Rod Side Clearance

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6

69Chrgr

Charger/Cuda
Joined
Jan 29, 2007
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Midlothian, Texas
O.k., yeah, another snag. I just switched over from an Eagle cast crank to a forged Scat crank. Problem is, when I reinstalled the Eagle Sir rods into the Scat crank, the rod side clearances were WAY too tight, as in no clearance. I fine filed the side of two rods, and gained a little, but did I sacrifice the rods? Have any of you had this problem? Do I need Scat rods to match the crank? It's a 408 Magnum that I am trying to put back together because I installed the top rings in backwards(if anybody can screw it up, it's me! lol). Please help. Ya'll always do.

Thanks,
Darren
 
Did you check to make sure that your rod bearings are chamfered to fit the bigger radius on your crank? I'm thinking that if they arent they may push your rods closer to each other and decrease your clearance between the two. Post a pic if you can
 
What he said... check the bearings. My guess is you need to run the chamfered bearings with the forged crank you changed to. If you see a shiney ring around the outside edge of the shells, you need the chamfered bearings.
 
Yep. Thats it. This is getting old, this not fitting that stuff. I bought the crank and bearings from Bob Mazzolini. I would have thought he could have sent me the right bearings.
 
If I can achieve side clearance, do I still need to get chamfered rod bearings? Do I need to rebalance as I had my machine shop balance everything with these bearings? :angry7:
 
Yes, you need to get rid of that sharp edge as it will deform and may cuase issues elsewhere, in addition to causing heat in the end of the rod and bearing. Not all brands need the narrower bearing, but you cant go wrong just running them on everything. No balancing stuff is required. It's not a huge deal. And if the side clearance is big on that one set of rods, dont sweat it. Side clearance means very little in the big picture.
 
Thanks moper, I really appreciate your advice and will get a set of chamfered bearings. I value your experience and knowledge as well.

Thanks so Much,
Darren
 
Is it possible that you have the rods in backwards?
On most V8 rods, the bearing is not as wide as the rod and it should be offset exposing the chamfer machined into the rod. The chamfer must be installed toward the fillet radius ground into the crank.

Good luck
 
Yeah, I checked that out, and the chamfer on the rods are towards the fillets in the crank. I guess I just need those chamfered bearings.
 
Really? That's odd. When you look at the bearing shells after you take the rods off the crank... where is/are the shiney spot(s)?
 
It's on the outside edges of the shells. I called Bob Mazzolini whom I'd purchased my Scat crank from and he told me after speaking with Scat, that I had the correct bearing. Could it be that I'm using Eagle I-beam SIR rods with a Scat crank? Do I need H beams instead? I could probably switch a few rods and get side clearance, but I'm just anal about measurements because in my work(building turbine engines) measurements are there for a reason. Now I'm thinking chamfered bearings wouldn't matter either as these are just more narrow, eliminating the need for the chamfer.
 
No, your concern is justified. A shiney spot indicates trouble on the bearings. My question is why dont they work? I've used Eagle and Scat and I used that bearing on both before, plus the Callies ones. That's what makes me nervous.
 
The way that bearing works as I recall is it is slightly offset to the "rod" side rather than the fillet side and is slightly narower. Which is why I find it odd that it still hits. Did you try mounting them on than one throw yet?
 
I haven't switched any rods around if thats what you are talking about. Yes they are offset to one side, away from the chamfer. However I am still finding the shiny spot on the edge of the bearing. Would it help to change rods in some different locations?
 
The shiny spots are on the opposite side of the chamfer of the rods. They are not shiny on the chamfered side of the rod.
 
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