« Reply #3 on: July 13, 2019, 07:40:07 PM »
You shouldn’t notch your block based on someone else’s photos. First you need to decide if you want to notch due to valve/block interference or to unshroud the valve for power purposes.
Notching due to interference: You need find the exact interference locations for your head/valve/block combination. Remove the springs from at least 1 valve. If you have a checker spring install it. If not you can check for interference with no spring on the valve. You’ll need to hold the valve on its seat while you install the head on the block (2 bolts is enough). I would hold this valve on its seat by using tape on the stem above the valve guide seal. Next remove the tape and push the valve off it’s seat while looking into the bore. If the valve hangs up on the upper edge of the deck then you’ll need to notch the block. If it passes the block with sufficient clearance then you’re good to go, no torching required. I’m not 100% sure what “sufficient clearance” is. I’m sure some of the builders on this site can address their opinions on this. But for me if you have .050” between the valve and the block at it’s closest point your OK. If anything less you’ll have to grind some clearance at that point. Mark that point with a sharpie, remove the head, install a thin coating of Prussian blue and scribe a small area adjacent to the interference. You only need to grind enough to all the valve to clear the block by the minimum amount discussed above. Before grinding you should cover all oil passages and lifter bores with tape. You need to keep these iron filings out of the engine. See below for more aggressive grinding.
Unshrouding for power: like I wrote above you still need find the exact notch location for your head/valve/block combination. Start by installing the head on the empty block (2 bolts is enough) and reach up thru the bore and mark the cylinder wall with a sharpie approx 1/2”-3/4” each side of the point where the valve is closest to the cylinder wall Do this on all 8 cylinders. Then remove the head, install a thin coating of Prussian blue on the deck, then lay the head gasket on the deck. Then scribe an arc from the sharpie mark in the bore to the head gasket then to the other sharpie mark. This should give you the upper grinding limits.
Next you need to determine the location of your top piston ring at TDC. I recommend mocking up the engine with 1 piston to find this instead of using calculations (remove any possibility of an incorrect calculation). Take the upper limit and leave yourself some room for error (like .050”+). In other words if the upper limit of your top ring at TDC is .200” below the deck, mark your grinding limit to .150” below the deck.
Next mark your lower grinding limits (in the bore) by scribing an arc from the ends of the scribe marks you left on the deck down to your lower grinding limit back up to the other scribe mark. You should now have two arcs scribed, one in the deck and one in the bore.
Do this on all 8 cylinders then make sure they all look symmetrical and in the exact same location in each cylinder.
Before grinding it’s a good idea to reinstall the head and look thru the bottom of the cylinders to confirm your scribe marks are centered over each valve. If not, reapply Prussian blue and adjust your scribe marks accordingly. If the marks are centered then prepare the block for grinding by covering all oil passages lifter bores etc with tape. It’s much easier to clean iron shavings from an oil passage if there aren’t any in there to begin with.
Now it’s time to grind. Go slow and stay within your limits. If you go outside your limits there’s a good chance you’ll ruin your block it at least be in for costly welding and resurfacing or reboring repair.
After completing your grinding make sure you didn’t leave any sharp edges then thoroughly clean up the block including all oil passages and lifter bores.
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ERA 427SC Cobra: Iron ‘67 625hp 482” SOHC, TKX 5 speed, TrueTrac 3.31 IRS, Magnesium Halibrands, Avon CR6ZZ tires.
1969 Shelby GT350, 4 speed.
1967 Mustang Fastback: Close ratio T56 Magnum, Fab-9, Wilwood superlite brakes, Torque arm rear suspension, TCI-IFS with shock tower delete, (Coming soon, FE motor TBD)
1970 F250 4x4 Mud Truck, 557 BBF, as cast P51 heads, 900 hp @6700rpm, 801 tq, Q16, C6.
2012 Cobra Jet Mustang factory drag car, 5.4 liter 4.0 Whipple, 970 RWHP.
1964 Galaxie 500XL, 35 spline 3.70 Strange S-Trac, 6R80, (Coming soon: Pond Aluminum 525 SOHC, 800hp)
