« Reply #2 on: July 11, 2019, 02:21:30 AM »
I’ve done it on a 460 based 557 cid motor with Kaase P51 heads. I haven’t tried it on an FE but I plan to do so on my next build. On my 557 I don’t know how it affected power but I know the motor makes 900 hp with untouched heads. I think it works well to unshroud the valve al low lift. The valve passes the shrouded area twice, once while opening and again when closing. The way I look at it, every little bit of added air flow is more power. And for very little effort. If you can add few extra horsepower here and there enough times it eventually adds up to a noticeable difference.
When I relieved the top of the cylinder bore I made damn sure not to grind down to the top piston ring at TDC and I didn’t grind back to the head gasket. I used Prussian Blue (I think they call it something else now) to mark my limits and I took my time not to grind outside my lines. And I only ground on the area adjacent to the intake valve.
I don’t know how to post pics but I found some pics on the internet I’ll try to post soon.
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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)