Rod Side Clearances

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6

69Chrgr

Charger/Cuda
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Jan 29, 2007
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Midlothian, Texas
What rod side clearances should I see on this 408 buildup? I'm getting as much as .024 between #4 and #5 and as little as .008 between #8 and #7 rods. Do I need to try to push #8 and #7 rods apart to see if I can get more? Sorry for all the questions, my first stroker build. I'm used to building turbines and my neighbor says I need to chill. :cussing:
 
I think the spec is .007-.012 or some nice round figure like that. If you have between .010 and .030, i wouldnt sweat it much. Tighter than that, you will want to make sure the chamfer on the bearings is deep enough. On some cranks and with some bearings they may be a little tight. The more side clearance, the more windage you may have, and the more oil on the cylinder bore walls for the rings to scrape. So I like to try to keep things under .015. But I know of engines others run with more than .030. What kit/rods/crank/bearings are you using?
 
I'm using an Eagle Crank, Eagle SIR rods, and clevite bearings. I only have about .008 between #7 and #8 rods. However, I also have about .012 between the rods and the crank on each side of the rod.
 
Can you swap the rods and piston assemblies around so you get more even side clearance ? Just an idea.
 
Well, yes I guess I could. I'm wondering if maybe the .012 between the rods and the crank will help out with the .008 between the rods. Do I need to start over?
 
I'd measure the rods themselves with a caliper to see which are thicker/thinner. Then use a thinner with a thicker etc, assuming that it is not the crank journal that is narrower in one case and wider in another. You could use an inside caliper to roughly check that as well, at least be able to get an idea. Hope this helps !
 
Thanks Buddy. I called Indy and they said to just take a fine tooth file and shave a few thousandths to achieve .015. Does that sound stupid or am I anal? I'm used to turbine engines here, so I'm somewhat in the dark as to tolerances.
 
Measure the various items first, then decide. If you decide to take material off the rods - I'd use emery cloth (200 or 400 grit) on a flat surface to reduce the dimensions, polish the side margins of the rods, a slow but controllable way to handle things. Match them up slow - I'd just bring them into spec and call it a day. Make sure you check the specs according to a service manual. Have at it. I am the same way as you, pay attention to the details and the rest takes care of itself.
 
Um...side clearance, at leas tas I understand it, is measured with the rods pressed out to the crank...then you measure the space in the center with feeler gages. So you should have "0" on the outside of either rod, and there should be the gap in the center. Scat cranks dont have a huge radius, but I havent used an Eagle yet. Sometimes the radii are so large the rod cant slide all the way "out", and then you end up with tight side clearance, even tho the rods are fine. The bearing will show a mark where the radius contacts it. Side clearance can be adjusted, but I dont consider a file to be the best route. I would try the rod swapping deal long before you file anything. I have used emery on a flat table to take material off a cap. At least that way it's removed roughly evenly.
 
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