Alternate BBC OVAL PORT intakes


The Grumpy Grease Monkey mechanical engineer.
Staff member
Mark said:
I currently am pleased with my combination although I can't leave well enough alone.
I'm limited to a low profile intake beacause of my steel hood and don't want to change it.
Currently I run an aluminum oval port, split plenum OE style quadrjet intake port matched and a hand made
0.060 thick adapter plate to fit my square bore EFI. I developed peak torque at 3900 and HP stops at 5900.
The torque curve is prettty broad and I am wondering if an open plenum will move my HP up the RPM range enough to make a difference. The bottom end is REALY HARTY so 6500-7000 to it is no issue.
Any thoughts?

the edelbrock


is your best option with that hood clearance issue, its easily worth a few extra hundred rpm and maybe 12-15 extra hp and takes about 20 lbs off the car.
removing the divider wall in that O.E.M. cast iron intake plenum does little but reduce the off idle torque

Mark said:
I will admit that I don't want to lose any off idol torque but this engine combination really delivers on the low-end so it's probably of no major harm.
Rear wheel measurement I'm getting about 300 foot pounds at 2500 RPMs and going up as high as 460 at 4,000 RPMs

I doubt youll notice any negative results if you go with that torquer intake, the fact that the
edelbrock intake design has a common plenum designed to flow better than the stock intake,
should help the EFI on that larger displacement..noticeably

my brother-in-laws swapped from the factory cast iron intake to that intake on his 1974 BBC,
low compression 454 and while it failed to provide a huge power boost
its maybe 15 hp increase was a marginal improvement he felt happy with,
and it removed a good deal of weight and looks noticeably better than his old rusted intake did.
he had the same hood clearance issue on his 1974 corvettes and did not want to change the original hood.

Mark said:
I guess what's driving this is that comp cams tells me my camp should continue to pull up to 6300 RPMs and when I took it to the dyno it was tapering out at 5900 so I'm losing 400 RPM somewhere.
I'm going to run it on the Dino again but this time I'll leave the air cleaner off and I'll make sure the butterflies are fully open. The car had its original throttle linkage and there is a bit of playing it of course 50 years old so I've now converted to a cable and that should manage the butterflies a little bit better

probably more related to well worn valve springs than much else, a new set of beehive valve springs,
of the correct , seat and open load value and the smaller and lighter weight retainers they use should correct that issue.
this thread should be in MUSCLECARS ENGINE section, do you have any problem if I move it and maybe some of your other conversations concerning parts,there?

Mark said:
If it was an old motor I would tend to agree. The heads are about 1 year old Brodix with all the trimmings. I have verified with them and the spring manufacturers that the setup is good.
You may recall I run a throttle body EFI from FiTech. Out of the box it flowed 850 on a bench (so I was told). They used a QuickFlow baseplate for the 4150 and it looks like the 1 11/16" unit (need to measure). Keeping in mind this system does not have any boosters hanging in the way I really expect it should flow more than that. I figure with my parts combination I may be in the high 80s of VE. That being expressed the 850 should support "my" 496 up to 6500 since (496x6500)/3456 = 932cfm for 100% VE. By my calculations if I was to be 90-92% VE the throttle body volume is not the issue. I am thinking that either my manifold wont flow well enough or either my air filter limited me or my butterflies we not reaching 90°.
I'll check later since I logged my dyno pulled and it will contain my TPS counters. That will tell me a good deal.


THE edelbrock intake design has a common plenum

designed to flow better than the stock intake,
should help the EFI on that larger displacement..noticeably

remember the stock intakes split level plenum won,t work as well with the EFI

Mark Bradley

Da guy in Newbury
Time will tell if I made the correct choice although after calling BRODIX I just pulled the trigger on the low profile dual plane "HV2017-r" from BRODIX.
It is the Dual Plane oval port CNC port matched manifold that matches my heads specifically and has a RPM range of 3000-6800.

I measured the existing manifold and it has a sloped carb base measurement of 4.8125" (rear 5.375" & front 4.250"). The HV2017 has a flat carb base at 5.175".
I am anticipating since my 14" air cleaner will now be flat rather than sloped the slight increase (0.3625) in the middle will be fine and the high point (5.375") at the rear of the existing is taller than the new (5.175").
The reason why I did not choose the Edelbrock is I wanted to avoid an open plenum if possible since I drive this car daily.


The Grumpy Grease Monkey mechanical engineer.
Staff member
thats a common assumption based on the effective operational rpm band of most open plenum single plane intake designs,
but the low profile oval port intake has a rather small plenum in comparison and while it is a single plane intake its designed to operate in the nearly same rpm range as you listed
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The Grumpy Grease Monkey mechanical engineer.
Staff member
let us know the details of how it fits and functions once its INSTALLED AND TUNED

if your taking the effort to do accurate research BEFORE,
you start buying and assembling parts

Mark Bradley

Da guy in Newbury
Well the new BRODIX HV2017 manifold arrived from JEGGS today ($440.00). Not really impressed with the finish work and I AM GOING TO CALL BRODIX. They spent the time to CNC cut the ports to match my BRODIX heads but they left the flashing inside the plenum. It is a "Dual Plane" although there is not divider so it may as well be an open plenum with two floors.
I'll clean it up but REALLY!!!! For what this thing costs the airpath finish should be tidy.
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Mark Bradley

Da guy in Newbury
Well the installed height is identical so there are no clearance issues.
I'm going need to give it a little time for the ECU remap if needed.
A very interesting observation is that the intake ports are so different that BRODIX does not use the bolts above/between the runners.



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Mark Bradley

Da guy in Newbury
Let me just say "what a difference" the manifold made. The proof will be in the Dyno results but it will be a few weeks before I do that again ($$).
I expected to get a little bog off idle because of going to a dual plane without the separator.
Because I use Electronic Fuel Injection it is simple to modify the fuel delivery on the fly.
I simply dialed up the systems Accel setting and sensitivity to TPS so that it over comes the bog.
OMG this manifold changed my motor beyond my expectations.
I had installed Dunlop W rated tires previously and could not break them lose from a roll... ultill today. 20mph stabbed the throttle and they busted lose without hesitation.
I do see my vacuum is now MUCH lower at idle.

Time will tell.


The Grumpy Grease Monkey mechanical engineer.
Staff member
yes that single plenum design works better with most EFI systems

Mark Bradley

Da guy in Newbury
I think the debate as to whether EFI likes single plane or to a dual plane will probably be raging for a long time.
The value for me is the flexibility it provides day over day can't be touched by a carb.


The Grumpy Grease Monkey mechanical engineer.
Staff member
yes thats true enough, but a centrally located throttle body and injectors is a bit similar to a carb in that the runners flow a fuel/air mix, so any turns in the runner at least in theory restricts potential max flow and potentially allows some fuel to drop out of the air flow, as it impacts the runner walls
while mpfi with a dedicated fuel injector supplying every individual cylinder. is even more consistent
a dual plane design plenum effectively divides the engine into two 4 cylinder engine operating in the same block on the same crank,this has well documented advantages in the lower and mid rpm ranges but tends too restrict upper rpm power

an engines Torque peak is almost always very closely related to the point in the rpm curve where the most effective/efficient cylinder fill, cylinder fill is related to both intake port cross sectional area and exhaust scavenging,efficiency, and is limited by port stall, and cam duration in relation to displacement, compression and valve train stability, ...all factors are easily calculated
a spit dual plenum tends to increase air speeds but restrict max flow rates at peak rpms and certainly has less consistent flow rates between individual runners,






larger intake manifold plenum volume TENDS to allow higher rpms
throttle body efi acts like a carb, as the injectors dump fuel/air in the plenum







direct port fuel injection has a separate, individual fuel injector feeding each cylinder, the plenum essentially runs mostly dry air free of fuel


a single common plenum allows all air flow through the throttle body to supply all runners equally



useful RELATED INFO you might want to read port size headers head flow required head flow rpm stress limitations

calculate horse power from intake port flow rates[/quote]

a runner that flows only air ,and has an individual fuel injector fogging fuel into the cylinder head port rather than having the fuel mist in the plum being carried by the air flow into the manifold ports can be more consistent,and the most tuneable versions (individual stack injection) allow the tuner to change the intake runner length to maximize the inertial pulse strength and frequency to maximize cylinder fill rates by matching the exhaust scavenging timing






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Mark Bradley

Da guy in Newbury
It has been a week or so now and it is time to check how the EFI has adjusted.
The off idle start had been a little difficult since changing to the new manifold. Idle vacuum dropped from ~10" to 7.5". Cruise (2400 to 3000) vacuum does not seem to be much different from before.
I used the EFI logging to conduct a few experiments on the performance around drivability.
The tests were..
Cold start - warmup
Casual stop sign roll away
Casual gear climb
Flat 1 minute cruise
Passing lane acceleration (same gear)
Deceleration with engine brake (no brake, lift foot off the throttle).
The image above is a warm up cycle and the key is the IAC. This is the equivalent of adjusting your idle circuit and EFI changes it for me as it warms up. An ideal IAC would be between 3 & 10 when warm.

This is the chart of the cruise followed by a moderate and brief acceleration. The key is general consistency of AFR target vs measured at cruise.

This would be my passing lane change test followed by deceleration.

In the last image I know it is pretty busy but there are a lot of points of interest. The two orange circles just indicate fluctuation between desired vs measured AFR at some noisy points.


The Grumpy Grease Monkey mechanical engineer.
Staff member
looks like your getting things under control, what is your general consensus,
as to the intake change and the resulting changes youve seen,
and potential power gains and drive-ability,
your experimenting over lower,rpm, mid rpm, and peak rpm power?

Mark Bradley

Da guy in Newbury
I won't have hard numbers until I take it to the Dyno maybe 30 days or so.
Overall I am happy from a drivability perspective. Initially the early bog was a concern. Fortunately tuning with EFI is so much easier than jets and squirters.
Having REAL data to work with is great.

Mark Bradley

Da guy in Newbury
Stil have not made it to the dyno although I figured out the cause of my low vacuum. Rather humbling to be honest.
I had two failing spark plugs and I dismissed them because they only had a hundred miles or so on them. Fortunately by habit I change plugs more often than most people and I save my previous set. It was clear that one plug on each side was soot covered. In with the spare set and the vacuum came up.
See folks... this is what happens when we say “it can’t be that because they are new”.
Generally the bottom end is still a little soft but 3000 plus feels much better.
It is almost trivial to over power the tires so rolling into the throttle is amazingly fun.
I have spent zero time with tuning although I will and can probably help some of the low end with some more fuel... logs will help.
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The Grumpy Grease Monkey mechanical engineer.
Staff member
Oval Port Big-Block Chevy Cylinder Heads - The Big O

The best way to illustrate the power potential of performance cylinder heads is on the dyno.
Richard Holdener May 18, 2012
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Ask a big-block enthusiast what they need to make 600 hp and chances are they will point to some sort of rectangular-port head. No one in their right mind would select an oval-port head to make that kind of power, let alone one with a diminutive 265cc intake port, right? Well, big-block fans, times have changed and so has that well-defined line between the pedestrian oval-port and rectangular-port performance heads.

Back in the day, all the factory high-performance Rat motors were sporting rectangular-port heads and the street/strip crowd followed suit. But that was then and this is now. The aftermarket has stepped up in a big way and produced oval-port heads that not only out-flow any factory rectangular-port version, but do so while dramatically reducing port volume. The combination of more flow and less port volume makes these oval-port heads a much better choice for your street/strip motor than their rectangular-port counterparts. For motors up to and even beyond 600 hp, especially small-displacement big-blocks (under 500 inches), the hot setup today is more than likely an aftermarket oval-port.

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With oval-port heads taking the street/strip market by storm, we decided it was a good idea to take a long hard look at them and thoroughly check out the performance potential. This meant gathering a number of different oval-port cylinder heads and putting them through their paces, both on the flow bench and the engine dyno.

First up, we needed a suitable test motor. We decided on a 0.060-over 454 equipped with a forged crank and forged rods from Procomp Electronics matched to a set of forged pistons from Probe Racing. The pistons feature an 18cc dome to help provide a streetable static compression over 10.0:1 with the 110cc chambers employed on a couple of the oval-port heads.

Many of these heads offered combustion chamber volumes below the 120cc range used on most rectangular-port heads. The smaller chamber (relative to factory rec-port heads) improved power by increasing the static compression--always a plus. The test motor also featured a healthy hydraulic roller cam in the form of an XR300HR from Comp Cams. It a 0.560/0.580 lift split, a 248/254 duration split, and a 110-degree LSA. All testing was run with an Edelbrock Victor Jr. intake fed by a Holley 950 HP carb.

Before being run on the engine dyno, each of the heads had to be mocked up to determine not only the appropriate pushrod length, but also the correct head bolt/stud combination. Our 2.25-inch dyno headers presented a problem for the heads equipped with stock port locations and required use of head bolts in the lower holes to provide adequate clearance. A few of the heads required different middle stud lengths, but ARP helped cure the situation. All we had to do was juggle the necessary bolts and studs to properly secure the heads. Thanks also goes out to Fel Pro for supplying the necessary head and intake gaskets for our test.

The test Rat was finished using a set of hydraulic roller lifters, timing chain, and a couple of different sets of pushrods from Comp Cams. Comp also supplied the aluminum roller rockers (1.7 ratio) for our head shootout.

The finishing touches included a Milodon oiling system, an electric water pump, and balancer from Procomp Electronics. Prior to their time on the test mill, each head was given the once over on the flow bench, then set up to measure port and chamber volumes.

The heads supplied for the test shared the oval-port configuration, but that doesn't mean they were all the same. We started with a factory oval-port head to establish a baseline, in this case the peanut-port variety. We hoped to include a traditional oval-port head as well, but it fell through at the last minute.

The heads from Dart and Procomp Electronics were as-cast with no additional machining of any kind. Heads supplied by Brodix and Trick Flow Specialties both featured port matching, but the Brodix head carried it one step further with CNC work on the combustion chamber. The AFR, Edelbrock, and 049 heads from Dr. Js all combined full porting and chamber work.

As expected, the level of work applied to the heads resulted in differences in flow and power. Take note that the combustion chamber volumes varied from 110 cc to 121 cc, resulting in a difference in static compression of 1 full point. This alone was worth 3-4 percent in power, so bear this in mind when reviewing the results.

The one upgrade we would like to see on many of the heads is more valve spring pressure. At the top of the power curve, some suffered slightly due to inadequate spring pressure.

Power and price usually go hand in hand, but check out the retail prices to determine how your favorite does in the all-important bang-for-the-buck category. Next month, we'll be testing some popular rectangular port heads on a larger-displacement Rat.

Test 1: Chevy Peanut-Port Heads

Our intention was to run a set of stock peanut-port heads and a set of stock oval-port heads, but our oval-port heads fell through. The stock peanut-port heads featured a 2.06/1.72 valve combination with 118cc combustion chambers. Closer inspection revealed that even our "stock" peanut-port heads had been milled sometime in their long life. The small valves, port volume, and flow numbers made them less than ideal with this healthy hydraulic roller cam, but they surprised us by exceeding 500 hp with peak numbers of 512 hp and 514 lb-ft of torque. Looking at the graphs, the peanut-port heads actually ran neck and neck with the aftermarket heads up to 4,500 rpm, which makes them ideal for intended low-speed truck applications. With a little porting, they make good heads for a mild street BBC, especially a small-displacement 396.

  • Notes: Out-of-the box 360 castings
  • Retail Price- N/A
  • Intake Valve Size-2.06
  • Exhaust Valve Size-1.72
  • Intake port vol-253 cc
  • Chamber Volume-117 cc [milled]
  • Peak Power-512 @ 5,800 rpm
  • Peak Torque-514 lb-ft @ 4,800 rpm
  • Avg HP [3,500-6,300]-453.4 hp
  • Avg TQ [3,000-6,500]-489.9 lb-ft
  • Tq @ 4,000 RPM-508.5 lb-ft

Flow Data: CFM @ 28-ins

Lift In EX
.050 33 24
.100 57 51
.200 117 94
.300 185 128
.400 233 158
.500 247 179
.600 250 297
.700 250 211


Test 2: Airflow Research 265

The AFR 265 heads didnt produce the highest peak power and torque numbers of the test because of peak flow numbers. In fact, every aftermarket head we tested actually offered better flow number numbers at 0.700 lift (and many at 0.600 lift) than the AFRs. Even the ported 049 heads outflowed the AFRs at 0.700 lift, but our 0.580-lift cam never made it to 0.700 lift. Besides, power doesnt come from peak flow, it comes from maximizing flow in the usable lift range. Since the valve must open up to the maximum lift value, then close down, it spends twice as much time in the rest of the lift range as it does at the peak. Using the additional mid-lift flow offered by the AFR 265s, the 468 BBC produced 613 hp and 559 lb-ft of torque. The spring package provided by AFR allowed the hydraulic roller motor to rev cleanly to 6,500 rpm. In terms of average power production from 3,500 rpm to 6,300 rpm, the AFR 265s produced 501 hp and 536 lb-ft of torque, while knocking down 520 lb-ft at 4,000 rpm.

  • Notes: Fully ported, chambers worked
  • Retail Price- $2,238
  • Intake Valve Size-2.19
  • Exhaust Valve Size-1.88
  • Intake port vol-266 cc
  • Chamber Volume-112 cc
  • Peak Power-612 hp @ 6,400 rpm
  • Peak Torque-559 lb-ft @ 5,300 rpm
  • Avg HP [3,500-6,500]-501 hp
  • Avg TQ [3,500-6,500]-536 lb-ft
  • Tq @ 4,000 RPM-520.3 lb-ft

Flow Data: CFM @ 28-ins

Lift In EX
.050 37 30
.100 73 63
.200 164 141
.300 241 196
.400 298 239
.500 332 260
.600 331 273
.700 316 280


Test 3: Brodix Race Rite Oval 270

The Brodix Race Rite oval-port heads featured 270cc intake ports that flowed just shy of 340 cfm--enough to support nearly 700 hp on the right application. Obviously, our mild combination could not take full advantage of what the Brodix heads had to offer, but they performed exceptionally well on the 468 nonetheless. Unlike the AFR or Edelbrock offerings, the Brodix Race Rite heads relied on CNC porting only in the combustion chamber. The intake ports received a minor gasket match, but the cutter was not allowed to do any serious work. The lack of CNC porting didnt seem to hurt the flow rates, as the intake and exhaust ports of the Brodix heads flowed 336 cfm and 270 cfm, respectively. This allowed the Brodix-headed 468 to produce 591 hp and 553 lb-ft of torque. The BBC averaged 492 hp and 528 lb-ft of torque while thumping out 512.8 lb-ft at 4,000 rpm.

  • Notes: CNC'd comb. chambers, intake ports
  • Retail Price- $2,796
  • Intake Valve Size-2.25
  • Exhaust Valve Size-1.88
  • Intake port vol-269 cc
  • Chamber Volume-111 cc
  • Peak Power-591 hp @ 6,100 rpm
  • Peak Torque-553 lb-ft @ 5,100 rpm
  • Avg HP [3,500-6,500]-492.7 hp
  • Avg TQ [3,500-6,500]-528 lb-ft
  • Tq @ 4,000 RPM-512.8 lb-ft

Flow Data: CFM @ 28-ins

Lift In EX
.050 34 30
.100 69 64
.200 149 127
.300 220 163
.400 275 193
.500 315 225
.600 336 254
.700 333 270


Test 4: Dart Pro 1 270 Oval-Port

The Pro 1 name from Dart has always meant power and this new 270 oval port cast was no exception. The Pro 1 was one of only two full as-cast heads to be tested. All others featured some sort of CNC porting, chamber work, or port matching. Obviously the designers were earning their money, as despite the virgin aluminum, the as-cast Dart Pro 1 offered impressive flow numbers. It's always easier to improve the flow with porting, but getting the results from a casting takes real talent. With enough airflow to easily support our test motor, the Dart-headed BBC produced 593 hp and 554 lb-ft of torque. The 111cc combustion chamber makes the Dart Pro 1 a perfect candidate for head swapping on a 7.4L truck motor. Yank a wrecking yard mule, stuff in a cam, and ditch the peanut ports in favor of a set of Dart oval ports and you have one serious street motor. The smaller chambers on the Dart head (compared to a typical 119cc chamber on peanut-ports) add both flow and compression to further increase power. The Dart Pro 1s showed the power of oval ports by averaging 494 hp and 529 lb-ft of torque and offering 509 lb-ft of torque at 4,000 rpm.

  • Notes: Totally unported, as-cast
  • Retail Price- $2,995
  • Intake Valve Size-2.25
  • Exhaust Valve Size-1.88
  • Intake port vol-274 cc
  • Chamber Volume-111 cc
  • Peak Power-593 hp @ 6,100 rpm
  • Peak Torque-554 lb-ft @ 5,300 rpm
  • Avg HP [3,500-6,500]-494.0 hp
  • Avg TQ [3,500-6,500]-529.0 lb-ft
  • Tq @ 4,000 RPM-509.8 lb-ft

Flow Data: CFM @ 28-ins

Lift In EX
.050 36 34
.100 71 69
.200 158 117
.300 235 159
.400 290 204
.500 323 234
.600 324 252
.700 325 267


Test 5: Dr. J's Ported 049 Oval

Popularity, availability, and cost all make a factory oval-port head appealing. Because so many enthusiasts not only have heads, but decided to massage them, we opted to include a set of ported 049s in this test. The factory 049 heads came from Dr. J's and were treated to their typical valve upgrade, full porting, and even a slight milling to get the chamber volume down to 118 cc. It is all but impossible to get the chamber size down to the 110cc range offered by the aftermarket heads, but the flow numbers were certainly right in the ballpark. The drop in compression caused by the larger chamber volume hurt power slightly through the entire rev range, but the ported 049s demonstrated why so many BBC owners insist on porting the stock stuff.

Equipped with the Dr. J heads, the 468 produced 576 hp and 538 lb-ft of torque. Torque production exceeded 515 lb-ft from 4,500 rpm to 5,800 rpm, while the BBC averaged 481 hp and 515.8 lb-ft of torque. Down at 4,000 rpm, the iron-headed big-block produced 504.7 lb-ft of torque. The one problem with iron heads is obviously the weight.

  • Notes: Reworked factory heads
  • Retail Price- $1,599 (porting customer-supplied castings)
  • Intake Valve Size-2.25
  • Exhaust Valve Size-1.88
  • Intake port vol-267 cc
  • Chamber Volume-118 cc
  • Peak Power-576 hp @ 6,000 rpm
  • Peak Torque-538 lb-ft @ 5,100 rpm
  • Avg HP [3,500-6,500]-481.4 hp
  • Avg TQ [3,500-6,500]-515.8 lb-ft
  • Tq @ 4,000 RPM-504.7 lb-ft

Lift In EX
.050 33 34
.100 73 71
.200 152 120
.300 228 162
.400 282 188
.500 320 215
.600 336 238
.700 329 246


Test 6: Edelbrock RPM Xtreme

The name Edelbrock has been around since the dawn of hot rodding, but it still has a few tricks up its collective sleeve. Case in point: Its RPM Xtreme heads, which offered the highest peak airflow of any of the heads we tested. Unfortunately, our test Rat, or more specifically our cam choice, was not able to capitalize on the available airflow, as it occurred at 0.700 lift, though the RPM Xtreme heads flowed nearly as much at 0.600 lift. These heads featured CNC porting through the intake, exhaust, and combustion chamber, and the power numbers reflected the extra work. Only the Edelbrock and AFR heads allowed the 468 to exceed 600 hp, as the Edelbrock-headed BBC produced 601 hp and 552 lb-ft of torque. The average power numbers also reflected the port work, with average horsepower and torque checking in at 498.2 hp and 524.1 lb-ft, respectively. Down at 4,000 rpm, the Edelbrock heads managed 514.9 lb-ft of torque and averaged over 515 lb-ft from 4,100 rpm to 6,100 rpm.

  • Notes: CNC porting throughout
  • Retail Price- $2,597 (porting customer-supplied castings)
  • Intake Valve Size-2.25
  • Exhaust Valve Size-1.88
  • Intake port vol-303 cc
  • Chamber Volume-111 cc
  • Peak Power-601 hp @ 6,200 rpm
  • Peak Torque-552 lb-ft @ 5,300 rpm
  • Avg HP [3,500-6,500]-498.2 hp
  • Avg TQ [3,500-6,500]-524.1 lb-ft
  • Tq @ 4,000 RPM-514.9 lb-ft

Flow Data: CFM @ 28-ins

Lift In EX
.050 35 29
.100 63 61
.200 133 125
.300 210 186
.400 280 225
.500 327 257
.600 351 277
.700 353 285


Test 7: Procomp Electronics

Procomp Electronics has made its name by providing affordable performance. Its BBC oval-port heads qualify on both counts, as the as-cast aluminum heads maximized airflow and minimized cost. The second of the true as-cast heads, the oval-ports from Procomp Electronics featured no porting or CNC chambers and instead relied on the as-cast port shape to maximize flow. With a peak flow number of 346 cfm, the Procomp Electronics casts had plenty of potential, but they were hampered by the largest combustion chamber of the group. The 121cc chambers dropped the static compression 1 full point compared to the other competitors. If each point is indeed worth an extra 3-4 percent in power, a comparable compression ratio would put these heads right in the hunt in terms of power. But equipped with the 121cc heads, the 468 produced 555 hp and 527 lb-ft of torque. Since compression hurts power everywhere, the average numbers dropped to 471.1 hp and 506.1 lb-ft of torque. Though down on power, Procomp Electronics should have no trouble selling these at a retail price of just over $1,000 a pair.

  • Notes: As cast, no porting
  • Retail Price- $1,095 (with spring upgrade)
  • Intake Valve Size-2.25
  • Exhaust Valve Size-1.88
  • Intake port vol-311 cc
  • Chamber Volume-121 cc
  • Peak Power-555 hp @ 6,200 rpm
  • Peak Torque-557 lb-ft @ 5,200 rpm
  • Avg HP [3,000-6,500]-471.1 hp
  • Avg TQ [3,000-6,500]-506.2 lb-ft
  • Tq @ 4,000 RPM-507.6 lb-ft

Flow Data: CFM @ 28-ins

Lift In EX
.050 36 29
.100 77 61
.200 140 126
.300 214 174
.400 276 210
.500 314 241
.600 331 264
.700 346 284


Test 8: Trick Flow Specialities 280

When talk turns to performance cylinder heads, naturally Trick Flow Specialties has to be included. It stepped up for this test with a set of its PowerOval 280s. As indicated by the name, the PowerOvals combined 280cc intake ports with a 2.19/1.88 valve combination. Despite choosing the smaller intake valve (2.19 vs. 2.25), the PowerOval heads offered plenty of flow. Though the heads featured as-cast ports and chambers, the intake port did receive a minor port match. Even without the aide of CNC porting, the PowerOval heads offered flow numbers of 337 cfm on the intake and 261 cfm on the exhaust. These flow numbers translated into a peak power output of 576 hp and 544 lb-ft. The PowerOval heads offered a broad torque curve, bettering 515 lb-ft from 3,800 rpm to 5,700 rpm. In terms of average numbers, the TFS heads produced 485.7 hp and 521.7 lb-ft of torque and managed 517.8 lb-ft of torque at 4,000 rpm. The PowerOvals are affordably priced at under $2,000 assembled and ready to run.

  • Notes: As cast no ports and chambers
  • Retail Price- $1,849 (with spring upgrade)
  • Intake Valve Size-2.19
  • Exhaust Valve Size-1.88
  • Intake port vol-279 cc
  • Chamber Volume-113 cc
  • Peak Power-576 hp @ 6,100 rpm
  • Peak Torque-544 lb-ft @ 5,200 rpm
  • Avg HP [3,500-6,500]-485.7 hp
  • Avg TQ [3,500-6,500]-521.7 lb-ft
  • Tq @ 4,000 RPM-517.8 lb-ft

Flow Data: CFM @ 28-ins

Lift In EX
.050 32 30
.100 67 62
.200 143 122
.300 212 160
.400 266 189
.500 302 221
.600 328 244
.700 337 261

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The Grumpy Grease Monkey mechanical engineer.
Staff member
Air Flow Research
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The Grumpy Grease Monkey mechanical engineer.
Staff member
I recently ran across a couple posted photos of a guys BBC engine that was having issues burning oil,
if you look closely the pictures are rather useful in diagnosing the issues source.
if you look at the intake ports youll notice the lower 2/3rds show visual indications,
of oil flow contamination while the upper 1/3rd shows far less staining,
if the oil flow was coming from leaking valve guides , and spread through the runners during the valve over lap,
where the air flow may momentarily reverse direction in the plenum and runners at lower rpms, the oil stains,
would tend to be more uniformly spread, but the darker stains in the lower runners points more strongly,\
at the lower edge of the intake gasket that prevents oil from the lifter gallery are not fully sealing, it is very common if the heads have been milled
(ESPECIALLY ANGLE MILLED) or the person using the intake gasket used extra thick intake gasket oil seals.
yes I'm well aware this is a rectangle port head, but all the info applies to both oval and rectangle port heads.
this is one reason many guys prefer to dimple the under side of the intake manifold and block china wall mating surfaces,
and simply apply a bead of silicone gasket sealant to both adjacent mated surfaces then install the intake manifold,
with a thick intake gasket and a thin 1/8" bead of sealant around the ports and coolant passages.
keep in mind the oil flow out of the push rods that lubes and cools the rockers and valve springs cascades in a mini waterfall,
back into the lifter gallery as it drains from the heads at a rate of several gallons a minute,
theres plenty of oil in the lifter gallery for the leaking intake port gaskets to draw from if they are not properly sealed.


notice the upper intake runner walls have far less oil stains, and the oil flow flowing over the hot intake valve back surface,
this un-wanted oil flow leak, rapidly forms a burnt ash coating,
that can and does reduce air flow and cylinder fill efficiency.
notice the lower 1/2 of the intake runner gaskets sealing surfaces below, are oil soaked and covered with burnt oil residue


I also have to point out the intake runners in the heads are not port matched to the intake gasket,
this, and not matching the matched intake runner exits to the intake gaskets,
is generally going to cost you a measurable loss in potential extra air flow at peak rpms

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The Grumpy Grease Monkey mechanical engineer.
Staff member

Ive suggested your average skilled mechanic or hot rod enthusiast,
spend time in doing research in, and then if they choose too,
cleaning up the bowl area under the valves , of casting flash,
and valve seat machining ridges,getting a multi angle valve job,
narrowing the valve guides port matching the heads/intake manifold,
and polishing and ccing the combustion chambers,
you should not be significantly altering or enlarging the ports or runners,
multi angle valve jobs should be left too the pros with the correct machinery,
and precise measuring equipment,
but a home shop can certainly lap valves and clean up the port and bowl area ,
and port match, and blend , polish and cc combustion chambers, etc.

reading links and sub-links generally helps
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