Rod spec

[83rampage]

Got my rods back from the machine shop the other day. I measured the big end, and seems like they are .001 too big (they are all the same). Only spec I could find was on the Allpar site.

Can someone with a factory service manual look up what Chrysler has listed for a spec?

Thanks in advance.

[cordes]

What type of device are you measuring with?

[Directconnection]

What type of device are you measuring with?

Exactly.... dial calipers are not the way to measure your clearances at all. Only a dial bore gauge. Also, make sure you use the exact same lube (and torque) that they used when they re-sized them as it DOES make a difference.

[83rampage]

Not sure where you guys saw I was using a dial caliper???

I was using snap gauges and an outside micrometer. I've used inside mics, well as snap guages and found the snap gauges are as accurate as an inside micrometer. Yes the rods were torqued to spec.

[Directconnection]

Not sure where you guys saw I was using a dial caliper???

I was using snap gauges and an outside micrometer. I've used inside mics, well as snap guages and found the snap gauges are as accurate as an inside micrometer. Yes the rods were torqued to spec.

Telescoping bore gauges require a feel with a LOT of experience to be accurate within .0010 total (+/- .0005") I can get mine to repeat within .0002-.0004 TOTAL, which is far better than their intended purposes. But, I still will not use them to get my clearances. The mic has to be adjusted perfectly (meaning: backlash adjustment) and your "feel" dialed in, as well.

I suggest a dial bore gauge. Even a cheapy is far more accurate than telescoping gauges. Measure your rod journal, then lock the locking ring to keep the backlash in check, and use the mic to set the dial bore gauge with bearing installed in the rod. Always use the lock when transfering one measurement to another no matter how well the backlash is adjusted.

[83rampage]

I used to use snap gauges/mics on a near daily basis, so I KNOW I have the feel. I get what your saying about the dial bore guage, but I'm fairly confident in my measuements to know they are .001 too big given the specifications I have found.

I don't think you guys are getting what I'm asking. I want to check the rod diameter to ensure I have enough bearing crush, and know the machine shop didn't take too much material off.
I havent even got to the point of checking bearing clearances yet.

Do you guys check the work of your machine shop, or just slap it together and hope everything is fine? I just want to make sure I'm getting the proper info before I go back to the machine shop.

For a simple question this sure has turned into a general assumption I don't know anything about measuring.

Maybe a simpler question is required.


Can anyone verify with a factory service manual that the spec for the connecting rod big end diameter is 52.992-53.008mm?

[rbryant]

Can anyone verify with a factory service manual that the spec for the connecting rod big end diameter is 52.992-53.008mm?

The 86 FSM that I have handy lists the crankshaft rod journal OD at: 49.979mm-50.005mm

The bearing clearance is supposed to be .019mm-.079mm (.0008"-0031")

The speed secrets book gives the same specs but not exactly what you are looking for. It appears that you need to have the bearings installed in order to size them. :)

-Rich

[83rampage]

Thanks Rich!

Seems funny the service manual doesn't give a spec for the inside diameter of the rod. I think I'll dig up some rods I have and compare them to that, and talk to my machinist.

As I said I'm just worried he got a bit too agressive and re-sized them too big. Thing is they are all the same, so either he used the wrong spec, or I have the wrong spec.

[Directconnection]

Just check them with the bearings installed.

Google the rod housing bore size as you may find it there as well... I have it at work.