Reply to "AFD Alum heads"

Hi Kevin,

Again, you are making good choices, I will spend most of this post writing about cylinder heads, but I want to touch on the subjects of crankshaft weight and intake manifolds (inlet manifolds for you Aussie guys!).

Regarding lightened rotating parts, I don't want to put myself in a position of providing info contrary to Dennis Q, he makes a living building engines, so I'm not going to write anything controversial, I'll just provide the facts and let you make your own decision.

The weight of the rotating assembly in the 351C was not chosen haphazardly. It was engineered by the designers of the 351C based on many factors, including ease of operation in the vehicles it was intended for installation (Torinos & Mustangs). Lightening the reciprocating assembly is a two edged sword. A heavy rotating assembly is easier to accelerate from a stop, easier to operate at slow speeds like in parking lots, less prone to spin the tires, easier to operate in stop & go situations. A lighter rotating assembly accelerates faster, which is very fun once the vehicle is moving and traveling faster than parking lot speed. But there are 2 drawbacks, first it makes the vehicle more difficult to accelerate from a stop and operate at slow speeds, second it makes the vehicle more prone towards spinning the tires, i.e losing traction. The first drawback is not a consideration if the vehicle is strictly a competition vehicle, but its a bear if the vehicle is operated on the street. A lighter rotating assembly "can" be an advantage on certain race tracks, but it can be a disadvantage on other tracks, it depends upon how good the traction is on any given day. The fine line between having traction and losing traction under acceleration becomes more difficult to control as the rotating assembly gets lighter. It is one of the things professional race teams juggle when setting a vehicle up for a particular track, both in motorcycle racing and auto racing. Spinning tires do not accelerate a vehicle, they slow a vehicle down and make it too difficult for the driver to control. With motorcycles we will add weights to the ignition rotor, we'll have several rotors with various amounts of weight added so we can experiment to find the ideal set up, we also replace aluminum clutch plates with steel plates to achieve the same affect. I will make one strong statement, do not lighten your rotating assembly if you plan to ever drive your Pantera in the rain, on wet surfaces.

A Pantera is lighter than a Mustang or Torino, so no doubt the reciprocating assembly can stand to be lightened a small amount without ill effect. And I can't argue that building a much more powerful cleveland motor, something other than the oem cast flywheel is needed. You'll also need more clutch, to transmit the additional power without slippage. It doesn't matter what material the flywheel is made of, steel or aluminum, the question is, how much weight can your new clutch & flywheel assembly lose in comparison to the oem assembly, before your Pantera becomes a SOB to drive on the street. You may want to speak with Coz, as he recently installed an alloy flywheel on his Pantera.

On to intake manifolds. For the powerband you are aiming for, a 2 plane manifold would be the best choice for a single 4 barrel carbureted engine. But I think you are wanting a high rise single plane poking out the back. That's OK, you aren't alone by a long shot. I think it looks BITCHEN too. The long runners of the high rise intakes actually make more torque, but the 2 plane manifolds work better below about 3000 rpm. You'll notice the advertised powerband for most single plane intakes starts at 3000 rpm. However, many high rise intakes are designed with small volume runners & plenums because the designers had low rpm throttle response in mind. So it is possible to run the high rise intake on the street without much penalty in the way of throttle response, especially with the heads you'll be running. This does normally require some custom carb jetting however, so be prepared.

Finally getting to the subject of cylinder heads, I agree with you, with such good choices in alloy heads available for about $600 extra bucks, it doesn't make much sense to pour money into the iron heads. I had to give you choices however, not knowing where your mind or budget are at.

If you want to run Ford Motorsport high port heads, the best choice would be the smallest port, C302 head, and matching A331 Jack Roush intake. If you're buying used heads, you'll want a pair that have had very little porting done. If they've been ported to operate at 8000 rpm, they have been ruined for your uses. Those parts were popular among the Pantera crowd because at one time they were the only choices if you wanted alloy heads. Pantera headers are available for these heads. You cannot just go out and buy these parts, you have to hunt them down. The combustion chamber design in the Motorsport heads is 30 years behind the times. But the ports are very good.

Ford A3 & B351 heads: big ports. Blue Thunder heads: big ports. Brodix BF 300 heads: big ports. Yates heads: the valves aren't canted, they require Yates pistons & Jesel rocker arms. You could run these heads on the street, but I think better street heads are available.

I'll spend the rest of this post writing about the alloy street heads that are readily available. And I am going to throw 4 of the alloy heads out the window right off the bat. The Edelbrock head so far is very much an unknown commodity, and people are speculating its aimed at the show & truck crowd more so than the performance crowd. I really can't say, its performance is too unknown for us to consider at this time, so out it goes. The CHI 185cc 3V head is aimed at the 351 cubic inch motor, and not at strokers, out it goes too. The CHI 4V head would only be a consideration if you were wanting to run a specific 4V intake manifold, like the Holley Strip Dominator or Blue Thunder; you're not, so out it goes. The last head to get the axe is the AFD 4V head, that head is a high rpm strip head. Very big ports. The intake ports are close in size to the intake ports of the Ford Motorsport A3 head. It is aimed at use with the Parker 4V funnelweb intake, another big power item.

That leaves for your consideration the CHI 2V head, The CHI 218cc 3V head and the AFD 2V head. I see your needs as being best met with a motor that emphasizes torque in the lower rpm range (in spite of the fact you're going to run a single plane intake). I agree with David Webbs choice of his 2V heads, but I don't quite understand why CHI recommended the 218cc 3V head over their own 2V head, unless of course they want to sell you an intake manifold as well, because they don't manufacture 2V intakes. Lets look at these 3 heads, there are shades of differences between the 3. I'll start with the "smallest" head and work my way up.

The CHI 2V head has an intake port of standard height and 190cc in volume. The AFD 2V head has an intake port that is raised 0.10" and 200cc in volume. The CHI 218cc 3V head has an intake port that is raised 0.375" and 218cc in volume. Compared to the first 2 heads, this last head will emphasize torque production at a higher rpm. As a side note, the intake port of the CHI 218cc 3V head has close to the same volume as an "out of the box" version of the intake port of the Ford Motorsport C302 head. Without running these parts side by side on a dyno, it is foolish to say which one would work best for you. All 3 would be good choices, there are no dogs in this trio. I think you can see the CHI 2V head will emphasize torque production at the lowest rpm, the CHI 3V head will emphasize torque production at the highest rpm and the AFD 2V head falls somewhere in the middle.

For intakes, with the CHI & AFD 2V heads you'll want to run the Parker 2V funnelweb. AFD is advertising a new line of manifolds designed in house, but I have heard nothing about them, I don't even think they're on the market yet. The Parker manifold is a known good intake. With the CHI 3V head, your best choice will be their own intake designed for the 218cc 3V head and Holley 4150 carb, on the Cleveland block. Be ready for sticker shock, these Aussie intakes run about $500 clams USD.

Is that enough info for you to make an intelligent choice? If so, the next thing to discuss are the needs of the Cleveland engine in regards to rebuilding the short block. Whenever you're ready.

Kevin, if you or anybody has questions, fire away!

Did anybody notice I didn't confuse the issue by talking flow numbers? They all flow good enough, there is no such thing as a bad Cleveland head.

your friend on the PIBB, George