Author Topic: M42/M44 OEM con rods (Read 6620 times)

Boyracer · « **on:** December 23, 2009, 12:55:21 PM »

Anyone have any knowledge which ones are better suited for high rev applications?

M42 rods are heavier but are they also stronger?

I would send question to Metric Mechanic but their site is dead

e30guydownunder · « **Reply #1 on:** December 23, 2009, 03:35:43 PM »

M42 are also forged, M44 are not. You could lighten, balance and polish the m42 rods probably to a similar weight as the M44 but maintain quite a lot more strength.

Boyracer · « **Reply #2 on:** December 25, 2009, 05:49:06 AM »

Hmmm, are you sure? I have set of rods from both engines in hand and they look materialwise very similar but M44 rods are a thinner design.

I know M42 crankshaft is forged and M44 cast, is it really same with the rods?

wannam42 · « **Reply #3 on:** December 25, 2009, 08:45:39 AM »

From what I've read, the M42 rods and crank are forged. M44 rods and crank are cast.

It doesn't necessarily mean that the M44 is inferior. AFAIK, lighter is better for high rev applications.

e30guydownunder · « **Reply #4 on:** December 27, 2009, 05:00:22 AM »

I'm only going from speculation on the internet. I have never disassembled an M44. The cranks however are definitely cast in the M44. But as wannam42 mentioned, lighter rotating assembly is better for more revs

visionracingdevelopments · « **Reply #5 on:** December 27, 2009, 08:05:44 AM »

You aren't putting extra force on the rods you're making them work faster so as mentioned above the lighter option would be best.

Boyracer · « **Reply #6 on:** December 28, 2009, 06:49:47 AM »

Ummmm, I am pretty sure that if you increase revs, you will increase load conrods have to endure because piston will travel faster but the distance is the same hence acceleration must be larger. And force (load) = mass x acceleration so it is easy to see increasing revs -> piston speed will increase load.

Lighter is better of course but are the lighter conrods also as durable?

e30guydownunder · « **Reply #7 on:** December 28, 2009, 06:41:56 PM »

How many revs are you looking to do? Whats your budget?

wannam42 · « **Reply #8 on:** December 29, 2009, 07:12:50 AM »

Quote from: e30guydownunder;83754

How many revs are you looking to do? Whats your budget?

+1 to this.

Make sure you get everything balanced too.

visionracingdevelopments · « **Reply #9 on:** December 29, 2009, 12:25:25 PM »

Quote from: Boyracer;83728

Ummmm, I am pretty sure that if you increase revs, you will increase load conrods have to endure because piston will travel faster but the distance is the same hence acceleration must be larger. And force (load) = mass x acceleration so it is easy to see increasing revs -> piston speed will increase load.

This is true

The way I was thinking of it is it isn't like FI where you are ramming more into the same space and pushing harder on the rod compared to NA, but as you rightly say 'piston speed will increase load'.

Boyracer · « **Reply #10 on:** December 29, 2009, 01:23:00 PM »

Quote from: e30guydownunder;83754

How many revs are you looking to do? Whats your budget?

8500

Budget is limited but I guess I have to pay whatever it takes...

Anyway, I just found a local source from which I ordered set of 4 billet rods with ARP 2000 bolts for 400�.

Those should be enough to atleast 8500 rpm with my lighter forged pistons

wannam42 · « **Reply #11 on:** December 29, 2009, 05:39:19 PM »

What will you be doing for the valvetrain?

Boyracer · « **Reply #12 on:** December 30, 2009, 04:11:43 AM »

Quote from: wannam42;83823

What will you be doing for the valvetrain?

- Solid lifters with under-the-bucket adjustment
- 290 degree / 11.5 mm lift cams (already have these)
- 15% stiffer valve springs with 14 mm lift coil bind from Dbilas (already have these)
- Supertech +1 mm oversize valves

With much lighter valvetrain (valves, lifters) and stiffer springs 8500 should not be a problem. S50B30 ITB's should help engine to breathe on high revs too.