Stock 427 MR cam

[Chaplin]

Does anybody know what the specs of a stock 427 mr cam are? How does it compare to an Edelbrock Performer RPM or a Comp Cam 292?

Thanks,
Mike

[mr0077]

Mike, I dug out an old dusty book I inherited with my block, with some information, on the production Medium Riser camshaft (C3AZ-6250-AA) and the upgrade Ford part, recommended for the MR and HR motor (C4AE-6250-B):
Both cams are mechanical flat-tappet, 0.025" lash, 0.500" lift, with other specs as follow (C3AZ-6250-AA first/C4AE-6250-B next):
duration 306 deg/324 deg
overlap 78 deg/112 deg
intake opens 40.5 BTC/56 BTC
(14.5 ATC/TDC)
intake closes 85.5 ABC/88 ABC
(29.5 ABC/28 ABC)
exhaust opens 88.5 BBC/88 BBC
(33.5 BBC/31 BBC)
exhaust closes 37.5 ATC/56 ATC
(18.5 BTC/3 ATC)
(I can't tell you what the extra set of numbers in parentheses are on the open/close events, just copying the info from the book).
For comparison, my comp cam (FB282S-10) has 0.022" lash, 0.571" lift, 282 degrees duration (@ 0.015" lift), a 110 deg lobe separation. Cam timing (@ 0.015" lift) is
intake open 35 deg BTC, close 67 deg ABC,
exhaust open 75 deg BBC, close 27 deg ATC.

[Chaplin]

Ken-
Thanks. I knew someone out there would have it. How do you like your Comp Cam? Would you install the same cam if you were doing it all over again? What are its pluses and minuses?

Thanks,
Mike

[mr0077]

Mike, I like my cam very well...it has a nice lope to it, idles at 750 with no problem, and is very tractable in traffic. Pulls like a demon from just about any RPM, 1200-1500 RPM on up. It seems to "get on the cam" about 2800, and seems to run out of steam about 6200 or so. Based on dyno results, my engine guy said I needed a bigger cam (and better manifold than my Edelbrock RPM), and I had planned to change both out this winter, but after reading my description, I'm thinking I oughta just leave it alone!
I guess my cam a good match for my car (close ratio toploader, 3.31 rear gears), but with a wide ratio or a 5-speed, and/or shorter rear gears, a higher lift and longer duration cam could be a good/better choice.

[Ron61]

Miike,

I have an Isky flat tappet cam in my big block 427 bored to 439. It has 312 degree duration with a 96 overlap and .630 lift. It is not good at all under 2500 RPM and the car really smothes out and starts to run good at 3400 which is 70 miles per hoour with my gears. I like the cam but would not recommend it for a daily driven car. I have had it since I got the car in 1969 as it was dealer preped and that is what they used.

Ron61
Ron Widener

[Jeff Frigo]

Ron:

A 427 bored .060 over? Never heard of that before, are you sure? BTW, it is a 438 if its .060 over, not a 439.

[Ron61]

Jeff,

I had to show the pistons to a local Ford drag racer before he would believe me. The bore is 4.19 with a stroke of 3.984. That comes out to a 439.5 CI by the math. I did say 427 but I meant a 428SJC. However if you do the math on the 428SJC it is still a 427, they jusy downsized the bore a little and lenghtened the stroke and kept the 427 size. Sorry about the misrepsentation. This is a 1969 Torino Cobra special build car that so far as the Fairlane Club of america has been able to determine is the only one ever built exactly like it. There were 97 that are in the registry that are very close but mine has some factory and dealer options that none of the others had. It has all NASCAR running gear and I should have paid more attention to my post when I stated the engine size. Don't blame you for questioning my statement as I questioned the dealer when I came in to take delivery about the .060 over. But that downsize of the bore made it possible however the car does run around 200-220 degrees and has ever since it was new. I really wish they had only gone .030 over but everything is original and I don't want to change anything now.

Ron61
Ron Widener

[Jeff Frigo]

Ron:

Now it makes sense. Both of our calculations are correct, I was using 27 numbers, you were using 28 numbers. .060 over on a 428 is believable. Not trying to be smart, I am glad you responded the way that you did.

[Ron61]

Jeff,

I never try to be smart as that only shows my ignorance. Thanks for the reply and any time I do make a mistake I appreciate someone calling it to my attention. I was so busy looking at my cam specs I just hit the wrong key. To old to do two things at once I guess. Have a great day.

Ron61
Ron Widener

[Chaplin]

Ken-
Thanks for the response. What kind of dyno numbers did you get with that cam? What were the peak hp and torque figures? At what rpm did they peak? I am interested in putting together a streetable motor that will make apx 450 hp and 450 ft/lb of torque without having to run it to 6k rpm. From what I have seen and heard, your cam sounds like it might be the one to go with.

Thanks in advance ,
Mike

[mr0077]

Mike, my motor (from memory) turned 436 hp at 5500 and was still climbing...torque was 501 @ about 3700 (I'll verify), but that was with std rockers, exhaust vented into the dyno room (they couldn't hook the exhaust onto the sidepipes), a set of truck pulleys, and the carb was out of whack a bit. I'm guessing that with the underdrive pulleys and roller rockers, and reworking my carb, it's putting out an easy 450+ HP, 500+ lb-ft of torque, under 6000 rpm, and very streetable.
Good luck

[Mr.Fixit]

CAM selection
That $100 has more influence over your car's characteristics than any other variable. If you are in doubt about which one to run, you will 99% of the time be happier with the smaller duration cam. Often faster too. But if you spend all your time idling around show grounds(not driving in the real world), big duration sounds mean.

[Clois Harlan]

Mike,

When you are talking about Dyno results are you refering to the hp at the rear wheels? I am running 428 CJ bored .060, TRW Flat top pistons and rods, w/a Lunati 572 lift and 292 dur /, Performer RPM 4V manifold, Edelbrock Alum heads, a Holley 750, MSD Dist and box, and as of this weekend, Sig Erson roller rockers. I recently spent over an hour on the dyno and my results were near your expected hp mark but only at the flywheel. My rear hp rating was under 400. The lunati cam almost exactly morrows the Performer RPM Cam.

Nice rumble at idle and it really kicks in about 3000 RPM great top end all the way through the lights.

Clois Harlan

[Chaplin]

Clois-
I'm talking about at the flywheel (although I'd love to have that much at the real wheels ). I think your set up is pretty close to what I am going to go with (except I'm thinking about the Blue Thunder intake and am undecided on the cam). What kind of torque numbers did you generate with that cam?


Ken-
What heads do you have on your motor?

Thanks,
Mike

[mr0077]

Mike,
r. Fixit is right about when in doubt goin' conservative/smaller on the cam, but it's a big temptation to get radical...Clois almost has a 428 version of my 427, but I'm running a little higher compression (10.7:1) on my Edelbrocks, with a street port and flow job. I'm soon to switch to 2x4s (600's to start, 390's for comparison), and my dyno numbers were, of course, at the flywheel. I wish I had gotten a Blue Thunder right off the bat, that's a good (the best?) choice, I think.