What is the average weight of a cast iron headed big block vs. a cast iron headed small block?

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91 Camaro RS 5.0L Black Convertible 700R4
** Added so far **
*GM Wonderbar,Alston SFC's,spohn LCA's and Panhard rod
*Turbo City Inj Spacer
*Dual Snorkel Air Filter
*March Performance Pulleys
*GM 3.42 Gears with OEM Zexel POSI
*Edelbrock headers
*3" High Flow Cat
*3" Dynomax Exhaust
*Walbro 255 lph Fuel Pump
***Future 330hp Vortec Crate with LT4 hotcam and 454 TBI

 

A big block (long block) is roughly 200 pounds more. You can make it lighter by installing a mini starter and an aluminum water pump.

When I did my swap I only gained 175 pounds.

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87 IROC-Z SuperPro ET Bracket Race Car
461 naturally aspirated Big Block

Best ET on a time slip: 11.242 altitude corrected to 10.89
Best MPH on a time slip: 121.52 altitude corrected to 125.89
Altitude corrected rear wheel HP: 497.9
Best 60 foot: 1.546

Racing at 3500 feet elevation but most race days it's over 5000 feet density altitude!
Member of the Calgary Drag Racing Association

87 IROC bracket car, 91 454SS daily driver, 95 Homebuilt Harley

 

In the '57, I went from a 350/TH350 with cast iron intake, stock brass radiator, and headers, to 396 with TH400, aluminum intake, aluminum radiator, headers, trunk mounted battery - the car gained 70 pounds. In the process, I cut the side transmission brackets off of the frame, which probably weighed 20 pounds, and added side engine mount brackets and tranny crossmember, which probably weighed 15 pounds total. The battery tray to battery box was probably a wash. Going from cast iron intake and brass radiator to aluminum pieces probably saved me the most weight.

I don't know what all you had to do to put the BBC in your 3rd gen, but 100 pounds is the number I've always heard the BBC weighs more than the SBC.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 2.93 limited slip. Cat-back from '91 GTA, ZZ3 intake, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 w/'87 LB9 block, ZZ3 cam, ported World 305 heads, Hooker headers & y-pipe, 3" Catco cat & 3" cat-back, Spohn SFCs).
57 Bel Air, my 1st car. '66 396, 9.7 CR forged TRWs, Weiand Action+, Edelbrock 1901 Q-Jet (Holley 3310 on the way), GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlocks, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Idles smooth @ 600 RPM in D. Best 15.02/95.06 @ 5800' Bandimere (corrected 13.93/102.4 @ sea level).

 

Complete cast-iron small block versus complete cast-iron big-block works out to just about 200 lbs (give-or-take a little).

I dirt-tracked for many,many years and ran both engines back to back and always re-weighed the cars after the changes.

One bb head weighs the same as both sb heads (about 85-88 pounds), the bb block adds another 50-60 pounds, cast-iron bb intake adds around 40 pounds, the bb crank adds about 15 pounds, the water pump is a couple pounds heavier in a bb, and a few other bits and pieces.

If you start putting aluminum parts on either engine changes the difference.

I once had an aluminum-headed (aluminum intake), 4-bolt, 467 bb that changed the small-block weight by about 120 pounds.

However, to balance the cars back out, I had to add an equivalent weight on the back. Didn't bother the bb, though. They had enough power to easily overcome the extra weight.
jms

 

Thanks guys. My poor 92 Truck may thank you. Its 350 is toast at 87k miles and since it weighs 4050 pounds on our truck scale here at work. I know its going to take some serious power to make it move. So since GM put 454's in the SS and 3/4+ tons I know I can easily squeeze it in there. I was looking at the GM 454HO Crate engine 425hp/500lbs of torque with over 400lbs at 1700rpm which is where their dyno graph started. It has roller cam and aluminum intake for $4350 from Paceparts.com. The cam profile is rather mild and 8.75:1 compression should be more computer friendly than a moderate 350. I just don't know whether my NV3500 5speed can handle that torque and whether the 454 TBI injectors can flow that much. I can have turbo city bore my 454 throttle body some to help with air flow.

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91 Camaro RS 5.0L Black Convertible 700R4
** Added so far **
*GM Wonderbar,Alston SFC's,spohn LCA's and Panhard rod
*Turbo City Inj Spacer
*Dual Snorkel Air Filter
*March Performance Pulleys
*GM 3.42 Gears with OEM Zexel POSI
*Edelbrock headers
*3" High Flow Cat
*3" Dynomax Exhaust
*Walbro 255 lph Fuel Pump
***Future 330hp Vortec Crate with LT4 hotcam and 454 TBI

 

Ack! I just got my engine back from the machine shop. The new Merlin heads are 40 pounds heavier (each) compared to factory heads. I just added 80 more pounds to the car but probably also made an extra 50 hp with the new heads.

Aluminum is starting to look interesting but expensive for the ones I want.