type iv connecting rod tolerances

[whc03grady]

Here's what I got:
#2: 0.023" / 0.584 mm
#4: 0.017" / 0.432 mm
#1: 0.018" / 0.457 mm
#3: 0.022" / 0.559 mm

Spec is 0.027"? I think? Time for new rods?

[satchmo]

With 1700/1800 Type 4 con-rods, there are no new OEM rods, only reconditioned ones (unless you want to spend a bundle and get some fancy I-beam type rods).

Did you do your measurements with your broken crank and old bearings? Doesn't count. You need new bearings and must make your measurements on the crank you will be using.

Tim

[whc03grady]

Thanks. The Wilson book talks about measuring them before you take them off the crankshaft, but I suppose that assumes you're reusing the crankshaft.

[Amskeptic]

Here's what I got:
#2: 0.023" / 0.584 mm
#4: 0.017" / 0.432 mm
#1: 0.018" / 0.457 mm
#3: 0.022" / 0.559 mm

Spec is 0.027"? I think? Time for new rods?

Don't even worry about it. These figures seem really sloshy, but remember what this tolerance is for: this allows the crankshaft to expand longitudinally from the #1 bearing back as the engine heats up, and it allows the rods some room for crankshaft endplay. If the crankshaft has .007" endplay let's say (a typical reading), the rods have to allow the crankshaft to glide back and forth under them. The important measurements for rods are bearing clearance (.0018" to .0025" is very nice), wristpin clearance (.0008" to .0012" is lush), bolt length and diameter and thread health, and straightness. With very clean oil and new nuts, your rods would be capable of decent high rpm hard work for hundreds of thousands of miles.
Colin

[whc03grady]

Thanks, all. One less thing to worry about, probably.

[Amskeptic]

Thanks, all. One less thing to worry about, probably.

Do exactly what you have to do to get rid of the half-assed "probably". Educate yourself and execute the correct reconditioning so you KNOW what you have under you when you do that wind-out on the freeway onramp.
Colin