Well here is my (LONG) logic in concluding that the Ford HiPo solid 274-275-276 and 306 duration are all the same grind:
From NHRA Blueprint files:
Solid FE cams: Published Lift (In & Ex all same)
Year Eng PI HP
60 352 ----- 500
61 390 440 499 (ie net)
62 390 439 500 (ie net)
62 406 ----- 500 (ie net)
63 390 465 ----- (ie gross)
63 406 ----- 525 (ie gross)
63 427 ----- 525 (ie gross)
64 390 439 ----- (ie net)
64 427 ----- 500 (ie net)
65 390 465 ----- (ie gross)
65 427 ----- 525 (ie gross)
Nota that NHRA cites net lift in some years and gross lift in other years, since we know that the 390PI had .440 net and .465 gross lift.
This supports a single HiPo cam lift of .500 net and .525 gross.
Dec 1960 Hot Rod:
“Ford engineers told us that they tried every camshaft grind they had, then tried everything they could buy from outside cam specialists and there was nothing they found that could match the grind they used in 1960 HP engines so they used the same grind again for 1961.”
IF both these (NHRA and HotRod) are right, then since the 1961 cam has .500 lift, which we assume is net since the 390PI is listed as .440 lift ie net, then the 1960 cam has to also be .500 NET lift.
So we are talking about the HiPo cam as either
276-276 duration, .480 .480 net lift
Or
306-306 duration, .500 .500 net lift
LIFT wise, it doesn’t make much difference. If duration is the same, going from .500 net lift to /480 net lift only loses 1 hp on the 352HP, and only loses 3 hp on the 390HP. I’ve just always had the hunch that the 352HP was in fact .500 net lift, same as the 390HP, 406, and 427 – and that’s why the early 352HP springs couldn’t get the job done.
DURATION is another issue.
As far as the 352HP or 390HP cam being 276 duration, as in 30 degrees less duration than the 427 cam at 306 duration, I just don’t believe it. The 352HP and 390HP would be way down on power, and just not capable of turning in the MPH numbers the cars ran.
Changing duration at .050 from say 228 to 206 loses 15hp on the 390/375.
The 390PI cam is usually listed at 282-282 advertised duration, compared to the 306-306 HP cam.
If there was a 276-276 advertised solid cam and it was really down 30 degreed duration across the board, the 352HP and 390HP would idle and run like a kitten.
So I think the 276-276 vs 306-306 are the same, just measured at different lobe lifts.
Not uncommon in those days.
Supporting this is the March 1960 issue of Rod Builder mag on the 352/360HP.
“It includes a hot cam (306 degree-valve-opening duration).”
Rod Builder continues:
“The cam is wild, to say the least: 306 degrees duration for intake and exhaust. The maximum lift at the cam is .298 inches, which together with a 1.76 rocker ratio, produces a valve lift of .525 inches.”
That may be the 1st time I’ve seen the 306 number – but where else would they have gotten this number (in March 1960) unless it was the real 306 duration of the 352/360HP? Also the 1st time I’ve seen .298 lobe and .525 gross lift for the 352HP cam. This is consistent with NHRA showing .500 net lift for 1960-61. Again, I think 276 duration & 306 duration are the same cam, just measured at different lobe lifts.
It can be confusing looking in the later MPC books as they look backward: If you look in eg the 1960-64 MPC published in 1968, you’d think there was a factory 390 Tunnel Port running the .600 lift “D” cam! But since this Rod Builder article is from March 1960, if that 306 degree .525 gross lift cam wasn’t for the 352HP where’d they conjure up those exact (later 427) numbers?
H&M lists the good old c3az-aa “306-306” cam at “275-275” duration.
And they list the “324-324” c4ae-b “B” cam at “290-290” duration.
http://www.holmanmoody.com/parts1.htmlThat’s another reason I’ve concluded that the (276-276 or 275-275) cam is in fact the 306-306 cam. And also that the (288-288 or 290-290) cam is in fact the 324-324 cam. They just measure the events at different lobe lift.
For example, when I degreed a clone of the 324-324-114 c3az-k 427-8v cam I get
244 duration at .050 lobe
279 duration at .020 lobe (maybe this was the “288” advertised duration)
331 duration at .006 lobe (maybe this was the “324” advertised duration)
You can see why “advertised” duration drives everybody NUTS.
Same cam, but ~40 degrees difference in “advertised” duration, depending how it’s measured.
I still think this is what’s going on.
The discussion here, circa 2004, at least for the 427, reinforces my hunch/conclusion:
http://www.clubcobra.com/forums/fe-talk/59944-stock-425hp-solid-cam-specs.htmlNotably the discussion by Ted “Y-Block” Eaton.
“As I use to run the "K" grind back in the late Sixties, I went back to the old Ford parts catalogues to see exactly what the specs was on that particular piece. It was the C3AZ-K camshaft with 290°/.500" and was listed for use in the '66 427 both in the 1X4 and 2X4 engines.
Going back a little further I find that the 1963 and 1964 427's had different cams for each year while the 1X4 and 2X4 versions were also different. The 1X4 cams were C3AE-M (276°/.525") and C3AE-U (274°/.525") for '63 and '64 respectively. The 2X4 cams were C3AE-AA (288°/.525") and this one carried through into early 1964 on the 2X4 engines where it was changed out for the C3AE-V cam with 290° duration. Date codes on the engines play heavily on the cam listings in my old reference books and there appears to be a myriad of service cams offered including the aforementioned C3AZ-AA with 306°/.500" specs. I spared you the listed intake/exhaust opening/closing specs.”
The (274-274 or 276-276) and 306-306 durations for the 427-4v are talking about the same cam.
And the (288-288 or 290-290) and 324-324 durations for the 427-8v are talking about the same cam.
At least very, very close.
Now, is the 276-276 “427” cam the same grind as the “276-276” 352HP and 390HP cam?
Based on all this, I think so. But again I’ve never measured any.
But knowing Ford, anything could happen.
I’d happily degree some old cams to be more definitive, but I don’t have any.
I’ve degreed an old 352/300 solid cam from 1958 but don’t have any old original HiPo cams.
There could be some further confusion regarding the HiPo 276 degree cam (which I still think is the identical 352HP-390HP-406-427-4v grind, .298 lobe, 306 or 276 advertised). The 390PI used a solid cam with lesser lobe lift of .264 and a 282 advertised duration.
In one of the Shop Manuals (1961 IIRC) in the engine section, it calls out the engines – 390/300, 390/330, 390/375HP, and then in the cam section, just says Lobe Lift = .232 for all. Well that’s the 390/300 Lobe Lift but not the others. In another Shop manual, the 1962 Ford, the 390/300, 390/330PI, 390/375HP-4v, and 390/401HP-6v, ok got em all. Then it lists .264 Lobe Lift for all solid cams – 390/330PI, the 390/375HP-4v, and the 390/401HP-4v, which is obviously wrong.
There is, nonetheless, reference to a 352HP-390HP-406-maybe solid HP cam with .480 net lift. Other than subtracting the lash twice, I can’t find any substantive reference for this cam. Maybe it never existed, or maybe it did, and Ford cut the net lift from .500 to .480 as a valve spring crutch, since it only Gonkulates to a loss of 3hp.
Documentation or measurements of any of this would sure help the history!