Gary Lewis Posted September 21, 2020 Share Posted September 21, 2020 Well I found a leak. I got another carb and took the top off and used duct tape. It leaked at the throttle shaft so I just thought I'd take the carb off and seal the intake and use the brake booster line to smoke. Lifted the carb gasket and saw two black marks on both sides, about half inch long. I still sealed the intake and tried blowing in but all I got was back pressure so I'm going to say the intake gaskets are good. Got another gasket and put a light coat of RTV around the skinny sides of the intake and as soon as the starter touched the flywheel it fired right up. Had about 20" and then I hit the throttle a bit and it would barely idle but I caught it before it died and turned the idle screw in. Then it was idiling and I blipped the throttle again and it idled really high. I backed the screw off and its back to having the screw not touching for idle. Vacuum was about 14". I also had the idle jet screws all the way in and it was still idling. It got lower but it didn't die. I dont know if I should've maybe let the RTV sit a bit more and its leaking there again or what. It was at like 10" before all this. So 14" is better but isn't the 20" I first got when I first did this. Also the screwing in the idle jet screws all the way and bringing the idle down a bit but not killing it has me concerned. Congrat's! You are making progress, but there are apparently several problems. First, RTV doesn't work well around gasoline. So using it on a carb gasket is not a good idea. And the two black marks suggest you have a mismatch between the carb and the intake. Like maybe a spacer is missing. Can you post a pic of that area and especially the black marks? It runs in my mind that Edelbrock sent a thin steel plate that was to go between the carb and the intake on some applications to close off a passage, like the EGR. It was to be carb, gasket, plate, gasket, manifold. Do you have that? Second, if you have the idle mix screws all the way in and the engine is still running then there's another source of fuel to the engine than the idle circuits. But the only way I know of that happening on an Edelbrock 1406 is if the fuel level in the carb is too high. Or if the check valve has been left out of the accelerator pump mechanism. Edelbrocks only like about 5 psi of fuel pressure. More than that and the fuel level at idle can rise because the pressure is lifting the float via the needle. What pump are you running? And if you've answered all of these questions before I apologize as I've not taken the time to go back over the whole thread. But I didn't see the answers on this page. Link to comment Share on other sites More sharing options...
Weberman Posted September 21, 2020 Author Share Posted September 21, 2020 Congrat's! You are making progress, but there are apparently several problems. First, RTV doesn't work well around gasoline. So using it on a carb gasket is not a good idea. And the two black marks suggest you have a mismatch between the carb and the intake. Like maybe a spacer is missing. Can you post a pic of that area and especially the black marks? It runs in my mind that Edelbrock sent a thin steel plate that was to go between the carb and the intake on some applications to close off a passage, like the EGR. It was to be carb, gasket, plate, gasket, manifold. Do you have that? Second, if you have the idle mix screws all the way in and the engine is still running then there's another source of fuel to the engine than the idle circuits. But the only way I know of that happening on an Edelbrock 1406 is if the fuel level in the carb is too high. Or if the check valve has been left out of the accelerator pump mechanism. Edelbrocks only like about 5 psi of fuel pressure. More than that and the fuel level at idle can rise because the pressure is lifting the float via the needle. What pump are you running? And if you've answered all of these questions before I apologize as I've not taken the time to go back over the whole thread. But I didn't see the answers on this page. I already cleaned the black marks but I'll try to make a pic later. It was like half way on the skinny sides if you're looking at the engine. I can post a pic of the gasket. Im running an Edelbrock electric as this engine had the Ford TBI, so no fuel pump hole. I had no idea about this plate til yesterday. I called O'Reillys and I kept asking for a gasket and they kept talking about this plate and I thought they meant like a 1" spacer but it was just a plate and came with 3 gaskets. Link to comment Share on other sites More sharing options...
Gary Lewis Posted September 21, 2020 Share Posted September 21, 2020 I already cleaned the black marks but I'll try to make a pic later. It was like half way on the skinny sides if you're looking at the engine. I can post a pic of the gasket. Im running an Edelbrock electric as this engine had the Ford TBI, so no fuel pump hole. I had no idea about this plate til yesterday. I called O'Reillys and I kept asking for a gasket and they kept talking about this plate and I thought they meant like a 1" spacer but it was just a plate and came with 3 gaskets. Depending on which pump you are using you could have too much pressure. Do you know the pump model or #? And are you running the three piece gasket/spacer setup? Link to comment Share on other sites More sharing options...
Weberman Posted September 21, 2020 Author Share Posted September 21, 2020 Depending on which pump you are using you could have too much pressure. Do you know the pump model or #? And are you running the three piece gasket/spacer setup? I believe I'm running the 38gph, 4-7psi pump. I just put a gasket on since I had no idea what the plate was for. Link to comment Share on other sites More sharing options...
Gary Lewis Posted September 21, 2020 Share Posted September 21, 2020 I believe I'm running the 38gph, 4-7psi pump. I just put a gasket on since I had no idea what the plate was for. Edelbrocks don't like more than ~5 psi of fuel pressure so it is possible that the pump is giving you too much. Is it adjustable? As for the gasket, you should be running both gaskets and the plate. That may well be the cause of the problem. Link to comment Share on other sites More sharing options...
Weberman Posted September 21, 2020 Author Share Posted September 21, 2020 Edelbrocks don't like more than ~5 psi of fuel pressure so it is possible that the pump is giving you too much. Is it adjustable? As for the gasket, you should be running both gaskets and the plate. That may well be the cause of the problem. Put the plate on with some fighting.. got the gasket and rtv off, put the plate in and as I was tightening up I noticed that one bolt wasn't really getting tight.. I looked and half the stud had come up. So then I almost bought a helicoil but just out of curiosity, I got a tap out and ran it down the hole. I cleaned some up at the bottom it felt like. Got a different stud, put it in, put a couple nuts on and tightened it down some and it held when I put the carb back on and tightened the nuts down. Vacuum may be 1" or 2" better, but its steady. The needle would bump around here and there before but now its a solid reading. Idle is still high but it also kept dying here and there. I think the last time before I called it quits was maybe due to an fuel idle screw but idk. I did mess with them some and still were pretty shut for idiling. I noticed on the last few that I would have to hold the throttle a bit for it to start. Flooding itself from pressure?? Link to comment Share on other sites More sharing options...
Gary Lewis Posted September 22, 2020 Share Posted September 22, 2020 Put the plate on with some fighting.. got the gasket and rtv off, put the plate in and as I was tightening up I noticed that one bolt wasn't really getting tight.. I looked and half the stud had come up. So then I almost bought a helicoil but just out of curiosity, I got a tap out and ran it down the hole. I cleaned some up at the bottom it felt like. Got a different stud, put it in, put a couple nuts on and tightened it down some and it held when I put the carb back on and tightened the nuts down. Vacuum may be 1" or 2" better, but its steady. The needle would bump around here and there before but now its a solid reading. Idle is still high but it also kept dying here and there. I think the last time before I called it quits was maybe due to an fuel idle screw but idk. I did mess with them some and still were pretty shut for idiling. I noticed on the last few that I would have to hold the throttle a bit for it to start. Flooding itself from pressure?? If you have the idle fuel mix screws shut and it is still idling there is certainly a problem. In my experience that can come one of two ways. First, if you left the check ball or weight out of the accelerator pump setup. Second, too much fuel pressure. Is your pump adjustable for pressure? If so, dial it down to see if you can get the thing to idle properly. Link to comment Share on other sites More sharing options...
Weberman Posted September 22, 2020 Author Share Posted September 22, 2020 If you have the idle fuel mix screws shut and it is still idling there is certainly a problem. In my experience that can come one of two ways. First, if you left the check ball or weight out of the accelerator pump setup. Second, too much fuel pressure. Is your pump adjustable for pressure? If so, dial it down to see if you can get the thing to idle properly. No, I'll have to get a pressure regulator, there's no adjustment on the pump. I know that the check ball is there Link to comment Share on other sites More sharing options...
Gary Lewis Posted September 22, 2020 Share Posted September 22, 2020 No, I'll have to get a pressure regulator, there's no adjustment on the pump. I know that the check ball is there Before buying a regulator I'd call Edelbrock's tech support and tell them what carb and pump you have and see if they think it can be too much pressure. They may say I'm all wet, in which case don't spend the money. Link to comment Share on other sites More sharing options...
Weberman Posted September 24, 2020 Author Share Posted September 24, 2020 Before buying a regulator I'd call Edelbrock's tech support and tell them what carb and pump you have and see if they think it can be too much pressure. They may say I'm all wet, in which case don't spend the money. I called Edelbrock today. He said that the fuel pump should be okay. I guess its self regulating but how would it know? Still thinking about getting a regulator so I know my settings would be right. How do I know if I'm tuning the carb for 4psi or 6psi? As for the screws, he said make sure that the throttle screw isn't too far in, I said well heres the thing, its not touching at all. So he said major vacuum leak still and its causing the primaries the fuel and its not on the idle circut, which makes sense. I guess I'll take the top half off of my carb and then do a smoke test through there. He says unless the carb base isn't straight or theres a bent shaft, there has to be one somewhere. He also said that I should definitely get rid of the mounting plate since its the same mounting pattern. The only thing I can think of is that since its a dual plane manifold, the leak might be on the otherside of the manifold. The brake booster vacuum only went to one side of the intake. Link to comment Share on other sites More sharing options...
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