I know y'all probably get questions like this all the time, but I'm hoping to at least get a good starting point reference. Let me start with some background info on what I got:

1971 F250 4WD with a 1976 460 by previous owner. Have installed the "straight up" timing set, blocked EGR port, Edelbrock 1406 carb, Duraspark distributor. Probably not relevant, but factory A/C, and also added by PO are power assist brakes and PS. Pretty much stock other than that. NP 435, Dana 44 front, 60 rear, 4:10 rearend. Truck weighs about 6300 lbs.

Got a set of C8 heads that have been rebuilt, but have done nothing to the exhaust ports. Stock valves and springs. Have a Holley 3310 780 cfm, which was recommended to me. I don't have any experience with Holleys, but I've rebuilt this one, and we'll see how easy it is to dial in. The 600 cfm Edelbrock does an OK job, but I feel it's lacking when I put my foot into it. Looking for an iron C8 intake, but will probably end up using an Edelbrock Performer 2166 if I can't find one. Thinking about working the exhaust ports on the D3 heads after they come off, although it would be smarter to just do the C8 heads and then do everything at once.

The truck is my daily driver, about 40 miles or so a day. I might do some light hauling, and I don't really use 4WD much except around the farm when necessary.

So I know I'm going to need rocker arms, studs, guide plates and springs. From my research I learned that these heads used positive stop shouldered studs and rail type rocker arms with 1.73 ratio. I'm having a really hard time finding stud-mounted non-roller rocker arms with a 1.73 ration. I've found some that are 1.7 but I'm not sure I can use them. I know that I'll have to measure for the right pushrod length. (An excuse to buy a new tool!)

I don't have a clue as to what cam I need. Somebody told me that "topping guides is a priority if you want valve lift above .530"... I don't even know what that means. Since I'm trying to stay away from any machine work, I have came to these conclusions based on my meager knowledge:

Hydraulic flat tappet - even I have figured out that much

Less that .530" lift - due to the statement quoted above, which I do not fully understand.

RPM range - Idle (or as much as 1000) to 4500 - based on my belief that I want the cam to "come in" early and that I won't be running high RPM's.

Duration 270 to 280, maybe less. Don't know if that is advertised duration or duration @ .50" lift. My choice on duration is based on my guess that this is relatively short and that for low end torque I will want a short duration.

I am eager to hear any corrections that you all may have.

So the cams I have been looking at are all similar to this Comp Cam #34-231-4. Spec are:
Advertised Duration 256/262
@ .50" Lift 210/218
Lift .514/.514
Lobe Separation Angle 111

Summit sells a kit with this cam, lifters, valve springs, retainers, locks and valve seals for about $400. The range on this one is 1000-5000 RPM, don't know if that is too high for me.

To tell you the truth, I have no idea what RPM range this truck operates in. Normally it's not like me to not know this sort of thing, but I've never had a tach on it. I just recently bought a used handheld tach so I can tune it properly. I'm not sure it's working right because I wound it up to about 2000 and it sounded like it should have been a lot higher. But it registers the idle at about 900, and that seems right to me.

I've also read arguments back and forth that that say something about having to mill .230 off when you use C8 heads on a D3 block. I'm talking from memory here and I can't find where I ran across that. Some say yay and some say nay, so I was hoping someone here could shine some light.

I guess the reason I'm having so much trouble finding definitive information on the innerwebs is that so many guys are building monster 500 or more HP motors and seems like they build a new motor every weekend with left over parts. I'm just a poor farm boy/shade tree mechanic working with a hammer, a pair of pliers and a propane torch. I figure to spend about $2000 on this -- I know that's not really much, and I've already spent about $600 of that.

Thanks for listening,
Norton

 

Im not too familiar with early block and head combos so I can't offer too much advice on that.
However that comp cam is what I am running, and I would highly recommend it. I am running it with 9.5:1, and it is very well behaved, some lope at 500 rpm idle, pulls 18" of vacuum, has a great torque curve and generally runs very well. I am at 400 ft/lb at 2000 rpm and peak at 505 at 4500. HP is 400ish at 5000.

 

Great! Thanks for the reply. Did you have any machine work done on your heads? The reason I ask is because when I go to look at the cam's specs on the Comp Cam website it says "Requires machining on cylinder heads" in the notes under the description. But, I can't find anything that tells me what the machining it is that needs to be done. I'll call the techline this week when they're open and see if I can clear that up.

I ran a wire from my coil into the cab of my truck today so I could hook my tach up while I was driving. At 60 I'm turning about 3500, 70 is about 4200, 75 is 4500 and 80 is at about 4800 RPM. Of course, that's assuming my speedometer is right. I'm pretty sure it reads too slow. Anyway, my daily commute is usually 70-75 once I hit the highway, by my speedometer.

So this sounds like it might be a good cam for me. I gotta get the lowdown on machine work. Then there's all the conflicting information on whether or not it's necessary to mill .230" off the pedestals to install guide plates. The source I trust the most insists that it's not necessary.

Oh, another thing that's in the notes at Comp Cams -- it says that adjustable valve train required. I've adjusted valves on motorcycles and once on a Chevy straight six. Sounds like a messy lot of fun on a V-8. Is it really necessary?

Thanks again,
Norton

 

Woa, just read back over that. 500 RPM, I reckon it does seem to lope. I'm idling at about 900 thereabouts. I'm hoping my compression will be about 9:1. I've wondered if maybe this cam might be a little too aggressive for me, I really don't know. But you shed a little positive light on it for me.

 

My heads are ported only; I went with comp's reccomended single springs(926-16) rather than the dual springs(924-16) because the singles don't require machine work, and my nearest automotive machine shop is 3.5 hours away. Same goes with the lifters, the 832-16 High energy lifters don't require adjustable valvetrain while the 862-16 Pro Magnum's do. No guide plates either.
This is what I mean by well behaved: That is all just barely off idle, pretty high load, and it sounds like I had the idle set around 750 or so that day, this is just where a bigger lumpier cam would fall on it's face, keep in mind I am turning those 44's with 4.10 gears, and a close ratio t19 that doesn't have granny low, the old 460 doesn't get any breaks, it is contoniously under high load at usually low rpm. I can pull it down to the point the tach no longer registers, give the pedal a couple pumps and it pulls right back up.
When I get heavy on the skinny pedal it will do stuff like this:

With my idle set anything above 750, there is no telling that I don't have a stock cam until I stand on the loud pedal.

I would reccomend stepping up to a performer rpm intake over a standard performer, the standard isn't a big improvement over the stock one other than weight reduction, and the rpm doesn;t penalize low rpm like the rpm range suggests it would, I run one with a 1" carb spacer on top.

Your rpm sounds very high, so your tach or your speedometer is off a ways, with 4.10's, a 4 speed and a stock sized tire(31" tall, 235/85R16) you should be right about 2800 at 60.

 

Thanks for the clarification on the machining. Yeah, I though my rpm sounded pretty hegh too. I'll have to find a way to check my speeds for sure. Your truck is badass.

 

I just got off the phone with a guy at Lunati. I was asking about their #80460. Specs are:

Advertised Duration 265/277
@ .50" Lift 216/228
Lift .518/513
Lobe Separation Angle 112

It shows that the operating range is 1800-5000 RPM, but he said that it would come in at around 1400. This is the only thing that kind of puts me off this cam. 1800 seems a little high to me. I can get the whole deal with lifters, springs, retainers and locks for around $300 from Lunati. Still trying to figure out what length studs I would need. He also said that I would have to cut the pedestals down for guide plates.

I'm experiencing the snowball effect now. I'm thinking it would be a shame not to go ahead with new pistons as long as i'm doing everything else. That might be a whole nother can of worms.

 

i think you would be better off with the comp cam, it has a much lower power band.

 

I would like a lower power band for sure. I'll poke around some more.

 

I got a reply to an email that I had sent in to Lunati this weekend. They have a very detailed questionnaire to fill out when you request cam recommendations. They suggested the #10340700:

Advertised Duration 250/256
@ .50" Lift 207/213
Lift .503/.535
Lobe Separation Angle 112/108
Ranges Idle-5000

or the #10340701:

Advertised Duration 256/262
@ .50" Lift 213/219
Lift .535/.540
Lobe Separation Angle 112/108
Ranges 1000-5500

Not really knowing where the line is between a mild cam and a more radical cam, my first reaction is that these cams look a little too aggressive for me, just looking at the number compared to what I had been looking at before.

 

I'll fire up engine analyzer when I get home and punch in the numbers so we can see what kind of power curve they deliver. Both of them look to be not too agressive.

 

Hey thanks. I was wondering if that was enough lift to worry about the pistons with no relief cuts. But then I have dished pistons, so shouldn't be a worry anyway, should it?

 

With the lower duration, the idle will be good and shifts the power band lower...the extra lift (by comparison) will have an effect of almost port relieving the heads...it will definitely make the engine BREATHE!!!!!! This will really wake up the torque/throttle response of the engine!!!!!!!!!!!!!!!!!!

 

I got an app on my phone to day to check against the speedometer in my truck. It's at least 5 MPH too slow, depending on how much you trust GPS speed measurement.

 

Sorry it has taken me forever to get this done, my internet connection has been down at home, sometimes not being on a wired connection sucks.
This is a generic 460, so the peak numbers aren't that important, we are out to compare power curves here.
This is the first Lunati Grind:


The Second:


Both together:


Same engine with my Comp X4 256/262:


Almost has me wanting to change cams.
You can see the drop in low rpm power the bigger cam causes pretty readily though.