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<  Performance  ~  Nord rods - how many revs

PostPosted: Wed Apr 11, 2012 11:03 pm
PlatinumPlatinumJoined: Sat Nov 25, 2006 9:14 pmPosts: 304Location: San Jose, California
Hi guys, I'm rebuilding my Alfetta engine.

I was wondering what a safe limit is for a 1979 2 liter with factory rods. Is it advisable to use ARP bolts? If I get cams, they likely won't be anything radical. Is 6-6500 rpm asking for too much?


BMW's are the ultimate driving machine!

I'm kidding -- please don't ban me.
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PostPosted: Tue Apr 17, 2012 10:05 pm
VerdeVerdeJoined: Tue Nov 30, 2004 12:10 amPosts: 1696Location: Athens,Greece
6500 is no problem and even a bit more to ~6700, but the question is how many billion revs have the particular rods seen? When we were doing 6500-7000 in Nord 2liters it was in the 80's when these things were still 'young' or 'middle aged'. If you can find NOS rods, then no problem at all -there are vendors that still sell them.
Other than stock rods, your best bet is to get a set from Maxspeedingrods in eBay. I've tried them several times and they're excellent.
Jim K.

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PostPosted: Tue Apr 17, 2012 10:07 pm
User avatarVerdeVerdeJoined: Tue Oct 11, 2005 8:56 amPosts: 774
How about magnafluxing, will that guve a better picture of the rod's condition?

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PostPosted: Wed Apr 18, 2012 7:11 am
VerdeVerdeJoined: Tue Jun 13, 2006 9:47 pmPosts: 765Location: Fresno, Ca.
Magnafluxing will show cracks only. It doesn't show age or fatigue or thinning (streching). There are no tests, destructive or non destructive, that will show you when a part will fail. All we have is cycle testing done to failure of new parts that give some idea of lifetime and rev limits....that was done by an engineering departmen many years ago by a company that likely wouldn't want to give out that kind of information.

Testing to destruction (cycle or rev limit) at best will give an AVERAGE of when the parts will fail. The factory would then set the engine rev limit so that there would only be 'x' number of failures in ,say, 1000 engines, or design the rods for a number of failures per 1000 engines at 'x' rpm.

JK's position is that since you don't know what kind of life your particular set of rods led, if you want a higher reving engine, buy new rods. Otherwise its a crap shoot.


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Machinery Repairman USNR
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PostPosted: Sat Apr 21, 2012 12:38 am
PlatinumPlatinumJoined: Sat Nov 25, 2006 9:14 pmPosts: 304Location: San Jose, California
Thanks guys!

BMW's are the ultimate driving machine!

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PostPosted: Thu Jun 14, 2012 10:50 am
GoldGoldJoined: Sun Apr 29, 2007 9:45 pmPosts: 88Location: Milpitas CA
hmm that is different then I have been told.
what little of know of metallurgy is a steel if not stressed past a certain point will have a almost Infinite life span (not counting things like rust) but metals like aluminum start to go as soon as there are cast and there is nothing you can do about it.

steel can work harden if the parts get stressed past a certain point. Which I think can happen in a rod. But I think all you have to do it have them De-stressed aka shot peening.

The normal rod reconditioning should check for bending stretching and cracks redo the holes. shot-peen and recheck for cracks.
as well as polishing any sharp point that might start a crack. as far as I know if this is done and a rod no matter how old it will be like new or better then new. ( if a good steel) I have seen junk stuff crystallize but I think that was all crap steel. I think alfa used very good stuff in the rods.

As far as I know old steel is better as a lot of the internal stress have worked out. aka seasoned steel. Is that not why BMW back in the day use old junk yard blocks for there F1 motors.

correct me where I am wrong. but this is my understanding.

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