Crane Cam Blazer 284-2H (.465"/.488" 284/294 duration, 224/234 @.050" tappet lift) (2200-5700 RPM range) 112 degree lobe separation angle, 9.5 to 10.75:1 static compression ratio advised.
springs 99848-16 e,f
or springs 96802-16 j
retainers 99915-16 f
or valve spring and retainer kit 11308-1 e,f
valve stem locks 99097-1 m
e standard diameter valve springs, no machining required.
f for 1967 to 1987 with 1.700" installed height.
j standard diameter chrome silicon valve springs for 1.750" installed height.
m machined steel, heat treated.
With the piston crown dish you have, here are the approximate SCR's you would end up with using different chamber volumes....
64 cc 10.8:1
68 cc 10.4:1
70 cc 10.2:1
76 cc 9.6:1
Your "stack" of parts will measure 9.0". Crank stroke radius 1.875", rod length 5.700", piston compression height 1.425" add up to 9.0".
Stock SBC block deck height is ~9.025". On a 350 block, you can play with the piston deck height (distance from the crown of the piston to the flat part of the block deck where the heads bolt on) a little because there are some thinner composition gaskets available such as 0.026" and 0.028", but there is nothing like that for a 400 block, so you have little choice (If you're going to run a tight squish) but to cut the block decks to zero (9.000") and use a conventional 0.040" composition gasket that is punched for steam holes. That will put your squish at 0.040". You have a nice flat portion above the ring pack on your pistons that will come up to meet the underside of the cylinder head as the piston comes to TDC, to "squish" the mixture out of that area and jet it across the chamber. The turbulence will homogenize the mixture and eliminate rich and lean pockets in the chamber that might or might not burn when the spark plug tells them to. Motors with a tight squish have shown to be more tolerant of low grade fuel.
Personally, if I were building this motor for a daily driver truck, I'd build it 9.6:1 with a 0.040" squish and be able to burn a lesser grade of fuel. If you build it right up against the wall and then take on a bad load of fuel, you'll have to open the hood and take some of the ignition timing out of the motor to prevent holing a piston or breaking the ring lands off the crowns from detonation. 9.6 is within the range that Crane recommends for the cam you have, so it should all come out smelling like roses.
I'd use a set of 1 5/8" long-tube, tuned length headers and install an H or X pipe before the mufflers. If looking for max power from the combo, I might use 1 3/4" primaries instead of 1 5/8". Recommend an Edelbrock Performer RPM intake manifold with carb of your choice and a 14" x 4" air filter arrangement. Let 'er breathe. If you get any cold weather where you are, recommend the regular RPM intake, not the Air Gap model. The RPM, especially on a 406, will make more power from idle to max revs than any other manifold you could bolt onto the motor.
Almost forgot....begin by checking the roundness and parallelism of the main bearing bores. If they're out, align-hone or align-bore back to spec, then jig the block up on the main saddle to cut the block decks.
The 5.7 rods will need a little grinding at the bolt head area to miss some of the cam lobes, or you can buy a real nice set of Scat forged rods for about $260 that have already been manufactured with clearance. Look for Scat Pro Stock 5.7" SBC rods.
Using a flat tappet cam can be risky, please read and follow these instructions carefully......