Rod/main bolts?
Rod/main bolts? Are OEM rod & main bolts TTY, or are they reusable? When I pull my oil pan I plan to pull a couple bearing caps and inspect the bearings on my 77k mile LM4. Figure since the pan will be off anyways, I'd rather be safe then sorry.
Yes , You can re-use rods and main bolts once or twice as long as You don't have it supercharged or turbocharged and You're not going to spin it past 6000 or 6300 . Head bolts You for sure want to replace whenever You remove the heads .
I'm planning on setting the rev limiter to at least 6500. Perhaps swapping to a 'vette damper, or better yet a good fluiddamper would be a good idea?
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Someone will say you can do it on stock bolts safely, but I have and would at the least upgrade you for bolts and recommend main bolts too. If you go with Katech rod bolts they are a direct replacement...Oct read where some of the ARP bolts require machine work
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Why are bolts an issue? I guess I need to find out what the stroke is on these cranks, I can't see why such a short V8 crank is going to have issues with higher rpm's. We spin the BMW I6 cranks (M/S50 series engines) to ~7200 rpm. Anything higher (on a regular basis), since they're such a long crank you get into their 2nd order harmonics, and they'll shake themselves to pieces, shear oil pump shafts, snap cams/cranks, etc. The S54 revs to 8500, and has a MUCH bigger crank damper, and 4 big bolts to hold it down vs 1 on the M50's.
I'm guess I'm just asking what is it about stock bolts that aren't adequit at 6500 rpm's?
I'm guess I'm just asking what is it about stock bolts that aren't adequit at 6500 rpm's?
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There are quite a few on here that have used stock bottom end racing and supercharging and turbocharging without issues . GM says to replace them every time it is dissassembled but from what I've read on here it's not nearly that critical but if the engine is going to be pushed , I would upgrade . Go over to Youtube and search 5.3L, LS1, LS6, 6.0L supercharged dyno and check some of them out . I saw 1 guy boosting to 2000hp supposedly on stock bottom end . You could probably do it but would'nt last very long . The stroke of the 4.8L is 3.267" and the rod is 6.275"
OK. This comes back to my original question, but WHY? What is making them stretch, what kinds of forces is the crank creating that is making rod bolts stretch? Is it because of the length of the stroke, or is it just overall a poor design without enough torque on the bolts? If somebody knew the yield point of stock bolts you could probably stretch them appropriately (1-time use) and get a good bit more holding force from them.
However, when using aftermarket bolts like ARP's, what are they being torqued to? If they're being torqued higher, is that distorting the bearing shells at all, and also decreasing oil film thickness on parts of the bearing surface? No real information as to whats going on here, this is my first time dealing with an engine who's factory bolts are apparently inferior, so sorry for what may sound like a stupid question. However, Im one who likes to think that 9 times out of 10 the factory 'did it right', since where I come from (BMW world) the factory bolts have been stronger than any of the aftermarket 'upgrades' for many years now, factory intakes and TB's are designed best and have proven over and over and over again on the dyno that aftermarket 'upgrades' make all of 0hp, and sometimes a loss in torque, etc. For example, ARP just recently released a new 10mm headstud for the E36's engine family that is finally stronger than factory head bolts, thanks to a local friend who's an automotive/racecar engineer who designs turbo kits and factory ecu tuning for BMW's.
However, when using aftermarket bolts like ARP's, what are they being torqued to? If they're being torqued higher, is that distorting the bearing shells at all, and also decreasing oil film thickness on parts of the bearing surface? No real information as to whats going on here, this is my first time dealing with an engine who's factory bolts are apparently inferior, so sorry for what may sound like a stupid question. However, Im one who likes to think that 9 times out of 10 the factory 'did it right', since where I come from (BMW world) the factory bolts have been stronger than any of the aftermarket 'upgrades' for many years now, factory intakes and TB's are designed best and have proven over and over and over again on the dyno that aftermarket 'upgrades' make all of 0hp, and sometimes a loss in torque, etc. For example, ARP just recently released a new 10mm headstud for the E36's engine family that is finally stronger than factory head bolts, thanks to a local friend who's an automotive/racecar engineer who designs turbo kits and factory ecu tuning for BMW's.
TECH Addict
Joined: Sep 2009
Posts: 2,481
Likes: 5
From: PA/MD
OK. This comes back to my original question, but WHY? What is making them stretch, what kinds of forces is the crank creating that is making rod bolts stretch? Is it because of the length of the stroke, or is it just overall a poor design without enough torque on the bolts? If somebody knew the yield point of stock bolts you could probably stretch them appropriately (1-time use) and get a good bit more holding force from them.
However, when using aftermarket bolts like ARP's, what are they being torqued to? If they're being torqued higher, is that distorting the bearing shells at all, and also decreasing oil film thickness on parts of the bearing surface? No real information as to whats going on here, this is my first time dealing with an engine who's factory bolts are apparently inferior, so sorry for what may sound like a stupid question. However, Im one who likes to think that 9 times out of 10 the factory 'did it right', since where I come from (BMW world) the factory bolts have been stronger than any of the aftermarket 'upgrades' for many years now, factory intakes and TB's are designed best and have proven over and over and over again on the dyno that aftermarket 'upgrades' make all of 0hp, and sometimes a loss in torque, etc. For example, ARP just recently released a new 10mm headstud for the E36's engine family that is finally stronger than factory head bolts, thanks to a local friend who's an automotive/racecar engineer who designs turbo kits and factory ecu tuning for BMW's.
However, when using aftermarket bolts like ARP's, what are they being torqued to? If they're being torqued higher, is that distorting the bearing shells at all, and also decreasing oil film thickness on parts of the bearing surface? No real information as to whats going on here, this is my first time dealing with an engine who's factory bolts are apparently inferior, so sorry for what may sound like a stupid question. However, Im one who likes to think that 9 times out of 10 the factory 'did it right', since where I come from (BMW world) the factory bolts have been stronger than any of the aftermarket 'upgrades' for many years now, factory intakes and TB's are designed best and have proven over and over and over again on the dyno that aftermarket 'upgrades' make all of 0hp, and sometimes a loss in torque, etc. For example, ARP just recently released a new 10mm headstud for the E36's engine family that is finally stronger than factory head bolts, thanks to a local friend who's an automotive/racecar engineer who designs turbo kits and factory ecu tuning for BMW's.
