talk about the cart before the horse....

 

John, you're talking sense here. Can't have that.

 

there appears to be a few misinformed people here.....sense is lacking for some

 

Actually John, you don't machine the parting surfaces smooth. That's how you resize the old school stuff, but not a cracked cap rod.

You actually install the bolts, torque them, and hone about .002" out to get a round, concentric bore again. Clevite makes a .002" oversized O.D. "P" bearing for just such an operation (CB 1776P). Most shops will charge about $75 to do this.

 

well then me and you are talking about 2 different things.

why resize the old rods when new ones will come with those bolts, be forged and just as affordable. (scat)? they do come in a 6100 for either floating or pressed pins. this is all assuming that the rods will ONLY be out by that much.

again ask any machine shop to machine a PM rod...they dont like it. i know a few around here that dont like it.

 

I think you guys offer SCAT I beams for ~$300 after all is said and done right? You'd save about $150-200 with a stock rod and ARP upgrade as opposed to a SCAT rod. That would make for a pretty decent spring package. Plus they are all already visually checked and machined within tolerance. I know I've had to hone several sets of Eagle and Scat rods to get them within spec.

Like I said, I've seen them out-of-round over .001" with ARP bolts, but not .002". My point is that you don't resize these rods like you would the old school stuff. You don't cut the parting surfaces. I know that's not the first time I've explained that on this forum, and I'm sure it's not the last. Arguing whether or not it's a viable option is more based on the application.

 

i think your not understanding how these rods are resized. you dont smooth the parting surface, you leave it alone and hone the rod out .010 at max, and install a larger OD bearing with stock ID. that is how you resize a cracked PM rod.

 

i talked to 2 ASE master machinests here at school just a few minutes ago, and they said that is the proper way to resize a PM cracked rod. if your just installing ARP rod bolts, it is smart to resize the rods. again, after 1000 miles my rods were .0015 out of round. thats pretty bad considering the spec is 0002 new and .0004 replace.

 

Ok. Cost is never effective in that way. I was talking about paralleling the caps. i did state that. i have had it done both ways. but it did not cost anywhere near $75. it was $40 per rod. this was on a V6. math says that is $240. maybe i got taken....but anyway, thats almost close to those scat rods. and the eagle rods may be that way, but i have not seen a scat set recently that was that messed up. usually the lesser expensive rods to lack a little fit and finish yes, but for the price, it is really to be expected. I know that people usually go to 6.125 rods, but i still do sell a descent amount of the 6.100 scats as well.

 

we are not telling the op to take out the rods and perform all that machine work, we are just warning him that it takes allot of work to do it properly. yes it makes sense to throw in forged rods if you are pulling the motor out, but do not think he is going that route.

i think you are misinformed. why don't you call up a good engine builder and tell him that you want to change your rod bolts with the motor still in car and not perform any machine work to the rods. don't forget to mention that the new rod bolts have a higher torque spec then the factory ones.

 

I'm a little confused here but how can replacing the rod bolts change how round the big end is?

The replacement bolts are torqued up to the same specs as the original bolts. So the clamping force is the same. Their advantage as I see it is they are a stronger bolt and less likely to break under more severe loads.

I think it's more likely that the rod went out of round due to the reciprocating forces rather than the change of rod bolts. Or perhaps the simple fact of loosening and tightening the bolt.

cheers

Michael

 

Stonger rod bolts have to be torqued to a higher spec to get the proper amount of bolt stretch to keep them from coming loose. Thus making the rod get out of round.

 

Sorry if I misunderstood you, it sounded like you had said resizing these rods required machining the parting surface smooth...

If the machine shop you use cut the parting surfaces smooth, that's the reason you were charged $240. All they had to do was hone the big end and skip that step altogether! For me, this is a VERY cost effective option for anything under 600bhp, and for an average consumer, it's a great way to save a few bucks and put it somwhere that would make power. I'm not trying to talk anyone out of buying any of the products you offer, but nowadays every penny counts. I wouldn't want people reading this to think their only option is an aftermarket forged rod.

 

Torque isn't the important factor, stretch is. Think of a fastener as a spring. The more you compress a spring, the harder it is going to push back. The more you stretch a bolt or a stud (usually higher tq specs), the more it is going to try to pull itself back to it's original length. A better material will be able to pull harder, resulting in more clamping force, which can change the concentricity of the housing bore.

 

I would call katech a reputable engine builder. and i never said dont get the rod resized and change them in the engine did i? i did say it is a problem most times.....