BBC Rod length

I'm building a 540" blown alcohol BBC but still trying to decide on rod length. I'm stuck between 6.535" and 6.700". Should have enough room for the ring pack and still have enough thickness in the piston crown with the 6.700" ?


540 BBC
4.500" bore,4.250" stroke,10.2 Donovan block,1.094" pins,buttons 35psi+ boost

 

I went 6.70" with mine. The pin buttons are in the oil ring but plenty of room. Lots of piston dome thickness. Arias pistons and GRP rods.



Corey

 

We've done 6.660" on alot of our stuff with that stroke and deck height. Have also used that same exact rod on 4.5" stroke, just had shorter piston pin height and its worked well also.

 

Is there as much to gain with a long rod combo in a blown alcohol combo compared to a naturally aspirated motor? I'd rather have a stout piston with no ring issues?

 

Both of our 540's have a 6.70 rod (4.25 stroke--10.2 deck) around 10.5 compression ratio.. Have used Arias, Ross, and Venolia pistons with no problems. Staying with this combo for our twin turbo setup. $.02......JW

 

!.395 CD with buttons, 6.665 rod and .450 down on the top ring land works pretty good on a chevy with a 4.250 stroke.

 

Thanks for the info. Any ring preferences? Comp ratio?

 

.017 Dykes top, 1/6th second and 3/16th oil. I like the chrome stainless A&C rings. 11.5 comp ratio should be fine with 35#.

 

I went with the longer rod strickly to reduce the side loading on the piston as much as I could.I don't really think it will build any extra power, thats not the real reason I did it.