[Dylanic_350]

hello I have a 73 gmc c-15 pickup. It has a new 355 with edelbrock eps intake, demon jr. 625 carb, comp extreme energy 268 cam. It also has a turbo 400 with stock converter and shift kit. The truck starts up great and idles fine at about 900 and has a nice choppy idle. All is good until I put it in gear and it rpm's drop to 400-500 and dies. There is no vacuum leaks and in park it idles fine and has great throttle response. Please help

[68NovaSS]

Sounds like you need a stall converter, what does the cam manufacturer recommend?

[riceharvester]

Bump your idle up to 1200....
You can't run it low with a lumpy cam.

[SSedan64]

Comp says -(Largest cam for stock converter). A low compression engine may still need a higher stall as 68NovaSS said.
If after rasing the idle rpm the truck wants to pull forward too much while holding the brakes try a 2000-2400 stall converter.

[klutchmaster427]

I would say the same thing. Raise the idle a bit.

[Dylanic_350]

thanks to you all....got the crappy demon carb running alittle better and now she runs...i'm thinking a hughes 2200-2500 stall would be good. All in all i'm buying a 650 double pumper!!!!

[Tech @ BG]

Originally Posted by Dylanic_350

thanks to you all....got the crappy demon carb running alittle better and now she runs...i'm thinking a hughes 2200-2500 stall would be good. All in all i'm buying a 650 double pumper!!!!

It amazes me but always seems to be the newbies on here trashing us when the carb is not even at fault. If you buy the proper size and series carburetor per our recommendation charts they work a lot better. Accoridng to the specs on the cam you provided this motor should have had a Speed Demon on it instead of the Road Demon JR as they are basically for stock camshaft motors with no more then .220 at .050 on the cam duration. Here is the specs on the 268 Extreme.
.................................................. .................................
Brand COMP Cams
Manufacturer's Part Number CL12-242-2
Part Type Camshaft and Lifter Kits
Product Line COMP Cams Xtreme Energy Cam and Lifter Kits
Summit Racing Part Number CCA-CL12-242-2
Cam Style Hydraulic flat tappet
Basic Operating RPM Range 1,600-5,800
Intake Duration at 050 inch Lift 224
Exhaust Duration at 050 inch Lift 230
Duration at 050 inch Lift 224 int./230 exh.
Advertised Intake Duration 268
Advertised Exhaust Duration 280
Advertised Duration 268 int./280 exh.
.................................................. ..................................

Notice it is .224 and .230 @ .050 which is well out of the range for the carb. As one of the others mentioned you are probably going to need at least a little converter to get it to idle in gear but the carb is going to need some serious adjusting if you are going to get it close. With that cam you will need to crack the secondary butterflies and will also need to set your base timing in the 14-16 degree range if you have not already done so.

[Dylanic_350]

it doesn't even matter....the carb has been a piece since i've bought it....metal shavings and machining imperfections in and on the fuel bowls...Even on the stock 350 the damn thing wouldn't idle....and non stick gaskets (what a joke)....when you try and adjust the float level gas would spray every where. might as well but on the quadra bog back on....Then you ask if you can send the carb in and all BG wants is money....worst 300 dollars i've ever spent!!!! just build a better carb

[fast68]

have had this trouble with old carb engines due to incorrect carb base gasket

most recently a late '70's 351C that we put a remanufactured out of the box motorcraft 2bbl on from the store and still didnt run right and would die coming to a stop etc.

new correct base gasket turned it into a perfect running truck

EGr passages in the EGR plate were not covered up correctly with whatever gasket came with the carb that he put on it.