26ftcobraBBF Posted December 29, 2020 Share Posted December 29, 2020 The need to disconnect and cap the vacuum line is only if it's hooked up like it should be -stock- You don't have a 4180 and aren't using manifold vacuum, to a thermal vacuum switch, so none of this matters... If you can't find a vacuum leak one of two things might cause your problem. A) the secondaries might be cracked open. Either sticking on the EGR spacer or the stop screw (bottom side between the rear barrels) has them adjusted open. B) you have an internal vacuum leak, where one of the runners is sucking from the valley. You can usually see this as an oily plug Ok thanks for the info, I'm going to call it a night here at Cobra Headquarters, and head home. I was able to get the idle down a little more by turning the fuel mixture screws inward, but upon doing that the engine loped with a range of approx 1000 RPM between ups and downs. When you say "runners"are you taking about the valve guides? One of the perks of having a van chasis is I've got access to the back of the motor is but geeze try looking down the carb. I do have a bore scope though may be able to check secondarys with it. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted December 29, 2020 Author Share Posted December 29, 2020 Ok thanks for the info, I'm going to call it a night here at Cobra Headquarters, and head home. I was able to get the idle down a little more by turning the fuel mixture screws inward, but upon doing that the engine loped with a range of approx 1000 RPM between ups and downs. When you say "runners"are you taking about the valve guides? One of the perks of having a van chasis is I've got access to the back of the motor is but geeze try looking down the carb. I do have a bore scope though may be able to check secondarys with it. Don't use mixture to kill rpm's. Adjust for highest vacuum or idle speed and use the throttle stop to adjust rpm's. If the stop screw isn't touching and the butterfly is still cracked, disconnect the throttle cable. Fix the cable attachment like I said in the first post. If the cable doesn't let the throttle close, or won't open all the way with a brick on the pedal, then you need to address that. Start at the beginning and do everything in order. Like I said, you need to get A done before you start B. You need to finish B before you start C. ......... Link to comment Share on other sites More sharing options...
26ftcobraBBF Posted January 1, 2021 Share Posted January 1, 2021 Don't use mixture to kill rpm's. Adjust for highest vacuum or idle speed and use the throttle stop to adjust rpm's. If the stop screw isn't touching and the butterfly is still cracked, disconnect the throttle cable. Fix the cable attachment like I said in the first post. If the cable doesn't let the throttle close, or won't open all the way with a brick on the pedal, then you need to address that. Start at the beginning and do everything in order. Like I said, you need to get A done before you start B. You need to finish B before you start C. ......... Hi Jim sorry for the delay in reply, the Cobra is stretching her legs this holiday weekend. Were 100 miles from home, and she performing. I've got a little tinkering to do, but this is the best she's ever ran. Merging onto the freeway is effortless once the secondarys open up. After my first fuel stop i calculated 6.6 mpg, but there was three fairly large mountain passes we went over. Last time I took this route before I had done all the work I was lucky to get up to 35 mph on these passes, now I'm able to keep up with traffic, passing big rigs with a little pedal left. Before leaving I was having idle issues. I did all the steps in order before asking and was able to get the idle back down. I believe the butterfly was sticking cracked open a tiny bit. The last couple days on start-up I've been having hard start, and idle issues. This time it was way to low today . Today it cranked longer than it should of to start on startup. I was looking around and discovered my choke was stuck open. Not quite sure why. It closed immediately when I touched the fast idle cam. I've still got to go through and adjust the fuel mixture for best vacuum, and figure why the choke is a little sticky. Hopefully I did right when I bent the choke linkage a little bit to adjust the pull off, and that's not why it's sticking. Couple of questions, my Cruise control isn't working, and did before I took it all apart when replacing p/s pump, steering gear, water pump, and intake manifold. Is there a fuse? All vacuum lines are new and inplace. Also in your response to my question you mentioned something about pulling vacuum from internally. Was that through the valve guides? Also wondering if running a dash pot nesessary? I've added a few images of what shape the intake manifold gasket was in before replacing, and was wanting to know if all the built up burnt oil that is stacked up on one side center is normal to see. Â Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted January 1, 2021 Author Share Posted January 1, 2021 Hi Jim sorry for the delay in reply, the Cobra is stretching her legs this holiday weekend. Were 100 miles from home, and she performing. I've got a little tinkering to do, but this is the best she's ever ran. Merging onto the freeway is effortless once the secondarys open up. After my first fuel stop i calculated 6.6 mpg, but there was three fairly large mountain passes we went over. Last time I took this route before I had done all the work I was lucky to get up to 35 mph on these passes, now I'm able to keep up with traffic, passing big rigs with a little pedal left. Before leaving I was having idle issues. I did all the steps in order before asking and was able to get the idle back down. I believe the butterfly was sticking cracked open a tiny bit. The last couple days on start-up I've been having hard start, and idle issues. This time it was way to low today . Today it cranked longer than it should of to start on startup. I was looking around and discovered my choke was stuck open. Not quite sure why. It closed immediately when I touched the fast idle cam. I've still got to go through and adjust the fuel mixture for best vacuum, and figure why the choke is a little sticky. Hopefully I did right when I bent the choke linkage a little bit to adjust the pull off, and that's not why it's sticking. Couple of questions, my Cruise control isn't working, and did before I took it all apart when replacing p/s pump, steering gear, water pump, and intake manifold. Is there a fuse? All vacuum lines are new and inplace. Also in your response to my question you mentioned something about pulling vacuum from internally. Was that through the valve guides? Also wondering if running a dash pot nesessary? I've added a few images of what shape the intake manifold gasket was in before replacing, and was wanting to know if all the built up burnt oil that is stacked up on one side center is normal to see. I suggested you must have an internal vacuum leak IF you've done everything externally and the throttle stop still could not idle the engine down. I'm not sure why a new carburetor is sticking open, but you've found the problem yourself, so it seems none of the intake ports were pulling from the lifter valley. It is not uncommon that exhaust carbon and cooked oil build up around the exhaust crossover, and even on the bottom of the intake manifold without the valley pan type gasket. But if you read the instructions for any aluminum intake, they'll say not to use one. Because the steel pan and aluminum intake expand and contract differently. The one intake stud was definitely seeing coolant though! That's why you use a little dab of RTV in the corners and I always add a light smear around the coolant passages in each corner. The dashpot is just there to help smooth the return to idle. Suddenly chopping the engine's air supply can lead to stalling under some conditions. It is not a bad feature, but I'm not running one at this time. Yes there is a fuse for the speed control. Documentation>electrical>EVTM's>1985 EVTM>speed control> Hope you're enjoying your New Years shakedown! We'll have to work on that choke/starting issue when you get back. Link to comment Share on other sites More sharing options...
26ftcobraBBF Posted January 9, 2021 Share Posted January 9, 2021 I suggested you must have an internal vacuum leak IF you've done everything externally and the throttle stop still could not idle the engine down. I'm not sure why a new carburetor is sticking open, but you've found the problem yourself, so it seems none of the intake ports were pulling from the lifter valley. It is not uncommon that exhaust carbon and cooked oil build up around the exhaust crossover, and even on the bottom of the intake manifold without the valley pan type gasket. But if you read the instructions for any aluminum intake, they'll say not to use one. Because the steel pan and aluminum intake expand and contract differently. The one intake stud was definitely seeing coolant though! That's why you use a little dab of RTV in the corners and I always add a light smear around the coolant passages in each corner. The dashpot is just there to help smooth the return to idle. Suddenly chopping the engine's air supply can lead to stalling under some conditions. It is not a bad feature, but I'm not running one at this time. Yes there is a fuse for the speed control. Documentation>electrical>EVTM's>1985 EVTM>speed control> Hope you're enjoying your New Years shakedown! We'll have to work on that choke/starting issue when you get back. Jim, I figured it out, my idle, and starting issue. Well actually a second set of eyes spotted it. I was talking to my neighbor about the issues I was having with high idle, and rough start. While he was there I verified timing, idle was still to high. I told what you said could be causing it. Then while trying to back the idle off and actuating the throttle he noticed that the dash pot bracket wasn't allowing the throttle to close all the way. I hadn't been running a dash pot anyhow, so I removed the bracket, re- adjusted timing, and curb idle, backed the choke off a bit, and reset the fuel mixture off best vacuum, and wa'la.... She's s runner now. Gotta be carefully not to get a speeding ticket merging onto the freeway....and that's no BS... Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted January 9, 2021 Author Share Posted January 9, 2021 Jim, I figured it out, my idle, and starting issue. Well actually a second set of eyes spotted it. I was talking to my neighbor about the issues I was having with high idle, and rough start. While he was there I verified timing, idle was still to high. I told what you said could be causing it. Then while trying to back the idle off and actuating the throttle he noticed that the dash pot bracket wasn't allowing the throttle to close all the way. I hadn't been running a dash pot anyhow, so I removed the bracket, re- adjusted timing, and curb idle, backed the choke off a bit, and reset the fuel mixture off best vacuum, and wa'la.... She's s runner now. Gotta be carefully not to get a speeding ticket merging onto the freeway....and that's no BS... Congratulations! It's interesting the bracket was holding the throttle open. There must be some dimensional difference from when it was mounted on the 4180? Anyway, glad your friend spotted it. Much easier than chasing a non-existent vacuum leak. Link to comment Share on other sites More sharing options...
Gary Lewis Posted January 9, 2021 Share Posted January 9, 2021 Jim, I figured it out, my idle, and starting issue. Well actually a second set of eyes spotted it. I was talking to my neighbor about the issues I was having with high idle, and rough start. While he was there I verified timing, idle was still to high. I told what you said could be causing it. Then while trying to back the idle off and actuating the throttle he noticed that the dash pot bracket wasn't allowing the throttle to close all the way. I hadn't been running a dash pot anyhow, so I removed the bracket, re- adjusted timing, and curb idle, backed the choke off a bit, and reset the fuel mixture off best vacuum, and wa'la.... She's s runner now. Gotta be carefully not to get a speeding ticket merging onto the freeway....and that's no BS... Congrat's!!!! I love free fixes! Link to comment Share on other sites More sharing options...
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