04/29/98 – General Stuff, Recommendations
Stopped out to TWE today, Jay at TWE did the engine rebuild. Had a very interesting discussion. Two things prompted the stop. The first was to thank him for doing a great job on the engine. Now that I’ve put a few hundred miles on it I can tell it was done correctly. It’s running very good, very strong low end. The second prompt was a few questions about what kind of performance to expect. A short discussion with him and it’s obvious he takes pride in his work and has spent a lot of time learning how to do it right. Great amount of knowledge about metallurgy and the mechanics of engines..
So, first question was “What is the top end for an engine like this ?” He said that the 215 was designed to enable a big heavy Buick to be hauled around town full of the family and such, so it’s design aim was a good low end, not high revs. He recommended staying under 4800 and the peak of the torque curve is somewhere around 4200 for this one. The best pull for this engine is on the leading side of the torque curve, that’s where it’s design point was. This led to a discussion on shift points, the conclusion being that if the engine is feeling like you need to shift, your shifting to late! By the time you feel it, your sliding down the far side of the torque curve. When you shift, your going to pick up the engine in the next gear at too high of an rpm to take full advantage of the available torque, in other words your working on the peak and slide down, not the whole crest of it’s best pull.
Makes sense to me. He said that’s the purpose of shift lights in dragsters – you want the driver to use the best crest of torque, so he has to shift before it’s bleed off, if he shifts by feel, he lost it and endangered the engine.
I then told him how I was running a 180′ thermostat and switched to a 160′ to see if the radiator had the cooling capacity to keep it down there. He recommended staying with the 160′. It would be all around better for the alum. engine. I asked about running too cold and getting plugs fowling, etc. He advised treating the plug problem, not raising the temp of the whole engine just to cure a plug problem, and that the fowled plug thing would only arise if the car was driven on a lot of short trips and not allowed to come up to temperature. If that did happen, just change to a hotter plug, raise the temp around the plug up, not the whole engine. this led to some facts about aluminum and it’s reaction to temperature. He said the aluminum does not expand evenly according to temp. That around 200′ it moves a whole lot more than it does at temps below that. The problem is it moves a lot faster at 200′ than the stuff around it (like bolts, gaskets, etc.) and that’s when you run into problems – blown head gaskets and such.
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