Loosening rod bolts

General engine tech -- Drag Racing to Circle Track

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jtb032295
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Loosening rod bolts

Post by jtb032295 » Fri Feb 02, 2018 5:38 pm

Hey guys/gals, just a quick question... What's everyone's thoughts on removing (and only removing) rod bolts with a battery impact wrench? I did a quick search and didn't find a conclusion. Specifically ARP8740 bolts, if it matters.

Thanks

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Re: Loosening rod bolts

Post by SupStk » Fri Feb 02, 2018 5:48 pm

Just my opinion here with no real basis one way or the other. i don't use impact tools. They get loosened by hand.
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Re: Loosening rod bolts

Post by Morgo » Fri Feb 02, 2018 6:17 pm

I don't see any problem in that.Anything that loosens the bolt is just loose bolt.Of course you can try measuring the torque the bolt break loose but that would be meaningless info..
"when uncomptent order unwilling to do unnecsessary the probablity of failure is high"

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Re: Loosening rod bolts

Post by KnightEngines » Fri Feb 02, 2018 7:01 pm

No probs with rattling stuff apart, but only hand tools for assembly!

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Re: Loosening rod bolts

Post by MadBill » Fri Feb 02, 2018 7:03 pm

I like to feel the breakaway torque; it can spotlight potential issues.
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Re: Loosening rod bolts

Post by Roundybout » Fri Feb 02, 2018 10:19 pm

I like to use hand tools just for the "feel". Don't know how scientific it is but if one busts loose a lot harder or easier for instance it can mean something. Same for heads, crank or any critical fastener.

The video of the top fuel team buzzing everything off shows it probably doesn't matter lol.

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Re: Loosening rod bolts

Post by tresi » Sat Feb 03, 2018 12:58 am

Top Fuel with 45 minutes to get engine serviced go for it, in the shop it doesn't take that long to grab a long handled ratchet
.

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Re: Loosening rod bolts

Post by hoodeng » Sat Feb 03, 2018 2:02 am

Fuel motors nearly know their own way back together!! they are assembled every time with torque wrenches and procedure , a lot of critical fasteners will have a designated amount of cycles ,also the fasteners are all high end products.I wouldn't want to be the crew member responsible for a given task, stripping or breaking a fastener and causing a rush no one wants or expects [no beer for him that night]

Cracking fasteners loose on any production engine for overhaul as has been stated by others before can give important information by feel ,all fasteners in a given type of assembly i would expect to crack off or release in pretty much the same manner .Any hanging up or doughy feel needs to be investigated ,for me anything like what i have described would see a change of fastener on reassembly, after they are cracked loose or released and backed off a turn or two a rattle gun set on minimum torque will speed things up a bit, and you can still monitor the speed and sound it back off at in case something tightens up.

Cheers.

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Re: Loosening rod bolts

Post by joe 90 » Sat Feb 03, 2018 3:11 am

MadBill wrote:
Fri Feb 02, 2018 7:03 pm
I like to feel the breakaway torque; it can spotlight potential issues.

I've stripped lots of engines prior to rebuilding.
When they come in you often don't know what's actually wrong with them.
After a while of noticing some headbolts not as tight as other head bolts, I got into the habit of checking the tightness of all the critical ones on pulling apart. Headbolts, main bolts , rod bolts and crank bolt.
It's a whole new learning curve.
Engines with aluminium heads.......overheated, the head bolts are ALWAYS loose.

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Re: Loosening rod bolts

Post by Sparksalot » Sat Feb 03, 2018 3:28 am

In my experience across several pursuits from NASA to racing there is information available to the observant during disassembly of any machine. The felt undoing of every fastener is one of them. Why deny yourself that information?

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Re: Loosening rod bolts

Post by jtb032295 » Sat Feb 03, 2018 4:30 am

Thanks for the feedback everyone! I understand the need for "feel" when disassembling a build and think it's a good idea to use hand tools in that scenario.

For the sake of conversation, how would you feel about breaking lose rod bolts via impact if they were brand new, right out of the box, just to remove the caps for the first time? No problem?

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Re: Loosening rod bolts

Post by benno318 » Sat Feb 03, 2018 4:38 am

yeah, im another that likes to loosen initially with hand tools, after that the battery impact wrench (which wont really "ugga dugga" once tension is not there!) or drill with 1/4" drive 6" extension works well for sump bolts and the like.

ps theres nothing worse than a customer "doing you a favour" and pulling an engine down with zero f...ks given, and handing you a box full... i hate that...

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Re: Loosening rod bolts

Post by modok » Sat Feb 03, 2018 4:43 am

If the rods arrived with the bolts tightened, I'd want to know what value they were tightened to.
Mark the position of the head, loosen 1/4 turn, see how much torque it takes to put it back where it was. Not every one, but maybe a few to get an idea.
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Re: Loosening rod bolts

Post by midnightbluS10 » Sat Feb 03, 2018 5:21 am

benno318 wrote:
Sat Feb 03, 2018 4:38 am
yeah, im another that likes to loosen initially with hand tools, after that the battery impact wrench (which wont really "ugga dugga" once tension is not there!) or drill with 1/4" drive 6" extension works well for sump bolts and the like.

ps theres nothing worse than a customer "doing you a favour" and pulling an engine down with zero f...ks given, and handing you a box full... i hate that...
That's my usual route. Break loose by hand, then run the bolt out/nut off with the ¼“ air ratchet or small 12v drill with adapter and extension.

Removing the head bolts on my Trailblazer last year, they all came out really funky, except the 3 that broke. They were all nice and quiet. The others all came out creaking and moaning and groaning the entire time where the 3 that broke were quiet from the moment I started putting any force on them. I could tell right away something wasn't right with those. Somehow, the first one broke, but didn't break the last thread holding the top piece of the bolt to the bottom piece. It unscrewed just like that, with maybe .5 mm of thread holding the pieces together. I spun the 2nd bolt out with a pick and the 3rd with an ez out. Only because it kept catching on something with the pick and would turn past a certain point. It was also under the edge of the firewall, so there was that.
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Re: Loosening rod bolts

Post by mag2555 » Sat Feb 03, 2018 7:29 am

Not a issue as long as you fill the side clearance gap with feeler gauges.
What you really need to be concerned with in a race motor is the fact that once rod bolts have been torqued up 4 times they need to be replaced or you take a good chance of them failing dependant on how much of there ultimat strength your counting on!

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