C8AX-6250D Cam

[blykins]

A lot of the opinions here are based on assumptions.

First off, I don't have a concern about power in the lower rpm ranges, And a lot of engine builders build the motors for their customers for specific needs, most of which are street motors with off idle throttle response, which is what most of their customers want, so cams are chosen for those needs.

Now it's been said these D cams are out dated, they have lazy lobes and so on.

Mike posted this when he had the cams spec's checked:
"mkopmani:
 I didn't mention it, but once we measured the lobe profiles, Billy said other than running a little more lash, the ramp profile design was more than 20 years ahead of its time - quite a statement from the Comp Cams guru' Billy Godbold . So while an older design, this cam is not as dated as most think. As two of the three cams were still in original cosmolene, we also benchmarked surface finish (Ra, Rmr, Wt, Wcvx, Rpm, Rvm) and they were very similar to limits for what Comp uses today.
-Mike"

There was a remark about the 3:50 gears I intend to run on the street with this cam, I may even go back the 3:25's I have, the reason, I need a freeway gear and the 4:57's in the car now won't work well on the freeway.  And at some point after I get the car running, I'll be going an over drive auto, then the 4:57's will go back in.

I am not building a motor and then just throwing in a big cam,  which I have done before, I thru together a 390 with a cam with 258' @ .050" and I loved it.  Most of these street cars we build are for the street, they don't have big money suspension & tires that can hook a motor with 500 hp and 500 ft pds of torque, which is what is being built regularly and and the power is moved lower in the rpm range, which is well and fine for a dedicated 1/4 mile car.   

One of my favorite cars was my 68 Impala Custom.  I built a 327 SBC, I borrowed the Dontov 30-30 from my 69 Z28 302 motor, and thru the 327 in with a 2500 stall in a power glide, cam didn't come on till 4,000 rpm, but it flew on the freeway. Sad thing was, the car got stolen.

The Z28 302 motor, came out of a  Corviar set up for mid engine, that I bought, that came from Detroit, couldn't keep U joints in the axels, the body was so rusted the suspension moved so much when you got on the car it kept eating U joints, ended up pulling the motor and junking the car.

So what do you think, a 468 with the D cam you think it will have 500 ft pds of torque ?  My car weighs 3,600 pds, with the 390, that 258' @.050" cam, 3,000 stall, a detroit locker with 4:57's and 10.5" wide 29" tall slicks I was finally able to get the car to hook, no such luck with the 9" wide 27" tall street tires.

A stock 390 4v engine was rated 335hp, with the cam, heads, int, & exh change I think it ended up close to 400hp.

Now, the 468, at least 500hp and 500 ft pds of torque, do you think I will able to get this to hook, it will never happen, regardless where the torque range is.

It's been said that more hp can be made with cams with less duration, but you can't really use a roller cam for a fair comparison a more aggressive faster opening lobe can be used with a roller than a flat tappet, with a roller you have less duration but the lift has been increased, I don't deny roller profiles are superior, but so is the cost.

I, use what works for me and I hope everyone else will use what will work for them, the other 24 people who bought the cam, I hope this topic helps you decide how you will use this cam or not.

I speak with Billy on occasion, when trying new lobes.   He's a very sharp cat and is very helpful.   With that being said, a camshaft that's 20 years ahead of its time would still be a 1988 camshaft.    A 1988 camshaft is still 32 year old technology and would probably be something like a Comp 280H, 282S, etc., which work well in and of themselves, but are still outdated and can be improved on.   

Do I think your 468 will make more than 500 lb-ft?  That's 1.06 lb-ft per cubic inch.  To be honest, if you didn't have Blair's heads, I'd say no chance, and I'm still on the fence about it, with his heads.  Remember, when you move the horsepower peak up, the horsepower can go up, but the torque goes down.  500 lb-ft is easy to make hook up with the right parts out back.   Guys do it all the time.  I rarely send an FE out of here that doesn't make 500 lb-ft, and most have 550-575 lb-ft.  If your goal is to flat-foot it off idle and never slip a tire, that's one thing, but most people know how to pedal until the car gets moving fast enough to not be traction limited. 

I understand that some guys don't want to run roller camshafts.  That's fine and I still build flat tappers frequently.   However, you don't need a roller and a modern flat tappet would be superior in almost every aspect in comparison to the D cam.

Richard, with your heads and intake, you have the HUGE potential for horsepower.   There is no reason why you can't make 575-600 hp with Blairs heads and Joe's intake, with the right camshaft.  To be completely honest, with a custom, I think you could make 550 hp and keep the powerband as such that your 3.50 gears and 3000 rpm stall would work all the time. 

My goal is to help guys not have to settle or build band-aid engines.  With this camshaft, lots of guys are going to have to be applying band-aids to even have a combo that will work ok. 

[Barry_R]

Holding the camshaft as "fixed" variable while changing the engine around it is a very different way of looking at things.  Approaching Fantasy Island type stuff.

I feel that on a torque basis, a number over 500 is pretty reasonable with a 468 inch engine running this cam and a good set of iron heads.  The aforementioned tunnel port I tested achieved a torque per cubic inch number of +/-1.1, which on a 468 would translate to +/-513 at peak. 

Problem (if you want to call it that) is that the tested tunnel port was said to have really high compression.  If you want to apply some of the common (and very loose) assumptions regarding compression benefits as a percentage of power, you might see perhaps a 15% gain () in going from common pump gas territory to something in the 13-14:1 ranges.  The 468 engine's displacement is approximately 9.5% greater than the tunnel ports 427 inches.   Assuming (with damn near zero data to back the assumption) comparable air flow potential and a comparably appropriate intake - the smaller cross section port 468 wedge should run close or even better.  Its about cylinder pressure management, and you are trading compression for cubic inches, normally a good strategy for the street.

In this case, the functional RPM ranges for the 468 combination should be lower due to airflow, but I suspect that other variables such as intake and/or throttle body sizing may have been holding the tunnel port back a bit.  If that particular cam is indeed "driving the bus" I suspect that either package is gonna want a bunch of gear and a bunch of converter to get it working.  We can definitely do better now, but this is really getting pretty dang close to the old 454 strokers I ran in the middle 1980s, and they seemed to do best at under 6500 RPM with 4.30s and a 3600-3800 stall on an 11" slick.  Based on that old experience I would say that running a comparable package with a lesser converter and 3.25:1 gearing would sound great at the drive in, but would be a flat dead cat if you punched it from anything below four grand.  And in those circumstances the geared up tunnel port would eat your lunch and come back for dessert.

[My427stang]

You are getting good advice here from both Brent and Barry

I will tell you, if I were to build that engine and you were insisting that cam, I would run 11.25:1 to an absolute max of 11.5:1 on the street, ensuring that cam ended up on 102 ICL, no later. I'd be sure I tightened the quench up to .040, and run a decent amount of initial, likely 18-20, and adjust total for max power.  Then, I would err on the side of MORE gear than 3.25, not the 4.57, but not 3.25.  I think you may balance what you want with a 3.89-4.11, that would put you at 3300 rpm on the street at about 65 with a 3.89.  It's not a perfect combo, but with some good tuning, it'd live better than the 3.50 or 3.25

However as Brent said, the same care in building with a more modern grind will make more power, much more, and if you have very good heads, it's hard to recommend not taking advantage of them

I will say this though, blowing the tires off doesn't have to happen on slicks.  One potential possibility, I have one car I work on, 440 cid Rat motor, we kept dropping the launch RPM and it kept going faster, then we shifted 1-2 early and it kept getting faster and quicker.  I know suspension work is a bear, but that and tweaking every launch and shift point along with the suspension will likely get you there better than a gear change.  Owner didn't believe it, used to rev it to the moon at launch and 1-2. 

[cjshaker]

Everyone seems to be ignoring this 'first hand' and 'informed' comment, by someone who actually used and raced with this particular cam. Theory and conjecture mean squat compared to actual experience, and this experience says a lot, IMO.

"I'll go on record as one of the NHRA S/S racers that tried the "D" cam in a legal MR427, 2x4 TW manifold and was unable to even match the performance of the period Crane Z300-8 in the same setup. I posted my experience on the old FE Forum and was seriously flamed for the heresy of posting a negative review of a historically revered factory effort."
SSdynosaur

[Ranch]

About 6 month ago I sold an OEM C8AX-D for a hundred bucks, it was brand new never opened the tube sept to make sure I wasn't selling the guy a rusty stick.  I bought it back in the 70's along with the C4AE-B to replace my C3AZ-D cam in my 406 I even had my heads (C8AE-J) prepped for the big lift of the 'D' cam.  All I know was what a difference the 'B' cam made with 12-1 comp, but my experience with with the 'B' was it was not a so friendly on the street (also the days of heavy Zoom clutches) and that is what made me just put the 'D' up on the shelf for next 45 years. Now I have Comp 282-S with 9.8-1 definitely not as strong as the old 'B' but but still get compliments on the sound (2 1/2" MF 13256) and it pulls right out at idle.

[gt350hr]

   The D cam is very similar to the Crane F 260. In "roller terms" it would be like a solid roller with (around) 255-256 @ .050. As MANY have noted "every" engine doesn't need long duration cams! The D cam was good "for the time". Shorter duration higher lift solid and roller cams have surpassed it's potential. It is what it is and time has marched on. For those who want to own/run a legendary cam , they have the option. Many of us use the "modern" option instead.

[My427stang]

Everyone seems to be ignoring this 'first hand' and 'informed' comment, by someone who actually used and raced with this particular cam. Theory and conjecture mean squat compared to actual experience, and this experience says a lot, IMO.

"I'll go on record as one of the NHRA S/S racers that tried the "D" cam in a legal MR427, 2x4 TW manifold and was unable to even match the performance of the period Crane Z300-8 in the same setup. I posted my experience on the old FE Forum and was seriously flamed for the heresy of posting a negative review of a historically revered factory effort."
SSdynosaur

Good catch....

[WConley]

Let's not forget about reversion at low rpm.  A street engine spends a lot of time at idle or just putting around.  A big overlap cam in those conditions will eat spark plugs like candy    Intake port velocity is your friend!

[Joe-JDC]

My 452 FE MR with the D camshaft would go through spark plugs so quickly that I thought something was wrong with my MSD.  I raced the Mach I with 4.57 and 4.88 gears.  Joe-JDC

[1968galaxie]

Good to hear from actual users!

I have a copy of the "old" Ford muscle Parts Manual - a 79 page booklet - made in the 70's I believe.
Shows "stages" of performance increases - interesting reading for sure.
It certainly does make mention of the C8AX-D camshaft.

"This big stick's whopping 0.600" lift and 330 deg duration makes it strictly a full race strip and track cam. It will turn your mill to the 7000 plus range. So we only recommend it for engines that have been properly set up to handle those extremely high rpms. You can use it in a medium riser, but most likely you'll find it works best in a high riser or tunnel port 427"

There are plenty of modern recommendations that would make better power for street and race these days. For a replica of what people back in the day used it would be a fun project. (As long as the end result would be understood.)

Power output of a race 427 in the late 60's? 500 HP?
Power output @ 427"with today's tech?

[GerryP]

...
Power output of a race 427 in the late 60's? 500 HP?
Power output @ 427"with today's tech?

I don't believe anyone is taking the position that the "D" cam is the ne plus ultra example of a modern performance cam.  Your point is well taken, though.  The prevailing opinion of those screwing motors together with regularity and whose reputations depend upon abundant and reliable power have already staked out their positions, and have done the analytics to know what they're talkin' about.

This whole thread, while fascinating, has two incompatible perspectives;  1) The dyno proof and knowledge of camshaft events as experts who deal with this as a data solution, and;  2) those who have an emotional investment into the particulars of building an engine with this cam.  It will be very difficult for those two perspectives to coincide.

I say stab that cam in there and if it becomes too much of a pain, then take it out.  I would only offer that you should have a good "Plan B" cam and pick valve springs that will work with both cams to save yourself the expense.

[Gregwill16]

This whole thread, while fascinating, has two incompatible perspectives;  1) The dyno proof and knowledge of camshaft events as experts who deal with this as a data solution, and;  2) those who have an emotional investment into the particulars of building an engine with this cam.  It will be very difficult for those two perspectives to coincide.

I say stab that cam in there and if it becomes too much of a pain, then take it out.  I would only offer that you should have a good "Plan B" cam and pick valve springs that will work with both cams to save yourself the expense.

+1

[1968galaxie]

+2

[Katz427]

I think some of the discussion is how much power did the engines actually make back in "the day". I was having some conversation with an old racer, just a day ago. Dick ran a Ford powered super-modified up on Northeast tracks like Oswego, NY, and Thompson CT.  He changed to a BBC when he was able to buy a 496 BBC. His recollections are useful, I think. Dick always felt the hi-riser was a better all-around head for a 427 Ford. He said his driver's thought the hi-riser pulled better off the corner, as compared to a Tunnel port.  Jim Shampine (rip) told me the same many years ago. Jim told me Holman Moody claimed about 550 hp with a 780/850 Holley. He ran that setup in his modified. Jim's super was a 427 hi-riser with mechanical Hilborn injection, which pushed it up considerably as well as they ran Pennsylvania "jungle juice" for fuel. Jim also switched to a BBC when Ford shut down the race program. The BBC didn't turn any faster lap times  ( than the 427 Hi riser) until he too got a 496 BBC.
I know this doesn't settle the camshaft question. But there are a couple of interviews with Robert Yates (rip) and his recollections were a NASCAR 427 tunnel port was making around 580-585 hp. The Nascar Boss 429 he said was producing about 620 hp in 1969. Another side was  Robert felt with "today's" technology ( year 2000) he would have been near 1000 hp with the 429.

[blykins]

...
Power output of a race 427 in the late 60's? 500 HP?
Power output @ 427"with today's tech?

I don't believe anyone is taking the position that the "D" cam is the ne plus ultra example of a modern performance cam.  Your point is well taken, though.  The prevailing opinion of those screwing motors together with regularity and whose reputations depend upon abundant and reliable power have already staked out their positions, and have done the analytics to know what they're talkin' about.

This whole thread, while fascinating, has two incompatible perspectives;  1) The dyno proof and knowledge of camshaft events as experts who deal with this as a data solution, and;  2) those who have an emotional investment into the particulars of building an engine with this cam.  It will be very difficult for those two perspectives to coincide.

I say stab that cam in there and if it becomes too much of a pain, then take it out.  I would only offer that you should have a good "Plan B" cam and pick valve springs that will work with both cams to save yourself the expense.

That's probably the best synopsis that I've read so far.   Lots of emotional arguments in this thread. 

The only thing that could blow-up though if he tries the D cam, is if it wipes a lobe.  Playing with flat tappets can be good data, but each time you swap one, you play roulette.   Non-coated tool steel lifters can help, but IMO, I don't use tool steel lifters without nitriding the camshaft too.