What kind of power/torque did the various stock nailheads put out? What kind of power/torque can you build on PUMP gas (regular would be nice, at $3.00 a gallon)with a Q-jet, affordable headwork, and a lopey but streetable cam?
Can't answer any of those questions but the streetable and lopey cam describes my 1965 old Riviera with a 425. My great uncle worked in Buicks engine plant and he said that engine was fine line between stock and performance cam. Very strong and in a light car should be very impressive.
Nailheads...with their valve design and arrangement were originally designed to produce lots of torque while sacrificing high rpm horsepower. A '59 401 only made about 325 HP, but 445 LB-FT of torque. In '63 the 425 could be had with 340 HP and 465 LB-FT. They upped it again to about 360 HP in '64. I've heard that the 322's are easiest to get hop-up parts for. But I could be mistaken. Those higher horsepower nailheads already had fairly lopey cams...like up around 290/290 and .440 lift. The heads are the limitation. The valves are just on the small side. If you're going to have head work...see about having larger valves installed. Original heads had decent intake flow, but the exhaust was on the restrictive side. The advantage to the nailhead is that it is lightweight and compact. And obviously you can make 'em go fast...look at Tommy Ivo. On top of that they just look cool. Keep in mind the stock vavles were already kind of small for stock motors...so if you do them up right...you'll make more power with a nice cam. But on the other hand...you may bring the HP and Torque figures closer together. If you want lots of torque...I'd leave them stock...if you want less torque but more high rpm HP...go with bigger valves and headwork. Maybe try just polishing the stock heads and see how it feels.
Buick was notorious for that lumpy cam. I think it's probably the 290/290 .440 lift cam I was thinking of.
The stock cams in the 364/401/425s had a nice lump to them at idle. They make tire melting torque. Carmen Faso has some very nice aftermarket cams available as well....
Nailheads dont like to spin..Small valves and inefficient valvetrain with limited adjustability. But thats the great part you dont need to spin them up anywhere past 5000 RPM. Just rebuild them pretty much stock. Clean up the heads a little and put. To me the ultimate 425 Nailhead is the '66 with the Q-Jet intake (1 year only for this intake) Put a big Q'-jet on it and your all set. U-Joint breaking axle busting torque. All on a stock bottom end no problem. Steel crank from the factory. I have one waiting for my '54 Buick Special.
I'll vouch for the "Nailheads don't like to spin" statement. The 425 in my Murc is really great around town, but, for highway use it's aweful. I'm thinking about putting a 700R4 and way low gears in mine. Throw that motor in a really light, really low A or T coupe and have some fun. Just be sure to have a ggod supply of tires.
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