Super Low Gas Mileage

[olds307 and 403]

In town, sounds about right. Are you using ethanol gas? EGR and the lock up especially could effect mileage. I am betting there is a code set and putting it into limp mode. The air system can be bypassed but the connections must be plugged at cat and head connections. Also the belt should taken off the pump.

 

[Clone TIE Pilot]

FWIW, I put a Mountain Man reman QJ on my previous Bonneville, it performed very well As I recall, he was a GM tech for many years before he moved into his own business operation.

In my case, it cured the issues I was having, which could, I'm sure, have been cured by rebuilding the original, but it is my understanding that the CCC carbs require some specialized tools to properly set up and said tools are not widely available in today's market.

Personally, I would not hesitate to use him again, although it is nice to know that you have a wealth of knowledge about these systems.

Unfortunately, my current wagon (267, TH350, 2.41 axle) has had a good deal of butchery applied....when i bought it, it was still running the ECM and distributor, but had an earlier non-computer Dualjet on it. I did buy an old stock reman Dualjet for it, didn't really fell like replacing carb dist and intake at the time to go to non-electronic. EGR, EFE, AIR have all been axed by previous owner or their "mechanic" Consequentially, best mpg day-to-day is about 14. Of course, my daily commute is 80 miles, and 42 of that is turnpike at 75 mph.

You can make those tools yourself, Montecarloss.com has instructions posted on their forum.

 

[Ribbedroof]

Thanks for the tip!

Probably moot point for me, LT1 swap in the works, but good to know if I need them on another car.

 

[Z48LT1]

Thanks for the tip!

Probably moot point for me, LT1 swap in the works, but good to know if I need them on another car.

Ribbedroof, an LT1 (presume we're speaking about the mid-90's version) has been a basis of a fantasy mileage maker build of mine for years. In mid 90's B-bodies, 4200 pounds with everything working, stock LT-1s allegedly got 25mpg at highway speeds. I have to believe the 4.3L L99 - identical to the LT1 5.7L in every aspect except displacement would make a terrific econo SBC. This Gen II Chevy small block had a mature aftermarket for PCM tuning, although the emphasis was naturally higher performance. It seems to me that a mileage rear end, overdrive transmission, efficient intake and exhaust, and spot-on tune should have no problem getting 30 MPG on the highway. I bet it wouldn't embarrass you at the stoplight, either.

Your thoughts?

Best - Gary

 

[Ribbedroof]

I think the biggest drawback for MPG on a G body (especially wagons/sedans) is that we have the aerodynamics of a brick. Lots of sharp corners, and pretty big frontal area.

I have a friend that had an 85 Camino, 4.3 V6, OD and routinely pulled 28 mpg on highway usage (he was a an insurance adjuster for all the outlying/small town shops, lots of travel). I don't remember what gear was in it, but it was whatever it left the assembly plant with....2.XX I'm sure.

Better/more tuning possibilities of the Gen II system could certainly make it a possibility if one could keep their foot out of it. I have considered an L99 swap for the express purpose of commuter use, but good donors are still expensive, and kind of scarce. Doesn't help that they come in a vehicle that has a pretty high level of demand for use as donks/hi riders (apologies to Qdub, I am not well versed in the defining parameters of donks)

 

[Wageslave]

FWIW, I put a Mountain Man reman QJ on my previous Bonneville, it performed very well As I recall, he was a GM tech for many years before he moved into his own business operation.

In my case, it cured the issues I was having, which could, I'm sure, have been cured by rebuilding the original, but it is my understanding that the CCC carbs require some specialized tools to properly set up and said tools are not widely available in today's market.

Personally, I would not hesitate to use him again, although it is nice to know that you have a wealth of knowledge about these systems.

Unfortunately, my current wagon (267, TH350, 2.41 axle) has had a good deal of butchery applied....when i bought it, it was still running the ECM and distributor, but had an earlier non-computer Dualjet on it. I did buy an old stock reman Dualjet for it, didn't really fell like replacing carb dist and intake at the time to go to non-electronic. EGR, EFE, AIR have all been axed by previous owner or their "mechanic" Consequentially, best mpg day-to-day is about 14. Of course, my daily commute is 80 miles, and 42 of that is turnpike at 75 mph.

I'll give a 2nd vote for Mountain Man. I bought a Quadrajet off of him a few years ago for my old stepside with a 305. The thing was flawless and I could get about 20mpg with it.

 

[jiho]

but it is my understanding that the CCC carbs require some specialized tools to properly set up and said tools are not widely available in today's market.

http://thexton.com/