I have see the term blueprinted used to describe motors, oil pumps, injector, ect for years and I have no idea what it means. I search the forum and could not find a definition. In my younger days when I did a lot of bench racing I would hear guys say a motor was “balanced and blueprinted”. So that I would not show my ignorance I never asked what they were talking about. Now that I am older and "somewhat" wiser I have no problem showing my ignorance so.

What does blueprinted mean?

Thanks

 

Blueprint is a term for copies of the original design drawings. Blue because copies back in the day were blue and the lines on them were white.
These design drawings indicate the exact mesurements +- tolerance of each machined part.

When we say blueprinted, it means each physical part is measured and compared to the blueprint drawing and is modified to fall within the as designed part dimensions +- tolerance.

 

The previous poster pretty much summed it all up. It is the term for measuring all the tolerances in the engine and ensuring they are within spec.

 

From what I understand, it goes beyond that. Here's one definition that I found:

 

 

A blueprinted engine not only has all dimensions in tolerance but they are all the same within a few ten thousandths of an inch. For example, a combustion chamber may have a volume tolerance of 72.0 to 72.5 cc. The machinist will sink valves or otherwise open the smallest chamber to the maximum dimension so that all are the same high side value. Then, the head will be milled a few thousandths of an inch to bring the combustion chamber volume to some number VERY close to minimum, say 72.1 cc. Cylinder bores are not finish honed until the very end. A honing plate is installed and bolted in to full head bolt torque spec to simulate the distortion from installing the heads. Hot coolant is then circulated through the engine to bring it up to operating temperature and only THEN is each bore finish honed to the final dimension. Similarly, piston height in the bore at TDC is adjusted by maching the pistons until all are exactly the same and then the block is milled ever so slightly to make all the piston heights at the minimum dimension. Doing this "balances" combustion pressure but more importantly for a stock engine, it means the maximum allowable static compression ratio. Cams will similarly be checked to be sure the dwell angles are identical. Main bearing caps will be machined slightly and then the bearing journals "line bored" so that ALL main journals are EXACTLY in alignment. Oil pump passages will be deburred, flash removed, oil return surfaces smoothed and perhaps sealed with glyptal to speed oil return to the pan. You get the idea.

The results are rather striking. I have built blueprinted small blocks and the line bore was SO true that the crank could be installed, caps torqued to spec, and I could spin the crank in the engine with my fingers and it would continue spinning for a few seconds. THAT is a low drag engine.

There's a lot more to blueprinting an engine than I have outlined above, but it gives an idea of the precision involved and my little fingers are tired.

Charlie

 

You may have a point but I am sure there is no accepted standard to blueprinting you could hold one to (unfortunately). Back in the '60s and '70s blueprinting meant alot more than it does now as tolerances were much more liberal. I wonder how much diference on an engine dyno there would be in a factory LS7 vice a 'blueprinted' LS7 built exactly the same; and I would have to see proof not just anecdotal. Not that I don't think there is a difference; just wonder how much.

 

O.K. Got the blueprint part. How about the "balanced" part. My understanding of this is that if you have for example 100 rocker arms to choice from, you would choose the 16 that weighed closest to each other and/or closest to spec. Then do the same to pistons, pins, etc.
Sound right?

 

Balancing refers to the rotating assembly, crank, rods, pistons, rings and pins. There are two ways to balance:

1.) internally- the weights are on the crank counterweights with a zero balance harmonic dampner and zero balance flywheel/flexplate
2.) externally- the weight is on the flywheel flexplate and harmonic dampner. Internally balanced is better for higher reving engines. There are different degrees of balancing; I had my Ford 408 balanced to within a couple tenths of a gram.

Basically, you take the lightest piston, lightest rod, and make the rest weigh the same by taking off material. Bobweights are then added to the crankshaft to simulate piston/rod weight and the crank is spun. A computer tells which crankshaft counterweight needs weight added to it or taken off.

One important thing to remeber is to check piston to valve clearance before getting the assembly balanced, as you may need to have the pistons cut, thereby affecting their weight. James

 

You would weigh all of the pistons for example and make sure they all were of the same weight, by removing material from the heavier ones same with all of the other moving parts. I am certain there is a more conscise description but I am trying to be brief. Also there was a method called "CC" ing the heads using a plexiglass plate bolted over the combustion chamber in the head with the valves installed and measuring how much liquid could be poured into the chamber, I heard it was just usually clean water. There was usually a pharmacy or medical grade liquid indexed fluid column using "CC's" or cubic centimeters for the liquid connected to the plexiglass plate. Each chamber was then altered to provide the same liquid displacment. Now remember I seen this waaaay back in about 1970 so be nice to me, OK?

 

I was an NHRA tech inspector years ago and "CC'ing" was the process I referred to above in adjusting combustion chamber volume. The process is still used to check engines that run in stock class. A plexiglass plate with a small hole drilled in it is placed over the combustion chamber and held sealed in place with silicone grease or petroleum jelly. I used a mixture of rubbing alcohol and water to fill the combustion chamber. The amount of liquid used was measured by dispensing it from a laboratory tool called a pipette.


Point well taken. The LS7 is indeed a factory built engine that comes out of the crate with specs much the same as the best engines from 15, certainly 25 years ago. For example, the cylinder bores are final honed with a heavy plate bolted in place to simulate block distortion from the heads being installed. I'm fairly sure the incremental improvement of blueprinting the LS7 would much less than was realized in blueprinting a 454 LS6 engine in '70 or '71.

Charlie

 

This is great info. Thanks for taking the time to enlightening me