Trouble in open throttle

[mrladewig]

I'm having trouble with my new to me 78 K-10 with 350 and new quadrajet and distributor. Also, I have a 4 speed Muncie, not that it is the cause, but...

When there is alot of load on the engine, (low RPM and 3/4 to fully open throttle), the engine is putting very hard, and producing very little power. It also does not sound like the quadrajet is opening. If I let off the gas (to near idle) the power remains the same, and I can press down on the accelerator again lightly and get a little more power. But if I mash it, it goes back to putting along. If I very slowly work the engine up, it will get up to speed and reved up, and eventually the quadrajet sounds like it is opening. It will also lighlty backfire when I let off the gas.

The distributor is set at 10degrees BTDC instead of the 8degrees in the book, because I live at altitude and it seems to suite the engine. The engine idles nicely and will rev up without trouble if it is not under load. All of the vacuum hoses on the front side are new and fit tightly, the carb base gasket is also new (Mr. Gasket paper). Ignition module is new Accel. ( the old distrib was eating ign modules) The only vacuum hose which is not new is the line going to the brake booster, and it looks a little corroded. It doesn't make it feel like I don't have power assist on the brakes though. Vacuum measured off the vacuum port on the carb going to the vac advance is 8 lbs. I thought it was supposed to be 15...

I am planning to replace the brake booster vacuum line asap, but am getting a little frustrated and poor replacing parts. Anybody have a good method for checking for other vacuum leaks, or thoughts on other places to look. Anything else I might not have thought of? Thanks for the help