I'm looking for the inside diameter of a connecting rod off a 350 tpi motor. I'm looking for the measurement of the bare rod without the bearing installed. The big end of the rod. Can't find the measurement anywhere thanks!

 

I just ooked in my 89 sevice manual and found nothing on that measurement.
might try calling a machine shop.

 

2.100+/-.001 inches

 

I hope not or else I need a new rod. LOL! Im getting 2.250 +/- .0005

 

ok the connecting rod journal diameter should be 2.0978-2.0998
you are measuring the big end without a bearing installed getting 2.250-2.0978=.1522/2=0.0761-.0015=.0746
with a big end measureing 2.250 and a rod journal measuring on the low you need a bearing thickness of .0746 to provide enough oil clearance what do the old bearings measure?

what are you using to measure +/- .0005? hopefully not calipers...

 

The GM spec for the large end of a large journal connecting rod is as follows:

2.2247" - 2.2252" diameter
Taper or out of round not to exceed 0.00015"
No bellmouthing permissible

1976, GM, Chevrolet Power book, 2nd edition, p. 1-16

RBob.

 

ok thanks for the replies. Im using a telescoping gauge with the auto centering feature. It can hold up to +/-.0001. The out of round spec kills me though. I guess I'll just get a new rod. Thanks for the help I couldn't find that measurement anywhere.

 

If you're dealing with a stock rod, try to find one that has the big-end balancing pad close to the same thickness as the original to keep the balance close. (that is, if you're getting a used one and you have a pile to choose from)
I've encountered one out of round rod before and it must have been dropped with the cap installed during a previous rebuild. Thank goodness for plastigage!

 

Or better yet, just have the rod resized. It's $20/rod around here.

 

If it's wider (bigger) across the parting line of the rod how are they supposed to grind that part of the rod smaller?
\ <--> /
.\____/
I know they resurface the parting areas of the rod and cap, but the bore is vertical there. They would have to grind a bunch off of each to close it up.
I say pitch it!
You can buy a box full of rods at a junkyard for $20.
Or join the people that can't figure out why they have spun bearings...