hello! i just had arp rod bolts installed in my 03 6.0 engine that im going to install in my 60 chevy.i noticed the arps are a little longer than the stockers.so i has a friend do a weight comparison.the arp bolt was 2.7 grams heavier than stock. with both bolts making the rods big end 5.4 grams heavier and 10.8 grams on the crank pin. now im worried about balance issues.what do you guys think about the differance??? my machinist says to file the top of the rod bolt to get the weight down close to the stock weight.i should have just left the stockers in there i appreciate any and all input on this. thanks!!!

 

I am not a machinist but, i believe most street engines are balanced within or better of .5gram. Whether it be between piston/rod assemblies, or bobweight, of course this can all be done to the hundredths..

Where are the bolts longer, in the thread or the head/flange? You can probably file the bolts more preferably, or take a little off the rod cap as you have bolts out anyway, but if you do this, you will only want to work perpendicular to crankshaft or wrist pin orientation so you don't create any stress risers.

If it were my motor and i was just wanting the arp's, i would just do as your machinist has recommended to get the back within .5gram to the oem weights.

 

Might be a dumb ??? why not keep the stock rod bolts in there... They will hold just fine

John

 

True, unless your going to some extreme amount of boost or rpm, in which case, rods, and pistons should be done too, you shouldn't need them. Parish replaced them on his otherwise stock engine i assume for a bit of insurance pushing things as far as he did..

 

Exactly, I am spinning my 6 to 6300, on 7-8 psi, upping to 10 soon.. Guys are spinning much higher on stock bolts like 6800+. I saythrow the stockers back in


John

 

thanks for the input guys! the extra length is in the threads.yes i wanted a little stronger upgrade,but they seem to be causing more problems than good.i may put the stock bolts back in,since after the fact i found out they are a stronger bolt than the early ls engines.i have searched ls1 forums and found a lot of people just popped the caps off and installed these same arp bolts without checking anything with success,they didnt even remove the rod from engine.its recommended to check the rod bore diameter after installation,as i did with no affects.thanks again for the input.

 

i wouldn't do rod bolts for a paticulur hp or boost level. hp comes from downward pressure on the rod so there is no load on the bolts at that time. i would do them for an engine that you plan on spining up high. the rule of thumb has always been 6200. i certainly wouldn't take stock bolts to 6800rpm if i was looking for things to last.

maybe i am behind on the times and things have changed?

 

Theres you answer! ^^^^

If you are going to spin it over 6200 change them out, if not go stock! Advice probably doesn't get a whole lot more first hand there!

As for guys putting the bolts in and without balancing, i'm sure they will get away with it for now, maybe for a long time... But keep in mind a well balanced engine will ensure longevity and peak operating smoothness, maybe you can run an extra 100k miles who knows! In and unbalanced scenario, dynamic frequencies develope as you spin the rotating assembly up to redline and will actually cause the crankshaft to hammer in the journals shortening life. As with anything mechanical, its how precision you are with the details that provide you with the greatest gains in both power and life span of any component.

preach preach preach haha

 

the stockers are going back.didnt think about what parish8 said about all power is on the down stroke where the strenght of the bolt dont have that much of an effect.being this is gonna be a street runner with the occasional romp on the pedal. bad thing is i probably wasted about 125 bucks on this plan,oh well i guess i could use them for another ls project.

thanks again to all for your input!!

 

arent the stockers torque to yeild? the added weight is so mimimal i wouldnt worry. i would use ARP without a question.