Edelbrock Performer 1903 Carb Woes...

[FlatBlackBurb]

I have a '77 GMC K2500... About 4 years ago, it had the stock quadrajet on it, wasn't running good and failed smog so my buddy gave me his Performer 1903 that his truck just passed smog on. I put the carb on and it ran pretty good when cold, but when it was warm it felt like it wasn't getting enough gas, the motor would kind of sputter sometimes going up steeper hills. That was two years ago. It sat for two years and I just drove it the other day, started ok... still the sputtering problem here and there. So I rebuilt the carb. Now it doesn't even want to idle and dies under throttle. I rebuilt everything right and cleaned the s*** out of everything. Is there any way to tune this? Or some kind of guide? Maybe a vaccum diagram somewhere? I'm fed up with it and wasting my one day off just getting my knuckles bloody! any help would be nice thanks guys

 

[FlatBlackBurb]

I should add that when I pull the throttle all the way back the primaries barely open and the secondaries do not open. This is when the truck is off. The performer has always been this way is it normal? Could be a stupid question. I know the secondaries have to open under WOT because the thing pulls pretty good when it gets into the higher RPMs

 

[Hogback Fabrication]

Did you try rebuilding the Q-jet (and inspecting for worn throttle shafts, warped bodies/plates etc)?

If it were me I'd spend my time on the Q-jet rather than the Edelbrock.

 

[diesel4me]

The Edelbrock's secondary barrels butterflies open with the linkage,but they have an air valve over them thats opened by engine suction,it has a counterweight to keep it closed until sufficient suction is obtained..Q-jets have a similar air valve operated the same way,that has a spring to keep it closed until the engine can handle the extra fuel and air......................................................................................................The primary butterfiles should fully open with the pedal floored,even with the engine not running--if not,your cable needs adjusting or you have a thick floor mat keeping the pedal from being fully "floored"........................................................................................I'm not sure what CFM a 1403 Edelbrock is--might be a 500 CFM,which is a bit on the lean side for a 350 or larger engine..it may need larger jets installed,depending on altitude and other engine operating conditions............................................................................................I like Edelbrocks,but there is nothing wrong with a properly tuned Q-jet either,they behave better off road and in off camber ,hill climbing and bouncing trail applications...

 

[black dawg]

The Edelbrock's secondary barrels butterflies open with the linkage,but they have an air valve over them thats opened by engine suction,it has a counterweight to keep it closed until sufficient suction is obtained..Q-jets have a similar air valve operated the same way,that has a spring to keep it closed until the engine can handle the extra fuel and air......................................................................................................The primary butterfiles should fully open with the pedal floored,even with the engine not running--if not,your cable needs adjusting or you have a thick floor mat keeping the pedal from being fully "floored"........................................................................................I'm not sure what CFM a 1403 Edelbrock is--might be a 500 CFM,which is a bit on the lean side for a 350 or larger engine..it may need larger jets installed,depending on altitude and other engine operating conditions............................................................................................I like Edelbrocks,but there is nothing wrong with a properly tuned Q-jet either,they behave better off road and in off camber ,hill climbing and bouncing trail applications...

I put one of those 500cfm edelbrocks on my old carbed suburban and really liked it. had q-jet before, and with both carbs jetted accordingly the edelbrock got better mpg (13mpg). It did lose some wot power over the q-jet though.

 

[diesel4me]

I always had good luck with Carter AFB's,and I have had a few Edelbrocks,that are about as good,but the 625 CFM Carter's had better power and throttle response that the Edelbrocks for some reason--weird because they are almost identical clones,and not much different in CFM..........................................................................................................................my only gripes with the Edelbrock was the fact one on my plow truck would starve,flood or die when I climbed up a snowbank with a full blade!....the Q-jet would run until it tipped over without a sputter,but it had a aggravating flat spot just past idle I couldn't get rid of..........................so I swapped an aluminum intake on it and got a used 1406 Edelbrock cheap at a swap meet and parked the Q-jet on a shelf....my gas mileage went down a bit ,the square bore carbs are not as thrifty with fuel as those small Q-jet primaries are,but I liked how it boooted with the secondaries kicked in...........................................................................................................I never had that much love for Holley carbs,but I did have a 450 CFM one on a 1974 454 ,it was one that never came with any choke,not even a shaft or butterfly!--it sucked starting it cold ,and driving till it warmed up in cold weather was "fun",but man,that thing made that engine roar!...and I could get 15 mpg if I drove it like grandma,probably no choke saved a lot of gas??....another spread bore Holley 750 I had that was a Q-jet replacement "bolt on" deal worked very well,it had vacuum secondaries,all I had to do was change the spring in the secondary diaphram unit,to get it to boot in right................................................................................................................but I've also had a dozen other Holleys that never ran worth a crap,backfired,set the air cleaner on fire,no matter how you adjusted the floats,etc...the power valves were probably junk,I just went with Q-jets or Edelbrocks and Carters ,they seemed to run good with minimum fuss and you weren't always trying to "tweak" them...Holleys seem to need adjusting every day when the weather changes sometimes..I do think when the Holley decided to run well,they produced the most power..I liked the "Economaster" Holleys,I had a few of those that were 450 CFM's and bolted up to a Q-jet manifold (model 4360).......I have a 2 bbl one on my 307 in my van too....

 

[Greg Ducato]

The 1903 is a Q-jet and is no longer sold by edelbrock, I still have a couple of these on vehicles. I had one that was acting up that I couldn't sort out and sent it to Sean Murphy who calibrated it for my application and it is still on the truck running great 5 years later. That guy really knows his way around a Q-jet and would be worth contacting before you give up. www.smicarburetor.com

 

[Deuling]

The 1903 is a Q-jet and is no longer sold by edelbrock, I still have a couple of these on vehicles. I had one that was acting up that I couldn't sort out and sent it to Sean Murphy who calibrated it for my application and it is still on the truck running great 5 years later. That guy really knows his way around a Q-jet and would be worth contacting before you give up. www.smicarburetor.com

That looks like a sweet site there. How much did he charge for you to send him one to build and tune?

 

[Greg Ducato]

That looks like a sweet site there. How much did he charge for you to send him one to build and tune?

I honestly don't recall the price, he has built me several carbs over the years, but I'm sure it was less than a replacement carb. I'm sure he would be glad to shoot you a quote, I never felt I was overcharged for the quality of the work.

 

[Deuling]

I honestly don't recall the price, he has built me several carbs over the years, but I'm sure it was less than a replacement carb. I'm sure he would be glad to shoot you a quote, I never felt I was overcharged for the quality of the work.

Thats fantastic cuz I want a qjet but am to stupid to understand (or want to understand) how to rebuild them lol.

 

[FlatBlackBurb]

i did inspect all the plates they looked to be in good shape... is there anything I can do to get it to run better like maybe tweaking with the air fuel a little bit?

 

[MontanaJohn]

That looks like a sweet site there. How much did he charge for you to send him one to build and tune?

I orderd a Stage 2 750 cfm for my 415 ci SBC from Sean. Gave him all my specs and altitude, and he custom tuned it. Price was $375, and it was sweet. Better than new condition, almost perfect right out of the box. It snaps w/ no bog. Just had to adjust the secondaries.a little. He does beautiful work.