Finished building a 302 for our Maverick. The block was stamped 1968 but had C9TE heads. I've always liked the idea of tapping into factory heads to unlock "free" horsepower and since we're building a street car that'll frequent the strip from time to time, this was an opportunity for me to do some porting. My intention was not to port everything out as big as possible, but rather increase flow while keeping good port velocity. I worked the intake and exhaust ports, eliminating the thermactor bump, shaping the guide bosses, pushrod wall, addressing ridges, flash, etc. Once complete, I sent the heads to the machine shop where they were milled, fitted with bronze guides, screw-in studs, hardened seats, viton seals, and a 3-angle valve job. While I don't have flowbench numbers, I'm confident I made improvements. The factory iron heads leave a lot to be desired. The pics show the changes. If I conservatively increased head flow around 15 cfm, then according to my math (HP = .25714 x cfm gain x No. of cylinders), I should see about a 30 horsepower gain. Should respond well with the other mods to the engine.
You gotta' love the ragged edges on the ports from the factory. LOL. I am sure you will see an improvement here ... nice job.
Well do all you did to a set of 351w heads and you will add about 50hp. Putting on just stock 351 heads will add about 30hp.
I wouldn't disagree, if they were the earlier '69-'70 351W heads (with the larger factory valves and ports), which I actually have a set of, but was saving for another day. However, I wouldn't be surprised if I exceed my 'guesstimate'. Nevertheless, I believe these heads should outflow GT40 or GT40Ps. The rest of the engine mods should complement well, FST carb, Air Gap intake, Hypereutectics, Crane rollers, Lunati cam (230/236 duration @ .050), MSD ignition, long tube headers, then 4.11 gears and a 3500 stall in a prepped C4.
I agree with the 69-70 heads. Back in the day there was no aftermarket parts. Us Ford guys did what we had to do to keep up with Chevrolet and Chrysler.
Good work, definitely will make an improvement. Ford designed their heads with tight angles to fit in their cars with shock towers. I personally would have taken more out around the valve guides, even to the point of having them exposed. Except for P heads because they have a water jacket around the exhaust valve stem. But that's just me. Factory castings were really ugly back then...
Back in the early 90's I took '68 heads to the machine shop for screw-in studs, larger valves and porting. The Machinist told me that the heads are now breathing better than the stock GT-40 heads. I don't have any before/after numbers, but the butt-0-meter said yep, big difference
Thanks for the compliment I had actually thought about doing more around the valve bosses, especially the exhaust, however, I decided to leave some material hoping it would aid with valve stability at high rpms.
I believe it, I think even some basic smoothing in the bowls/ports to address hard ridges, casting flash, and bumps can result in good improvements.
