LS1 cast iron or Alum.

[94Z71]

I am looking to purchase the LS1 engine to swap in my 1994 Z71 and see both iron and alum blocks. Is there any major differences other than price ?
What is the best setup ?

[r.barn]

Iron blocks came in the truck and SUV's and weigh about 70lbs more
than alum. blocks.

Iron is stronger and cheaper to find
70lbs weight savings isnt gonna mean much to you in a 4,000lbs truck

[mean05]

Iron blocks came in the truck and SUV's and weigh about 70lbs more
than alum. blocks.

Iron is stronger and cheaper to find
70lbs weight savings isnt gonna mean much to you in a 4,000lbs truck

Aluminum will take just as much as the cast and the weight is about 140lbs difference...that's why i went with an LS2 block

[r.barn]

Aluminum will take just as much as the cast and the weight is about 140lbs difference...that's why i went with an LS2 block

Anyone got a link to weight difference on iron vs. aluminum.

I've seen everything from 65-140 lbs difference
Anyone have a reliable source for what it is ..... for sure ?

[low91]

Heres a link that was posted here earlier this week. the author says the difference is 65 pounds. Thats the answer I got the most when I started shopping around for my engine swap. The only thing I don't like about the aluminum block is that I've heard they can't be over bored much. The same link states that the aluminum block can only be bored .010 over, but I'm assuming thats for the 5.7LS1 block.


Gen III GM Small Block: Engine Builder


Quote:
"These blocks already have a 4.0? bore, so they're the best alternative for the guy who wants a bigger motor for his car as long as he's willing to put up with the additional weight (65 lbs.) of the iron block. The only other way to build a big bore motor with a stock block is to buy one of the new 6.0L aluminum blocks, but that's bound to be real expensive."

[beertestr]

For all intents and purposes, it's damn near 100#, like 97-99#. I weighed my bare 5.3L, and my bare LS2 block, and a junk LS1 block, came pretty close to that.


As for overbore, the LS2 and LS3 blocks OEM recommended overbore is 0.020", and you can get service pistons if needed. LS1 Blocks are recommended for a max of 0.010 overbore. The 4.8/5.3 Iron block allows the biggest over bore, I know you can at least go to to the 3.898" (aka 99mm) LS1 bore, not sure if you can 0.020 or 0.010 over that like on the aluminum blocks.

Not sure if this worth mentioning, but there is a very small number of the 5.3L aluminum blocks that are actually LS6 block CASTINGS, with the smaller 96mm cylinder liner. These can be overbored to 5.7L. Again, these are very rare, but they are out there in the LM4 equipped 2004 Rainiers, 2003-2004 Trailblazer EXT, 2003-2004 Envoy XL/XUV's, and 2003-2004 SSR's.

As for the other iron blocks, I have seen people going 0.060" over, not sure what is the max-safest overbore. OEM calls out 0.020, but what the aftermarket has been doing seems to be going a little further than that.

Just reading over the engine builder article revealed lots of incorrect info, but in general it's more correct than it's wrong.

[r.barn]

For all intents and purposes, it's damn near 100#, like 97-99#. I weighed my bare 5.3L, and my bare LS2 block, and a junk LS1 block, came pretty close to that.

lol

now have

65 lbs
99 lbs
170 lbs


Personally 100 lbs "sounds" about right. Thought 65 sounded low, but
thought 170 was high too.

For as cheap as you can get iron truck blocks for I just dont see paying
extra for the aluminum. Maybe in a drag car where you're counting 10th's
but dont see the difference in a 5,000 lbs truck.

[ma.racing]

lol

now have

65 lbs
99 lbs
170 lbs


Personally 100 lbs "sounds" about right. Thought 65 sounded low, but
thought 170 was high too.

For as cheap as you can get iron truck blocks for I just dont see paying
extra for the aluminum. Maybe in a drag car where you're counting 10th's
but dont see the difference in a 5,000 lbs truck.

what he sead if you had a race car it would be one thing but you have a 4x4 truck

[beertestr]

Can I vote twice? 100 is the closest answer... there, I'm stuffing the ballot boxes.
Maybe I should take some pics of me weighing them next time I have a bare iron block to weigh, the 2 I have right now still have cranks, cams and covers on them.

[George C]

i had read in the LS1 books it was 90#