<VV> Crank Nitriding/Engine case question Question

[Tony Underwood]

At 08:35 hours 05/17/2005, Chris wrote:
>Coming out of Lurk Mode for a moment...
>
>Considering building a 140 HP EFI in the next year or two and have a 
>couple questions. I want to use parts I already have on hand. Collecitng 
>info and pieces for now.
>
>1st question: have an EM truck engine. Can I use the block?


Yes, if you wanna spend some big bux clearing it out for the longer stroke 
crank.


>What changes are necessary?

Reliefs must be cut in the sides to clear the big ends of the rods.   Also, 
the cam should be checked to insure that it's a late (164 engine) variant 
which has reliefs carved into the edges of some of the lobes, same reason, 
clear the rods.    Might be easier to use a 164" crankcase.



>2nd question: what is the difference between the 110 HP and 140 HP crank 
>besides nitriding?

Nothing.    If the 140 hp crank was in an automatic car, it may well have a 
"cam-retard" gear on it.   Not hard to spot, somebody will say "info is in 
the tech guide", someone else will likely post a link to a page with a 
diagram.


>I was looking over some tech info for VWs and saw this article:
>
>http://www.geneberg.com/article.php?ArticleID=202
>
>"Now that our connection in Sweden has past, we have sought out a new 
>source for crank forgings. We found a forging company in the USA that can 
>do the job. We have redesigned our crank to be stronger than before. We 
>have found that the forging itself was excellent, however, the Nitriding 
>process of the crank created sort of an eggshell effect. The Nitriding was 
>done to help with wear resistance on the journals themselves not 
>necessarily for the strength of the crank. This problem showed itself with 
>the cranks getting a crack in the journal radius and eventually would work 
>itself into the center of the forging.
>
>The first time the crank bent it would crack -- not good. So, after some 
>research we found that by bringing up the core Rockwell and eliminating 
>the nitride we got the best of both worlds; not a soft core with a hard 
>shell covering it, but a harder core with enough hardness to prevent 
>premature wear on the journals. This took some researching to get the 
>right core strength without making the forging brittle, however, the 
>wearability on the journals suffered slightly. Now, after 100,000 miles 
>the journals will probably need regrinding unlike in the past where most 
>of the time it just needed a polish."
>
>Sound accurate?


Pretty much...

But then again, I've taken non-hi-perf Vair engines apart with well over 
100K on them and the cranks looked fine.   Spending bux on nitriding might 
be overkill, depending on what's gonna happen to the engine.   Lots of Vair 
engines out there have gone 200K or better without surface hardening.



tony..