Don't Loose Your Head

New Head for the Coupe

After the first few months when most of the bugs were worked out  my '28 Coupe has been running relatively well now for over twenty years. However, it has never been very powerful. If a stock Model A in good condition generates 40 hp, I'd guess the coupe has been down around 35 the whole time. About ten years ago I put a lower ration rear end in it to give it a little more top speed. Consequently it's a little down on power on starts from stop and on hills.

In June my dad came down for a visit. I bought some parts for the Model A's so we could tinker with them while he was here. We tuned and put new tires on the truck,  and we put a Snyder 5.5 high compression head on the coupe. The head swap went very smoothly. We  lapped the valves while we were at it and buttoned it up in just a couple of hours.

The engine's running character was significantly changed. During  a cold start the starter has a slightly tougher time turning it over, has to crank a little longer before firing and an easy start requires more open throttle than before. Even the sound of the engine changed somewhat.  I'm not sure I'd be able to cold start it with a hand crank any longer.
Driving around with the new head revealed that the proper spark advance settings have changed. Whereas before it was pretty much spark lever up to start and down to drive, now I can advance the spark only about 1/3 of the travel of the lever before I feel a pounding from the engine that I interpret as pre-ignition. I have taken it on the freeway for a short couple of miles and gotten the car up to 55mph. I was able to advance the spark more then, but there was so much wind noise and commotion I couldn't hear if the engine was knocking or not. I feel confident that now I could take the coupe on a longer trip and maintain 50-55 the whole time without any trouble.
Can't put my finger on it, but something still doesn't seem right since putting the new head on. The engine just doesn't run as smoothly. But it definitely has a bit more power.