anyone knows of any other conrod that could be used
in an A series thats around around 129-130mm?

wider main journals are fine but needs to be same bore size
A Finland builder of the 280hp A series found Honda 137mm
B16 rods fit his build with custom pistons for more RSRatio.

rod width for A series is at BE is .956 inches / 24.2824 mm
rod BE bore size is 48mm (like ca18de/t)
a15/ca18 rod length is 133 but can only go down to 132mm

Maxda B6 are pretty darn close from memory and around teh same length. Try BP engines?!?! E16?
Failing that, there's a mob at Morpeth NSw called Argo which will custom make anything you want.

So stock ca rods can be put into an a15 bottom end? How much stronger are they? What work needs doing to make them fit?

How much heavier I think you mean.
Weight kills an engines ability to rev to the days. That's the whole selling point of an A series.
However, The CA16 rods are very similar to CA18 ones, only a little bit lighter. They use the same size rod bolts as the Ca18 though.

Ive got some forged bike pistons with 24.5mm comp height so trying to get some more rod length to make up for it. Unfortunately none fit the bill due to the thinner BE width so far.

how much thinner are the ones that you've found so far that are ok length wise? Is it possible they could be brazed and machined to make them a little thicker (since there isn't massive compressive or other load on the rod ends (looking side to side, i don't mean the radial tension on the bearings or the load from the rod bolt clamping forces of course), the bearing takes the real load on that front.

hope its not too exxy?

the only rods I can find so far are these but there is possibly the mazda d5 rod which is 129 or 130mm c-c and thicker than the A if Im lucky.

The other is this one but adding 1mm each side too much?


M20B27, M20B20: C-C length:130mm
M20B25: C-C length: 135mm
Big end bore: 48.0mm
Big end width: 21.8mm
Pin diameter: 22mm
Small end width: 21.8mm

http://www.racetep.com/ppm.html

I'm aware of several modified engines where the BE side clearance is well in excess of the spec. It seems that as long as the SE does not contact the piston gudgeon boss as it floats back and forth or the BE oil feed gallery is not uncovered there is no concern. Not sure how much is too much but the one I saw was a TC Masters engine with a little over 3mm in total. Engine was bullet proof.
I'm told "piston guided rods" are popular in the US as a way to reduce BE thrust friction. Machined thrust washers are placed between the rod and machined gudgeon boss faces.
Be careful of the "long rod engine". This can require significant camshaft development work and can make for a road engine with less bottom end and midrange torque.

Good to know but would prefer 24.2824 mm

Still deciding if this is the way to go for this build
the longer rod with this combo would help the smaller
ports and valves I had planned.