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Old 01-13-2013, 05:19 PM
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Rod Bolt Question

Ive got a 383 SBC that I use for drag racing. I am upgrading my top end on and decided to replace my rod bearings and rod bolts. I replace the mains last year so am not going to mess with them. I will be replacing the rod bolts with the exact same model ARP bolts as they currently have. These are scat rods with very little use. My question is do I need to have the big end re-sized. I've read a couple threads where some people say that when you upgrade rod bolts that they need to be re-sized. I cant find anything about where the bolts are being replaced with the same bolt.

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Old 01-13-2013, 05:28 PM
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If the rods have very little use, why change them?
If you do change the bolts, cap screws in rods with an alignment sleeve do not to be resized. If the bolts are a press in with some sort of knurling or serrations, than you should at least have them checked for size/roundness after the bolts are changed.
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Old 01-13-2013, 05:42 PM
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i wouldnt be so much concerned with resizing if there is lilttle use on the parts, where you need to be careful is the weight and when you replace ANY parts of a rotating assembly you need to have the whole thing re-balanced to prevent vibrations
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Old 01-13-2013, 06:13 PM
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They have little use but I have had the pistons out a couple times. I am probably being overly cautious by changing them and am kinda wishing I hadn't already bought the new ones. I am assuming that since the bolts are the same exact part # that the weight will be close enough not to affect the balance.
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Old 01-13-2013, 06:25 PM
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What type of rod do you have?
Or, what is the part number of the new bolts?
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Old 01-13-2013, 06:35 PM
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They are 5.7" Scat I beams with 3/8 ARP Wave lock bolts part # ARP-134-6027. These are the bolts with the small head for stroker clearance.
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Old 01-13-2013, 09:49 PM
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Personally I wouldn't touch them, ARP's are theee best fasteners available and rarely break, specially parts with very little use.
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Old 01-13-2013, 10:36 PM
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I see no need for replacement unless the engine was abused/over revved or the rod bolts were over torqued.

Instead of replacing them I would invest in a stretch gauge. That takes any guesswork out of the torque and lets you chart them through repeated uses.
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Old 01-14-2013, 06:28 PM
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I wish I had done some checking before I ever messed with them. Ive already got one out to see how hard it would be so I figure I have to go ahead and replace them. I called the machine shop that balanced this setup originally and he said that 95% of them have to be re-sized. I am going to get them to him so he can get it done, He also said I will not have to worry about the balance cause he will hardly have to remove any weight at all. I want it to be as right as I can afford, so I am going to go ahead with it. Thanks for the info guys, I am going to check on a stretch gauge so that I can track the new set.
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Old 01-14-2013, 07:25 PM
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Quote:
Originally Posted by abritton77 View Post
I wish I had done some checking before I ever messed with them. Ive already got one out to see how hard it would be so I figure I have to go ahead and replace them. I called the machine shop that balanced this setup originally and he said that 95% of them have to be re-sized. I am going to get them to him so he can get it done, He also said I will not have to worry about the balance cause he will hardly have to remove any weight at all. I want it to be as right as I can afford, so I am going to go ahead with it. Thanks for the info guys, I am going to check on a stretch gauge so that I can track the new set.
If you got a fastner question arp has several fastner nerds waiting to answer such question. I was amazed at how eagar they were. Actually they would probably send you a new set if they didnt check out.

Always resize if they need it and after bolts are replaced they usally need it.
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Old 01-14-2013, 07:33 PM
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Changing the rod bolt's doesn't change anything as far as size.. If the rods are in good shape and never had a Brg spun, I'd mock it up and plastic gauge it. It'd be a good Idea to gauge them all anyway.
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Old 01-14-2013, 08:10 PM
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Quote:
Originally Posted by prostreet6t9 View Post
Changing the rod bolt's doesn't change anything as far as size.. If the rods are in good shape and never had a Brg spun, I'd mock it up and plastic gauge it. It'd be a good Idea to gauge them all anyway.
The only thing plastic gauge will tell you is approximately how much oil clearance you have between the bearing and the crank journal.
But your correct in at least have the rods checked for roundness after the new bolts are installed. If the rod housing bore is not round with in spec then have it re-sized.
Remember these are knurled shank bolts so they can distort the rod and cap.
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Old 01-14-2013, 09:00 PM
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Quote:
Originally Posted by blwilliams View Post
The only thing plastic gauge will tell you is approximately how much oil clearance you have between the bearing and the crank journal.
But your correct in at least have the rods checked for roundness after the new bolts are installed. If the rod housing bore is not round with in spec then have it re-sized.
Remember these are knurled shank bolts so they can distort the rod and cap.
If you rod is out of round it will show when you measure the plastic gauge. When you put the plastic gauge material on.. you should put enough on so you get you can measure both half circles after you Torque the rod down.

Yes they are knurled, but really not that tough to install them with a little common sense. If you any doubts you can torque the rod down off the crank and measure it with a inside caliper.
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Old 01-14-2013, 09:20 PM
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Originally Posted by prostreet6t9 View Post
If you rod is out of round it will show when you measure the plastic gauge. When you put the plastic gauge material on.. you should put enough on so you get you can measure both half circles after you Torque the rod down.

Yes they are knurled, but really not that tough to install them with a little common sense. If you any doubts you can torque the rod down off the crank and measure it with a inside caliper.
No it wont it will just trash the bearings out in 20k miles.

Rods are either heated or the rods bolts are beat out with a hammer either one can reshape the rod a little. The rod bolts are a little bigger than the rod hole or the same size so they must be forced into the holes. They dont just drop out. So no real way to guarantee they are straight without a dial bore guage. I just got one from amazon for 89 bucks 2-6 inches ten thou in half steps not the best but smooth and accurate as it reads. This will show if the rods are out of round and is quick and easy. Plastiguage is not quick or easy.
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Old 01-14-2013, 09:34 PM
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[QUOTE=hcompton;1634930] The rod bolts are a little bigger than the rod hole or the same size so they must be forced into the holes.

Isn't that what a Knurl is?? Lol
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