quik95lt1

iTrader: (7)

Figured I'd share some machining infortmation of what replacing rod bolts can and cannot do. Theres been much controversy over the years espically on ths site pertaining to swapping out rod bolts in an engine and not resizing the journal ends. Many say its ok just do it and many say no take it apart and resize. A recent customer engine I took apart for a rebuild had ARP rod bolts put in it about a year ago and never had the rods resized. Below are the bearings from the engine.

Here is the rod cap and bearing.....as you can see there is a wear mark about .75" wide right on the bottom of the bearing.....you can clearly see the wear is fresh compared to the rest of the bearing......



Here is the bearing shell from the rod.....again notice the 1" wear mark at the bottom of the bearing again.....


this was caused by the rods not being resized and the clamping force on the new bolts being different from the original GM bolts.......the arp 8740 bolts are supirior to the GM bolts in clamping force however the effect on the rod bearing is negated by the clamping force improvement. How this happens is the housing bore is distorted by the extra clamping force, it pulls down ths sides of the cap more which intern pushes the sides of the cap outward and pulls the top and bottom of the cap/rod inward. In essence "ovaling" the housing bore, had this motor been continued to be run and not taken apart failure wouldn't have been to far in the future. Hopefully this is some clear cut evidence for anyone replacing rod bolts and questioning whether to resize the rod ends. Basically, DON"T DO IT! When changing bolts if the clamping force is different the housings MUST be re-machined. This goes for rods and mains.

Hope this info is useful!!!



Mike

Bramlok

iTrader: (7)

If you're not resizing, better off going with Katechs.

lemons12

iTrader: (71)

Katechs do not have to be re-sized, correct? Thats what I plan on going with in a couple weeks when I start putting everything together.

mark21742

Correct...they are a direct replacement. Just stronger steel so they can be reused......if you go with the ARP bolts you need to have the rods resized because they actually grab better/different.

Good write up while95!

s346k

iTrader: (4)

katechs do not require rod resizing.

Jeremy@RPMTransmissions

iTrader: (12)

Im no machinest at all. I am asking because I have no idea.

Since the stock LS rods are cracked cap, how would you resize them?

quik95lt1

iTrader: (7)

with the cracked cap rods yes you are right you cannot machine off the parting line and then rebore........the stock rod iirc can be bored .002 as is then a thicker bearing is used to make up the difference.....clevite makes bearings to make up the difference......at that point its usually cheaper to just put a set of scat i beams in and call it a day

ohioz

iTrader: (9)

It never made much sense to me how some one can say that if you replace the rod bolts with arp's you need to resize the rods. But if you use katech's bolts you do not. As the op says its the extra clamping force that distorts the big end of the rod. So you guys are trying to say that katech's bolts are stronger than stock, yet yield no extra clamping force? Not trying to be a ball buster, I've just wondered this for awhile. I've read countless threads on replacing rod bolts and everyone says you have to resize only with arp's and not katech's.

91sonomast

I bought a set of rods with ARP bolts in them that have supposedly been resized. How do I check to make sure?

Tainted

iTrader: (9)

Take one off and measure

Jeremy@RPMTransmissions

iTrader: (12)

I gotcha. Boring the ID was the only was I could think about it work.

383camaroz28

iTrader: (22)

Thats my poor bearing lol

quik95lt1

iTrader: (7)

lol ill do a build thread for you mike when it goes back togheter.....

KCS

iTrader: (20)

Good info. Have you measured the housing bore with the ARP bolts torqued?

quik95lt1

iTrader: (7)

not on these rods but previously i have......i can pull one out of the trash can and check it when i go home though lol.......ill report back tomorrow with the #'s

Marc 85Z28

iTrader: (8)

There is controversy for good reason: because so many people have success with a basic rod bolt swap.

I swapped out my rod bolts for ARPs without resizing over 5 years and 30K miles ago. The engine sees 7K rpm EVERYTIME I drive it - lots of street abuse and dozens of track passes. I have no noise, good oil pressure, and no abnormal metals in my oil. And I'm not alone...

Your "conclusion" is flawed. You don't know the condition of the rod bearings before the bolts were changed.

SSdreamz

iTrader: (3)

good find and good info right here. I too have read countless threads pertaining to replacing the rod bolts (especially the 98's) cause of the inferior rod bolt. I was about to do this to my brothers engine when we did the oil pump, heads and cam swap.... glad we didnt

SSCamaro99_3

iTrader: (1)

Katech is superior tensile strength comapred to stock with the same clamping force

ARP is superior tensile strength compared to stock with additional clamping force.

quik95lt1

iTrader: (7)

my conclusion is not flawed, there is a much higher wear in the specific spot that would be affected by the bolts compared to the rest of the bearing which exhibited normal wear the only thing that would cause that type of bearing damage is an out of round housing.....and the rate at which it appeared to be wearing was not on par with the rest of the bearing.....find a GOOD performance machine shop and they will tell you the same thing......this is not the first time i have seen this......but it is the first time im sharing my find to try and save people some headaches............whether you chose to take the info or throw it out there is no sweat off of my back.......im merely stating a fact.......according to your theory then we can freely swap bolts in and out with no problem, interesting......do YOU have any data to back up your claims? any bearings or info from this engine you have other than the mileage you have on it and the wear that may or may not be on your bearings that you may be assuming? when it comes down to it can you take a chance on swapping bolts? of course.......will you have an issue.....maybe, maybe not.....but there are adverse affects to the change, me personally i work hard for my $$ and my reputation so id rather eer towards the side of caution

KCS

iTrader: (20)

If it has the same clamping force as an OEM bolt, what would be the advantage?