the new 215cc vortec heads


Staff member
HERES STANDARD VORTECS 170cc ... Vortec.cfm

matching the piston dish to the vortec combustion chamber and maximizing the quench area,
tends to reduce detonation, improve and speed up the combustion efficiency


MikeB said:
I've read a lot about max valve lift on stock Vortec heads over the years, and have heard everything from .440" to .480". Well, I just disassembled a pair, and here's what I measured for retainer-to-stem seal distance. (Checked 2 EX and 2 IN valves on each head using a dial indicator.)
its the attention to details and checking clearance etc. and time and care taken,
that makes the difference between a barely or average functional ,
and a rather exceptional engine build, yes the urge to get it running is strong,
but getting it done correctly is the goal


Head #1: .506" min / .509" max
Head #2: .535" min / .545" max

Allowing for .050" safety margin, and using the minimum clearance for each head, max safe valve lift on the two heads would be .456" for head #1 , and .485" on head #2.

Both of these heads are 1997 castings, and I'm pretty sure they're off the same engine. So it's true that there's a wide variance from head-to-head.

Conclusion: The guys on web forums who say they have safely run .480" cams are downright lucky, or using up a lot of of that .050" safety margin. I wouldn't run a cam with more than .450" lift w/o measuring first. Mine are going to the shop this week for a valve job and a little more retainer-to seal clearance.

On another note, the springs are very light with an average of 75# @ 1.700" and 180# @ 1.25". But hey, these STOCK 170cc L31 VORTEC CYLINDER HEAD engines were designed to make a torque curve as flat as Kansas from off-idle to 4000 RPM (or less)in a 350 SBC.
The L31 Vortec comes in two different casting numbers, 10239906 (#906) or 12558062 (#062). Originally, the stock #906 casting head was available in two versions. One version had an Inconel exhaust seat with single angle valve grind and was available on 1 ton trucks. The other version was the traditional three angle valve grind. Other than that, the #906 is the same as the #062 head.
GM Performance Parts Bowtie Vortecs are offered in “small port” (#25534351), which has 185cc intake ports/65cc exhaust ports, or the “large port” (#25534445), which features 225cc intake ports/77cc exhaust ports. Both GM factory and GM Performance Parts Vortecs come with 1.94 intake/1.50 exhaust valves. According to the engineers at GM, “Stepping them up to 2.02 valves doesn’t help them any, so it’s not recommended. The port was designed to match the 1.94 valves. With the Vortec flow velocity,

chevy has just announced NEW versions of the vortec heads which are designed for increased flow and are similar to the FASTBURN heads but the new vortec 215cc heads are CAST IRON with a 64cc chamber PART # 25534371 bare# 25534431 assembled
theres also a slightly improved 175cc version part# 25534351

read this link ... ck-engine/
Large-Port 215cc Vortec Cylinder Head Flow
GM part NUMBER 25534431
25534446 is the new improved version the older numbers been discontinued

Lift Volume Lift Volume
0.200 128.6 0.200 100.8
0.300 188.4 0.300 138.6
0.400 234.8 0.400 154.4
0.500 257.2 0.500 152.5
0.600 263.2 0.600 163.8
0.700 269.1 0.700 167.0
Vortec Bowtie Cylinder Heads. Vortec Bowtie cylinder heads are the most powerful cast-iron heads offered by Chevrolet Performance. These upgraded production cylinder heads are ideal for 400-450 horsepower street and racing (great for circle track applications) engines. Vortec Bowtie cylinder heads come with bigger valves, a thicker deck surface and 66cc combustion chambers. The heads provide outstanding low-lift flow numbers (the more air you flow, the more potential power) and Fast Burn performance all in an affordable, cast-iron head. Large Port Vortec Bowtie Cylinder Head Assembly. Completely assembled, ready to bolt-on. Improved air flow (281 cfm @ 0.600). 225cc intake ports. 77cc exhaust ports. 65cc combustion chambers. Use Fel-Pro® P/N 1470 exhaust gasket (minor trimming may be necessary). Bare head P/N 25534445, available separately. Technical Notes:. Cast-iron small runner or large runner cylinder heads. 66cc combustion chambers. 0.450 deck thickness. Hardened exhaust valve seats. Machined for 2.000/1.550 valves. Maximum 0.530 valve lift (without modifications). Straight spark plug design. No heat risers. Drilled and tapped for 7/16-14 screw-in studs. Dual bolt patterns for Vortec and early style intake manifolds (early model P/N 10051103; Vortec intakes P/N 12366573,12496820, 12496821, 12496822 or 12489371). Use intake gasket P/N 12529094 for Vortec intakes or dual pattern intake gasket P/N 12497760 for early model intakes or Vortec design intake manifolds. Dual bolt patterns for perimeter-style and center-bolt valve covers. Vortec intake manifold three-step torque specs: 2 lb.-ft.; 9 lb.-ft.; 11 lb.-ft. These heads are assembled with the following components:. 2363757 Intake Valves. 12363758 Exhaust Valves. 12551483 Valve Springs. 12552126 3/8 Rocker Studs. 10212808 Valve Spring Retainers. 10212810 Valve Stem Seals. 24503856 Valve Locks. Additional Required Components:. Head Gaskets 10105117 (2), 10185054 (2) OR 12363763 (2). Bolts 10168525 (14), 10168526 (4), 10168527 (16). Engine Application: 12366573, 12496820, 12496822, 12496820. Note: Larger intake and exhaust ports allow for more volume of air to pass through the engine. The more air you flow, the more power you can make. ... 857C0.aspx

these new heads are drilled and tapped for both old and new valve cover and both old and vortec style intakes, they have 2.00 intake and 1.55 exhaust valves and 65cc chambers
GM has also released a new 383 425hp crate engine part # `12498772

25534431 Vortec Bow-Tie Large Port Cylinder Head, Complete
Large-Port 215cc Vortec Cylinder Head Flow
GM part NUMBER 25534431
25534446 is the new improved version the older numbers been discontinued
matching intake


Lift Volume Lift Volume
0.200 128.6 0.200 100.8
0.300 188.4 0.300 138.6
0.400 234.8 0.400 154.4
0.500 257.2 0.500 152.5
0.600 263.2 0.600 163.8
0.700 269.1 0.700 167.0

GM Performance Parts' latest and most powerful iron cylinder head with "Large Port" for Street or Racing. This Vortec design Special Performance cast iron cylinder head features revised intake and exhaust ports and includes 2.00" hollow stem intake valve P/N 12555331 and 1.55" sodium filled exhaust valves P/N 12551313. The deck surface is .450" with 65 cc combustion chambers, 215cc intake and 77 cc exhaust ports. All Vortec intake ports are taller and narrower than early model Chevrolet heads. The valve cover mounting holes are for both early model flange and late model center. This head also includes intake manifold mounting holes for both early model 6 bolt main and late model 4 bolt Vortec design. The head has screw in rocker studs P/N 12552126, large valve spring pocket machining, and will accept up to .530" lift camshafts without modifications. Heads are identified with the Bow-Tie logo on the exterior of the head below exhaust flange and Vortec logo on top of intake port area. They also feature GM logo cast into bottom of intake ports. Includes valve spring P/N 12551483, valve seal P/N 10212810, and spring cap P/N 10212808.
Technical Note: You must use a raised runner design intake mainifold P/N 10051103 (6 bolt mounting), or Vortec design 12366573, 12496820, 12496821, 12496822, and 12499371 (4 bolt mounting) with this head. You can use production Vortec intake gaskets P/N 12529094 (torque spec. 11 ft-lb/ 15Nm) for mounting Vortec design heads or use P/N 12497760 (torque spec. 30 ft-lb) with conventional material when using on early model raised runner or Vortec design intake manifolds, this gasket has both 6 bolt and 4 bolt Vortec attaching holes. Head casting P/N 25534371C.

given a choice between the vortec heads , and if forced to use an iron cast head theres zero question Id select the larger 215cc port heads on a 383 and just select the dual plane air-gap design intake, compression and cam selection, and header design , rear gear ratio, converter stall or manual transmission gearing to tweak the power band up and down as required
the slightly larger port size on the larger heads allows you far more flexibility


the new larger port vortec heads have a far superior port design

GM Bow Tie Vortec Small Block Engine - Blue Thunder 355
This 632hp Small-Block Sports New GM Bow Tie Vortec Heads
Ro McGonegal Jun 1, 2005 0 Comment(s)

Grady began with a cast-iron, two-bolt main bearing block fitted with HTC steel billet main caps on the center three races that are secured with ARP studs. To strengthen the assembly, he also installed deck plugs. Then he prepared the block's lubrication system by plugging off the top of the engine, restricting oil to the top, and by the distributor boss.

"We plug the oil galley that goes around the distributor and feed it from the front. We also plug the hole behind the cam bearing and the one in front of the distributor. Then we drill a hole under the front cam bearing in the groove. This is something I learned from Ben Barnes."

Because Grady wanted to use a ring diameter of 0.040-inch, he held the bore at 4.039 inches. The idea is to make the most power possible with a flat-top piston so that the engine would seal exceptionally well, be able to pass a lot of air, and see as much compression as possible with the new GM Bow Tie Vortec cylinder heads. A common 350 block was stress-relieved and sonic-tested before the honing process. Grady used the same length studs used on the engine to secure the honing plates. By using a fine lapping compound under the spacers and washers, Grady makes sure that hardware doesn't spin when he torques the plates down prior to the honing procedure. If these pieces move upon the bolt-stretching sequence, they will likely distort the cylinder walls. Grady finishes the honing process with a Sunnen J83 stone. It's critical to use the same MLS gasket as you use on the engine and spray both sides of it with WD-40 (for extended reuse) so it won't stick.

Hank the Crank's billet arm is a jewel. Besides a Teflon-based oil-shedding coating (see sidebar), it hosts everything Hank Bechtloff has learned in 45 years of making crankshafts--though son Scott mapped out and executed the actual build. The 4340 steel assembly has been rifle-drilled to reduce weight, bringing the race-ready total to just 39 pounds.

Hank laid out the counterweights so the weight would be off the ends of the assembly and so it would not flex at high revs. He used a very small amount of heavy metal to retain balance, but only in the end counterweights, and in this way it was able to keep the oil-cutting surface of the counterweights absolutely smooth. Further, the shape of the counterweights and their placement is critical to gain horsepower. Hank employed a 1.8882-inch crankpin rod-bearing diameter (referred to as the Honda or Quad-4), the most popular size for Busch cars--and if you hurt it, you can easily go down to the 1.850-inch Nextel Cup size.

The mains are 2.300-inch (from 2.448-inch diameter main to a 2.2985-inch diameter) early-Chevy size to reduce the bearing speed with Clevite bearing spacer (MS1110HX). The crank has also undergone Accurate vacuum plasma ion treatment (the last of four heat treatments), a process that increases fatigue life 20-25 percent.

Grady likes Clevite products (PN CB1663-V) because he feels that they bed-in better than others. He buttons up the lower end with HTC steel billet main caps. For you hip street rats, HTC can supply an American lightweight forged steel crankshaft that costs $1,000 less than the billet unit.

The stroke was finalized at 3.470 inches and realized via 6-inch-long Carrillo steel connecting rods that weighed 525 grams.

The caps are secured with 3/8-inch Carr bolts that have a tensile strength of 285,000 psi. They use a 2.015-inch big end, and the rods have also been rifle-drilled to allow oil to pressure-feed the pins at all times.

The 100-gram Precision Products piston pins are 2.250 inches long with an 0.868-inch diameter, chamfered for wire locks, made from 9310 steel, and are Casidiam-coated, which is the critical ingredient when you run steel against steel as there is no bushing in the small end of the rod.

Featherweight 390-gram CP pistons have a flat top, a cam-shaped skirt, and flat-ring lands (note coated surfaces).

Ring seal is enhanced with a series of 0.062-inch gas ports (arrows). Scott Gabrielson broke out some special low-drag 0.043-wide plasma-moly top rings with a 4.040-inch diameter followed by a 0.043-inch second ring. Both are back-cut but only the second ring has a reverse bevel taper (RBT), and then some special 3mm SS50 stainless oil rings run with 10-psi tension. With these rings, the correct finish on the cylinder walls and the closer tolerance available with the piston coating, Grady sees an extra 35 hp.

Original L31 Vortec casting.
The new heads carry PN 25534371 and were the only ones in use at press time, but will be available through GMPP dealers by the time you read this.

New GM Bow Tie Vortec
Hank credits Lannie Barnes for securing them for Blue Thunder through the Scoggin-Dickey Parts Center. The 4371 castings have a much thicker deck than the previous Vortecs (see side bar).

The L31 exhaust port (top) looks like old tech;

GM Bow Tie port has definite D-shape, is raised up, and has a 77cc volume.

Grady puts them to the block with Fel-Pro 1144 MLS multi-seal gaskets. The 1144s have a stainless steel inner core and a super-bonding agent on both sides (less than $100 each). They feature a 4.100-inch bore size, a compressed thickness of 0.040-inch, and a volume of 8.5ccs. ARP studs secure the heads.

Vortec Bow-Tie Brief
There are two versions of the new GM Performance Parts Vortec Bow-Tie cylinder heads: This one, PN 25534371 (bare) and PN 25534431 (complete), with the larger ports, and another with smaller ports, PN 25534351 (bare) and PN 25534421 (complete) with 185 and 65cc volume, otherwise, the architecture and improvements over the L31 design are the same. We will test the smaller version very soon in a dynamometer exercise. We were able to get an exclusive look at the big-port heads just as they were used in a NASCAR-type application.

Out of the box, they feature revised intake and exhaust ports and are machined for a 2-inch intake and 1.55-inch exhaust valves. The deck surface is 0.045-inch thicker than the L31s, and it has 65cc combustion chambers, a 206cc intake, and 77cc exhaust ports (see Flow Chart). The head is also machined for 3/8-inch screw-in rocker studs and a large valvespring pocket, and it will accept up to a 0.530-inch lift camshaft without modification. These castings are identified by the Bow-Tie logo below the exhaust port and the Vortec logo on top of the intake port area. The GM logo is also cast into the bottom of the intake port runners.

All concerned will be delighted to hear that the head includes intake manifold mounting holes for both early-model six-bolt and late-model four-bolt Vortec design. Mandated GM intake manifolds include a raised runner-type PN 10051103 (six-bolt type) or Vortec design PNs 12366573, 12496820, 12496821, 12496822, and 12499371 (four-bolt type). Though production cylinder head and intake manifold gaskets are acceptable, the hot squeal is Fel-Pro (PN 1142 for the MLS and PN 1289 for the intake). As per Scoggin-Dickey, pricing is: small port 4421 complete, $499.95; small port 4351 bare, $269.25; large port 4431 complete, $539.95; and large port 4371 bare, $293.25.

Put Yur Coat On!
Harold Elliott knows better than most that the reciprocating parts must have an edge--a very slick edge--to compliment the engine builder's expertise and make his product a winner instead of an also-ran. He treated all the key elements of Harold Grady's bullet with a variety of friction-frying stuff. In a very brief explanation, this is how it goes:

Elliott coats the crankshaft counterweights with Teflon-loaded SL-11 in order so that the weights break the surface tension of the crank material so the oil won't stick to it and attempt to build up on the surface. The same goes for the connecting rods. He also uses SL-11 on the windage trays and the scrapers inside the Stef's dry-sump pan.

What he applies to the piston skirts, rod, and main bearings is called HM-30, which has is composed of a high percentage of molybdenum and makes the surface area much more durable in high-pressure areas. This allows the engine builder to tighten up his clearances as in the piston-to-wall area that will keep the piston straighter in the bore and aid ring sealing. Less clearance on the rods and mains means less oil leakage that will not collect in those areas, thereby not taxing the oil recovery system as much.

The HS-44 coating used on the tops of the pistons has a ceramic base, and therefore has very good heat-reflective properties. Keeping combustion heat away from the piston under the rings greatly improves the life of the piston and allows the builder to tighten the piston-to-wall clearance even more. Elliot does not stop there. Since the chambers, exhaust ports, and piston domes act as heat sinks during the combustion cycle and pull valuable power-producing heat from the area, he applies HS-44 to these surfaces as well. This coating is also applied to the tubular exhaust system in the interest of reducing under-hood heat and in presenting a very slick appearance.

"Invisible" Power
Strict rules tend to initiate creativity and engender the NASCAR racers' credo of "being competitive." In this case, we're not talking about bending the rules or exploiting their interpretation, but simply using the most effective (and legal) means to reduce power-robbing friction, increase parts longevity, and enhance power output. In no particular order, the arsenal includes the gas ports that are drilled beneath the top ring land to ensure the best and most effective cylinder wall seal. This venerable helper is worth about 20 hp. The right rings, gas ports, and cylinder wall prep can release as much as 40 hp. Coatings and treatments for piston tops, skirts and pins, bearing surfaces, and crankshaft counterweights yield another 25 hp. The smooth counterweights are good for 5 to 6 hp, the small main journals 6 to 10, and the small rod journals 4 to 6 hp. Hank figures that the HTC Dyna/Rev special center counterweights are worth 4 to 6 more hp.
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Staff member
Large-Port 215cc Vortec Cylinder Head Flow
GM part NUMBER 25534431
25534446 is the new improved version, the older part number
GM part NUMBER 25534431 has been discontinued

Lift Volume Lift Volume
0.200 128.6 0.200 100.8
0.300 188.4 0.300 138.6
0.400 234.8 0.400 154.4
0.500 257.2 0.500 152.5
0.600 263.2 0.600 163.8
0.700 269.1 0.700 167.0

The 355 Numbers
RPM Torque (lb-ft) HP
4,500 457.8 392.2
4,600 468.7 410.5
4,700 474.9 425.0
4,800 484.3 442.6
4,900 489.6 456.8
5,000 494.4 470.6
5,100 497.6 483.2
5,200 498.6 493.8
5,300 501.3 505.9
5,400 499.9 514.0
5,500 503.2 527.0
5,600 500.8 534.0
5,700 500.9 543.6
5,800 500.2 552.6
5,900 502.5 564.5
6,000 501.8 573.3
6,100 500.5 581.3
6,200 498.6 588.5
6,300 497.2 596.4
6,400 493.8 601.7
6,500 492.5 609.5
6,600 487.7 612.9
6,700 482.7 615.8
6,800 475.8 616.0
6,900 470.3 617.9
7,000 464.4 618.9
7,100 462.1 624.7
7,200 458.2 628.2
7,300 452.8 629.3
7,400 445.9 628.2
7,500 443.1 632.7
7,600 435.5 630.2
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Staff member ... ck_engine/


I've found BRODIX I.K. heads are very good quality, and decent value per dollar,
for a high performance street/strip style engine

trickflow 230cc makes a good racing sbc head choice

profiler 210cc is a good compromise race and street strip head

related info
USE THE CALCULATORS to match port size to intended rpm levels... but keep in mind valve lift and port flow limitations[/color]



yes theres no way you can ignore an engine that makes 632hp from only 355 cubic inches, its darn impressive.
but its basically an engine designed to race,
but as a guy thats built over 100 plus engines I can,t help but point out that if the same basic sbc engine was built on a dart block with 4.155" bore and a 3.875" stroke to build a 421 displacement and swapped to a set of heads like the profiler or AFR 210cc heads that flow in the 300cfm range,an edelbrock #2925 intake, 850cfm holley, and a serious solid roller cam on a tigher LSA with a bit more duration,and that same 12:1 compression ratio,a set of shaft rockers like that 355 used,

the results would be even more impressive
the large port iron vortec heads with mild port clean-up work can support in excess of 600 horse power, match those large port vortec heads to a 383-406 SBC with a single plane intake
and about 11:1 compression, too a low restriction exhaust, tuned headers,and gear the drive train to operate in the 3500rpm-6500 rpm power band and add a decent roller cam like a CRANE 119651 and you might be rather amazed at the results ... -23-degree
edl intake #2913 (vortec SBC head design)

also with the larger vortec heads (yes it would require a different single plane intake design
Large-Port 215cc Vortec Cylinder Head Flow
GM part NUMBER 25534431

25534446 is the new improved version the older numbers been discontinued

Lift Volume Lift Volume
0.200 128.6 0.200 100.8
0.300 188.4 0.300 138.6
0.400 234.8 0.400 154.4
0.500 257.2 0.500 152.5
0.600 263.2 0.600 163.8
0.700 269.1 0.700 167.0
watch the video, and like I stated many times,
its the combo of the engines,
displacement ,
cam timing
and the exhaust scavenging,
and the intake manifold design,
NOT the intake port cross-sectional area,
that are the most critical factors, in the engines lower rpm and mid rpm torque.
but for damn sure an intake runner port can be small enough to noticeably restrict upper mid-range and peak power significantly,
For 5 decades I've heard endlessly about how installing larger free-flowing cylinder heads would devastate the engine's ability to make any low or mid-rpm torque.
especially when Id suggest using a set of smaller 300cc-320cc, aluminum, rectangle port heads on a 496 BBC, or 200 cc-210cc heads on a 406 sbc, I was asked to build
yet on every engine I've ever had built or had some guy ask me to look at, to see why it ran a great deal less impressively than he expected it too,
they brought into my shop its was very obvious (at least to me) that it was the combo of low compression, too little displacement, with too much cam duration ,
a restrictive exhaust or some guy who was trying to save money and continuing to use a stock stall speed torque converter, or retain a badly mis-matched 2.87:1-3.08:1 rear gear ratio,
with an engine that he miss matched components by slapping a large carburetor , and a single plane intake on,an engine that will rarely exceed 6000 rpm, that was the major reason.
if you want an engine combo to run your first step is to logically match the list of components you,ll use to the application,
and that requires you stop, engage the brain and think things through carefully,
and the most common way to screw up the process is to over cam a low compression engine,
have a restrictive exhaust or mis-match the drive train gearing to the engines power band.
the most obvious option
,if your using iron vortec heads , and wanting to build a 383 from a later single-piece rear seal block,
is a dished piston,you want closer to 9.5:1 :D -9.8:1 :rolleyes: for pump octane gas
(I don,t know your high test or regular octane availability)
and Id use a .021 copper head gasket and only minimally deck the block,
lets say '002-.004 off to straighten the deck,or a deck height near 9.020
leaving more material for future work if thats required in the far future. max
be darn sure to order the pistons to match the bore diam,
as the pistons can be ordered in many over size options,
usually at little or no extra cost,
but if you fail to specify, exactly what you need..your screwed
Id call SCAT 1-310-370-5501

and ask if something rather similar,
in a balanced assembly
in a single rear seal,
3.75" stroke
18cc dish piston,
ideally with 7/16" ARP rod bolts,
in a 9000 cast steel or forged steel crank,
assembly with full float pistons
was available or could be put together,
I know Ive done so,
and got what I requested,
and for not much more cash in the past
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very impressive numbers even though it is pretty much an all out race combo. flow numbers are decent on the intake side but the exhaust seems to be lacking as is always the case with small block heads. id like to get my hands on a set of these to measure the actual port volume and see how rough they look in the seat /bowl area from the factory.


The Grumpy Grease Monkey mechanical engineer.
Staff member

reading the related info will be helpful
Cylinder Head Vital Specs - Power Curves
We Measure All Vital Specs on 8 Cylinder Heads
Bob Mehlhoff Jun 19, 2006
We tested power curves of several key cylinder heads and recorded the results. Our criteria for this examination was straight-forward: Each set must be under$1,000 in any port size and made from either cast iron or aluminum. We then flow-tested each set, bolted them to the same engine with the same camshaft, and dyno-tested the combinations for horsepower, torque, and power curve.

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Meeting our requirements were five sets of iron and three sets of aluminum heads. The advertised port sizes ranged from 165 to 220 cc, and of the eight sets sent, the Trick Flow heads eclipsed our $1,000 mark by $25.95. Rather than banning them, we took the opportunitiy to see how well they would perform under our scrutiny. The engine of choice was our invaluable mule, a 383 small-block Chevy fitted with a Comp Cams Xtreme Energy 274H with 230/236 degrees of duration measured at 0.050-inch lift and 0.487/0.490-inch valve lift. Why not? After all, it is very represen-tative of a typical performance engine found in most Chevys today. In the end, we not only gained tons of data, but also found that all the cylinder heads we tested demonstrated power curves to match a variety of performance levels at different costs.

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For days we beat the heck out of this 383 small-block. Eight paris of heads in three days. That means the cylinder heads and intake manifold on and off 16 times, 272 head-bolt torques, and 128 valve adjustments.

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To illustrate the difference between the heads, we placed them into three categories based on published intake-port size. Each category is matched to the engine's size and performance level. As an example, a moderately built 327 should perform well with cylinder heads from category I, whereas category III heads would be too large and should be selected for hot performance engines (typically larger than 400 ci). While greater port size does not guarantee increased airflow, properly matched port size and design promotes increased airflow without sacrificing velocity. This equals improved torque. Category I (179 cc and smaller) includes three heads: the Scoggin-Dickey upgraded Vortec 170, the Aerohead Racing 165, and the Edelbrock Performer RPM 170 head. Our Category II (180-199 cc) group includes three heads: the RHS 200, the Competition Products 180, and the Trick Flow 195. Finally for Category III (200-220 cc) we included World's Motown 220 and the Dart 215 cylinder head.On the following pages you'll see the specs for each head, including the true measured chamber and port volumes (as tested), valve size, weight of each head, and cost. Below that you'll find each cylinder head's airflow chart at a range of valve lifts. We've listed the torque and horsepower numbers for every rpm up to 6,100 and figured out the averages.

When surveying these test results, keep in mind the performance category you're trying to target. Your engine size, compression, camshaft selection, stall speed, and rearend gears each play a vital part in maximizing performance. Like all engine modifications, the cylinder heads you install, when matched to your engine's specifications, will help provide huge gains in power levels.

Quick Notes
We flog eight sets of cylinder heads
Five sets iron and three sets aluminum; advertised port volume range: 170-220cc
$1,000 or less



One of the bargains we tested was the Aerohead small-block Chevy head, featuring a larger com-bustion chamber than most tested. It should be noted that this netted a lower compression ratio. These reconditioned Dart Iron Eagle S/S heads pro-duced a healthy torque number of 475 lb-ft at 3,900 rpm and 430 horses at 5,700 rpm. With these heads you can gain power and save money.



The Edelbrock Performer RPM heads had excellent flow numbers, and they provided exceptional power and torque during our dyno testing. At 3,900 rpm these heads produced 491 lb-ft peak torque and 452 peak horsepower at 5,500 rpm, making them a great choice for many mild-to-medium street-performance engines.



The Scoggin-Dickey modified Vortec cylinder head was one of our price leaders at just $680 per pair. To allow the use of a 0.525-inch-lift hydraulic camshaft with these Vortec heads, Scoggin-Dickey adds high-performance late-model Z28 valvesprings with lightweight LT4 retainers and machines the valve guides for clearance. These heads produced an average torque number of 445 lb-ft, a large portion of it near the lower rpm band. Peak horsepower for this head ran in at 430, with an average of 392 at all measured points from 3,300 to 6,100 rpm. These heads make a great choice for a budget-built street car where good torque is needed. The use of these heads requires a special Vortec intake manifold and recommended head bolt kit. For our dyno run we used an Edelbrock Vortec Performer RPM Air Gap.



The RHS 23-degree cylinder heads come complete with high-quality Comp Cams components (valvesprings, retainers, and keepers). They unleashed 468 lb-ft of torque from the 383 small-block at 3,900 rpm and 422 horses at 5,500 rpm. This head incor-porated a larger 72cc cumbustion chamber, which produced lower compression on our test engine than the smaller 64cc chambers featured on many of the other heads.



At $880 the Competition Products cylinder head is the most economically priced aluminum head we tested, and the power numbers ran in at 470 lb-ft of torque at 4,100 rpm and 409 horsepower at 5,600 rpm. These heads produced good mid-range power.



This aluminum head from Trick Flow produced 496 lb-ft of torque at 4,000 rpm and 455 horses at 5,300 rpm. With its 195cc intake ports and 215-cfm flow numbers at 0.400-inch lift it was a good match for our 383 small-block test engine. Matched to a similar engine, you can have neck-snapping torque and big power. We went over our budget by $26, but at such a marginal cost, who are we to not test them? Besides, a week of brown-bagging our lunches made up the difference.



The World Motown 220 pumped out 478 lb-ft of torque at 3,800 rpm and 439 horses at 5,400 rpm. These heads, with their 220cc intake ports, are the biggest we tested, and it must be mentioned that the large port size would most likely work better on engines with more than 400 ci (such as the latest 427 and 454 small-blocks). Because our test engine was a smaller 383 we were not able realize the power numbers that these heads produce on big-inch small-blocks.



The Dart Iron Eagle heads pumped out 478 lb-ft of torque at 4,100 rpm and 450 horses at 5,600 rpm. The 215cc runners flowed 220 cfm at 0.400-inch lift and would be a good choice for larger small-block Chevys.

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