Reply to "AFD Alum heads"

Hi Kevin,

You've made some good choices, very reasonable, nothing wild & crazy. We can't do it "all" for $5K though. So, there's a couple of ways to go. One would be to do a good solid rebuild of the motor, install the parts that are within budget & plan a second partial tear down to install the parts you had to wait on. The second way to go would be to continue driving what you have and begin the rebuild when the budget has grown the necessary amount. Engine rebuilding/hot rodding always cost more than people anticipate.

The biggest bang for your buck will be the stroker kit. The 351C with 4V heads comes on the cam at 3000 rpm. Sitting on top of a 351 cubic inch motor, those big port heads want to run about 3000 to 7000 rpm. Add a 3.85" crank, and now the power band shifts downward to about 2500 to 6500 rpm, the increased displacement works the heads harder, improving throttle response. There is no question the heads are capable of "feeding" the extra displacement. The extra displacement AND the extra leverage of the longer stroke crank make more torque, and they make it in a more streetworthy powerband.

The second biggest improvement is a hydraulic roller cam. They open the valves quicker & higher, hold them open longer and then close the valves quicker too. The extra lift also works the Cleveland head harder and improves throttle response, BUT since you are now taking better advantage of the breathing characteristics of those heads, they reward you with big gains in torque (bhp) as well.

Lets talk about torque for a minute. Torque is what a motor makes Horsepower is simply [torque x rpm / 5252]. At 5252 rpm torque always = bhp. Making the most average torque over a wide band of rpm is what you want to accomplish, if the powerband is moved to a higher rpm, the bhp numbers get bigger, but the torque is still the same. Drag racers build engines that run at high rpm, they make big bhp numbers BUT they launch their cars at 4000 rpm or more. I doubt you intend to launch your Pantera at 4000 rpm, so a reasonable powerband, like 1500 rpm to 5500 rpm is a good choice and it makes me smile that you set your goal at that point. Your bhp numbers will not be as big, but you can make the same torque, and launch off the line at 1500 rpm just where you've chosen for the motor's powerband to begin.

You could do the partial build, and then find you like the motor so much you may decide you don't "need" alloy heads, unless of course the alloy head "look" is what you're after.

One question that people always ask, just because you've selected to go with a cam that provides a power band of 1500 to 5500 rpm, that doesn't mean your engine won't rev higher, it will. An engine will rev until something limits it; either the exhaust system, the carb/fuel system, the ignition system, the cylinder heads or the valve springs. If you do this engine right, in your case it will be the valve springs.

The crank kit & roller cam is where I would suggest you start, if you go that route, and add the alloy heads at a later date.

I strongly urge you to rebuild the motor and not just bolt hot rod parts on a "seasoned" short block. That's a formula for disaster AND you won't make the power you would with a fresh short block. More than anything else, making big power numbers is all about getting the rings to seal. Hot rod engine builders secret #1. I feel like I'm exposing the magicians secrets, but thats the truth. Power production is very much proportional to the amount of time spent on the rings. I have spent too many late evenings of my life filing rings & fitting them in cylinder bores!

There are some other important pieces involved in putting your motor together right, which is why the $5K budget isn't enough. You'll need to purchase a new balancer or have the current one rebuilt (a company called Damper Dudes rebuilds them). A 30 year old balancer is a problem waiting to happen, ask Murphy when that will be (you know, the guy with the "Law"). You will need a "good" set of roller rockers to compliment that high lift cam kit, rockers you can rely on not to fail & throw needle bearings around in your fresh new engine, Crane's gold series or perhaps the cast stainless steel rockers sold by Comp Cams & others. You'll need to install adjustable valve train in the Ford heads (if you go that route). If you retain the Ford heads, you'll also need new one piece valves & good spring retainers & keepers. I strongly urge you to invest in a large capacity, baffled oil pan, consider it motor insurance. You need a new ignition system, a distributor with an advance mechanism that works smoothly & reliably, and an ignition that will provide better spark at higher rpm than the stocker. You need a better exhaust system than the stocker, a good set of headers and larger diameter exhaust tubing feeding the Ansas, the oem 2" stuff is too restrictive. You're going to find Pantera exhaust systems are pricey! But without an exhaust system, your new engine will not run to its potential, you might as well not even begin the project, it's that important. You need a good carb to feed fuel to this motor, the spread bore Autolite will work, but not the early square bore Autolite. A 750 Holley is my recommendation beyond the spread bore Autolite. It doesn't matter if the Holley is a double pumper or a vacuum secondary, one gets better fuel economy, one allows faster acceleration, but they both flow the same. The Holley may need tuning by a pro depending upon the model you purchase. You'll also need a better fuel pump than the stocker to feed fuel to this new motor. The Autolite carb limits your chioces in intake manifolds, the Holley will fit just about everything.

This is a good point for me to stop, the intake manifold leads me to a question for you. What sort of an induction system are you invisioning, a high rise single plane manifold that pokes up through the engine screen and looks bad ass, or a manifold that keeps everything below the engine screen, nice and discreet?

Besides that question, which direction are you thinking of taking, waiting for the budget to build up, or doing a 2 part engine build up?

How'd I do so far? If I haven't made something clear enough, feel free to fire questions back at me.

your friend on the PIBB, George