What is 'blueprinting'?

[cantfindausername]

A friend and I were discussing engine building and blue printing came up. Be understand that it includes the measuring of each component, but what else is there to it? What do you do with the measurements you've obtained?

I figured this would be the best place to get that answered.

Thanks in advance,
Ant

[Lowtechguy]

"Re-machining each engine component to the precise measurements as indicated on factory blueprints"

[cantfindausername]

Excellent. Thanks very much :!:

[Guy Croft]

The phrase goes back to the days when engineering drawings were reproduced using Hershel's cyanotype process invented in the mid 1800s. The prints came out blue with white lines.

In pre WW2 manufacturing and in fact for about 10 years after it was common to find significant deviations form design intent in the engines coming from a production line. This was mainlly due to drift and wear in machinery, hand setting and measuring methods, less advanced metallurgy (particularly with iron castings) and relatively crude inspection systems. If any. So, long before the introduction of computer aided design (cad) and manufacturing (cam) it was common for tuners to 'rework' an engine to achieve the actual dimensions and tolerances stated by the designer on his blueprints. It followed that you needed to have the blueprints to do that, and logically it assumed that those features were ideal - otherwise why copy them. The latter was not always true, and top tuners would derive their own regimes and still, of course, do.

These days engines are made much more accurately, that is to say that there is a far greater chance of adherence to specifications on a production run, and of course vastly superior inspection methods at hand. As a consequence the process of 'blueprinting' as such has fallen by the wayside in most repsects and as an individual, considering for example crank and rod clearances - some of the most crucial - you won't be able to get the 'blueprints' because they're no longer used electronic printers put paid to all that, and of course most auto design offices now run completely 'paperless' - everything is on screen. The closest you're ever likely to get to establishing the dimensions and tolerances is by referring to the data in the factory workshop manual. Toyota, eg. produce top quality manuals in hard copy which is great. In my experience of production units you'd be hard put to better much of the stated data, and only in an old, worn engine are you likely to find deviations.

I sometimes refer to 'blueprinting' valve seats, I never talk about blueprinting a whole engine because that would be an absurd target. In that case I'm using the word in a convenient (albeit loose) sense to describe reworking them to a higher standard than production. Ask me in detail what I mean, and some do, and I'll say that I am taking the the seat right out to true valve diameter to maximise the curtain area (cylindrical space under valve on lift) to gain as much flow on the valve event as possible.

If you took the expression literally it would turn out to be a bit of a misnomer, because you'd almost certainly find, on a modern engine, that even if the contact face wasn't optimised in that way, it was in fact placed exactly where the designer's cad said it should be. So in reality I'm not 'blueprinting' at all! But in truth there's more to it than that, because ask any auto designer how big the contact face should be and he'll say - as big as the valve diameter, but production engineers will rarely work so close the limit as that. Production engineers like to play safe and have things 'in the middle'. Same with valve throat, F1 tolerances will prove of little use on a production run (of even the most high performance road car) if on the last cylinder head in the line there has been so much machining deviation that the valves fall through the throat.

There are other 'blueprinting' tricks, balancing, porting (even just to tidy up casting intrusions and marks, you won't find those on any drawing!), piston to bore fits, ring gaps and so on and on. If you hear about a fully blueprinted engine, ask to see the engineering drawings.

Hope that sheds a bit of light on it.

GC

[cantfindausername]

Thanks Guy, thats really cleared things up for me.

The main reason we couldn't fathom out was what they were blueprinting against when they're using all aftermarket parts. For instance, bigger pistons.

Thanks again for shedding the light on this subject.

Ant

[Julian]

Just an afterthought on the matter - as Guy has rather thoroughly explained the term in detail (I'm impressed anyway).

The current term of blueprinting generally refers to rebuilding an engine using just the original manufacturers components. Most of the work (as mentioned) is just cleaning up the ports to remove flash lines and cherry picking parts for balance.

In racing terms this is basically a production tune buildup. Cleaning the ports up in this situation is contrary to the rules as the flash lines are used as a quick eyeball check to make sure no-one is cheating. A degree of lightening is generally allowed on some components but they have to remain within a percentage margin of the expected mass.

When it comes to the value of such work the actual performance gains tend to be pretty marginal compared with quoted figures but the reality is that a lot of engines do not produce the quoted figures to start with - in some cases they don't even come close. Reliability is a key element too as a blueprinted engine tends to be that little better in balance.

As the manufacturing processes improve the gains to be made will continue to diminish. For the moment though there are still gains to be made without investing in uprated components. The cost however continues to rise for a dimishing return making the blueprinting process a somewhat expensive venture unless you are constrained by a set of regulations for competition.

Once you start substituting in "foreign" components, even if from a different variation of the same engine you are pushing the limits of what the term means.