1969 GMC Short Fleet Build

[djmachinist]

Well, I'm having the engine worked on again. I was not happy with the original ZZ4 350. The engine ran on 93 octane only with the CR of 10:1. It did not idle very well for a fairly mild engine and its off idle street manors were not very good. On top of that, no way the engine put out the 355 HP that GM claims. Well I then went wild and had the ZZ4 stroked to a 383 ci.
with AFR 180 Heads, Comp Cams HR269H cam, Edelbrock RPM AirGap manifold and topped off with a Quick Fuels 680 Holly type carb w/ full headers and magnaflow mufflers. I have put about 3000 mile on this set up in the last eight months. The engine is pretty good. Puts out about 420 HP/ 430FT/LB
of torque. The low speed off idle responce has improved from the ZZ4, however the MPG is still pretty bad at about 9 mpg if I take it easy.

I thought I wanted this kind of engine, a real hot rod, however I have found I do not really want to live with this engine on a daily basis. So..... I am backing down the cam and carb specs. I am having Bumbera's performance install a milder Comp offroad cam that Comp tells me will improve the low end responce and torque and smooth out the idle with very good gas miledge over what I have now. I also am changing the carb from the QF Holly to a Sean Murphy built Quadrajet. I have read and talked to a lot of people about the Quadrajet. I've heard everything from the "Best Street Carb ever made" to the quadrajet refered to as "quadraJunk". My Engine man (Kenny Bumbera) says If built and tuned properly they are a very good street carb. The idea is the small primaries give you excellent off idle response and good gas miledge. And the huge secondaries give you decent power if you want it. I hope this will accomplish what I am trying to get too. I want an engine that has good low speed and idle manors with decent MPG. Yet will produce decent power.
I know I should not care about gas miledge on a vehicle I will drive only 3 to 4 thousand miles a year. But for some reason it bothers me I am only getting 8 to 9 MPG. I will post the verdict after I get a few miles on this set up.


Dale