for what you are using your car for. Quote Link to comment Share on other sites More sharing options...
240zip Posted May 3, 2012 Share Posted May 3, 2012 fuel economy ... sorry, had to laugh. On my 42 DCOEs I'm lucky if I get 14 MPG, and we haven't even gotten into the whole discussion of what you did to the motor prior to going the triple route. If you've gone with the upgraded cam, head work, headers, high compression ... then yes ... triples. This was before the mechanical advance ... see the little vacuum advance in the picture. Works much better now. Quote Link to comment Share on other sites More sharing options...
franky240z Posted May 3, 2012 Author Share Posted May 3, 2012 (edited) so i've done some digging. Car will be a 2.4, +50 over, piper 286 cam, e31 head, 10.5:1 compression, triple 40's, matched length manifold. dynamic balanced crank with ATI damper. I'm going for a mallory unilite, for ignition 685 or 6853m? How do they compare to the msd 6al's? the 6530 so you can program the ignition curve? For a coil is it worth getting the pro master? Edited May 3, 2012 by franky240z Quote Link to comment Share on other sites More sharing options...
240zip Posted May 7, 2012 Share Posted May 7, 2012 once you're further down the road (e.g. engine rebuilt, parts assembled) I'm sure you can revisit this topic. It took me nearly 2 years between having an engine and the 42DCOE's and completion. The direction you're going sounds fine. Quote Link to comment Share on other sites More sharing options...
sotaorava Posted July 18, 2012 Share Posted July 18, 2012 old topic but need info what does this mean "The distributor needs a ported vacuum source, not manifold" just interested because i am installing triples soon... i have fet manifold can i use vacuum advantage? Quote Link to comment Share on other sites More sharing options...
Leon Posted July 18, 2012 Share Posted July 18, 2012 old topic but need info what does this mean "The distributor needs a ported vacuum source, not manifold" just interested because i am installing triples soon... i have fet manifold can i use vacuum advantage? Check rejracer's comment. Quote Link to comment Share on other sites More sharing options...
Tony D Posted July 19, 2012 Share Posted July 19, 2012 (edited) There's not enough vacuum on the triples to properly make a vacuum advance work. <br><div><br></div><div>That's a function of the cam more than the induction. There are thousands of cars out there in OEM configuration (including the original Z-Car in 165HP L24 Configuration) that used vacuum advance on their Mikunis... In fact there is a little green canister with a Nissan P/N (or Toyota if you prefer) that was used on some OEM Mikuni Applications to eliminate the issue of excessive or pulsating idle vacuum to the distributor. Just take it off the Mikuni's first barrel port, and go from there, no log required! Returned 28mpg at 65mph steady highway driving on a 2.4L with stock cam, 4.11 gearing, and an autobox. Spinning the dyno to around 163 (back in 1989 when Aftermarket EFI was still a rich man's game.)</div><div><br></div><div>Webers? Sorry, no advance port, but Solexes have one, and for good reason, at light cruise vacuum advance saves gas, and there is no reason not to use it!</div><div><br></div><div>But to answer 'which one' can only be answered: "Recurved"<br><br><br> </div> Edited July 19, 2012 by Tony D Quote Link to comment Share on other sites More sharing options...
Tony D Posted July 19, 2012 Share Posted July 19, 2012 I have no clue WTF is going on with the data entry field, but it's FUBAR and trying to 'fix' the post through editing just makes it worse! Quote Link to comment Share on other sites More sharing options...
Lazeum Posted July 19, 2012 Share Posted July 19, 2012 You're talking about economy & Max power at WOT but the vacuum advance would benefit a lot also with smoothness & torque available for partial throttle, this is what matter the most to me while setting up a street driven car (besides WOT, of course). I'm in the process to deviate from my Unilite dizzy I can setup with no vacuum advance (~20mpg for info) to Megajolt for that reason (and also because I'm bored playing with springs & screws to setup my igniton for hours & guessing ) Quote Link to comment Share on other sites More sharing options...
240zip Posted July 19, 2012 Share Posted July 19, 2012 20 MPG from triples? My set-up works fine 42DCOE, mechanical advance distributor, MSD 6AL, Petronix, but 20 MPG ... not even close. I think I'm getting like 8 MPG at the track. Picture shows OEM distributor and vacuum advance. That set-up, did not work well. Classic bog at 1500 to 1800 RPM. In hindsight, I think timing advance had a great deal to do with it and not just the mechanical advance. We also took advice from Jeff Winters on the air corrector, idle jets, and other parameters. Even changing the plugs helped. So I can't say all my results were from the mechanical advance alone. Quote Link to comment Share on other sites More sharing options...
Lazeum Posted July 19, 2012 Share Posted July 19, 2012 (edited) This mpg was during 120mi trip on country side roads during end of break-in period (max rev. 4500rpm), not a track session with 80% of WOT action Carbs are dialed in with O2 WB sensor & small chokes (32mm). no bog or what so ever, engine is quite responsive when at WOT but there's some laziness in mid trottle action. Carbs balance is probably not the best. To get back on timing, my current dizzy allows me to adjust idle & total timing easily as well as how the curve is in between. Most of the power from the engine has to do with timing more than AFR. As soon as you modify the engine (VE accross rpm range to be exact), timing needs to be adjusted somehow (even if it works with stock units). That's the same exact reason, cam change on L28e(t) with stock ECU is not good. timing needs to be tweaked. Edited July 19, 2012 by Lazeum Quote Link to comment Share on other sites More sharing options...
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