I need to know the std bore of a GM tall deck bow tie and how much you can go over bore.

4.470 std. I have taken them 4.625 with no problems.
Mark

The Mark 4 blocks came through @ 4.250 std and can be bored to 4.630 max. I have 2 of these blocks BRAND NEW 4 sale - 10.200 deck Mark 4.

I need two blocks, the project I bought had popped frost plugs. I hoped for the best but after pulling the engines last night and removing the intakes I have bigger cracks than in a whore house. The blocks are GM bow ties with a bore of approx 4.58 using a cheap caliper. I will mike them later today to be more acurate and post the block casting # and a few pix. The pistons have no markings on them to tell me if they are oversize so I am asuming that they are std. Can I use a 427 tall deck truck block, I have no idea what the bore is on a 427

Ouch

If its std. bore, tall deck bowtie 502 style, then it should be around 4.470... You could get the tall deck bowtie in both bores as std., 4.250 or 4.470. The 427 tall decks are 4.25 bore, and can only be safely bored to 4.375. We build a lot of 535cid combinations out of the truck-427 tall deck. Its a great economical combination for a heavier Vee bottom. 4.350 bore x 4.500 stroke. Got them in stock, let me know if I can send you a couple! Mark

Just mesured bore 4.54 and stroke 4" gives 518cu/in have the dyno sheets 800hp and 800 ft/lbs torque with merlin heads 671 and superchille, peppy little buggar!

Well, Sounds Like You Got A Nice Combination. I Believe Your Best Bet Would Be To Bite The Bullet And Buy A Dart Block, Transfer All Your Good Hardware. A Tall Deck 4.500 Bore Dart Runs About 2k.
Mark.