- Feb 27, 2012
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A buddy of mine is looking at a car today that claims to have an R block 358. How can we visually tell the difference between an R block and a stock block?
How to identify an R block
- Thread starter Old Skooler
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BK_CAULEY
it's built for speed not longevity, woman
it will have screw in freeze plugs and support webbing on the outside of the block. the entire casting is different. if you are familiar with normal 351 blocks you can see it. the R is much smoother and has less flash. If its out of the car and torn down there are numerous visual cues.
BK_CAULEY
it's built for speed not longevity, woman
R-351 blocks did not have screw in freeze plugs. The new boss 302 and 351 blocks do, the picture you posted is a Boss 351. The R-351 blocks also have billet 4 bolt mains on all 5 main caps. The blocks are not 9.5'' deck height like a standard 351w, they are 9.2" deck height and have dry sump oiling.
There is a little bit of info on it here.
http://www.yellowbullet.com/forum/showthread.php?p=8333564
I just happen to have an R block sitting on the other side of my desk. This is an older block and has been around for a while. First picture shows an R inside the front timing cover area, Second picture shows the casting number, notice the "A4" part of the casting number, Third picture shows the standard style freeze plugs and 3 billet center 4 bolt main caps. Hope this helps..
BK_CAULEY
it's built for speed not longevity, woman
guess it doesn't have 4 bolt mains on all 5. mine didn't either. and I guess the one I had had the freeze plugs machined cause they were screw in and I also had the R cast in the front of the block as posted above. I was just trying to post visual cues from what I remembered.
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