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Old 01-16-2015, 08:25 PM
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Default Anyone know their bobweights??
I just calculated mine and curious how it compares. Please state what rod/piston combo along with rod length and bore size. I think mine is very light and can't wait to get it together and see how it revs.

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Old 01-16-2015, 11:07 PM
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1940

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Old 01-16-2015, 11:42 PM
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I've got BME 6.8 rods/ 4.211 Ross pistons = 1875.9 grams

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Old 01-17-2015, 12:07 AM
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That's light

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Old 01-17-2015, 12:14 AM
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Most of the 6.800" steel rod, shelf style pistons with big rings are around 2150g.

My little 400ci came in right at 1700g.

The 7.100" Carrillo rods weighed only 614g, had a short skirt flat top piston and .043" rings.

1875g is pretty light, what rod journal?

Calvin Hill
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Old 01-17-2015, 12:23 AM
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Scat 6.80 rods, RaceTec 4.31 pistons, bob weight 2185
Eagle 6.80 rods, RaceTec 4.185 pistons, bob weight 2149
Eagle 6.80 rods, Ross 4.180 pistons, bob weight 2110
RPM 6.80 rods, SRP 4.180 pistons, bob weight 2036.4

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Old 01-17-2015, 06:15 AM
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Quote:
Originally Posted by 65nss4spdGTO View Post
1875g is pretty light, what rod journal?
2.20

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Old 01-17-2015, 06:16 AM
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Quote:
Originally Posted by 65nss4spdGTO View Post
Most of the 6.800" steel rod, shelf style pistons with big rings are around 2150g.

My little 400ci came in right at 1700g.

The 7.100" Carrillo rods weighed only 614g, had a short skirt flat top piston and .043" rings.

1875g is pretty light, what rod journal?

Calvin Hill
Hill Performance
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I can't believe those steel rods are that light...wow.

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Old 01-17-2015, 09:53 AM
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Nitro Pontiac= 2420 grams 4.250 bore. BME 426 forgings, 1.094 pins, Big, thick BME pistons. Strength over weight. 8500 RPM. .Rods 6.7" Piston weight 630 Grams We overbalance 1%

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Old 01-17-2015, 01:37 PM
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Nitro Pontiac= 2420 grams 4.250 bore. BME 426 forgings, 1.094 pins, Big, thick BME pistons. Strength over weight. 8500 RPM. .Rods 6.7" Piston weight 630 Grams We overbalance 1%
When forcing nitro in, you definitely consider strength over weight. Your pistons are almost 200 grams heavier than mine, but mine wouldn't last for a burnout in your application.

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Old 01-17-2015, 06:47 PM
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Yea, you do need the extra weight in some power adder applications. When we were first working the tune-up a couple years ago we bent one of those 1.094 VascoJet wrist pins. I couldn't believe it!. It was bent .003" The flat top pistons are almost .400 thick. As far as pistons for NA and high RPM Pontiacs, Because of the short cylinders, I would try to keep as much structure and support in the skirt area as possible. Certainly around the pin boss and the underside of the piston, they can be light.

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Old 01-17-2015, 08:41 PM
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eagle 6.8 rods, probe 4.155 pistons, 2160 Bob weight

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Old 01-18-2015, 02:28 PM
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Quote:
Originally Posted by 65nss4spdGTO View Post
Most of the 6.800" steel rod, shelf style pistons with big rings are around 2150g.

My little 400ci came in right at 1700g.

The 7.100" Carrillo rods weighed only 614g, had a short skirt flat top piston and .043" rings.

1875g is pretty light, what rod journal?

Calvin Hill
Hill Performance
708-250-7420



Do you mean 6.100 rod ?

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Old 01-18-2015, 02:47 PM
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Those are dinky.

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Old 01-18-2015, 02:49 PM
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Quote:
Originally Posted by 1050goat View Post
I've got BME 6.8 rods/ 4.211 Ross pistons = 1875.9 grams
Not being a smart azz but you did double real big end and the rod bearing weight as well?

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Old 01-18-2015, 03:44 PM
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need 1 BME 426 6.625 with 927/2.200 ends to complete a spare Street motor.

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Old 01-18-2015, 04:33 PM
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In my 461 stroker, 4.155 ROSS pistons and 6.8 RPM Ultra Lite A beam rods came in at 1957g.

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Old 01-18-2015, 04:48 PM
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Not being a smart azz but you did double real big end and the rod bearing weight as well?
Yep. Don't have the numbers in front of me but the rods weighed 660 total (about 450 big end/210 small end), bearing about 50-ish, 444 for pistons, 145-ish on the pins, 7.5 support rails, 57 rings, 4.8 locks, added 5 for oil. Again, those numbers are off the top of my head but I know I'm really close on the numbers for the rods and pistons.

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Old 01-18-2015, 05:58 PM
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Bob weight 1972.7 gms

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Old 01-18-2015, 06:05 PM
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Quote:
Originally Posted by john marcella View Post
Do you mean 6.100 rod ?
No, these were used in my stock block 400ci.

SBC rod journal, .866" piston pin.

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