By Glenn Goodspeed (January, 1997)
It's been a couple weeks since I put the rebuilt engine in my '63 P1800, and I have about 300 miles on it so far. What have I learned? Well, IPD (the Oregon parts supplier) was right when they said it would need a richer mixture from the carburetors.
I took the car for a 40-mile cruise last Sunday, when the weather was sunny and the temperature about 70 degrees Fahrenheit. It ran well, but I had to use the choke constantly to keep the engine from fuel starvation.
Back at the house, I went out to the shed to look for my box of old SU carburetor parts. I found a pair of "KD" needles in good condition. According to the Speedsport guide to tuning SU carbs, the KD needle is skinnier than the stock ZH needle by about a hundredth of an inch, which makes the fuel mixture for the KD quite a bit richer. Since IPD recommends an SM needle for a B18 engine bored out to B20 size, I compared the sizes of the SM and KD. They were within a few thousandths of an inch.
Looked good, so I replaced the stock needles with KDs. After some adjustments to the speed and mixture at idle, the carbs (and engine) are performing flawlessly. I'm still babying it, of course, until the new bearings and piston rings are worn in, but judging from the position of the accelerator pedal during moderate use, the new engine is putting out twice the power of the old one.
I'm reminded every few days when I check under the hood that the valve cover needs to be tightened often after replacing its gasket. As I remember, it takes a month or two before weekly tightening is no longer necessary. I always smear the cork gasket lightly with wheel bearing grease before installing it. It helps make a tight seal, and makes it easy to remove the valve cover without damaging the gasket. That's important when you check the valve clearances often.
The overheating problem still has not gone away. A week ago, when the temperature was in the seventies, with the thermostat removed, the engine maintained normal operating temperature as long as I was moving. If I stopped for very long, the temperature rose alarmingly, but I never had to stop long enough for it to get too hot.
Then we got a cold front from the north, and the temperatures were in the thirties and forties. So I put the thermostat back in, and it acted almost normal, overheating only when I stopped for more than a minute. I'm hoping the overheating will subside as soon as the piston rings are seated. If not, I guess I'll have to remove the thermostat during the summer. If it runs too cold, I'll reinstall the thermostat with some holes drilled in the flange to let more coolant past.
The most striking difference in the new engine is the level of sound it makes. Since I went from a multi-pipe exhaust header to a stock cast iron manifold, the engine noise is much more tolerable. I know this doesn't make sense if you're looking for horsepower, but I was really tired of the constant bellowing up front. It doesn't have the classic sports car sound now, but it didn't before, either. And now I can hear the radio.