360 Mild Build Questions

894/X and 915/J,U,O are the same port some of the 915 had 202 intakes and some have 188 intakes.. The difference is the 894 heads had a smaller chamber due to the deck surface shorter. Always have heads CC'd when they are mismatched to insure one isn't cut farther then the other from being used from another engine that may have been cut. 68-70's 340's were advertised at 10.5-1 with 894 castings. 70-71's were 10.3-1 with 915 castings. This was noted in any engine manual but only quoted for 71 cars. when the compression loss was shown

This is why it was always an issue installing the bolts on a factory SixPack on a 68- 69 340 engine back in early 70's that had 894/X heads. Been down that road many times in the past. You could get them on but they were a ***** to get the bolts started.