Thanks for your help with the neighbor's car.

We replaced the points and condensor and adjusted the valve clearances with an old set of shims that I had leftover from my 142. It runs 90% better as a result.

Took it up on the freeway and it keeps up with traffic but sounds winded. No tach but going by ear the engine speed must be in excess of 3,000-3,500 rpm at 70mph. This is a '67 with B18B and M40. Don't know the diff ratio. About how fast is the engine running at 70? 75? Is there anything wrong with my neighbor using this car for a 30 mile R/T highway commute? Premature engine wear or just a decrease in fuel economy?

My 142 had overdrive and I almost never drove in 4th with the O/D off under 45-50mph.

Thanks again.

Adding an overdrive is not hard (car was designed for one) and is very straightforward. The difficulty is finding a good M41 for less than an arm and a leg.

I added one to my 1967 220 and the only extra costs were getting a proper output flange and a short front driveshaft (at $50.00 each) plus new front U-joints.

But overall, not difficult and *plenty* worth the effort for a highway car.

The first thing your neighbor has to do is get used to high RPM. The only bother it causes is to humans. The engine doesn't care. Overdrive will knock 800 rpm off I think, so it will still turn over 3k at 70mph. I run my 1980DL with a B23 engine at 4k and get 27 mpg. Here on the coast many run the I/O penta boat engines at 4k and that's at wide open throttle.
Don't worry about valve seat recession unless in happens, and if it does, you'll know it. Then the head can be modified. Some recess, some don't, and usually it has more to do with weak springs and valve bounce than with unleaded fuel.
Don't bother with thick head gaskets, just use premium.

Your ear-tach is about right. This car probably has a 4.10 rear axle, so it would be turning about the same revs as your 142 did in straight 4th (B20 cars with OD usually had a 4.30 rear) With one exception, this is not a recipe for rapid engine wear, but it will burn up a fair amount of gas (I had a 68 144, many years ago--B18, M40, 4.30--and it never did better than the low 20s, whereas my 71 142E with OD would easily do 30 on the highway)

The one exception is the valve seats. They are cut directly into the cast iron head, and are prone to rapid wear if unleaded gas is used. When you adjusted the valves (What do you mean about shims? Are you referring perhaps to feeler gauges?) were any of them, particularly the exhausts, way too tight? This is a sign of valve seat recession, which, once begun, will continue rapidly. The engine will begin to lose power again, after a few hundred miles, and the valve(s) will be found to once again have little or no clearance. The cure is to pull the head, and have hardened seats installed at a machine shop. New valves are probably a good idea at this time. The 68 B18B has 10.5:1 compression, and requires premium gas. Try to find an extra thick head gasket if possible, to reduce the compression a bit.

Once everything is back together, this car should be perfectly capable of the proposed highway commute, assuming everything else (with particular attention to brakes) is in good shape.

It may be that valve seat recession has not yet begun. However, it will eventually happen. Using a lead substitute additive in the gas, and driving gently will help delay the inevitable. I hope this doesn't come across as too discouraging, but it is the reality of using a 40 year old car as a daily driver.

It's a major job, but many 122 owners have added overdrive to their cars, which helps a lot with gas mileage, and makes it a lot more pleasant on the highway.