Mark Maras Posted July 17, 2022 Share #73 Posted July 17, 2022 Generally speaking, adding more fuel rarely increases the rpms unless the mixture is way too lean. Air is the most common cause of increased rpms. 2 Link to comment https://www.classiczcars.com/topic/67606-carburetor-conundrum-260z/?page=7#findComment-642515 Share on other sites More sharing options...
Captain Obvious Posted July 18, 2022 Share #74 Posted July 18, 2022 9 hours ago, Patcon said: If the front carb float bowl level was higher than the rear, wouldn't it run faster due to extra fuel? No, it would just run richer, not faster. Unless, of course as Mark suggested, it was running really really lean and wanted the extra fuel. I really don't think that has anything to do with what's going on here. Float levels will need to be checked before this is all said and done. but that's not what's causing the idle to be at 2500 RPM with the screws backed all the way out. 1 Link to comment https://www.classiczcars.com/topic/67606-carburetor-conundrum-260z/?page=7#findComment-642553 Share on other sites More sharing options...
DadAndLadZ Posted July 31, 2022 Author Share #75 Posted July 31, 2022 Been too hot to work in the garage but we finally had a couple nice days and I think we may have solved the mystery… You’re gonna laugh. Link to comment https://www.classiczcars.com/topic/67606-carburetor-conundrum-260z/?page=7#findComment-643082 Share on other sites More sharing options...
Captain Obvious Posted July 31, 2022 Share #76 Posted July 31, 2022 Well THERE'S your problem!! Yes, that nail was holding your butterfly open and not allowing it to close completely. Some answers to additional questions: That hole is intended to be a ported vacuum source to drive the distributor advance. There is supposed to be a vacuum tube nipple pressed into the carb body that allows you to connect a rubber tube between the front carb and the distributor advance diaphragm. It appears someone sheared the nipple off and decided to plug that hole with a nail instead. And about the "insert grease" engravings... It appears that someone drilled little holes in the carb mounting face with the intent of using them as lubrication grease ports to lube the throttle shafts. Probably a waste of time, but since they are sealed off by the gasket between the intake manifolds and the carb faces, it probably doesn't cause any harm either. So for both of those items... THAT'S something I've not seen before!! Bottom line... Plug that vacuum nipple with something that does not stick down into the carb throat and I bet your idle issue will be pretty much taken care of. Link to comment https://www.classiczcars.com/topic/67606-carburetor-conundrum-260z/?page=7#findComment-643089 Share on other sites More sharing options...
Captain Obvious Posted July 31, 2022 Share #77 Posted July 31, 2022 And can I just point out that when I said "I'm thinking that something within the carb itself is keeping that front throttle butterfly from closing completely"... I nailed it! HAHAHAHAHA!!!!! 1 3 Link to comment https://www.classiczcars.com/topic/67606-carburetor-conundrum-260z/?page=7#findComment-643090 Share on other sites More sharing options...
DadAndLadZ Posted July 31, 2022 Author Share #78 Posted July 31, 2022 (edited) 14 hours ago, Captain Obvious said: Bottom line... Plug that vacuum nipple with something that does not stick down into the carb throat and I bet your idle issue will be pretty much taken care of. That’s the plan now… JFC I was losing my mind. I know I should have just taken the damn thing off earlier but it always feels like opening a can of worms to me. You would think I’d be used to it by now lol… It does have a vacuum advance hose going to the distributor, it’s just attached a little farther back, behind the spacer on the manifold. I guess it’s a by-product of mixing and matching parts off different years of car. Many thanks again to everyone who has chimed in on this, here’s hoping the boys and I can start working on something else soon! lol Edited July 31, 2022 by DadAndLadZ Link to comment https://www.classiczcars.com/topic/67606-carburetor-conundrum-260z/?page=7#findComment-643111 Share on other sites More sharing options...
Captain Obvious Posted August 1, 2022 Share #79 Posted August 1, 2022 8 hours ago, DadAndLadZ said: It does have a vacuum advance hose going to the distributor, it’s just attached a little farther back, behind the spacer on the manifold. I guess it’s a by-product of mixing and matching parts off different years of car. Well that vacuum connection you are using now is full manifold vacuum, but the system was designed to use a ported source that peaked advance at light cruise throttle (slightly above idle). With your direct manifold vacuum source, you will have peak advance at idle, and it will drop from there. I'm no timing expert, but I'm not sure that's what you want. And I don't think your vacuum connection is really a remnant of mixing and matching parts from different years. I think it's a remnant of snapping off the original ported vacuum nipple and then looking for some place else to connect that vacuum line. Either way... So when will we get an idle report to see if taking that nail out allows the front carb to operate properly? 2 Link to comment https://www.classiczcars.com/topic/67606-carburetor-conundrum-260z/?page=7#findComment-643139 Share on other sites More sharing options...
DadAndLadZ Posted August 1, 2022 Author Share #80 Posted August 1, 2022 1 minute ago, Captain Obvious said: Either way... So when will we get an idle report to see if taking that nail out allows the front carb to operate properly? Wow, good info, thanks! We will put it back together ASAP! 1 Link to comment https://www.classiczcars.com/topic/67606-carburetor-conundrum-260z/?page=7#findComment-643140 Share on other sites More sharing options...
Captain Obvious Posted August 1, 2022 Share #81 Posted August 1, 2022 I have very little doubt that things will be a whole lot better now, but after four pages, I just want to hear it from you to be sure! 2 Link to comment https://www.classiczcars.com/topic/67606-carburetor-conundrum-260z/?page=7#findComment-643142 Share on other sites More sharing options...
DadAndLadZ Posted August 1, 2022 Author Share #82 Posted August 1, 2022 11 minutes ago, Captain Obvious said: I have very little doubt that things will be a whole lot better now, but after four pages, I just want to hear it from you to be sure! Oh you guys will hear for sure! lol … THANKS most sincerely for your patient help!!! Link to comment https://www.classiczcars.com/topic/67606-carburetor-conundrum-260z/?page=7#findComment-643143 Share on other sites More sharing options...
Jeff Berk Posted August 1, 2022 Share #83 Posted August 1, 2022 Captain Obvious, do you think its advisable for DadAndLadZ to reestablish that return line to the fuel tank to minimize the potential for vapor lock? Link to comment https://www.classiczcars.com/topic/67606-carburetor-conundrum-260z/?page=7#findComment-643144 Share on other sites More sharing options...
Captain Obvious Posted August 1, 2022 Share #84 Posted August 1, 2022 Yeah, I think I would recommend running a return line, but that (like a lot of other details) can wait. I just want it to idle correctly for now! Haha! I'm no regulator expert, but I'm not a big fan of dead-headed systems in carb applications. This non-expert would prefer a bypass regulator system with a return line. 2 Link to comment https://www.classiczcars.com/topic/67606-carburetor-conundrum-260z/?page=7#findComment-643146 Share on other sites More sharing options...
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