Closed-chamber heads

JWR,

I pick up cc heads on e-bay for less than $600, but by the time I pay shipping, they can be $500 to $600 for a pair. They usually cost over $100 per head to ship.

If you've read the other posts on this subject, you must understand the oem Ford valves, spring retainers & keepers are a liability and they MUST go before you install the heads. Read my comments regarding the Ford valve train at the following post:

http://pantera.infopop.cc/eve/forums/a/tpc/f/5650045562/m/2380067104

The heads will raise the compression of a standard displacement motor about 0.8:1; not even one full point. They are most welcome on '73 & '74 motors that had only 8.0:1 compression from the factory. Assuming your '72 Pantera has a cobra jet motor rated at 8.8:1 compression ratio, your compression ratio will be increased to about 9.5:1. The change in compression alone is only worth about 3 to 6 bhp. The heads improve the snap of the motor, and many performance cams need more compression than 8.8:1, so upping the compression is needed to compliment hotter cams.

The real benefits of the cc heads are realized after having the block "decked", bringing the dome of the piston level with the cylinder head mating surface of the block at TDC. This will allow your motor to take advantage of the squish design built into the heads, and is worth at least 20 bhp.

Please read the folllowing post on this topic:

http://pantera.infopop.cc/eve/forums/a/tpc/f/5650045562/m/6700079993

Your friend on the DTBB, George

Hello JWR! I ran Your before and after data through the Desktop Dyno and here is what it 'spit' out. First; The compression ratio in '71 was advertised at 11:1, but was more at 10.7:1 and the Horsepower for that year was 'Rated' at 330 (at the flywheel, ALL the figures to follow are AT THE FLYWHEEL!!). In '72 the comp. ratio was lowered to 8.6:1 and the '72L was lowered even more, to 8.0 (The same as My '74L) So I will give you the figures for the '72L at 8.0:1 Comp Ratio. If you do NOTHING MORE than change to the 'High Compression Heads'(leaving the dished pistons in, and NO other changes), Your ratio will climb to aprox. 9.5:1 and the valve size will be at 2.19 Int. 1.71 Ex. (I don't know if the '72 heads already had the larger valves or not). These are two of the most significant changes you can make to the 'ENGINE' other than a Camshaft/Lifter change and a Carburator/manifold change. You Already have 'Tube' Headers. Your HP and Torque will raise from 246/337 @ 4500/3000 to 274/362 @ 4500/3000 RPM respectfully. This figure is calculated with the stock 'Dual Plane' Intake manifold and a 600 CFM Holley. A change to a 750 CFM will net 286 HP @ 4500-5000 rpm, with the Tq at 368 Lb/Ft @ 3000. When you go to a Single Plane manifold, as I recommend, the reading is 303 Hp @ 5000 and 362 Lb/Ft @ 3500 RPM. If you were to make ALL of the improvements that I did to My Boss 358 (.030 Over 351C) You can achieve 529 HP @ 6500 and 463 Lb/Ft @ 5000. And that is with a Hydraulic flat tappet cam. A 'Solid' Lifter cam will make an emmense improvement to 558 HP @ 6500 and 483 Lb/Ft @ 5000-5500. We all know that the 'Roller Cam' is King! Bringing the figures up to 590 HP @ 7000 and 506 Lb/Ft @ 5500. And that is with a single 4 Barrel Carburator! A lot of people will argue this, but, this program for what it is worth; 'SUGGESTS' That Stroking the 351c; although builds more Tourqe and at a much lower RPM, does very little for increasing Horespower. I.E. for the same bore of 4.033, a stroke change to 4.00" increases '0' Zero HP. While a stroke of 3.85" adds 4 HP. All this HP STILL 'Peaks' at 6500 RPM. With the Tourqe of 537 Lb/Ft for a 3.85" stroke and 549 Lb/Ft for a 4.00" stroke; Both peaking at 5000 RPM. Beleive it or Don't! This program is + or - 4.0%. I have ran the figures of numerous other members, who have actually had their Engines Dynoed and the results have been 'Right-On'! Being with-in 4-5 HP. This should help many of you decide on some of the parts you wish to lay your money down for. That is all; good-Luck with it!

Thanks for the replies guys.I plan on a cam change when I change heads & was thinking of the 270 comp cam with new valve gear.I thought I'd be geting more hp with the cc heads but would it be better to deck the heads than the block.Would intake work if I decked either.George,when you gain more compression by decking,don't you increase the chances of knock or pinging.How much compression on street gas.Also,Marlin I'd like to know more about your engine build.Thanks guys,I love this stuff.

JWR,

milling material off the head does nothing to close the gap between the head and the top of the piston at TDC, it only reduces the volume of the combustion chamber and raises the comression ratio.

For "squish" to work effectively on a street motor, the clearance between the squish areas of the head and the top of the piston, at TDC, must be 0.045" +/- 0.010", ideally the thickness of the head gasket (piston dome flush with the deck of the block).

As I wrote in another post, the cc heads aid in controlling the timing of the occurence of peak combustion pressure at the right time during the piston's stroke. This improved control over the peak combustion pressure results in less of a tendency for detonation to occur (aka knock or pinging). In other words, with a decked block & cc heads, you can run higher compression than you can with open chamber heads, or with cc heads and a "non-decked" block.

The compression ratio of a standard displacement 351C with flat top pistons, zero decked block and cc 4V heads is about 10.0:1. With this set up you can run a typical street performance cam on pump gas.

Keep in mind, the compression ratio is determined by the camshaft, cylinder heads and type of fuel. The camshaft grinder should tell you what compression ratio to set the motor at.

After making any significant changes to a motor, such as heads and cam, the calibration of the ignition and carburetion must be checked and adjusted on a dyno.

Your friend on the DTBB, George