con rod research
 

Well since I started looking at different pistons I decided to do some research to find a con rod with near same sizes as ours or the pistons I may use and stock big end \ length

I've found the
A20\B20 honda rods use same size big and small diameter and is longer by 5mm

CA18DET rods have same big and little end and length as stock con rods.

I will update this as I find more info.

The real question is,... why?

There is no reason to get a longer rod. Are you going to make 5mm shorter custom pistons? You're trying to solve a problem that does not exist.

How can CA18DET PISTONS be the same length as CON RODS?

heh didn't notice that. fixed. Not looking for a longer rod.

Plenty of reasons to lengthen the rods with a stock crank. Less piston speed, more RPM capabilities, and better rod reliability to name a few. Longer rods let you shift the wrist pin up in the piston and improve the rod ratio of the motor. 5mm is a bit excessive since you'll interfere significantly with the oil control ring, but 3-4mm is doable and has been done.

+1. Longer rods have nice cascade effect. Who has done it on a BP?

OP, sometimes the rod width can be narrowed a hair at the bigend but not always.

Custom pistons will be needed, not a big deal.

b16a rods are 1-2mm longer from the specs I've seen with the same big end size

There is a rather long thread on this topic where some dude used honda rods in his BP block. I will not search for it as I am lazy

BMW M20B27 stock con rods
BE dia 48mm
PE dia 22mm
CTC 130mm

anyone aware of a con rod with a 140mm ctc and a 48mm big end?

I know Bike In Dirt from M.net has done it as well (Cali track junkie, N/A motor with ~175whp). If I ever get around to building an ethanol-specific 11:1 bottom end, it will be a longrod motor.

The only complication is that the wrist pin gets elevated into the oil control ring, which requires a bit of trickery to make work, but it's doable.

I think I may found some, I Got to check the M42\44 motors from bmw

I know MarkP talked about using Honda rods and pistons back in the day.

Would said 3 mm add'l length show noticeable benefits?

m42\44 140mm ctc
big end 48mm
pin end 22mm

BMW con rod, miata crank

http://img9.imageshack.us/img9/2940/dscn2433q.jpg
By techsalvager at 2011-04-18
http://img705.imageshack.us/img705/783/dscn2434x.jpg
By techsalvager at 2011-04-18

You can't elevate the wrist pin 7mm in the piston (8mm once you account for the additional wrist pin diameter). What's your plan for that?

I dunno but if those rods are from an i6, it's "buy two sets, get one free" for the miata.

Those bmw rods in the picture are out of a 325e e30
They are 130mm CTC, which is shorter than stock rods
If you get the rods out of a 325i e30 they are 135mm CTC

I don't plan to do anything with them, just documenting that they do indeed fit on the crank with no issues

A friend of mine uses a E-car bottom end with a I-car head. 400hp/480tq @ 25psi on the stock E-car bottom end. Those rods are super tough. Good find, the M20 is a seriously underrated motor.

stock piston, bmw rod
http://img833.imageshack.us/img833/4060/dscn2403g.jpg

Uploaded with ImageShack.us

note bmw rod uses bigger wrist pin