Chinese 3/8 "8740" rod bolts

SamT · Posted: Sat Sep 24, 2011 8:31 pm Post subject: Chinese 3/8 "8740" rod bolts

I'm assembling an engine with some chinese 4140 rods, they have some knock off rod bolts that are 3/8 and stamped 8740 on the head. I usually use ARP bolts, but I'm gonna run these bolts if I can figure out the torque/ stretch spec.

Can I use ARP data or would you just see how much torque it takes to get them to just under .0047 stretch or is that even the proper stretch?

mark tucker · Posted: Sat Sep 24, 2011 8:37 pm Post subject:

who knows,ask him. or his brother rong.I would think a 3/8, 8740 should go 48-52 with molly.but shit happens, better find out.or get some more bolts.

modok · Posted: Sat Sep 24, 2011 9:16 pm Post subject:

Torque them up 10% shy of ARP spec and check the stretch
If they don't have nice machined ends like arp then you can't really check stretch, toss em

Were the bolts torqued and was there lube on them as recieved?
If not how did they hone the rod?

SamT · Posted: Sat Sep 24, 2011 9:22 pm Post subject:

modok · Posted: Sat Sep 24, 2011 9:25 pm Post subject:

ok cool

you can mark the position of the head and loosen it, then see what it takes to get it back to that same spot

not high tech, but the more you know the better

mark tucker · Posted: Sun Sep 25, 2011 6:58 am Post subject:

some rods are sized with mule bolts. and you can always dimple the end. remember with moly it takes 3 torques to get to the corect torque.I doubt that is done when the rods are sized.

SamT · Posted: Sun Sep 25, 2011 7:40 am Post subject:

mark tucker · Posted: Sun Sep 25, 2011 8:00 am Post subject:

SamT · Posted: Sun Sep 25, 2011 10:22 am Post subject:

RockCrusher · Posted: Sun Sep 25, 2011 4:43 pm Post subject:

Having seen and used "one" set of AA rods and how crappy those bolts were I was much more sure of the EMPI 8740 bolts. The AA bolt heads didn't even all fit the socket and had to be modified....never again.

RC
_________________
[email protected] Please use email for all general inquiries.

I will be happy to speak to anyone who has a serious inquiry (meaning real potential business for RC enterprises) or a parts order. Due to machining noise causing missed calls all calls will be returned promptly.

modok · Posted: Sun Sep 25, 2011 5:00 pm Post subject:

The worst I ever saw was pro-comp
the bolts were rough machined, and they didn't torque the rods or lube the bolts.
They were torqued to like 25 ft-lb out of the box, and when I took out the bolts the threads jammed and got tore up.
When torqued, the big end assumed a kind if square type shape Laughing

It can't be worse than that

SamT · Posted: Sun Sep 25, 2011 5:05 pm Post subject:

well I was balancing some AA pistons today, they were as close as any Mahle pistons I have seen. Actually the pistons alone were within .3 grams, but the wrist pins were .5 grams difference between them, after juggling the pins around I only had to remove material from 1 piston to get within .1 gram.

These AA rods are another story, 7 grams of difference in total weight. Guess I'm gonna have to build a jig so I can balance the small end.

For reference I checked a set of CB Unitech rods and they were within 2 grams total weight. I read that .5 gram is acceptable.

RockCrusher · Posted: Sun Sep 25, 2011 6:09 pm Post subject:

I forget what the total weight difference was on the AA rod set we tried but it was very close....like 1 gram or less....I really forget. Embarassed

When doing small/big end though there was a large amount of difference to compensate for. It was the most difficult set I ever balanced. From the lightest untouched small end to the worst required a major almost rod polishing effort so as not to effect rod integrity. Like I said.....never again. I couldn't charge the customer for the amount of time I put into that set of rods because he went with them based on my idea that it was worth a try.

Don't even want to discuss the OEM rods for that engine that were supposed to be a balanced set but had about 8 grams total weight difference and the lightest rod had the heaviest small end.....what a nightmare.

Go figure....

RC
_________________
[email protected] Please use email for all general inquiries.

I will be happy to speak to anyone who has a serious inquiry (meaning real potential business for RC enterprises) or a parts order. Due to machining noise causing missed calls all calls will be returned promptly.

bomberbaja · Posted: Sun Sep 25, 2011 7:42 pm Post subject:

Yesterday I torqued my AA 3/8" bolt I-beams to about 42lbs with blue loctite.

modok · Posted: Sun Sep 25, 2011 8:06 pm Post subject:

why the locktite? you think they gonna come loose?
Razz

Just weld them nuts in place, that's fix it even better

bomberbaja · Posted: Sun Sep 25, 2011 10:48 pm Post subject:

earthquake · Posted: Sun Sep 25, 2011 11:52 pm Post subject:

bomberbaja
There is nothing wrong with a beam type torque wrench, they never need to be recalibrated. the only thing that clicker type have over beam is they are faster to do V-8 head bolts, I have both types and on a ACVW I will only use a beam type, with a beam type you can see when some thing is wrong. now If some one would make a BT with a ratchet head. I would like to have a 3/4" clicker type for gland and axle nuts

Casey
_________________
74 CLASS 11 LOOK-A-LIKE
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05 SCION XB SERIES RELEASE 2[#437]
95 Chevy C3500 dually
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Link to Kelly J. Nolte 3/20/53 - 11/6/08
https://time-zonelabs.blogspot.com/p/about-kelly.html
DEATH TO CHINGERS!
[From a military recruitment poster in the novel "The Stainless Steel Rat" By Harry Harrison]

modok · Posted: Mon Sep 26, 2011 3:48 am Post subject:

RockCrusher · Posted: Mon Sep 26, 2011 12:59 pm Post subject:

Just put a dab of JB Weld on the rod bolt threads....It goes hand in hand with JB welding the case halves together. Laughing

NOTE: THE ABOVE IS MEANT AS A JOKE
_________________
[email protected] Please use email for all general inquiries.

I will be happy to speak to anyone who has a serious inquiry (meaning real potential business for RC enterprises) or a parts order. Due to machining noise causing missed calls all calls will be returned promptly.

VIN · Posted: Mon Sep 26, 2011 1:03 pm Post subject:

HAHA!! another Sig. line quote for Darth!


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