Ford racers now have a slightly lighter cast-iron head for NASCAR Late Model Stock racing.
The top head is Fords N352; the bottom one is the Late Model Stock-legal N351. You c
Once the intake and exhaust manifolds and the valve covers are bolted on, the only visible
An exhaust port comparison. The smaller-volume port of the N352 is on the left. It is bett
The N352 head received extra material around the intake manifold bolt holes to prevent cra
...that the older N351 heads did not have. This is another change that does not affect com
Who needs soap operas when weve got racing? Mostly, the wild rumors, back-room dealings, and unsubstantiated gossip are confined to the team level at the trackswhos running a ported head, whos doctoring their tires, who has the tech inspector in their pocket. Recently, through a mixture of miscommunication and product evolution, a manufacturerFordbecame a prime player in the NASCAR Late Model rumor mill.
Although its the top attraction at many Saturday-night tracks, NASCAR Late Model Stock racing is not intended to be a professional-level class. The rules are designed not only to provide fierce door-to-door competition, but also to keep costs affordable for the regular guy. A big part of keeping the costs of racing down is consistency in the rule book. Even the slightest change can lead to competitors shelling out for a complete engine rebuild, chasing the absolute performance limits that the latest change will allow. The way Jerry Cook, NASCARs main decision maker for the Weekly Racing Series, sees it, as long as the competition is tight and every make of car has an equal chance of winning, there is no need to change a thing.
Running Change, or Redesign?
Thats why more than a few eyebrows were raised before the start of the 02 season when Ford unveiled an improved cast-iron head and called it a replacement for the venerable N351the only head legal for Ford engines in NASCARs Late Model Stock division. The head was actually considered an update, or running change, to the N351, so the part number would not change. Apparently, the original tooling for producing the heads had completely worn out, and Ford engineers had taken advantage of the opportunity to update the head while bringing the new tooling online.
Unfortunately (or maybe, fortunately if you are a Chevy racer), Cook and NASCAR quickly rejected the head on the grounds that it would upset the delicate competitive balance in the series. With the Late Models, weve got the Dodges, Chevrolets, and Fords, and theres one head for each model, explains Cook of his decision not to approve the new head. We saw no reason to change anything in (Fords) cylinder head from a competition standpoint. The cars are competitively pretty equal from what Ive seen since weve gotten everybody down to just one head (each). When Ford came through with these modifications, it was simply something that we werent going to approve.
This is the point where the rumors started flying. Some said the cost of retooling for a set of head castings was simply too expensive and Ford would draw a line in the sand: Either NASCAR would approve the new head or the Blue Oval would pull its support for racers in NASCARs Weekly Racing Series. Others theorized Ford would begin producing the old-style heads again, but it would be several months to a year before they would reappear on the market. In the meantime, a suitable (read: legal) head would become hard to find.
Thankfully, none of the rumors proved true. Ford gave the updated heads their own part number (N352), and pledged to continue producing the N351. As far as Ford and NASCAR are concerned, everything isand always has beenjust hunky-dory. But the solution of producing both versions of the head means that racers in a series not sanctioned by NASCAR but still required to use a cast-iron head may have a brand-new option open to them. To find out exactly what the difference is between the N351 and the N352 we traveled to Raceparts Distribution Incorporated in Cornelius, North Carolina, to have a look for ourselves.
Initial Inspection At first glance the only difference between the two heads is a significant chunk of the N352 has been carved away on top of the head to lighten the load. The N351 head was originally designed and produced with a lot of extra material so engine builders could raise the intake ports, explains Preston Miller, president of RDI. Of course, there arent a lot of series out there using cast-iron heads that allow porting. So the Ford engineers simply went in and took that extra material away and left the ports where they were. Theres about 7/8-inch of material removed at the top of the heads above the intake ports, and that saves about four pounds on each head.
Otherwise, the heads are almost identical externally. Without the part number below the exhaust ports, the 351 and 352 heads would be nearly impossible to differentiate with the valve covers bolted on. (If you are thinking ahead, the part numbers on the heads are raised, not stamped, and would be extremely difficult to alter.) The rest of the changes are internal, and most address dependability issues, not power.
Internally, the N352 head features more support posts inside the water jacket to eliminate any chance of cracking around the combustion chambers when the head has been decked. The intake manifold bolt holes have also been reinforced and raised on an angle so that more of the studs threads will make contact with the head. The combustion chamber hasnt been changed, but there does seem to be a little bit of material added between the valve guide and the back side of the intake runner bowl. Miller believes this is so the heads will more easily pass a ball test. Finally, theres a little extra machine work done around the pushrod holes to open up those clearances. Nothing major here, and certainly not enough to warrant a rejection by NASCARits the modifications to the intake and exhaust ports that raised Cooks eyebrows.
Although the changes are so slight its difficult to see, both the intake and exhaust ports have been changed on the N352 head, Miller explains. Overall, both the ports are slightly smaller to better match the two-barrel carburetors used in Late Model Stock and increase the port velocities. If you look at the exhaust side, you can see quite a bit of difference in the shape of the ports, but theres also a difference in area, too. The biggest exhaust header pipes they let you run in Late Model Stock are 1-5/8 inches (od), which is smaller than those exhaust ports. These smaller ports pose (of the N352) less of a restriction for the exhaust gasses as they exit the port and try to enter the header pipe. If you are in a class that is allowed to run 1-¾- or 1-7/8-inch exhaust pipes, the N351 head has a good exhaust port, but for 1-5/8 pipes the N352 head matches up better.
The good news is Ford is adapting the durability improvements of the N352 head into futureand NASCAR approvedupdates of the N351. Although the updated N351 head wasnt available at the time of this writing, it should be hitting the market by the time you read this.
For his part, Miller says he sees the wisdom in NASCARs decision to disallow only the changes that would have given the Fords a competitive advantage. Its just a financial hardship. If a change is allowed that will make just enough difference that it will provide an advantage, people racing Fords will feel that they have to buy the heads. Then to make the most of them, a cam change and other adjustments are required, which will have people getting entirely new engines built. Next thing you know, the Chevy guys will be screaming for a change so they can keep up. It just opens a big can of worms that would have zero change in the quality of the racing itself. All you are asking the people to do is spend a lot of money, but the end result is that everybody goes up one notch equipment-wise and the quality of competition doesnt change one bit.
The bottom line is if you get something that works, dont change it, Miller notes. If somebody has the money and ambition to race the absolute cutting-edge technology, they need to move up to another series.