In the early 1970s, NHRA Pro Stock allowed (tolerated?) repositioning of the valves, tubes where the exhaust ports used to be - lots of modifications normal people would consider insane.

If you’re hoping to unshroud the valves, you need a bore around 4.155 with stock heads and you can get that down to around 4.120 if you’ve got some excellent head work. If you’re going past 0.030, have each bore sonic-checked. (B) The tall-deck Cleveland block is ginormous, but it is still a thinwall casting. If it needs a 0.030 on the first rebuild, it’s been deliberately abused for a very, very long time. (A) Ford blocks are VERY hard when contrasted against blocks from other US makes, and usually will not need a bore job after 400,000 miles if they have been well-kept, but “reasonably well-maintained” blocks might need 0.010 after 250-500 thousand miles, depending. Second: 0.050 over is crazy in those blocks for a couple of reasons: You could buy FE blanks and have them machined with Cleveland crowns - but why not just buy Cleveland pistons and save yourself the headaches and cost? That pesky little item can be a PITA to find.įirst off: the valve geometry of the FE head is completely different from that of the Cleveland, so the valve reliefs will be all wrong.

Jeff is right about just swapping-out the crank and pistons however, you will also need the damper for the 400. Turn rod journals to 2.375' with RB Chrysler 6.768' rod.Turn rod journals to 2.200' with Big Chrysler 6.535' rod.No Mallory metal required for balancing.Requires aftermarket rods similar to 1.9L 4-cylinder rods.Ford Stroker Engine Bore and Stroke Guide

Ford engine codes 306