I just got a good deal on a new, in the boxes, stroker kit from a board member and noticed the label on the side of the crank box says it's for a 5.7" rod. The rods in the kit are 6.0". An engine builder friend of mine says it will just have to be balanced more for the longer rod. Do you think this will be ok or should I try to sell/trade this crank for one spec'ed for a 6.0" rod. Thanks for any help!

 

Are you sure the statement that "it's for a 5.7" rod" applies to the crank? It sort of non-sensical. The crank should be balanced for whatever rod/piston combo is being used, no matter the rod length. Some cranks have large diameter counterweights and may not be usable with short rods, but I can't see what would prevent you from using a longer rod. Maybe I'm missing something, but I suspect that the statement in question is referring to the pistons. The only other way it makes sense is if the manufacturer makes a number of different kits, some balanced for a particular 5.7" rod and others for a specific 6.0" rod.

Rich Krause

 

The label on the CRANK BOX containing the part number says its for a 5.7" rod. Cranks listed in most catalogs list different part numbers for different size rods.

"The crank should be balanced for whatever rod/piston combo is being used, no matter the rod length. Some cranks have large diameter counterweights and may not be usable with short rods, but I can't see what would prevent you from using a longer rod."

This is what I was thinking but why are cranks listed by rod lenght?

"Maybe I'm missing something, but I suspect that the statement in question is referring to the pistons."

No the pistons are for a 6.0" rod.

Sorry if my question doesn't make sense. Basically I need to know if this crank is going to work with this kit.

 

Maybe I wasn't clear. Cranks are usually sold with a minimum rod length. That's what you are seeing in a catalog. Not a maximum. IOW, if the rod is too short, it will bring the piston skirt too close to the the counterweights. But a rod can't be "too long" in this context. I am guessing they are just referring to their own kit and that the cranks for the 5.7" and 6.0 rod are identical, other than balancing.

I could be wrong, just my $0.02.

Rich Krause

 

I know Scat sells different cranks for 5.7 and 6 inch rods. I think they are balanced differently, but I am no engine expert. You will want to seek professional advice. I recomend Nutek or combination motorsports.

 

Thanks Rich, I understood what you were saying, I just needed to clearify what I was asking. I think you are right and it makes sense. I sent Nu-Tek an email to verify it. I just want to make sure all is good with this kit as I bought it from an individual.

 

I think what Rich was trying to say is that the rod length listed with the crankshaft part number means that the crankshaft has been clearanced for use with rods of that length. In other words, you can use a connecting rod 5.7" or longer and not have to worry about having the crankshaft machined to clear the skirts of the pistons.

No crankshaft is delivered pre-balanced, since there is no possible way that they could predict your rod and piston/pin combination and weight beforehand. You will have to have the crankshaft balanced regardless of what rod length is stamped on the box, but at least you know what choices you have available to you as far as rod length is concerned.

 

Exactly.

The difference is in the counterweights. The "5.7 crank" uses a shorter counterweight, the "6.0 crank" longer counterweights...... although "longer" isn't the correct term, I think you get what's being said either way.

That's the only difference. If you are breaking up a kit (assembly) then yes, you will need a rebalance as you will have a new bobweight.

-Mindgame

 

Thanks everyone. This has answered my question. I figured it was all in the balancing as my friend said, I just wanted to verify as I was confused on the crank listings by rod length.