This is probably a dumb question but what exactly is done when someone blue prints an engine? For example, what would be the difference in a blue printed LG4 and stock? Do you only blue print new engines?

thanks,
phil

 

The term "blueprinting" is probably one of the most misunderstood and misused in automotive circles. It's almost as pervasive as the famed, but elusive "full-race" cam.

Blueprinting is nothing more than the process of returning the engine to O.E.M. dimensions and tolerances. Unfortunately, many of these dimensions are less-than-desireable, and the tolerances are beyond what a good builder would allow on his shipping dock.

That's all it is. It isn't anything special, but is certainly misused and implied in that manner when the term is thrown about in casual aoutomoive discussions.

 

I would assume that a stock engine from the factor is within OEM specs. So does that mean that new stock engines are "blueprinted"?

 

It merely means that somebody paid attention to the critical dimensions. It doesn't necessarily mean that it's any better than stock, or even as good as stock; just that somebody measured some stuff.

As an example: the stock rod bearing clearance in a SBC is .001" - .002". If you take a typical production-line crank and production-line bearings and just stick them together, odds are, it will mostly be close. But, in the motor that you or I build, that might or might not be the clearance we want; for examplewe might want them all to be, let's say, on the high end of that, maybe between .0015" and .002". "Blueprinting" might mean that we checked them, and verified that they're "in spec"; or it might mean that we hand-tuned them all to be the same; or even that we chose a design value for some technical reason, and adjusted them all to that value.

It's basically a sales buzzword. It does not convey any specific meaning as to exactly what might have been done, like saying "cut spring pockets to 1.55" diameter to a depth providing an installed height of 1.900" with Comp 731 retainers and 5.011" long valves" does. I certainly wouldn't buy an engine if someone hadn't even measured anything as they were building it (i.e., if it wasn't "blueprinted"); but just because that word could be applied, doesn't mean that it's as carefully built as even a rank amateur as myself would take the time to make it.

 

They are right, it is misused and thrown around alot...BUT..

blueprinting an engine, as I was taught, is going the extra mile when putting the engine together.

For Example, you'll have a "range" of acceptable tolerances on bearing clearances. And more than likely, all will fall into that "range" but not be the same. Blueprinting is simply adjusting those clearances to the EXACT SPEC you WANT and making it the on EACH assembly.

Most "Rebuilt" engines are thrown together and the tolerances are checked...that's it...IF that.

I've "blueprinted" every engine I've built except for my first one when I was 14....it puked a rod...lesson learned.

But that's ME...I DO NOT WANT to have to go back into the shortblock because of a mistake I MADE....and because I'm lazy


"Blueprinting" usually means using higher quality parts too....some "econo" rebuilder parts won't even get you CLOSE to the specs you're trying to hit.....



Just my 2 cents...

 

Isn't it amazing how laziness can improve one's work habits and tolerance?