What they said.
But to add some...
Any particular year 351? I want to run a very smooth quiet engine.
As for particular year, you're not looking for a used cam are you? If not, then you don't really need to go by year, other than to choose between flat-tappet or roller lifters. Which is where jckkys' info could come in handy.
The cam manufacturers aren't usually making exact copies of the original Ford grinds anyway though, so year isn't important for that aspect. Just a good starting point.
Most, if not all, are making their own more modern profile versions of stock, and their own upgraded versions as well. Which is usually a good change.
In your case, if you just need the basic setup, then just pick a "stock replacement type" cam from the manufacturer of your choice. Just choose flat-tappet or roller for starters. Neither will likely be an exact copy of the original, but will act like it where it counts. Such as the idle and economy.
One area that may change by year, and what you intend to do in the future, is the makeup of the distributor drive gear cut into the cam. A flat-tappet would need one gear material for the driven gear on the distributor shaft, while I would say that almost all roller cams would require the other.
However, if it's an option to convert to roller, you might consider it. Other than the one jckkys mentiond, a later roller EFI cam will have the proper material to mate up with a later Ford TFI distributor, and more likely have a more compatible profile to the cam itself.
The typical Mustang or Explorer (or Frankenstein mix) will possibly prefer a wider Lobe Separation Angle in the 112° to 114° range. That would be found on later EFI 351 and HO5.0 engines.
A throttle body conversion however, would work with just about any profile.
Which brings up the question of what type of EFI you're going to be using?
An aftermarket throttle body setup like the MSD Atomic or Edelbrock E-Street are going to be compatible with your existing distributor and cam material no matter what you use.
A Ford type will utilize the TFI distributor with it's likely roller-only gear material.
There are exceptions for the 351 engines, like the Lightning engine mentioned I think, but I'm not sure about for the 302 based engines.
Here again then (I know, too much info!) you have options. You can change the distributor gear to a compatible material whenever you need to. And you might even be able to source a distributor already set up either way, if you can find that there is a compatible engine that Ford made.
See how much trouble it can be, but also how important it is that you're asking this stuff now? Glad you're at that point where you can think ahead.
It might make your head hurt now, but at least it gets it out of the way so it doesn't hurt when you get around to converting to EFI and need it to run!
So what years was the HO option available ? I ask because my 1970 302 has a 351 firing order and a pretty good lope.......
Like Viper said, your particular case would be due strictly to a cam change. And a lot more cams are now available in the "351" order anyway. Since it became more popular after Ford changed it somewhere in the '80's.
So no real telling when it was done. But it was never an option on an earlier 302.
Ford started using what we now call the "HO firing order" in the very early '80's I think. Probably started coming into production around '81/'82 or so. At the same time they still had different performance levels for different car and truck platforms, which is why the vagueness regarding exactly when the change happened.
By '83/'84, there may still have been only a couple of the old "302 firing order" engines left in the Cougars and T-birds. Or maybe they'd already crossed over too by that time?
Even that I'm not sure of. They were Speed Density setups instead of MAF of the Mustangs, but that doesn't mean they didn't get the new firing order.
So it's hard to tell without reading a Ford flow chart, or someone here posting up info they snagged upon finding such info.
It's vague, but you don't have to worry about it.
Someone just changed the cam and that's it. Dimensionally they're usually the same. Just the firing order was altered. And you can still get cams with the old firing order if you want.
Like was said though, the newer "351" order is probably just better all around anyway.
It helps when the PO tells you this kind of stuff up front though! Huge help orienting the plug wires when tuning up or trouble shooting. ;D
Paul
