XR2 (P7 heads) 3.89 bore, 9.20 deck 237 lbs....
The XR2's are little heavier than the XR1's due to 6 journal cam & few other things specialized to it.
It's since been CNC lightened & bushed for Keyway Jesels & taken to 9.08 deck & 4.175 bore. I'll have it out of CNC & get some pics & a final weight on it here in couple days & will post.
The XR blocks are most definitely heavier than an R series block. Kent's ritter racing logo alone is probably 2 LBS LOL
Both blocks are good pieces, but until a few things are cleaned up on the XR's & as long as the R3's are still readily avail I'll continue using R3's. I've got 6 new latest generation siamese 48* tall deck R3's in shop @ moment, all for "big" inch combo's this winter. The last generation of 673AD R3 blocks have really proven to be great pieces, MP cleaned up & fixed almost all notorious issues with them, & other than a little tight on the cam tunnels, these things have proven to be great blocks to work with lately.
On the billet main cap deal I think they are a little over-rated to be honest now that I've seen some big power nodular iron cap stuff live just fine for couple years under harsh abuse. I have a N20 434 inch W9 motor in shop right now that was never dynoed, but runs 9 teens on motor & has been 5.20's 1/8, 8.20's 1/4 on a 300 shot in a 5 speed Liberty car, steel rod motor so it "shocks" bottom end pretty hard on the spray.... Block has about 275 passes on it.... Stock R3 4 bolt 340 main nodular caps & ARP Studs... does not exhibit any unusual cap walk (more than you'd expect) & so far no cap problems.
Not saying the nodular caps are the greatest thing out there, but I think too many people think they need Billet caps when they probably don't, although overkill rarely hurts. Real difference in cost of the XR VS R3 is purely sitting in those main caps. I just wish Kent could have found a way to do iron caps for a lower $ version & offered the billet caps as an upgrade & get the XR in the $2400-$2500 range, they would sell way better. I know it sounds stupid, but that extra $500 turns off alot of prospective customers, even on a $20K engine build, people are weird sometimes.
But from what I've seen basically any R3, or XR block will take more power than you can ever put through them. I've yet to see a race block fail by itself... always something else goes wrong inside engine to hurt one.
