Likethe Small Block Chevy, the Rocket 88 Olds, the Ford Flathead and the ChryslerHemi, the Buick Nailhead engine is one of those that has the immortal smell ofhistory all over it.
Yet,unlike its more familiar brothers, cousins and even competitors, the Nailheadhas an aura of mystery about it as well.
TheNailhead had a big-bore, short-stroke design that offered tremendous torque, spreadout over a wide RPM range. Introduced in 1953, the overhead valve Buick designincorporated vertical valves (the small size of which gave rise to its somewhat uncomplimentary nickname of ?“Nailhead”) and a pent-roof combustion chamber. With itssmall valves and tight intake and exhaust ports, Buick used a very interestingcamshaft as its stock offereing, with higher lift and longer duration. Thedistributors were in the rear and the starters were on the driver’s side,unlike later Buick engines.
Builtfrom 1953 through 1966, the Nailhead family included a variety of displacementsincluding 264 c.i.d., 322 c.i.d., 364 c.i.d., 401 c.i.d. and 425 c.i.d.variations. There were other size Buick engines produced as well that resembledthe Nailheads?(such as the 215 and 300 V8s), but they had no partsinterchangeability with the Nailhead and instead are actually more closelyrelated to the V6 and later Buick V8.
Confusedyet??To clarify the history of these popular – yet often misunderstood– engines, I spoke with one of the true Nailhead experts in the country.Russell Martin, owner of Centerville Auto Repair in Grass Valley, CA, says “Thereason few people know much about these engines is because there is so much toknow. I have been amazed by the many changes made during the time the Nailheadwas used from 1953-1966.”
TheNailhead was campaigned perhaps most famously by “TV” Tommy Ivo, who raced atwin-Nailhead (placed side-by-side) dragster as well as a radical four-engine,four-wheel drive dragster named “The Showboat.” So what was it about theNailhead that makes understanding it so difficult?
“Foryears I heard guys ask what is so good about a Nailhead: ‘It has those smallports and valves!’” says Martin. “But they always ran better than they should.After doing a lot of research, here’s what I found: The less timing advanceneeded in an engine means it has a good combustion camber design; theNailhead has the least timing advance (30 degrees) that I know of and the sparkplug is right in the middle of the chamber for a short flame travel.
“Theblocks have a tall deck height for a good rod stroke ratio (the taller blockallows for a longer rod). The short stroke lets the engine spin quicker than alonger stroke engine. Smokey Yunick tried to get Chevy to correct this on theSB for years because its deck is way too short to use long enough rods forgetting the most power,” Martin explains.
Otherfeatures pointed out by Martin: the small bearing sizes mean the bearings runcooler and need less oil. Every Nailhead, not just the high performance models,had forged rods and cranks. Rocker arm shafts are much stronger than studs withrockers on them. The whole valvetrain is very light so softer valve springs canbe used for less engine wear and quicker revs.
Thesmall exhaust valve heads don’t have as much pressure against them when theyare being opened, meaning less preasure againt them when they are being opened.Cracks are rare in a Nailhead cylinder head,” he says. “And they rarely leakoil because of the way the valve covers are designed.” The ports are smallerthan most HP engines but designed with high velocity.
Ofcourse, great design does not always mean simple – and in the Nailhead’s casethat’s a fact you’ll have to come to grips with. First off, the Nailhead ismore correctly labeled a THEM than an IT. According the Marin, the sheer numberof variations can be staggering.
“Thereason few know much about these engines is because there is so much to know, Ihave been amazed by the many changes made during the Nailhead’s existence,”Martin says. “The 1953 322 is a separate motor, with a special block, heads andpistons, etc., but the 1954-’55 and ’56 engines also have many differences,both with the 322 but also with the 1954-’55 264 engine as well. The 322 wasalso re-designed and used in large GMC and Chevy trucks from 1956-1959 – thisversion of the engine was called the Torque Master.”
Hecontinues: “There were three (plus high and low compression models) 364 enginesmade from 1957-1961, with 3 different blocks, different con rods, headsand timing cover, rockerarms, and even starters! Buick made four different 401engines, three of which have different blocks. Plus, there were two different425s.”
Theimportant thing an engine builder looking at this powerplant should do is findthe correct year before starting the rebuild. “Certain engines cannot be usedin some Buick cars because of bellhousing, engine mount, block, oil pan andcrankshaft changes,” Martin explains. “Plus, since all Nailhead engines wereexternally balanced, mixing dampers and flywheels with some models is not goingto work.”
Gettingyour balance with a the Buick is critical. “Because all Nailheads areexternally balanced, the flywheel/flexplate must be installed with the indexholes lined up,” Martin explains. “They can bolt on six different ways but onlyone way will be vibration-free! The 1957-’66 Engines MUST have their damperstightened to 225 lbs ft. or the crank and damper will be damaged. They are alight press fit so the bolt must be this tight.”
Nailheadcylinder heads are very sensitive, explains Martin, who suggests allowing onlyexperts in the engine to port your heads – you can actually lose horsepower ifthe job is done incorrectly, he explains. The best Nailhead porter I know isMike Lewis of Pro-Tech, out of Fresno, CA,” Martin says. “He has spent monthsperfecting the technique of porting Nailheads and can improve flow by 25percent.”
Whilerodders often turn their noses up at the word “stock,” Martin points out thatthe stock Buick cam is hotter than the smallest Isky cam and with stiffersprings will rev to 5500 rpm. “If you want a bigger cam make sure it has atleast 214 degrees duration at .050? or you are just wasting money on a HP cam,”he says.
“Ifyou are using an aftermarket performance cam, ALWAYS degree in the cam,” Martincautions. “This is very important – do not skip this part of the build. I havetiming sets with 9 positions so I can correct any cam that is off. When notusing adjustable rockers we always use adjustable push rods, put the adjustsdown in the valley for easy adjustments, with a hydraulic cam you are onlygoing to do this once.”
Additionally,valve springs are critical. “I have the correct size high performance valve springsin several spring pressures including a special spring for stock cams,” saysMartin. “The spring pockets in the heads must NEVER be made deeper or enlarged,because doing so will put the spring into the push rod hole!”
Theearly 264-322 heads (up to mid-1955) have a very small pushrod hole that shouldbe enlarged if a larger cam is used, explains Martin. All 1959-1966 364, 401and 425 heads have the same ports and valve size; the 1957-’58 heads are thesame with smaller valves. However, he says the ’53-’56 heads are differentevery year. “Back in the day, hot rodders would swap the early round exhaustport heads for the ’57-’66 rectangular port heads for racing, custom pistonsand intakes were needed. I had Mike Lewis flow a ’55 264/322 head for me and evenwith the smaller ’53-’56 ports and valves they were still only 10% less thanthe ’57-’66 heads!”
Understandingthe Nailhead’s valve seat requirements is very important, warns Martin. “Youshould never install hardened seats. The coolant passages are too close to theseats, so you are likely to either cut into the coolant passage while cuttingfor the seat or the metal will crack while installing them! There are a handfulof Nailhead guys who can do it, but guess what? You don’t need hard seats.These heads have a high nickel content along with small, lightweight valves andsoft valve springs. I have rarely seen bad seats and the ’54-’58 heads can justuse larger valves from later engines as needed.”
Martinsays valve guides require another caution. “Don’t use anything but cast ironguides unless you are using roller rockers,” he explains. “The stock shortrocker arms eat up bronze guides in a short time.”
Valveseals were only used in 1966 and on the intake guides only. Martin says you canadd them to all Nailheads but never install exhaust valve seals. “Very littleoil is going to enter the exhaust guide and you need it so the it does not runtoo dry.”
Thenewest style head gaskets aren’t necessarily appropriate for these engines,warns Martin. “Without the right gaskets, engines can leak oil front and rearof the gasket from the oil passages that feed oil to the rockers. The gasketsshould have a raised circle around the oil passage hole but without it and theway modern gaskets are made from layers of material these tend to leak. I havetried sealers but now we use vintage style or factory steel gaskets with noproblems.”
Theprocess of building a Nailhead, Martin says, starts with a thorough cleaningand deburring of the block. “This makes the block stronger so cracks can’tstart and makes it easier to install the cam bearing without cutting yourfingers on the casting flash around the lifter bosses plus if a piece ofcasting flash breaks off later it can ruin your engine. These engine blocksrarely crack but if they do, the crack is usually hidden by the starter. Beforebuying any of these engines, remove the starter and look at the block closelyin this area. There are ways of repairing this but none are cheap, anotherblock is the best way to go.”
Martinnext pulls the oil galley plugs and cleans the passages. “I use a dent pullerto pull the first one so I can knock the others out with a long rod. We’ve hadthe correct oil galley plugs made; all that was available was 5/8? and that is.015? too large! I use two plugs on the galley hole behind the distributor –there is enough room without blocking oil passages unlike the 3 front plugs –and apply green threadlocker on all of them.”
Next,the engine gets squared up by decking. “I bore and hone it with a honing plate.The honing plate, distorts the cylinders just like when the heads are torqueddown so the cylinder will be perfectly round when the engine is together,”Martin says.
Allclearances are kept as close to factory specs as possible. Martin says heprefers to use the factory Buick oil pumps, whenever possible to preventbinding of aftermarket units that can occur unless the mounting holes areopened up and the pump is moved around until it doesn’t bind. “There arerebuild kits available,” says Martin, “so I rebuild the factory ones and packwith petroleum jelly.”
Martinsays the next step is to have the assembly balanced and then assemble it withoil (or assembly lube), NOT grease. “Grease can plug oil galleys and ruin yourfresh Nailhead.”
Hecontinues: “Before installing the crank we install the rubber rear main seal.We have had some problems with these seals, not because the seal is bad butbecause some blocks have shallower seal grooves machined in them than others.This causes seal distortion when the cap is torqued down. If the seal lip looksdistorted grind the seal ends a small amount where they butt and re-check theseal.”
Thenext step is to install the bearings and crank can be installed. The crankshould spin smoothly by hand. “To date I have had only one Nailhead that neededline boring of the main bores,” says Martin. “Line honing is not an option withthese blocks, because you can’t control how the material is removed. Boringlets the machinist control where the metal is removed so a minimum metal isremoved from the block – most is taken from the main caps. If the crank isbrought closer to the cam you will get a loose timing chain and you don’t wantthat, there are no oversized sprockets available to tighten the chain back up.”
Wheninstalling the pistons always oil rings and space the end gaps on the top tworings.
Martinrecommends that engine builders stake the front oil galley plugs. “Tapping forscrew-in plugs is not a good choice for these engines,” he explains. “There isnot enough room, you can block off oil passage holes and/or cam sprocket willnot clear them. I have never even heard of a cup plug falling out of one ofthese engines.
Martinexplains how on a recent Nailhead build, he used a rear sump pan along with acustom oil pump pickup with a larger tube. “Using this pan gave me some freehorsepower – you don’t want the crank and rods being slowed down hitting thatoil. The 1965-’66 GS version already has a lower level from the factory becauseBuick used a ’57-’61 6-quart pan with only 5 quarts of oil in it."
Thehardest part of a Nailhead rebuild, Martin explains, is installing the cambearings so he leaves the hard work to someone else. “I have the machine shopinstall mine. Always have an old cam for them to use to fit the bearing, andafter you get it home make sure they are installed with the oiling holes linedup and MAKE SURE THE FRONT BEARING IS IN CORRECTLY. This is a common mistakeand is a real pain to fix after the engine is in the car. If it goes in wrongyou won’t get oil to both lifter galleys. Another common mistake to watch outfor is leaving out the plugs in the oil galley behind the distributor.”
Next,all the threaded holes should be tapped and the whole thing should be scrubbedwith soap and water. “Get all the water off quickly and oil the insides,” saysMartin. “Get a paper towel with ATF and clean the grit out of the cylinders.Keep doing it until they are clean.”
Whenyou ready to assemble, Martin cleans the backs of the bearing and where theyfit with lacquer thinner. “That allows the heat to flow easier from the bearinginto the rod or block, keeping the bearings cooler,” he explains. “The rest ofthe short block build process is by the book.”
Formore information about the Buick Nailhead or Centerville Auto Repair, visitwww.nailheadbuick.com.
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