The Stovebolt Site Forums The Shop Area Engine Shop Snapped connecting rod bolt

Me and my buddy were tryin to tighten the connecting rod to the part it attaches to on the crankshaft on my Straight Six 250. It is supposed to be torqued to 35 ft lbs. i think. But when we got to 10 ft lbs, the bolt snapped like a twig. Anyway, the only place i can find the bolt is on Advanced Auto Parts, and it says its $55.99 for one bolt. Is that a typo or what? Anyway i was wondering if yall might be able to help me find another bolt. I put a link to the page on Advanced Auto. It's a 1968 250 CI(4.1L) Straight Six. Thanks in advance!


www.partsamerica.com/ProductDetail....mber=635010&PartType=149&PTSet=A

When I built my 350 cu. in. Chevy engine I replaced all my rod,main crankshaft bolts with ARP. bolts good for a lot more Torque Strength. These are the only way to go in my opinion. When it comes to the lower end I do not want to have to worry about breaking bolts. I know some here will say that it is overkill but better safe than sorry. ARP has a very good reputation with racing people as most use them exclusively. You might go to a wercking yard and get one or two from a bad engine or to the Chevy Dealer parts dept. as they might have them in stock.
62Blue
Don

55.99 is probably the cost for a complete set of bolts. If I had a bolt break, I would change all of them.

I would look at Summit Racing and get a set of ARP's Main Studs for $75 and not think twice. The block will break before these do

http://store.summitracing.com/partdetail.asp?part=ARP-132-5401&autoview=sku

Scott

man what ever you do be careful i have never seen a rod bolt break at 10 ft pounds before !

My buddy did most of the work. The mechanic that has been supervising the job is in Atlanta until tomorrow and we thought we could figure out the torque wrench. We converted 35 ft lbs. to newton meters, which is like 48 newton meters and we THINK we only torqued it to 10 newton meters. Personally, i think the guy that adjusted the wrench wasn't sure how. By the way, i checked out the ARP bolts and they didn't have a head, just a nut, how would that work?

Anytime a set of rod bolts is changed, the safest way to do it is to have the rods reconditioned at the same time to be sure the big end stays round, and the correct size. I ran the rod room for a big machine shop in Nashville for a few years, and that's what we reccomended every time we sold a set of ARP bolts.

The AERA connecting rod manual I have specifies 35-45 ft/lb. torque on all 250 connecting rods. (Yes, that is 48 N/M) If you swap for ARP bolts, remember the torque value changes. Follow the package directions, and I believe the stronger-alloy bolt needs 50 ft/lbs., not 45, and a special lubricant they provide in the package along with the new bolts. The "headless" bolt actually has a flat spot built into the top of the bolt that catches a corresponding flat area on the rod to keep the bolt from turning while it's being tightened. Always torque an ARP bolt at least twice after installing it. Drive the bolt into the rod body, lube the threads, torque them up, then loosen and retorque at least once to be sure the right amount of stretch is on the bolt. On the really hot race engines, we use a special micrometer and measure bolt stretch, not torque, to determine when the bolt is tightened properly.
Jerry

i have had one snap on a 250 as well, but it was right when it was about to reach final torque. it started to turn more than the torque reading was going up mabey for a 1/4 turn then- snap! if they start to feel "spongy" at the end you can always have them replaced. it will never be cheaper or easier than at this time. just be thankful it did it now. the 250 shares the 11/32 bolt as the 283 best i remember so they are able to be ordered fairly easily. i usually use the arp rod bolts like everyone has talked about, unless it's a stock rebuild, if you look for the 283 ones you will prob be able to find a deal. i have used the stock ones on my 250 but it was a stock rebuild. on my 292's i like the arp bolts. i always take my rods into the machine shop for reconditioning they don't charge that much and it's one job i like the idea of a pro doing. not that you couldn't do it but it's good to let them check it and you can recheck their measurements. hr

Yea, i have to order these things in the next hour or so, and i can't find them! ARP connecting rod bolts? Farther up is a link that Scott Danforth sent me, but it says main studs. Are those for my connecting rods? I have to order these within an hour, a clarification or a link to ARP connecting rod bolts would be REALLY helpful!!!

I found ARP connecting rod bolts for a 283, it's 11/32 and hoggy said it's same as the 250. Can anyone verify this before i buy them?

Here's the link.

http://www.northernautoparts.com/ProductModelDetail.cfm?ProductModelId=855

if you do not have a local shop that is an ARP dealer, I would just call ARP directly. I've had good service that way.
ARP contact info

Hoyt

also if you are just replacing the broken one most any machine shop should be able to have on hand the 11/32" connecting rod bolts for under $2 each with no wait on shipping. if you do spring for the arp set just toss the extra 4 my way. hahahaha the main studs or bolts are for the main bearings. i can't imagine you breaking one of those i bet the cast in the block would give way before the main bolt. good luck curious what you end up with. hr

I bought the ARP set, and if it gives me 16 for the V8(It never said how much was in the set) I'd be more than happy to ship the others to you, just need a delivery address.

thanks, but i was just kidding you. if i were you i would just save them back and after 2 more rebuilds you'll have a free set. that's what i do. good luck, hr