Installing a 4bbl on a 273 advice

Edfury426 said

I thought the LD4B was made back in the day for 340's and had 340 sized ports...and that it's the D4B, such as the one I posted, which have the 273/318 port size?

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Nope. D4B's had the odd 64 and 65 bolt angle with 273 sized ports. The LD4B's had the 66 and newer style 273-360 bolt angle and the smaller 273 ports. (which also includes the 318 size ports) The LD340 is a little different runner design with the 340 (and 360) sized ports.