Nothing lives prolonged detonation, it's just a question of what breaks first. I am in Blown 87's camp on this one, and I am sure you agree.

A bit of further push back on the bearing issue. It is my understanding that there are many reasons that contribute to the common rod 2/6 bearing failure. I think the consensus is that it's an oiling problem. Now, any oiling problem is going to be made worse by loads. As you say, at the rod bearing, detonation can cause temporary loads of say seven times the normal loads. That will hurt a poorly oiled bearing quickly. But I would say that permanent 25% reduction in load with lighter rods is the flip side of the same coin and simply has to help if there's a temporary oiling problem.

Does anyone have access to trimetal bearings that would fit 928? Perhaps someone could spring the $30k fixed tooling cost and have some custom made for us? ;-)

 

There's this shop in Utah that sells uberlight connecting rods. I thought I bought a set of them earlier this year. The rods that I thought I bought were very light imaginary connecting rods, that don't exist and are therefore extremely light. You might be familiar with these rods that weight 0g and are stored in an imaginary secret warehouse.

 

AS far as the fst951's rods go, you an test the weight of those rods by turning your scale on and pressing tare. The weight of these imaginary, non-existent connecting rods that they sell in Utah will appear on the scale.

On a more serious and productive note, Tass928 might have some ideas about how to test these parts for strength, both destructive and non-destructive testing.

 

Rob -- One more question. (You've been very helpful, and non good deed goes unpunished!) The width of the bottom end? 27mm? Also, if you take the centerline of the rod, how much is the big end bearing surface offset from the rod centerline? Does one of the sides stick 2mm further out? Thanks!

 

Tuomo-

Sorry, my rod terminology is weak- By 'width' of the bottom end, I mean if you put the rod face down, the big end is 27.1 mm high. Here are the dimensions I measure.




There is a definite offset of the centerline of the big end bore with the centerline of the beam:



I'm not sure how to measure this exactly, but perhpas this is correct:

Lay rod on 'narrow' big end bore flange, zero height comparator:



Flip rod over onto the 'wide' flange, measure height at (more or less) same place on beam: +0.066", or 1.69 mm:



Or graphically:




The height comparator has a ground marble block that is +/- 0.0005" flat. When I lay the rod 'narrow' side down, the big end and small end bores are lying flat on the block. When I lie it wide flange down and hold the big end flat on the surface, there's a gap at the little end:



Hope this makes vague sense.

 

Rob -- This is good news for my aftermarket rods. The external dimensions are "close enough for government work" with the stock rods. This to me tells that the rods are really drop in and that the offsets are such that the rod small end will land in the middle of the piston pin instead of being biased toward either of the pistron bin bosses. Thanks!