Yea I bought an eagle crank (3.48",large journal). Very awesome crank =) I also have the eagle h beam 6" rods. The rods are made for large journals. I looked at the part number on the crank they sent me and it says its for the 5.7" rods. Is this gonna make a difference? I mean the journal sizes are the same...Does it matter if the rod is 5.7" or 6" for the crank? I know on the eagle site they have 2 different listings for a 2.1 journal, 3.48" stroke one for the 5.7s and one for the 6s. I hope this isnt gonna matter cuz i dont feel like sending it back...If you guys know please tell me! Thanks...
I'd be getting on the phone and making a call to Eagle to make sure. I believe that if you use the combination you have now that even a flat top piston would be sticking above the top of the block...instant damage the instant you tried turning the engine over, if you could even get it assembled to begin with! So it sounds like you need to ship the crank back or get different rods. Deen
Stroke is stroke, so the crank won't "appear" to know the difference in rod lengths (the rod length difference is accomodated at the pistons), it would assemble and look "ok". The difference in the cranks for different rods is in the balance. I'd get the correct crank or you may have a lot of trouble getting it balanced.
Sorry, DeenHylon, but that is all wrong. A crank of a given stroke won't push the piston any further than its stroke. The pistons DO have to be matched to the stroke and rod length. A shorter rod will allow the piston to come closer to the counterweight. Go ahead and call Eagle, but I think you'll be fine using a longer rod than the "specified" catalog length. The other way around, you'd have a problem with the pistons hitting the counterweights.
Stroke is stroke, so the crank won't "appear" to know the difference in rod lengths (the rod length difference is accomodated at the pistons), it would assemble and look "ok". The difference in the cranks for different rods is in the balance. I'd get the correct crank or you may have a lot of trouble getting it balanced.
-Greg
That's right ... difference is in the balance ... which needs to be corrected. As mentioned, the difference in rod length is accomodated by the pistons. 6" & 5.7" pistons are like apples & oranges. Make sure you have the correct pistons for 3.48" stroke ... 6" rod pistons have a compression distance of about 1.260" ... 5.7" rod pistons have CD about 1.560". Standard sbc block's deck height 9.025". So, half of stroke is 1.74" + 6" rod + 1.260" CD + about 0.025" deck clearance (aka "piston down in the hole") = 9.025"
any crank you buy must be balanced to the rest of the rotating assy. only if you buy a complete rotating assy that is balanced from the supplier you will not have to have the assy balanced. pistons for long rods weight less than pistons for std length rods so you have to balance the crank to the pistons and rods unless you want a "shaker" some times the difference in the cranks for 5.7" rods vs 6" is the size of the counter weights so they clear the pistons at BDC. :chevy
yes you will need to take your pistons and pins,rods,rings,and rod bearings to the balancer so they can know what bob weights to use when balancing the crank. :chevy
Yes, I know about taking it to get balanced...but is it OK to keep this crank that was sent to me for 5.7" rods when I will be using it for 6" rods I have? Would it be better to exchange the crank for the one made for 6" rods or can I just have this one balanced? Thanks
Corvette Store
Crank
That's right ... difference is in the balance ... which needs to be corrected. As mentioned, the difference in rod length is accomodated by the pistons. 6" & 5.7" pistons are like apples & oranges. Make sure you have the correct pistons for 3.48" stroke ... 6" rod pistons have a compression distance of about 1.260" ... 5.7" rod pistons have CD about 1.560". Standard sbc block's deck height 9.025". So, half of stroke is 1.74" + 6" rod + 1.260" CD + about 0.025" deck clearance (aka "piston down in the hole") = 9.025"
