Asmodeus

I've heard conflicting stories, want to know if someone can clear it up.

camaroextra

iTrader: (10)

Same.

There is a slight difference in the blocks, but it makes no difference in the strength.

fast377

iTrader: (52)

Yep, ls6 just has little windows cut in it to allow for a few more rpm's. Now the early ls1's (97-early 99) are supposedly weaker that the later ones.

camaroextra

iTrader: (10)

yes that is true, the 97-98's had thinner cylinder sleves. you can bore a 99-04 out to 3.905 I think and the 97-98' only tolerate a 3.903 bore. If I remember correctly

moeZ28

iTrader: (7)

My 2002 block is bored to 3.908. I assume this is safe b/c if it wasnt mahle wouldnt make pistons for this size bore.

BOWTIE

I would check with some of the engine builders on here to get their impressions, but I personally suspect the LS1 block is stronger. I do not buy the line that GM went to the cast in windows to improve crankcase ventilation. I suspect that it was to save cost in raw material (aluminum) and reduce machining cost as they would no longer have to cut the holes in the bulkheads. Granted this is all based on theory as I have never actually machined or built one of these (yet), but having been a machinist for 14 years prior to 1995 that is the way I see it. Anyone with experience with Olds blocks is aware how weak windows in the bulk head can make the bottom end and anyone with experience with Chevrolets "improved cooling heads" of the early 80's (basically heads cast with less iron that were very prone to cracking at the exhaust seat) is well aware that they will spin a cost saving measure as an improvement.

camaroextra

iTrader: (10)

Thats a very interesting idea, I have never thought of it that way.

hmm. . .

Ferocity02

iTrader: (60)

It is commonly accepted that the LS1 block is stronger than the LS6 block due to the absence of the bay-to-bay breathing windows which can contribute to a weaker structure. However, for 99% of applications, both blocks are equally suitable.

camaroextra

iTrader: (10)

Well is that the failing point of the ls6 block? if it isnt then the block isnt weaker.

Beast96Z

iTrader: (21)

In stock form, the diffrences are negligable. If your going to be sleeving the block, the LS1 is the best way to go, and I believe the only one Steve at R.E.D. will use for sleeving.

Steve - Race Eng

iTrader: (1)

I have to agree with "Bowtie" on this one.

I actually do more MID installs on the LS6 block but prefer the LS1. LS1 blocks are getting hard to find. I will not do a 4.200" sleeve install on the LS6 block. Too much chance the block will crack in the aluminum between the sleeves with that gapping hole in the bulkhead.

The LS6 block should be fine for most builds. If you are going high boost or large doses of nitrous, stick with the LS1 even in stock form. The slight difference in cylinder wall thickness between the two is insignificant.

Steve

camaroextra

iTrader: (10)

Thanks for the great info. I had always assumed otherwise, but its always nice to learn something new.

rocky41584

anybody know what is the max HP(rough guess) that stock LS1 block can take vs what the LS6 can take?

Black Z28 M6

They say some 01 and 02 F-Bodys have LS6 just look at the block ID number in the back of the block
And say that the LS6 block is stronger
I saw this on GM High Tech the mag. They are the ones who say this. They say this is coming from GM Performance Parts themself
One was made in Canada the other some place else

NO-OPTION-2002

iTrader: (2)

GM Performance Parts' job is to sell parts.

GM high tech mag's job is to advertise for the people who sell parts.

Lot's (MOST) of GM parts are made in Canada. Do you think that is because it's better in Canada, or less costly?

Asmodeus

Well, it seems that people who build the engines in the aftermarket say the LS1 is a slightly better block, and better for higher HP/sleeving.

Then it seems that the people who read magazines say the LS6 is better... because gmhtp says so and because they used it in the vette and later F-bodies.

OK, I guess I got my answer, glad my block is an LS1 block (I actually am thinking about sleeving it someday).