FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: 66ford on October 10, 2017, 11:15:48 AM
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What say ye on rod bolt replacement, it is an absolute must to get the big end resized? What are the real world issues if not resizing?
Ive read data on both sides, some to resize, others not so much.
Thanks for the input.
Howard
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I've replace rod bolts and just measured them after the replacement; in most cases I have not found resizing to be necessary. But for sure they should be checked.
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I have seen distortion in stock 351C rods when replaced with ARP items and torqued to spec. But not every rod LOL. As Jay said, install and check - resize if necessary. A dial bore gauge and a decent 2-3" micrometer and you can tell what's what. If you have bearing clearance in the range above .002 or so, some minor variation would be covered. If you have close specs like some of the published stocker info - like .0008~.0015 (pulled out of my hat) then you may want to resize anyway to be sure nothing gets too close.
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I have never done it myself, and likely never would, but years ago, a buddy replaced the stock rod bolts on his 12 second 383 powered Dodge Dart, with ARP bolts, on the assembled and had been driven for a few hundred miles engine. He just pulled the oil pan, and doing it one bolt at a time, knocked out 1 bolt with a punch, installed the new ARP bolt, and torqued it before replacing the next bolt. I figured the thing would have kicked out a rod shortly after, but it didn`t, it ran strong until he sold the car a couple of years later. For all I know, it may still be running!Again, I would not do that, but he got away with it.
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You can get away with not doing a lot of things in life that you "should" do, but that's not a reason for not doing them. IMO re-sizing rods after replacing rod bolts is one of those "do it anyway" things.
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I would add that if the rods in question were stock and have not been reworked, for sure "no, don't try it". Production variances could bite you hard. Having the rods gone over can fix a lot of things - big and small ends are held to better tolerances than the factory, length variations can be corrected, magged for cracks before spending $ on rebuilding, etc. Rods and their bolts are some of the most stressed parts in the engine and can do some of the most damage if one fails. I spend more time on checking and installing rods than about anything else. Buy and use a bolt stretch gauge when installing - makes a huge difference vs just a torque figure.
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On a capscrew rod it's not an issue. On a through bolt ( nut and bolt) "most" of the time the new bolt distorts the big end to some degree ( tighter). Rory probably got by with it because the bearings were used enough that clearance was still there after the new bolts were installed. ARP wave locks are the "worst" for distorting the big end. "I" haven't seen a set yet that didn't need resizing after installing them. Great bolt but extra work.
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I once saw a guy installing pressed pins by squeezing the piston-pin-rod in a big vise. I didn't know him and it was none of my business so I kept my mouth shut. I saw him a couple of weeks later and asked if he'd got the engine running. He told me it was going great and that it now had several hundred miles on it. Go figure.
KS