AZGhost623 Posted February 26, 2013 Share Posted February 26, 2013 I came across an article on another website while doing some research on something, and it got me wondering. With a deadhead fuel setup on triple carbs, the fuel sits in the fuel lines and adds to the temperature gains from the hot engine. This can add to misfires, and mixture problems. If you change it over to a return setup, apparently the fuel has time to cool off by going back into the tank. It makes sense... Why does everyone say to do deadheads on these things? Is there a specific reason? Almost all race guys I have talked to say this is the way to go with a deadhead setup. But if Im also going to do an occasional drive during the summer nights in Arizona or early morning, Ive been told its nearly undrivable out here with that kind of setup due to the heat out here adding to the temp under the hood. Quote Link to comment Share on other sites More sharing options...
Tony D Posted February 27, 2013 Share Posted February 27, 2013 I don't know anybody that has run it that way due to pressure regulation issues. If you run a return system, you get hot gas I. Your tank if you run any significant time. Most high end systems run a return system, regulating backpressure on the carbs to allow full pump output to go to the carbs unrestricted (same as a non-return system) but without the drop-throttle float overwhelming high-fuel bowl level rich condition (leading to puddering and fat reapplication of the throttle)... Quote Link to comment Share on other sites More sharing options...
madkaw Posted February 27, 2013 Share Posted February 27, 2013 Run the deadhead but try to eliminate the fuel rail that rides right along the hot valve cover. I routed my fuel line along the firewall then straight to the carbs Quote Link to comment Share on other sites More sharing options...
AZGhost623 Posted February 27, 2013 Author Share Posted February 27, 2013 I thought of exactly what TonyD was saying to put a pressure regulator in after the carbs on the return side so the carbs continue to run unrestricted get the fuel they need. Didnt think to run the fuel line up around the firewall. Ill have to play with it this summer some and see if changing things around has any effect with its drivability in the summer AZ heat. Quote Link to comment Share on other sites More sharing options...
Tony D Posted February 28, 2013 Share Posted February 28, 2013 Heat soak on the carb bodies from Sam-side exhaust is a FAR larger factor in low-speed driveability! Routing return fuel through the stock Mikuni Cooling Bodies on the bottom of the carbs helps IMMEASURABLY. it's like Mikuni knew what they needed for a daily driver, as the PHH'S was an OEM Offering on Millions of Toyota DOHC vehicles through the 60,s, 70's, and into the 80's! Nothing like that for a Dell or Weber.... A One Gallon cool-can filled with 7# of ice usually lasts a tankfull blasting across the desert then into towns where you have to live in stop-n-go... Put it over the starter, make it from a water cooler and coil of copper pipe! Frigid Gas on a hot day...nice! Quote Link to comment Share on other sites More sharing options...
AZGhost623 Posted March 11, 2013 Author Share Posted March 11, 2013 So the return line keeps wanting to dump fuel out when pressure builds up since it wasnt hooked up. I put a bolt in a hose on the return line to block it off, but I am worried about how much pressure just builds up when it sits. When I remove the gas cap, its a pretty big pssh... my Titan doesnt even pssh out that loud when you take the gas cap off.. Maybe its just because of the restoration process and everything being new/cleaned out? Is this something I should be worried about, or is this par for the course like any car and I dont need to worry about? Quote Link to comment Share on other sites More sharing options...
Tony D Posted March 11, 2013 Share Posted March 11, 2013 That's because you plugged the EVAP line and didn't give expanding / contracting fuel any place to go. If your factory EVAP canister is in place, the diverter valve on the top handles venting and contracting gases from the fuel tank go some place automatically. If the conversion is done properly, nothing to worry about. Bodge job it and you can run your tank into high vacuum, run low on fuel, and be stranded dead at the roadside until you manually break the vacuum when the cap is opened. Of course, expanding fuel pushing out into a large puddle on the floor with someone smoking nearby insures healthy insurance payouts for someone's immolated car and house. You have insurance, right? Quote Link to comment Share on other sites More sharing options...
AZGhost623 Posted March 11, 2013 Author Share Posted March 11, 2013 (edited) Yes I have insurance, but I am trying to get answers to prevent having to go that route tony... Since I converted from EFI to Carb, all the Emissions control stuff went bye bye. All I have is two fuel lines and out and in. The Return is plugged, and the out goes right into the carbs from the tank. Whats the proper way to control this pressure vapor build up on a carb setup? Run a vented gas cap instead if I can find one that works? Edited March 11, 2013 by AZGhost623 Quote Link to comment Share on other sites More sharing options...
johnc Posted March 11, 2013 Share Posted March 11, 2013 The stock EVAP system on the S30 is a good thing. If you have the parts, it would be worth your time to put it all back on the car. Quote Link to comment Share on other sites More sharing options...
Tony D Posted March 11, 2013 Share Posted March 11, 2013 Liked JC reiterates, and I originally said: "That's because you plugged the EVAP line and didn't give expanding / contracting fuel any place to go. If your factory EVAP canister is in place, the diverter valve on the top handles venting and contracting gases from the fuel tank go some place automatically." Pretty self-explanatory. Quote Link to comment Share on other sites More sharing options...
Tony D Posted March 11, 2013 Share Posted March 11, 2013 The alternative has been posted several times by me, find it, I'm not writing all that again. Quote Link to comment Share on other sites More sharing options...
AZGhost623 Posted March 11, 2013 Author Share Posted March 11, 2013 (edited) hrm, yes Tony, found your stuff through the google on other websites on this topic. As far as Im aware of I didnt plug any of the evap line to that canister. Like I said I just originally had everything open, until pressure was building up on its own. It should still just be "open". Ill need to go over those lines it appears to make sure that "third" steel line is not clogged or some how got shunted closed. Still have all the parts from what I removed JC. So I can still add it back on, but it appears there might be a bigger issue if its not venting on its own through that open pipe. The fuel tank itself was pulled and sent off to be throughly cleaned, and then bolted right back up to how it used to be. Didnt do anything with the evap tank, or the lines itself from that evap tank in the rear. All four hoses were put back onto the tank as it came off... Edited March 11, 2013 by AZGhost623 Quote Link to comment Share on other sites More sharing options...
Tony D Posted March 12, 2013 Share Posted March 12, 2013 "Ill need to go over those lines it appears to make sure that "third" steel line is not clogged or some how got shunted closed." Spock agrees, this is the only logical course of action. As I have posted before, a Geo Metro Evap Cannister uses second generation activated charcoal, and is MUCH smaller. It can be housed outside the engine bay, or even in the back by the differential. There is nothing that says WHERE these components have to be mounted. MAKE SURE YOU GET THE RIGHT HOSE BARBS IN THE TANK ACCORDING TO WHERE THEY NEED TO GO! Chances are good spooge has blocked something. It is fairly common. This wouldn't be the first tank to come off for cleaning to come back with plugged off vent lines from pooled or accumulated sealant! Most good shops run a brazing rod through each nipple in the tank to make sure they are free, and so do I when I get one back! Burned by that on at least three occasions! FYI, the Geo Metro I chose due to comparable tank storage and EVAP capacity. I prefer mounting the canister in the back, out of sight, and love that I have more room up front (and a second large-bore line front-to-back to use as I see fit! Quote Link to comment Share on other sites More sharing options...
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