z-ya Posted November 26, 2014 Share Posted November 26, 2014 Get the AFR in the 12.5 to 13.5 across the RPM range. I would not run more than 34 degrees of advance on that engine. Checking float levels is easy. Also check for any clogged filters. Once you get it running right in the current configuration, then you can decide to change things like cam timing and compression ratio. Change one thing at a time, take a measurement. Repeat. Quote Link to comment Share on other sites More sharing options...
bradyzq Posted November 26, 2014 Share Posted November 26, 2014 I know you're not fixated on the numbers, but if the PO is to be believed, the closest match is that the car was run in 3rd, which would mean your torque is actually 2.3% higher than indicated and your engine RPM is 2.3% lower than indicated. Not a big deal. What do you mean by "didn't sound good?" Did it run on all 6 cylinders for the full run? If you lose ignition on a cylinder, that will introduce a lot of unburnt oxygen into the exhaust, and show lean on a wideband O2 sensor. Did the car smell? Any smoke? Do you have an electric fuel pump? If so, is it getting good voltage? Is the fuel filter clean? Quote Link to comment Share on other sites More sharing options...
ThaPimpShrimp Posted November 26, 2014 Author Share Posted November 26, 2014 I know you're not fixated on the numbers, but if the PO is to be believed, the closest match is that the car was run in 3rd, which would mean your torque is actually 2.3% higher than indicated and your engine RPM is 2.3% lower than indicated. Not a big deal. What do you mean by "didn't sound good?" Did it run on all 6 cylinders for the full run? If you lose ignition on a cylinder, that will introduce a lot of unburnt oxygen into the exhaust, and show lean on a wideband O2 sensor. Did the car smell? Any smoke? Do you have an electric fuel pump? If so, is it getting good voltage? Is the fuel filter clean? When he hit about 6,000 I heard what sounded like a backfire, don't think it was pinging. No smells and no smoke. I'm actually going to drop my tank tomorrow and redo all of the vapor and fuel lines in the rear, I've needed to do that for a while anyway. When I reinstall the tank I'm mounting up a Carter P4070, with an inline filter between it and the tank. Also have a holley FPR coming in. Only fuel filter I have is the one in the engine bay and it's a brand new WIX. Quote Link to comment Share on other sites More sharing options...
NewZed Posted November 26, 2014 Share Posted November 26, 2014 Seems like a float valve or fuel pump issue. If you can't keep the floats full, you'll eventually run lean which seems to be what's happening here. Float levels are too low. Way too low. I'm actually going to drop my tank tomorrow and redo all of the vapor and fuel lines in the rear, Checking float levels would be a lot easier. You might be focusing on what you're comfortable with instead of what needs to be done. Quote Link to comment Share on other sites More sharing options...
ThaPimpShrimp Posted November 26, 2014 Author Share Posted November 26, 2014 (edited) Checking float levels would be a lot easier. You might be focusing on what you're comfortable with instead of what needs to be done. I already had most of the parts and was planning on doing this anyway, but I will also take a look at the float levels. I have the DVD from ZTherapy, but I believe you can check it with a piece of clear tube right? Edit: Found a few articles on it, I'll get it done this weekend hopefully! Edited November 26, 2014 by ThaPimpShrimp Quote Link to comment Share on other sites More sharing options...
ThaPimpShrimp Posted November 27, 2014 Author Share Posted November 27, 2014 Float bowl levels measured just about 23mm from the top of the bowl on both carbs. Quote Link to comment Share on other sites More sharing options...
ThaPimpShrimp Posted November 28, 2014 Author Share Posted November 28, 2014 Tank is out! A little beat up but the inside is rust free, so that's good news. The filler neck looks like it was leaking a bit where it connects to the tank.. but I'm unsure whether that is due to it being bad or the clamp.. clamp looked original but the neck still feels pretty good. Happy Thanksgiving! Quote Link to comment Share on other sites More sharing options...
ThaPimpShrimp Posted January 3, 2015 Author Share Posted January 3, 2015 Here's an update for you all. Thanks for your help and input thus far. Unfortunately the issue has not been solved yet. Like I think I mentioned before I checked the float levels and they were good - remember these are ZTherapy rebuilt carbs so I'd hope so Since, I have installed a carter electric fuel pump, holley FPR, and a fuel pressure gauge. Removed the mechanical pump and put on a blockoff plate. Fuel pressure is a constant 4psi to the rail now. The only way I really have to test this issue is via butt dyno and test driving, as I can't afford $200 every change to go to a dyno and have them check the AFR's (though I am somewhat considering a wideband... seems so unnecessary though). Today I ran a 3rd gear pull and it seems the same, no power gain above that 3500 mark or so and it won't even pull past 5500. What's next? I'll be calling the guy who helped me build my engine tomorrow to see if he's got any ideas. Quote Link to comment Share on other sites More sharing options...
inline6 Posted January 3, 2015 Share Posted January 3, 2015 (edited) Float bowl levels measured just about 23mm from the top of the bowl on both carbs. I think you have a fuel delivery problem. The 23 mm measurement for float level in the Factory Workshop Manual (FSM) is from the fuel level with the float sitting in it, to the highest point on the inside of the roof of the float chamber cover. How are you checking that dimension? Since I couldn't determine an effective way, I used a section of a nail cut and then ground to a length of between 14 to 15 mm (the other spec shown in the FSM), and then pulled the SU tops off, used some wire nose pliers to hold the nail in position between metal strip on the float top... to the inside of the roof of the carb cover. I would then adjust the float arm just far enough so that when the float, nail, and top were all "bottomed out", I could not blow air through the fuel inlet pipe (with my mouth). You said you had the advance in the distributor reworked. I would hook up a timing light and spec out your advance functionality so you can verify it is not contributing to the problem. You should be able to see initial advance at idle, and then record advance movement as rpms increase. Full advance (record that amount) will probably be achieved somewhere between 3000 and 3500. Edited January 3, 2015 by inline6 Quote Link to comment Share on other sites More sharing options...
Tony D Posted January 3, 2015 Share Posted January 3, 2015 Make sure your starter system allows the jets to return to where they're supposed to be. If one is down further, or stuck "on" partially it will act like a Rev limiter. Regardless of float levels one bowl will eventually be sucked dry, and you flatten out in power...like a Rev limiter. Quote Link to comment Share on other sites More sharing options...
inline6 Posted January 3, 2015 Share Posted January 3, 2015 (edited) Make sure your starter system allows the jets to return to where they're supposed to be. If one is down further, or stuck "on" partially it will act like a Rev limiter. Regardless of float levels one bowl will eventually be sucked dry, and you flatten out in power...like a Rev limiter. Whenever mine did that, I had a way to rich situation, not way too lean... but easy enough to check. Similarly to Tony's point, how is the syncing of the carbs? Ztherapy can't do that - it has to be done on the car. Edited January 3, 2015 by inline6 Quote Link to comment Share on other sites More sharing options...
ThaPimpShrimp Posted January 3, 2015 Author Share Posted January 3, 2015 I think you have a fuel delivery problem. The 23 mm measurement for float level in the Factory Workshop Manual (FSM) is from the fuel level with the float sitting in it, to the highest point on the inside of the roof of the float chamber cover. How are you checking that dimension? You said you had the advance in the distributor reworked. I would hook up a timing light and spec out your advance functionality so you can verify it is not contributing to the problem. You should be able to see initial advance at idle, and then record advance movement as rpms increase. Full advance (record that amount) will probably be achieved somewhere between 3000 and 3500. I found a method online where you attach some clear tubing to the bottom of the float bowl, then let the fuel pump fill up the bowl/tube. Then you can measure the fuel level to the outside of the bowl. I will definitely check the timing again, I had the same thought as you when I was thinking over the issue in my head last night. Make sure your starter system allows the jets to return to where they're supposed to be. If one is down further, or stuck "on" partially it will act like a Rev limiter. Regardless of float levels one bowl will eventually be sucked dry, and you flatten out in power...like a Rev limiter. Interesting, I'm not super familiar with the internals of these carbs yet, so I'll do some reading and try to check this out. how is the syncing of the carbs? Ztherapy can't do that - it has to be done on the car. Carbs are synced with a Unisyn. Quote Link to comment Share on other sites More sharing options...
Tony D Posted January 4, 2015 Share Posted January 4, 2015 It's external. The levers only push your jets DOWN they have a spring to return them up to adjusted height. If it sticks down, you suck the float bowl dry and run on one carb. If that doesn't cause lean starvation, I,don't know what would! Lift off WOT and the engine pulls higher... Sometimes... Quote Link to comment Share on other sites More sharing options...
madkaw Posted January 4, 2015 Share Posted January 4, 2015 'Wideband seems so unnecessary', you still think that? Like stated, are you 100% sure on your ignition? Quote Link to comment Share on other sites More sharing options...
ThaPimpShrimp Posted January 5, 2015 Author Share Posted January 5, 2015 It's external. The levers only push your jets DOWN they have a spring to return them up to adjusted height. If it sticks down, you suck the float bowl dry and run on one carb. If that doesn't cause lean starvation, I,don't know what would! Lift off WOT and the engine pulls higher... Sometimes... Ah I know what you're talking about, but no mine aren't getting stuck. I had that issue in the past but I've since solved it. 'Wideband seems so unnecessary', you still think that? Like stated, are you 100% sure on your ignition? Haha well no not entirely, I'm definitely considering it. Definitely would be nice. Still need to check out the ignition - haven't had any time this weekend. Quote Link to comment Share on other sites More sharing options...
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