Talking about politics, sex and cars

I dislike hanging around most car guys. There is something about cars, motorcycles, guns, politics and sex where almost all guys think they are experts at the prior mentioned, no matter how lame and inept they actually are about the subject. Guys, usually the less they know will argue passionately for eons about these manly subjects, and data and facts will not sway their opinions. It is quite irritating for those in the know. Sometimes however, it can result in manly challenges, which can be good for the well-versed nerd, especially if they involve wagering cash!

Then it comes to car guy subjects that have a veil of mystique around them, where it sounds good but most don't know what it's about. Words like Turbo, Supercharged, Posi-Traction, NOS and Blueprinting. Blueprinting is a subject that is brought up and argued about time after time again. So if you want to school the macho know it alls who inhabit sports events, bars and parties, read on. In this and next months column we will be getting into the specifics of Blueprinting. Blueprinting is not some weird magic nor is it snake oil, Blueprinting is merely shifting the manufactures tolerances for the engine to the side of the tolerance that will give you the best power. The tolerances involved are the weights of the rotating and reciprocating engine parts and the clearances of the bearings, pistons and rings.

The opinions of which side of the factory clearances works best to produce the most power varies depending on the engine builder. Many experts feel that the most important aspect of blueprinting is getting the bearing clearances to the loose side of spec to reduce friction. Most experts also feel that getting the cylinder piston to wall and ring end gap clearances to the tight end of the spec to maintain good ring seal and reduce blowby are important. Of course other experienced engine builders will have differing opinions on the correct way to set things but the important thing is to make sure that the clearances are all equal and controlled.

My personal take on this is that you always want to try to maintain close to the minimum clearances possible on the pistons and the crank and rod bearings for any engine for longer life, less windage-loss causing oil slingoff, to maintain better long term ring seal and to maintain bearing oil pressure better.

Blueprinting bearing clearances on import motors is easy because they feature select fit bearings. These are bearings available in several different thickness' so the exact clearance can be maintained for each journal even if there is variation in the machining from journal to journal. The block, rods and crank are stamped with a code for what bearing size is used for each journal and you can use a chart in the factory service manual to decode the stampings. If you want to tighten or widen clearances, you can go up or down a size from the encoded bearing size.

Because most import cranks are so tough, it is rare that they have to be turned undersize, when the engine is gone through. If the engine has some miles on it, it is usually enough just to lightly polish the journals and use the next tighter sized bearing on the service manual chart.

Another important aspect to blueprinting is to get the piston to wall clearances for each cylinder equal. This is done by measuring each piston and having the machine shop match each piston to its bore with the exact same piston to wall clearance. Good machine shops can do this easily by honing each bore after rough boring for a precise fit. Like the bearings, most import engines have select fit pistons with the size used stamped on the block in a code that can be decoded with the factory service manual. If you are replacing the factory pistons, you can specify a piston grade a little bigger and hone the cylinder to get the fit. This gives you the benefit of a nice fresh bore surface with tight, like-new clearances, as you never want to put new rings in a used bore, they will not break in properly and will not seal that way.

Well that's it for this episode feel free to e-mail me with your questions on plasmaim@yahoo.com and I will do my very best to answer your queries.