It's common to bush rods for a performance build, easily done and you can get it to the size required. The rod "looks" heavy, did you weigh it? How is the side clearance when you had it on the crank?

 

following..

 

you could have the rod bushed differently.... but you mentioned that it is shorter than stock BP

edit: aaaaaaaand i didnt see page 2.

 

BTW, a little quick math says that 400hp on 6 cyl isn't that impressive...
i.e. 400 / 6 = 66.66 hp/rod
66.66 * 4 = 266
So that's the ball park of power per rod that kills miata rods, having 2 more cylinders helps spread the load a bit Your buddy needs to turn the boost up some more, imo

 

This is why I am also doing piston research between 78mm to 81,5mm pistons.

Of course a 1.8l person can research for their own setup as well for pistons

 

I was just using him as a quick example. That was that power was made using a Holset hx35 (can't remember exhaust housing size) and a unported intake manifold. With a bit more work he pulled a 6.9 @ 103. Plus you have to remember that this is a OEM rod that you can find for DIRT cheap.

Now, he is using a Borg Warner S376 and is aiming for a low 6 in the 1/8th. Should be on 30-40psi. AAAAAAAAAAAAAAAAAND he will still be using the same bottom end with the same stock E-car rods.

 

The M20 was never underrated with regard to how much the bottom end can take. It is the single cam, low cfm head, and 12 valves that make NA expensive and typically advised against.

 

Just got all 6 rods for free from 325e m20(thank you e30 buddies)

I'll hold on to them and see what happens with this thread. I'm all about experimenting

 

It was weighed and is indeed heavier than stock but should take more power than stock rods can before giving, side clearnance is same as stock.

 

What bottom end work did you do to your 1.6 to make it into a 1.7? just bore up?