What do you guys think is a decent bobweight for a BB? - Moparts Forums

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Re: What do you guys think is a decent bobweight for a BB? [Re: 440Jim] #1741043 01/30/15 11:36 PM 01/30/15 11:36 PM
Joined: May 2008 Posts: 5,399 Aurora, Colorado 451Mopar master
451Mopar master Joined: May 2008 Posts: 5,399 Aurora, Colorado	FWIW, First set of numbers is the 4.25" 440 source stroker kit for the 0.030" over 440. Second set of numbers is the 4.15" 440 source stroker kit for the 400 block. Both kits have the old "I" beam rods, 7.1" for the 4.25" kit, and 6.76" for the 4.15" kit. The bearing weights are different because the 4.25" kit uses the 2.200" GM bearing size, and the 4.15" kit uses the Mopar 2.375" bearing size. Recirocating Weights (average) Piston-- 598.2 / 494.8 gms Pin----- 158.2 / 157.8 gms Locks--- 4.4 / 4.4 gms Rings--- 57.7 / 67.9 (with oil ring support) gms Rod----- 242.3 / 226.6 gms Rotating Weights Rod----- 528.5 / 512.2 gms Bearings 47.8 / 55.6 gms Oil----- 4 / 4 gms

Re: What do you guys think is a decent bobweight for a BB? [Re: 451Mopar] #1741044 01/31/15 11:49 AM 01/31/15 11:49 AM
Joined: Feb 2006 Posts: 1,051 The Great White North RAMM super stock
RAMM super stock Joined: Feb 2006 Posts: 1,051 The Great White North	My 2014 440 EMC combo with a Scat 4" lightweight crank, Scat I-Beam 6.2" and custom Diamond pistons came in at 1850g bobweight. Small 4.185" bore though. J.Rob 2009 PHR\EMC Competitor 2010 PHR\EMC Competitor 2011 PHR\EMC Competitor 2012 PHR\EMC Competitor 2013 PHR\EMC Competitor 2014 HotRod/EMC Competitor 2015 HotRod/EMC NoShow 2016 HotRod/EMC 3rd place SPEC Bigblock 2018 HotRod/EMC 7th place G3

Re: What do you guys think is a decent bobweight for a BB? [Re: StealthWedge67] #1741045 01/31/15 12:08 PM 01/31/15 12:08 PM
Joined: Jul 2004 Posts: 19,317 State of confusion T Thumperdart I Live Here
Thumperdart I Live Here T Joined: Jul 2004 Posts: 19,317 State of confusion	Quote: Quote: I did nothing exotic, in fact my motor is a flat out budget effort. Re-worked 413 crank, Scat Rods, Iconn pistons. I believe it weighed out at 2380. (low-deck RB-rod, 451) I have no idea if thats good or not, but everything I read in preparation said these motors typically check in at around 2400, so I figured I had the right parts stuffed in there. Well, I stand corrected. Dug out my balance sheet, and my budget 451 bobweight is actually 2314! Don't know why I was thinking 2380 before....?? You and me both...................mine`s closer to 2240......... 72 Dart 470 n/a BB stroker street car `THUMPER`...Check me out on FB Dominic Thumper for videos and lots of carb pics......760-900-3895.....

Re: What do you guys think is a decent bobweight for a BB? [Re: Thumperdart] #1741046 01/31/15 12:37 PM 01/31/15 12:37 PM
Joined: Nov 2003 Posts: 10,384 Upstate NY Bigcube I Live Here
Bigcube I Live Here Joined: Nov 2003 Posts: 10,384 Upstate NY	Here's mine. GRP 7.100" rod, GM .990 pin and Journal size. Both are old and new are the same with a reduction of 14 grams for the my new low compression pistons. Old pistons were Ross with a good size dome, new are diamond with a reverse dome. 8413748-BobWeights.jpg (46 downloads) Jim

Re: What do you guys think is a decent bobweight for a BB? [Re: Bigcube] #1741047 01/31/15 12:43 PM 01/31/15 12:43 PM
Joined: Nov 2003 Posts: 10,384 Upstate NY Bigcube I Live Here
Bigcube I Live Here Joined: Nov 2003 Posts: 10,384 Upstate NY	I should add, that is with a 4.440" bore, 4.5" stroke. It's a short piston. 8413755-NewPistons.jpg (62 downloads)

Re: What do you guys think is a decent bobweight for a BB? [Re: Bigcube] #1741048 01/31/15 01:38 PM 01/31/15 01:38 PM
Joined: Mar 2006 Posts: 9,835 MI, usa dvw master
dvw master Joined: Mar 2006 Posts: 9,835 MI, usa	A lot of room for interpretation here. Bore size from 4.250-4.560, Low or high deck, stroke, dome, no dome, pin thickness and length, rod length, rod material, ring pack. I'm sure a low deck, long stroke, small bore, thin ring, light pin, aluminum rod will be the lowest. What do you need to get the job done? Depends on the power level, nitrous, boost, Etc. The best would be something that's strong enough not to fail over the intended life span. Those parts will determine your bobweight. Doug

Re: What do you guys think is a decent bobweight for a BB? [Re: StealthWedge67] #1741049 02/06/15 01:15 AM 02/06/15 01:15 AM
Joined: Jan 2003 Posts: 1,807 Mopar Country, Mi ccdave The Ultimate
ccdave The Ultimate Joined: Jan 2003 Posts: 1,807 Mopar Country, Mi	2342 grams here Scat 4.250 crank Scat 6.800 rods Diamonds pistons

Re: What do you guys think is a decent bobweight for a BB? [Re: ccdave] #1741050 02/06/15 01:44 AM 02/06/15 01:44 AM
Joined: Nov 2004 Posts: 6,890 North Alabama M Monte_Smith master
Monte_Smith master M Joined: Nov 2004 Posts: 6,890 North Alabama	He has pretty much run of the mill "off the shelf" parts and the weight reflects that. Even a fully lightened "blower piston" is gonna be heavy. It has to be. Same for the pins. Doubt I would have popped for taper walls in a blower motor............Bottom line, the BW is what it is and that is neither light, nor is it extremely heavy. It's normal and won't make a lick of difference unless he intends to turn it to the moon........which I doubt........LOL!!! Monte

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