loehr78

Hi all , i have a 86 gt that i rebuilt back in march , its a mild 306 , and i did away with the efi and put on a carb . I had an odd holley given to me and i used it for a while but could never get it to run right , so i bought a used eddy 1405 and cannot get it to idle , when it drops bellow 1300 rpms it will die or idle will surge up and down and then die like it has a air leak , but i have checked and cannot find one , and the holley idled just fine , just didnt perform like i wanted , and seemed like it blew a power valve everytime i started it . I put a rebuild kit into the edelbrock , adjusted the floats , adjusted the idle mixture screws , checked for leaks , used a vacuum gauge it reads 15hg and and will jump back and forth up to 17 , wont hold steady , but the rpms arent holding steady either . I dont think the metering rods are bent , but i tried pulling them up while running and it seemed like it picked up im also going to put some different step up springs in it and maybe jets but i wouldnt think that it would cause that , and it seems to be ok being choked but when you open the choke it falls flat , above idle its great , has great throttle response and runs good so im kinda baffled , any help would be great , thanks . Andrew

dawson1112

You say you adjusted the mixture screws, but how did you adjust them ? There is no set amount of turns in or out for these carbs it is totally dependent on how the engine reacts to each setting. They all differ , Ive had some carbs that ran better with the mixture screws out 1 1/4 turns and some run better at 3 turns out. Try to richen it up a little and I think your troubles will be over.
Scince you say you put a rebuild kit on the carb I would assume you also replaced the float valve. A sticky float valve will make it hunt like that. As will a vacuum leak.

loehr78

Im not sure what you mean by float valve unless you mean the screen that fits in the seat, i did replace the needle and seat and screen, but it does seem like the floats are sticking , like its emptying out and trying to fill up causing it surge. It also seems like an air leak that was my first thought and have went over it several times with carb spray but with it idling like that its so hard to tell plus the other carb didnt do this , and the mixture screws i started at 2 turns out and they dont make much difference at all even turning them almost all the way out , it is deffinatle running to lean and pops out of the exhaust , also on the metering rods i popped them up while it was running and it seemed to idle a little better like it was starving for gas , guess ill try adjusting the floats again for the 3rd time , also i put a regulator on and set it to 5psi (was running at 7/12 ) when i put this carb on so i know its not the fuel pressure . The motor only has about 900 miles on it since i rebuilt it dont know if that would matter tho it should be broke in by now . When i rebuilt it the 2 things i didnt replace were the lifters and push rods , i probably should have but spent way more than i intended . Thanks for your reply .

Mike T

Sounds like something is stopped up that you failed to replace or bad metering rod.

loehr78

That was my thoughts also along with air leak , i blew it out with compressed air when i rebuilt it tho , dont know how to tell if its a metering rod without replacing them , i checked the travel on them and they arent sticking or hitting i suppose it could be bent enough to cause it to do that tho. Have any ideas on how to check the base plate for warping ?

tinman

Baseplate can be checked for flatness using any good striaght edge.
Piece of aluminum extrusion works for me..........

Mike T

If you think the base plate is warped, spray carb cleaner around it while it's running and if the rpm's go up it's pulling in air. By the way, if you have a metering jet stopped up, compressed air will not necessarily unstop it.

loehr78

Should there be fuel dripping out of the primaries at idle ?

loehr78

Also noticed when i adjusted the floats the other day that they were sitting cockeyed , would that cause them to get stuck on the baffles in the fuel bowl ?

Mike T

Yes, that's possible.