Engine Blueprinting?

[autobonrun]

This is a term I've seen used for years but am not sure I really understand the process. Could someone please explain to me

1) The advantages of blueprinting
2) When it should be done
3) How much cost this adds
4) If the members doing engine rebuilds are also blueprinting the engine

thanks

[Superman]

Unless I'm not properly understanding the term "blueprinting," then I'd say it's a silly word. I think it means making sure, in rebuilding the engine, that it is built the way it was designed. Verify that it meets specifications.

Duh.

[movin]

Blueprinting can also mean narrowing specification tolerance and assuring consistancy in fit or clearance throughout. A very tedious undertaking.

[911pcars]

The term "blueprinting" is not as big a deal with Porsche engines as they are built to a very high level of tolerance at the factory. During a normal rebuild, you just need to pay attention to the "usual" build list (correct head studs, etc.) and check/verify the regular clearances before assembly.

However, if one were to make sure the engine is put together "as designed", then you could perform the following:

- verify and equalize combustion chamber volume ( and thus compression ratio)
- verify and equalize deck height and cylinder height
- verify and equalize connecting rod lengths
- verify and equalize reciprocating/rotating weights ("balance" the engine)
- cross drill the crank journal oil passages
- micro-polish crankshaft main and rod journals
- match the port dimensions at the intake manifold-to-cylinder head juncture.
- Verify proper valve spring pressure and installed height
- Verify and adjust valve-to-piston clearance
- Lighten piston and connecting rod
- Replace reciprocating weight with lighter components (e.g. ti con. rods, valve retainers)
- Contour and polish in/ex. valve heads/replace with lighter units
- Adjust port size and finish for best gas flow

Some of the above items are in the gray area of modifying the engine rather than building the engine to strict blue print standards. I've probably left out a bunch more stuff, but that's an idea of what could be done above and beyond a "normal" rebuild.

Hope this helps,
Sherwood Lee
http://members.rennlist.org/911pcars
www.seinesystems.com

[masraum]

Exactly, do a good thorough job as close to factory or better specs as possible and is often combined with balancing to give the most power, smoothest running, and most reliable engine possible.
Or, at least, that's my understanding. Tedius, but there shouldn't be any other way. It seems everything should be mic'ed and checked, not just plastigage and see if it turns when put back together.
That explains why rebuilt engines (in general, not P-specific) rarely seem to last as long as factory engines, even the big Domestic car co's.

[APKhaos]

Steves list is fairly daunting, but he is right.

I did 1,2,3,4[rods and pistons only], and 8 on my recent rebuild.
Had no intention of doing any of this, but the machine shop guys really gave me the low-down on how a little time spent on this really makes a difference in performance and service life.

They got me on this jag in a major way when they offered to lend me their cylinder volumetric tester.... this cool little trick measures combustion chamber volume [with silly precision] based on the resonant frequency of the chamber. Think blowing across the top of a coke bottle and you'll get the idea. Managed to get all cylinders within 0.05 on compression ratio.

With just 300 miles on the rebuild, plus the fact that the engine runs and responds far better due to the rebuild, its way too early to tell if the balancing made a difference, but it was a great learning excercise. Have not taken it past 5,000 or 30% throttle yet, but will be doing that soon - after the 500m valve adjust.

[autobonrun]

I now understand what's involved, and can infer the fact that some specialized measuring equipment is needed and that it's very time consuming and probably very expensive unless you do it yourself. Sherwood, your list of items are things that I believe Porsche probably does at the factory that other auto manufacturers may not do, and is one of the things that makes a Porsche a Porsche.

If I were to ever rebuild my engine, I can see that checking these items is something I would want to do. I guess it's an inherent weakness with being an engineer. I can't believe just slapping new parts back into the casing would get the engine back to factory tolerances without some degree of adjustments. It would still probably outperform and outlast 95% of the cars on the road but the thought of raising that number to 99% is what would drive me to do it.

thanks again.

[J P Stein]

This probably means different things to different people.
To me, it means optomizing engine performance within the manufactures tolerances, while exceeding them where permissible.
Probably the main place this came from was the "good old days"
of heads up drag racing in the "stock" classes.

A couple instances:
The cam profile has a tol of +/- .01 lift......make damn sure yours is + .01 from nominal.

Compression ratio is 9.0:1 +/- .5 ......yours is +.5.

All using factory bits. They'd tear you down to check, also.

Carry hunderds of other parameters out to the Nth degree (all slanted towards performance, none towards longevity) and one can see that this gets expensive in a hurry......thus, these classed died, but not before your basic 283, dual Rochester carbed, Duntov camed engine was pushing out 400 bhp at 8K rpms.....or thereabouts......stock as a stove.

Very little of this goes on any more.......Ask Randy bout the cost of his blueprinted 3.2L.

[HawgRyder]

Blueprinting as such for opposed type engines is not as necessary as for other types (V8..V6..etc).
I have assembled engines that were out of balance on purpose. I used very large barrels on one side and stock on the other (Volkswagon 4 cyl).
No noticable problems...engine revved to past 5000 rpm with ease...ran for seveal months in the parts getter car.
I think that the flat design helps this situation, but would not do it on a road car for reliability reasons.
It does make me think that we can get away with a lot on P-car engines though.
Bob

[APKhaos]

Sorry Sherwood - I mistakenly attributed your excellent list to Steve. It was Steve M quality, but your work. My bad.

Guys that build engines for PCA/POC class racing make the point that 'blueprinting' in its various forms can mean the difference between a third and a first place in a club race. Every little bit counts when the specs are closely controlled.

No personal knowledge or expertise here - just what I've picked up through this rebuild process. YMMV yada yada.

[911pcars]

TonyK,
Quite all right. I probably took the words right out of Steve M's mouth anyway.

When prize money is at stake, cubic dollars tend to flow into an engine to squeeze every last ounce of HP, torque and engine longevity. That is why (though not always) a pcar engine "rebuild" can cost $3000, $10,000 or $20,000. This is not to imply that you can't rebuild one for $3000. It depends on the overall plan, what you need to farm out and what you can/are willing to do yourself.

Your tech's technique of finding cylinder volume sounds interesting. Can you describe this tool? I assume this works on an already built engine. BTW, have fun with your recent rebuild.

Sherwood Lee