From home (Denver area) to Lincoln, Nebraska, via I-76 & I-80. Cruise control held speed at 75 mph within the needle's width. First leg, 275 miles, averaged 22.4 mpg, filled up with 89 octane "super" (10% ethanol). Had some part-throttle no-downshift accelerating pinging with the 85/89 mix. 2nd leg, 215 miles, averaged 24.2 mpg, topped off with 89 again. Pinging gone.

First time it's been at a lower altitude. Doesn't feel a lot different in 1st (probably is, just didn't "feel" like it), but seems to pull a lot harder in 2nd (based on one on-ramp "test"). Had to back off before hitting 3rd.

We'll see how it does on the return trip next weekend.

 

You certainly can't whine about the fuel mileage, and the direction it is going. It may be a little difficult to determine what combination of altitude, accumulated mileage, fuel blend, and tuning may be the reasons for the changes. Maybe your fuel mixer doesn't like to be light-headed.

 

NICE, MPG numbers from a carb. We keep preaching the Q-jet and others go to a Holley.

Anyway, I can see first not feeling much stronger, mainly due to the lower gear ratio of your 700r4. In first gear, you really can't tell 305/350 stock or modified, it is still pretty quick. Hit 2nd or 3rd though and that is where the difference is.

 

Well, I don't know about that 1st gear theory. The 350 is .2 sec quicker in 60' than the 305 was. You can certainly feel that.

 

Those are really good #'s. Thanks for sharing. It sounds like a fun car to take on a trip.

 

Well, it was okay on I-80, which is fairly smooth. Coupled with a slight rear snow tire shake, I-76 came close to shaking some teeth out. Needs a quieter muffler, too.

 

I should have filled up with 87 before heading out. The high-altitude 85 octane just doesn't do it when the altitude density goes down several thousand feet.

It seems to enjoy the 89 octane 10% ethanol gasahol that's all over Nebraska.

 

5/7 does your car have a knock sensor?, If you were detonating on tip-in, that could be the difference in power in 1st gear.

My 1st gear difference was based on 4 different combo's (355 A, 355B, 312A, 312B) of mine all getting to the 60' mark between 2.2 and 2.4 seconds. All three in varying states of power output, and still hitting the 60' mark at about the same time. 330' still looked pretty similar. The difference really became apparent about 660' though.

 

It has a knock sensor. I noticed the pinging when hitting Resume on the cruise from 45 mph - the TC was locked, the tranny didn't shift down, it rattled a bit. It didn't make a peep the time I floored it.

I really didn't get on it a lot because I was trying to see how it would do on mileage. However, the one time I did get on it was on the tank that averaged the 24. Around town after filling up, I played around a little more and it generally felt stronger and didn't ping.

If I spent any time at sea level, I'd probably drop the base timing down a couple of degrees.

 

You couldn't handle the pressure...

 

Not bad--when I was running my EQJet/ZZ4/T56/3.89 combo, I got 24.5 on the highway on average. Fear the QJet

 

24 mpg, runs low-13's - something to fear indeed.

 

Thanks to a Nebraska State Trooper westbound on I-80, I learned the 77 mph I set the cruise on was a little closer to 81 mph. No, he didn't tell me that through the window, I figured that out pacing him in the right lane (didn't feel like passing him on the right). So, for the trip home I was going about 5 mph slower, and mileage was 25.1 on the last leg.

I'll figure out the total trip average later. It will be skewed by some in-town driving and some on-ramp T&T's in the middle fill-ups.

(If anyone reading this is in Lincoln, and you happen to be on the southbound NW 48th St to westbound I-80 on-ramp, you may find some evidence of one of those T&T's . . . )

 

1096 total miles, 50.2 gallons used, 21.8 mpg average.

 

Very nice- especially considering you've got a bit of a cam in that motor. Bigger cams usually mean economy takes a bit of a dump, but that's really not bad. Almost right up there with the kind of mileage my stock 94 LT-1 fuel injected Formula got- AND I had the benefit of a double overdrive 0.5:1 6th gear cog in the (manual) tranny.

I averaged around 18 in mixed driving with a best of about 27 on the highway.