Weight difference of 421-429 vs LS2?

[Pro Stock John]

Anyone know?

Hi Andrew. :)

[tom s]

depends how you build the 421,alu block and heads would be light,iron block and iron heads 600ish.All pontiac except for a short deck motor will be about the same weight no matter if 350 or 455.Tom

[b-man]

The bill of lading stated the weight of this complete LS3 (iron exhaust manifolds included) along with the shipping crate was 450 pounds. No accessories, just a water pump with pulley and harmonic balancer. I'd say the complete engine weighs in at no more than 420.

http://i137.photobucket.com/albums/q230/b-man64/LSX%20swap%20pics/DSC02254.jpg

http://i137.photobucket.com/albums/q230/b-man64/LSX%20swap%20pics/DSC02261.jpg

A Pontiac V8 fully dressed is supposed to be 650 to 675 pounds, with iron intake and exhaust manifolds.

Subtract 25 to 30 pounds for aluminum intake and another 50 for aluminum heads. An IAII aluminum block weighs 125 pounds, it would remove about another 60 pounds compared to a stock iron block that is said by GM to weigh in at 183. Some earlier blocks are a little lighter, Pete McCarthy once compared a '64 GTO 389 block to a '68 400 block and said the '64 block was 16 pounds lighter.

Either way, at the best you'd be saving about 140 pounds over a 600 to 650 pound all-iron engine if you went for the aluminum block and heads on a Pontiac V8.

Subtract another 35 pounds if you are running a rare factory aluminum block that weighs a little under 90 pounds (highly unlikely).

If you kept the stock iron block and ran aluminum heads and intake, you're really only knocking off about 80 pounds (add back 20 pounds or so if you add aftermarket steel main caps and fill the water jackets with block filler).

Add back about 50 if you're running a the IA iron block, they outweigh the stock iron block by quite a bit at 235 pounds. Add another 7 to 8 pounds for the tall-deck block, this info is good for the first IA iron blocks and I would assume the latest IAII is pretty close to that.

Headers versus stock iron exhaust manifolds are pretty much a wash weight-wise. The weight of a set of 'regular' long-tube headers (made of a decent tubing thickness with 3/8" flanges) compared to standard stock iron exhaust manifolds and long enough head pipes to match up with the length of the headers is virtually the same.

[Pro Stock John]

Wow thanks for the info.

[andrewb70]

Anyone know?

Hi Andrew. :)

I never really weighed my GTO with the Pontiac engine. I can tell you that compared to my old combo, which was an aluminum headed 502, the LSx engine lost about 250 pounds.

Andrew

[Pro Stock John]

Wow that's significant.

Hi Andrew. :)