6/4/24:
More observed differences in the Alloy blocks to the commonplace Iron Blocks:
1. Rear main Seal Uses same Lower Seal Retainer as the Iron Block withan additional "alloy only" top seal retainer that had more of the the "L seals" to the block and another sealing surface on the top. According to Lou, the top sealing surface can be reproduced with RTV type sealant - I have yet to build one of these, but I would tend to agree.
Stock Iron RMS Retainer Bolt shown for comparison.
2. Rear main seal retainer bolts are different i.e. longer- 3/8" -16 UNC with a ~ 4 1/2" UHL, You can easily and cheaply setup yourself up for 2 alloy slant 6 engine builds with these from McMaster-Carr
3. Main Bearing Caps Will have numbered mating top iron caps with special main bearing bolts that are longer and have smaller shoulder sections for oil flow to the main bearings.
According to the 1962 Aluminum only service manual section Main Cap bolts are torqued to only 50 Ft/#'s The in service 1960 Block that I have acquired (installed in a 1961 Car possibly due to Engine Code AR22) has split lock washers under the main cap bolts, they are just as crusty as everything else so I assume that they were part of the engine on it's original disassembly and end of service.
4. The Front oil gallery plug is a freezeplug type / press fit.
5. Rear oil gallery plug is a threaded part with an o-ring installed with it. Part may be shared with Max Wedge / Hemi Crossram / 7 1/4" Rear end drain plugs. I have yet to completely verify this.. just operating on assumption here for now.
6. Head Gasket is unique and according to the 1962 service manual the "SPECIAL" Head was developed with smaller chamber diameters to promote sealing on the top of the block. I do believe many people over the years have been able to successfully use a standard non "Special" head with proper results as well - YMMV.
7. Longer Head bolts (4 15/16" long) for more thread engagement. - Torque on these is the same specification as the Iron block.
8. No Freeze / Frost Plugs - Just a small coolant drain plug nestled in between cylinders 5 & 6.
Some documentation of the blocks I acquired:
Block #1:
AR22 - (1960 Metallic Blue engine paint) (vin / coded as a 1961 car / engine) Production 225 was ran in a car for some time.
77# weight- bare block with main caps, Main Studs, Rear Cam Plug and Front/Rear Oil Gallery Plugs.
Casting # 2121355-1
Block #2:
No Vin / Engine Stamping near the Alternator "Pad"
Likely a Prototype Alloy G block 170 non production engine block.
This engine appears to either never have been run or just run to verify parts at the dyno cell - it is very clean and Has silver paint over the aluminum on the outside.
Code appears near the bell housing bolt area on the back of the block:
0202-P9C-X35
Some of the code is written again on the inside of the crankcase with the date of February 2nd, 1960:
Casting # 2121475
Weighs 67# with Main Caps and Studs installed.
I hope some of this is helpful to you Alloy builders out there!
Greg