Can someone briefly descibe the physical part differences between the LS6 and LS7 crate motors?

Also, was the 14015445 (4 bolt version) block ever used in these assemblies? Particularly in reference to the 366250 LS6 crate engine.

TIA

I assume you are talking about the wonderful old-school 454s here.

The original LS6 had closed-chamber rect port heads and was rated at 11:1 CR from the factory. The crate versions in the 80s were open chamber if I remember correctly....10-10.25:1 CR...possibly less. All forged components, believe 7/16 bolted con-rods, .520/.520" 'street' mech cam.



My pal Tom had bought a crate LS7.....this was 1980...all premium components, 12.5:1, open chamber....think the cam was .560/.600 cam. Had a FLYWHEEL and Corvette long sump oil pan w/trap door. This was a "take no-prisoners" kinda engine!!!! I believe my friend when he said with 3.31s he could hit 140 mph on the 91 freeway heading toward Riverside.

I believe but could be wrong....think they were all Mk IV, 2pc rear seal.

Don't know about the casting numbers....

They used the same block casting for both and cylinder heads.
LS6 crate will have a XAA suffix,LS7 XCH