Engine Blueprinting

[greg]

What does it mean? Am I being a muppet and it just means check every clearance and measure everything etc .... as you would if you were building an engine properly.

 

Greg, Q 86 NTM (Green 185BHP XF)

[DanB]

It has (I think) two slightly different meanings which people use interchangeably. I'm not sure which one is correct, although I *think* I know

 

As i understand it engines are built to certain tolerances, such as the amount of meat on the cylinder head, the piston ring clearances, the bearing clearances etc. A blueprinted engine is built so that, while being within the manufacturers' tolerances, each tolerance is taken to whichever figure will produce the most power. So, if the engine manufacturer says the cylinder head must be between 250 and 252mm in height (for instance ) and by skimming the head you can get down to 250mm, raise the compression ratio and improve power, then you do that as part of blueprinting the engine. Same with bearing clearances. If by increasing the bearing clearances you can run higher revs due to less friction and reduce parasitic friction, then you run the largest bearing clearance within spec (if you can get away with it). Obviously it's way more complicated than that, but i think that's the principle.

 

The other meaning is just building the engine within tolerances but checking it all carefully, which I don't think is blueprinting but I've heard the term used in this context.

 

Dan

[Peter Carmichael]

In some classes, engines have to be *original* spec. Engine specs include tolerances. Blueprinting is the process of building an engine within original spec tolerances, but selecting the components whose actual dimensions are at the optimum end of the tolerances, whatever that might mean. It is a way of building a very expensive ordinary engine.

[scooby dooby doo]

it is very expensive and doesn't gain you much. in a tightly controlled one make, production spec only series it may be worth it. otherwise it isn't.

 

you see a lot of adverts in the less well informed magazines selling an engine as blueprinted, and therefore the best possible spec, for some extortionate price. you'd get far better results from a bit of porting for much less cost.

 

HOOPY R706KGU come to cam7 - we don't bite ❗

[greg]

Thanks Gents, I thought it ment doing lots of measuring and using the "best" bits.

 

Greg, Q 86 NTM (Green 185BHP XF)

[Simos]

Depends on the tolerances really doesn't it ? A reasonable compromise might be to make it mean you check that all the rods are the same length rather than have their lengths spread randomly through the tolerance range (as an example).

 

I recall a conversation once where if you totted up worst possible tolerances in the suspension of a Ford sierra you could get one wheel 1cm further forward than t'other. Maybe not, but you get the drift... a blue printed sierra suspension might then have its merits

 

Of course you could just call it due dilligence or professionalism.

[AMMO]

This is just my opinion but I think it's shared by people I know who build engines for a living.

 

I consider a blueprinted engine to be one that has the correct tolerances for best power. It aslo means in the case of a race engine that you can give it stick from the word go without bothering too much about running in. When building an engine I consider it essential to check every single measurement. From guide to stem clearance, shaft endfloats, valve spring weights and stack heights etc. Valve to piston, in some engines valve to valve. Piston bore clearances, squish clearances. Weights of rotating and reciprocating components, balance of crank etc. etc. etc. The list goes on. In other words you do everything neccessary to make the most power and for the engine to survive.

 

Most race engines take between 40 hours to 80 hours work.

 

My Moto Guzzi race engines would take around 40 hours. Road engines around 24 to 28 hours. when visiting the Guzzi factory I went on the production line I asked one of the workers how long did it take to build an engine? He told me they were allowed 96 minutes.

 

For me hat's the difference between a production engine and a blueprinted one. The amount of time you dedicate to it to make it the best it will ever be. Is it worth it? Yes and no. If the base engine is known to be a bit all over the place you can improve it. If the tolerances are known to be good as in a lot of modern engines then maybe not a lot. I do it anyway to my own engines as all it costs me is my time. If I had to pay for it I just wouldn't be able to afford it.

 

 

 

AMMO