broken rodbolt

[reeldutch]

I installed 4 new pistons and rings after reboring and honing the cylinders.<br />i kept everything in order and i had no problems so far.<br />i connected al the conecting rods and i torqed the rodbolts 42 lbs.<br />with 3 out of the four connecting rods i did not have any problem.<br />but with one of the rods when i was torqing down the rodbolt didnt want to get tight to 42 lbs. it kept on turning and finaly snapped. so i thougt bad rodbolt no big deal.<br />the second time i tried with a new rodbolt and the same thing hapend again bud just before it snaped i mesured the torqe and it was 25lbs. When i put it on 30 lbs it snapped again.<br />i think that the tread in the conectingrod is worn?? can i retap this and with what tap?<br /><br />thanks reeldutch

 

[Dhadley]

Re: broken rodbolt

What motor?

 

[reeldutch]

Re: broken rodbolt

1990 115 hp v4 bubbleback

 

[G DANE]

Re: broken rodbolt

Odd - I once set my wrench wrong and overtightened awfull but nothing broke.<br />Did you turn the rodcap by coinsidence so the hole is out of line with threads ??

 

[Dhadley]

Re: broken rodbolt

Torque for a crossflow rod bolt is 29-31 ft lbs.

 

[reeldutch]

Re: broken rodbolt

thanks dhadley,<br /><br />i was looking wrng on the chart i looked at newton-meter and torqed lbs-ft.<br />i loosened the rodbolts and got 8 new ones because the other oncen might be over stessed.<br />i wit torqe them down now at 30 lbs and a drop of locktite<br /><br />reeldutch

 

[voodoo]

Re: broken rodbolt

Maybe you want new rods now?<br />Ask a rebuilder if this was a fatal error.<br />Shame to pooch a "new " motor.

 

[Dhadley]

Re: broken rodbolt

Different rods would be a good idea. They dont necessairly have to be new. No loctite is a good idea also.

 

[G DANE]

Re: broken rodbolt

Scale mistake was exactly what I did too. However the bolts got loose in a snap and threads looked fine. I just changed bolts, these are stretchbolts, but that was on a far less expensive motor. It still runs after 4 years now. i sold it later on.

 

[reeldutch]

Re: broken rodbolt

i dont think i need new rods. the bolds came out fine i could not see any damage on the treaths.<br />the bolds were in there for maybe 3hrs.<br />i will replace the rodbolts with new ones.<br /><br />so dhadley i should not use loctite?<br />and why not?<br />i think it is a little extra insurance.<br />but i might be wrong.

 

[Dhadley]

Re: broken rodbolt

I'm not too worried about the threads but rather where the halves come together on the inside (where the needles ride). It may not have done anything to the mating surface but I'd sure check before putting it together.<br /><br />I'd be especially concerned with the rod that started to act odd at 25 lbs torque.

 

[reeldutch]

Re: broken rodbolt

thanks dhadley,<br /><br />do you suspect i warped the inside?<br />do i have to check the inside for an edge or something like that?<br /><br />why cant i use loctite?