What is a nailhead?

I have had some "know it all" tell me my engine in my 65 skylark is a nailhead. What exactly is the definition of a nailhead, what size and how do you tell? (yes, I know , I'm dumb as a rock) o No:

 

Unless your '65 Skylark is also a Gran Sport, it is not a nailhead.

The nailhead was a V-8 engine used by Buick from the mid-1950's through 1966. By 1965, it was the Buick big block version, with 401 or 425 cubic inches. The valve covers sit almost straight up. You probably have the 300 engine, which also had vertical-style valve covers, but is not a nailhead design.

 

It's a nailhead because of the position of the valves
http://images.search.yahoo.com/sear...ch&fr=FP-tab-img-t-229&toggle=1&ei=UTF-8&vm=r

 

nail head

Nailheads started in about 1953, at 322 cu in , then went to 364 , to 401 and to425. by 1966. They were the toughest of all buick engines. :Brow: They had forged steel cranks, forged steel rods, and a unique under and over rocker arm system that put the valves in a straight up position on the inside of the rocker arm shaft. All this was done because Buick wanted a v8 that would fit inside the frame that was built for a straight eight. The design makes for a very narrow v8 engine. A added bonus was the bunches of torque at a low rpm that they put out. The oiling system is good and the cooling system is good. I have never seen a burned valve on a nailhead buick engine in 40 yrs. the only things that I have seen go wrong with one is an occasional busted piston. [3 in 40 yrs] and once I saw the harmonic balancer crack in the key way. I moaned and groaned when I found out that Buick was dropping them in 66. :ball:

 

Nailhead was a nickname because of the small valves, read the first scan in this thread. :Smarty:

 

You know, that's what they say... that the valves look like a nail, but I was inspecting a pair of 401 heads and the valves look mighty nice to me. Definately not "tiny".

 

nail head

Exactly, Yardley, the valves are not as small as the "ignorant" like to make out like. I once had a mechanic tell me all about how lousy the valves in my nailhead were. His Olds 442 was much better he said. That was just before I beat him twice in a row in a drag races. :laugh: