Corvette Fuel Consumption

When driving to see my friend at Tampere, I also finally measured the fuel consumption of my car. I filled the tank when leaving, drove about 190km and idled a bit while measuring the exhaust gasses. This took 30 liters of fuel.

So the car drinks about 15-16 liters per 100 km. Or does about 15 miles per gallon to US readers.

Could be much worse but with 1,65 € per liter (or $7.9 per gallon) of 98 octane fuel in Finland at the moment, it's not a cheap car to drive...

Wheel Alignment, Carb Tuning And Transmission Fixing

It's been a while since I last fiddled with my Corvette so it was time to go back to business. I drove the car about 130km to Tampere to see my car mechanic friend. We had a few tasks on our list: check the wheel alignment, see if the carburetor was tuned correctly after my rebuild and open the transmission to check the shifter linkage.

The drive to Tampere went fine except for the heat. The cabin of the car got pretty hot after a while and it was quite noisy. The Corvette also didn't seem to like the highway. If driving over 100km/h (62mph), the temperature of the engine rose. Not enough to overheat but enough to limit the speed to about 90km/h (55mph)...

Carburetor tuning

We began from the carb as the car was hot after drivin it to the garage. I had rebuild my Holley 80457-S during winter so I had no idea if it was tuned correctly. We placed the probe in both exhaust pipes individually and checked the readings. Idle HC was about 100ppm on both sides and CO about 1%. This meant the engine was running pretty lean!

We loosened the idle screws and got the HC values to about 300-350ppm and CO to about 5% - 5,5%. This was much better.

Next we tested the engine at 2200 RPM. CO dropped to 1% again. I guess this means the carb needs larger main jets. This could also be the reason why the engine gets hot on the freeway as a lean mixture burns hotter.

Left exhaust reading

Right exhaust reading

Wheel Alignment

Next on the list was the wheel alignment. I drove the car on a lift and my friend set up the gear. I didn't know how to use the equipment so I just stood out of the way and looked. It took some time but finally we had the results: both front and rear alignments were within specifications! This was surprising as a lot had been done to the suspension since the last alignment: front springs had been cut, rear had been risen a bit, rear bearings had been changed etc. Oh well, I'm not complaining as this was a much easier job than expected.

Transmission Surgery

I already opened my TH-350 transmission once during winter to tighten the shifter shaft nut. This cured the missing first gear for a while until the nut loosened again. So I knew the transmission was working but the shifter was not.

We drained the oil and dropped the pan. After some examination, my friend had a revelation. Here's the old photo from winter.

It's a bit hard to see but there is a washer on the shaft. But not between the nut and the plate but between the plate and the clip that holds the shaft in place! We removed the clip, opened the nut and pulled the shaft out. Quickly we saw that with the washer in place, the plate never locked to the shaft but just rotated around. We switched the washer to the other side of the plate and put the transmission back together. Wow, even after working with the car for this long, we still find surprises like this...

Finally we decided to switch the speedo driving gear too. The only one I had found before had 10 teeth but after driving a while, I learned I would need a 8 teeth one. The speedometer was showing way too high. Changing the driven gear would not help as I would need a 24 teeth one, but the largest one for TH-350 had 22.

So we pulled the end of the transmission and removed the old, blue gear. I got the correct black one from US-Parts again but something was wrong! The gear was really loose on the transmission shaft. The old one was really tight but this new one was about 1 millimeter larger in diameter. This also meant that the clip that should hold it in place didn't work.

We had to cut the gear up a bit and push a split pin under it to hold it in place. We could only hope it would work and put the transmission back together. Unfortunately it didn't work as the speedometer didn't work at all after this... *uck!

On the return trip the engine still got hot on the freeway and cooled after a few kilometers of slower driving. I need to adress that issue later and go back to the speedo gear too...