Can 1 of these be a 4.370 bore and not be junk and if so what overbore is that? Sounds like a 409 overbore to me idk? Don't want to put too much into a block that's junk. I know about sonic checking but block has to be shipped.
655 348 truck block bore
- Thread starter 63impalass409
- Start date
Standard bore is 4.3125
Sorry I posted a standard 409 bore.
It is extremely rare for a 655 block to go anywhere near the .187 thousandths that would be necessary.A fellow member here[Buildit] has checked several and he says that most won't go .125.Will your block take it,sonic testing is the only way to get an accurate answer.The bore size that you listed is .0575 larger than a stock 656 block already making it one rare bird indeed.
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And on the casting number the last number is ground out and looks like a 5 but hard to tell, could be a 6 as the block is not here. Did gm ever mess up a 656 block and grind the last # then stamp it? Rare but anything is possible. Could use it as a coffee table if it's too thin and I would rather have a w motor table than one from IKEA but wife might disagree.
Well I just bought it for 400 plus the ride. I know it's a truck block for sure with the single notch in the cylinder but it sure would nice if it turned out to be a 409 instead of a 348. He also had an 881 with 2 eddy 1405's he sold right after he put them up for like 450$
Ishiftem thanks for the info and can't believe I got another 409 for only 400$ . I only have 6 now
I guess, Why would anyone want to bore a 348 out so far when every block should be bored as far as necessary to get a smooth bore. Stroking any W motor isn't difficult or expensive. Try and shove a 409 piston in a 348 just never makes sense because as soon as you are done you have a junk block that you can't even use.
Back in the days before the common availabilty of stroker cranks the quickest way to gain dispacement was to bore.There were a lot of 283 blocks.and BBC blocks that were bored .125 over to gain max displacement or to make room for bigger valves,in those cases they just blew right by the cleanup bore to reach their goals.A lot of the older engines such as the olds could stand large overbores and thru trial and error a lot of shops quickly learned how much they could go, a lot of the old timers could tell how thin the wall was getting by listening to the boring bit.Sometimes when you find a block that has a large overbore it was a result of days gone by,back before it was easy to buy a stroker crank.While it is hard to do during a prospective purchase,if you wind up with one in your possession you might want to have it sonic checked before you junk it.
Maybe you should help Mark Steele get a 409 block so he can prep for this coming race season. You'll make a profit on selling the block so you can parlay that into your next block purchase. I've been selling stuff off to finance this coming racing season myself.
I wouldn't want a 348 block either for that kind a money!
I'd bought it too! 
Now about that crank...
Well my 400$ block showed up and it is definitely a 409. Next step is get it to the matching shop to get its pap smear when I pick up my 690's and 583' from getting nagged. Block looks beautiful and is stamped QD and is a 656 truck block but I'm not bitching. So is a 4.37 bore 60 or 80 over?
That piston in the hole is a old std 409 piston I had laying around.
Nice
I have seen two 409 #656 engines where the the last "6" was stamped in. The last is still in a cabover C80 truck, and I'm waiting for the owner to sell it to me. (I already bought two complete 409s from him.) As everyone knows, the "eyebrow" notch in a 409 truck block is considerably larger than the notch in a 348 #655 block. When you bore them to where cylinder wall thickness gets down to .120", they become difficult to finish hone, because half-way down the bore, the cylinder walls flex away from Sunnen hone. This tries to leave the bore slightly smaller in this area. Not a good thing for a performance build.
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