BIG BLOCK CHEVY 300cc OVAL PORT ALUMINUM HEADS BY PROCOMP
FULLY ASSEMBLED, FOR USE WITH HYDRAULIC ROLLER CAMS UP TO 620 LIFT.
119cc COMBUSTION CHAMBERS
This sale is for a set of heads (2 heads).
This ad may have references to pictures and graphs that are not visible in the description. To see this ad in it's complete form click the "buy it now" tab. This will not in any way commit you to buying the product. It will bring you directly to this ad in its entirety on our actual website. You will then see the ad displayed with all the pictures and dyno graphs throughout the ad. in great detail.
The Procomp bbc heads are perfect for 427, 454, 496 and 540 street/strip engines. These are what we use on our 505 and 555 bbc engines. They will produce up to 680 hp with the proper cam and intake manifold on pump gas. This is an outstanding trouble-free set of heads. Fully built, ready to install.
In the lower section of this ad you will find valuable information on how these heads perform when used with various engine sizes and cam combinations in street rod form. Please read the complete ad before purchasing.
Fully assembled with premium PBM race grade valves, Melling springs, PEP retainers, viton valve seals, spring ID locators, high grade Comp Cams 10 degree locks. The hardware setup in these heads is for use with hydraulic roller cams. Below is a detailed breakdown of the hardware used in these heads. We do offer these heads set up for all types of cams. See our other listings.
Valve size 2.250 and 1.88. These heads have the correct seat diameter to allow use of these valves.
We know of many sellers of aluminum high performance heads that claim to use good hardware. Chances are they don't know the difference between low grade and high quality hardware. Failure to follow proper assembly procedures and the use of low grade hardware are what cause most problems. Good quality hardware and proper installation can determine how well the heads will function and hold up under hard use.
SEE OUR OTHER LISTINGS FOR THE REC. PORT VERSION.
Please note: Due to a high volume of sales at this time, these heads may take up to 3 business days to complete and ship. Please let us know if you are under a time constraint with this order, and we will do our best to accommodate your request.
These are true multi-purpose heads for street, drag race, and power boat applications. This set is an excellent upgrade over OEM cast iron heads on your big block engine. We honestly feel there is not a better set of heads for the price. These heads are tried and proven. The intake runner volume is 300cc, and the combustion chambers are 119cc.
You can reduce your engine weight by around 100 lbs. with the use of aluminum heads. You can also increase your power up to 250hp over an OEM 454 engine, depending on choice of cam and intake manifold.
We do our own assembly on our heads. See details below about our hardware and assembly procedure.
We also offer variations of these heads for use with all types of cams. Be sure of what type cam you plan to run before purchasing. Read the ad completely before purchasing.
The horsepower gain from the weight reduction of aluminum heads alone is noticeable, not to mention the fact that aluminum heads will allow you to run a bit more compression without the risk of detonation. The benefits are many to running aluminum heads. The most expensive cars in the world all run them. There are no drawbacks!
Tech support is available. We are confident that we offer the best advice in the business.
We also offer these heads in bare form, as many customers have selected a machine shop of their choice, as well as their own hardware. We hope you will check out our other listings for the many other items we have available.
Here is a rundown on the hardware used in these heads and the assembly process.
PBM Competition Series Valves.
PS824 forged high temp stainless. 10% reduced weight. Hardened keeper groove.
We use what we consider to be the best valves on the market: the Competition series PBM backcut valves. These valves are considered very high quality. Do a search on this brand of valves and you will find them to be very highly rated.
PBM has three different series of valves. These are the top line. The backcut feature reduces valve weight by an average of 13 grams per valve. This weight reduction of approx. 208 grams for the complete set has a great effect on acceleration, deceleration, and will extend valve train life. The valve spring compression and rebound action will remain stable at a higher rpm with the use of reduced weight valves. The instability of a valve spring at high rpm is known as valve float. This is very damaging to the heads, and valve train components.
The backcut feature is not be mistaken for an undercut. These valves have both features. Backcutting is an additional radius put on the head of the valve to increase the flow numbers and reduce valve weight. The flow increase is usually around 3-6 points on the flow bench, and possibly more, depending on the initial flow rate of the heads. According to one of our machinists who built Winston cup engines for 15 years, the exhaust valves had an additional radius cut on the outermost edge that allowed a better escape of the exhaust gas. This cut on the exhaust valve is in addition to the backcut feature.
The Competition series is made from a much higher temp alloy than most other stainless valves. There are at least three levels of stainless valves on the market, excluding those used in very high level racing such as pro-mod. The PBM Competition series is compared to the highest level of those three.
Notice in the picture below the concaved face of the valves. You will only see this on high end valves. Most other valves are either flat faced or have a dimple in the center.
The pictures below show our PBM valves installed in set of CNC'd combustion chamber heads. This is not actual combustion chamber of the PC heads. The pictures are to show you the valve face design.
Pictured directly below in the first pic. is the PBM competition valve, and the other pic. is of our conventional style valve. It was difficult to show the back-cut feature in the picture, but note that the valve that is hand-held (PBM) has a third radius cut.
These valves are swirl finished, back-cut plus undercut style, and have a very well designed lock groove. The exhaust valves have an additional feature: a blunt face on the outermost edge to assist in the elimination of exhaust gases. Low temp valves will fail with ease under the right conditions. High temp valves are not just for those running to extremes; they are essential for all carbureted engines. Should your engine lean out for any reason, the combustion temperatures can rise in an instant. Carbs that are not working as they should (and all carbs have their moments) can cause a lean condition and you will most likely not know this is happening.
Using a low grade stainless valve on a BBC engine will cause problems sooner or later. If you're running a blower, your valves must be of the highest grade stainless. Marine engines require a premium valve due to the fact they are run at high rpm (usually 85% of max rpm) for long periods of time. This sustained high speed is more than any standard stainless valves can take, and not just due to the heat. The stems must be perfectly designed and constructed with high end alloys. These valves are used in many 800 hp BBC engines. You simply can't do this with low level stainless valves, or they will fail.
Melling High Performance Dual Springs.
Our Melling springs are 1.46 diameter, with an inner spring and internal damper. Others are using springs that are much smaller in diameter. Smaller diameter springs may be in the correct spring pressure zone, but they usually have a shorter life. Melling springs are made in the USA. All of our engines using the Procomp BBC heads use these springs. Spring failures are near non-existent.
10 Degree machined valve locks.
We use only Comp Super 10 degree machined locks. Our head builder noticed the low grade locks on the market fit more loosely than he felt they should, not to mention the possibility that they were made of inferior metal. He envisioned the engine being much more prone to dropping a valve at high rpm. Using these locks, coupled with our PBM valves, we have yet to have an engine drop a valve due to a valve lock failure.
Precision Engine Parts (PEP) Co. Chromoly retainers.
Our retainers and ID locators are Precision Engine Parts brand, made from 4130 chromoly steel. These retainers have a perfect fit with the Comp valve locks and PBM valves. We have used these on all of our engines for many years, and have had zero failures.
We hone all of the bronze valve guides with a ball berry flex hone to establish not only perfect clearance, but also a semi cross hatch finish for oil retention. We finish off with a natural bristle brush. The heads are then placed in our parts washer and cleaned with high pressure hot water, then pressure dried. Before installing the valves, we apply a heavy coat of engine assembly lube to the valve stems. The coating on the valve stems is essential to protect the bronze guides from gaulding on initial startup.
Our next step is to set the spring pressure to a predetermined pressure using a spring height checking device, most suitable for street rod use. The springs we are using allow for a near perfect seat to nose ratio. Be warned that some sellers of aftermarket heads may not be checking the installed height when assembling the heads, and may not be setting them up to the correct pressures. We have a full scale machine shop with several very knowledgeable engine builders that know and fully understand how to properly assemble a set of heads. Combine the possibility of poor assembly methods with incorrect or low grade hardware, and it is easy to see how failures can result.
Guide plate recommendation.
We strongly recommend the use of the Dart adjustable guide plates with these heads, or with any BBC aluminum heads for that matter. These guide plates will allow better rocker tip alignment due to the fact they are fully adjustable. We use them on every set of BBC heads we install on our engines, including the Dart Platinum Pro-1's, and AFR heads. The rocker tip may end up offset to one side more than is acceptable when using fixed guide plates, and the Dart adjustable guide plates allow a decent amount of correction. The variances in stud position to valve guide alignment vary on all brands of heads. The rockers could also contribute to this issue, as the trunnion or rocker body could have variance. By having proper rocker tip alignment, you are distributing the pressure on the valve tip evenly. This not only reduces uneven valve tip wear, but also prevents undue stress on the valve guides in the heads. The part number for these guide plates is BBC-ADJ-GP. See our other listings for these items.
Do not use stock GM pushrods with these heads.
The spring pressures on aftermarket heads are somewhat higher than on OE heads. Combine this with the larger lift and duration cams often used, and stock pushrods may flex or permanently bend. They will most likely be the wrong length. The stock pushrods are usually made from a mild 1810 steel that has been heat treated. Under high rpm, they will usually flex and cause a loss of lift, resulting in a power loss. The engine will usually run erratically when pushrods are flexing. The Spintron valve train dyno proves that inadequate pushrods will flex to a great degree as engine rpm increases.
Some GM pushrods have a welded ball on them, and they stand a greater chance of breaking off with the use of larger than stock cams and increased spring pressure. We offer high quality USA made, Howards brand pushrods made from 4310 chromoly. They are superior to any stock pushrod. Our prices on them are the best you will find.
You will see many low cost pushrods on the market, but these are totally unsuitable for use with these heads for the many reasons mentioned above, and they are not guide plate compatible. These pushrods will cause problems when used on a high performance setup.
Pushrod lengths of 7.800" intake side and 8.600" exhaust side are needed when running a hydraulic roller cam with these heads. There are many factors that determine what length pushrod is needed, but usually these sizes will work perfectly. Should you purchase a set of pushrods from us and find that the length is not suitable, you may return them, and we will send out the size you request.
IMPORTANT NOTE CONCERNING ROCKER ARM STUDS.
If you have been a regular shopper with us, you will have noticed we do offer some knock-off products that are made off-shore. We do also sell many products made in the USA. We have always been very particular as to the quality and workmanship of such products, while considering the cost. We scrutinize our products very carefully and refuse to sell products that simply don't meet our standards. We have now eliminated another of the low cost knock-off products from our line. The low cost imported rocker arm studs have shown numerous problems unlike those in the past. We have looked at several others on the market, and still find many issues with them that are not acceptable.
Many of the studs had run-out in the shaft of up to an eighth of an inch. This caused major problems with rocker alignment, and depending where the position was when the stud tightened up, would determine the direction of the rocker misalignment. If the warped stud was facing toward or opposite the valve, then the roller tip would would not be centered to the valve tip. This would then create a loss of lift and cause increased wear on the valve tip.
If the warped stud tightened up in a side to side position, then this would allow the rocker tip to be cocked on the valve tip. This would then side load the valve tip with undue pressure, creating a serious wear problem on the side of the valve tip and create excessive wear on the valve guides in the heads. This also side loaded the rocker trunnion and front roller, creating an excessive wear issue in the roller rockers.
We also found a difference in the tread pitch and depth compared to the ARP studs. The rocker studs in an engine are under a tremendous upwards pull and improper thread design may cause the studs to pull out of the head. The ARP studs screw into the heads with a very precise fit and feel.
After thoroughly comparing the ARP studs and several off shore models, I am convinced that we will never offer the off shore studs again, regardless of the price difference. They were never as bad in the past as what weâ€™re seeing now. This run-out was most likely caused by improper heat treating methods.
We are aware of only one other rocker arm stud besides ARP on the market of decent quality, and that's from the GM Performance division, and it's fair to say they are most likely supplied to GM by ARP under private label.
We have rejected many products that are outright junk and would cause serious issues in your engine only to see other sellers offering those same exact products. It's all about learning where to draw the line.
The correct ARP rocker stud part number to use with these heads is #100-7101. See our other listings for these parts.
Studs and guide plates are NOT included. Other sellers may include these items but rest assured, they are usually not suitable for these heads. We use nothing but the Dart adjustable guide plates and ARP rocker studs when we build an engine using these heads, as they allow for perfect alignment of your rockers. See our other listings for a full selection of accessories.
We are glad to offer many great low cost items, as well as the high end products, but will always give careful consideration to quality, functionality, and overall value.
IMPORTANT NOTE, MUST READ!
We have noticed several sellers offering these heads with a one size fits all valve springs for dual use on hydraulic flat tappet and hydraulic roller cams.
We are sure this is not the proper way to setup the heads.
If they have this one size fits all setup somewhere in the middle spring pressure values of what is required for a hyd. flat tappet and a hyd roller cam, then it would be too much for the hydr. flat tappet cam, and create a wear issue. Putting too much pressure on flat tappet cams is a sure way to kill the cam. If these middle of the road springs were used on a hyd. roller cam, then the spring pressure would be too low. Valve float and its damaging effects, along with a loss of performance are sure to occur.
We use the correct spring for your setup and it is never the same on a hyd. flat tappet as it would be on a hyd. roller cam. As mentioned above, the spring requirements between a roller cam and flat tappet cam are dramatically different. Even the odd ball solid flat tappet cam has its own unique setup depending on the lift. The one size fits all hardware claims also to work on these cams. We know of several sellers offering this insane setup to unsuspecting buyers, and itâ€™s not the proper way to set up a set of heads. We would not even consider using a spring setup like this, and believe me, the simplicity of it is appealing.
SPEC INFO AND RECOMMENDED ACCESSORIES FOR FOR THESE HEADS.
Intake Gasket: Felpro 1212 For oval port heads.
Intake Port volume: 300cc
Intake Port Dim:
Int Port Location: Stock
Intake Valve Dia.: 2.250"
Exh Valve Dia.: 1.880"
Exhaust Port Dim:
Exh Port Location: Raised
Exhaust Gasket: Depends on what type exhaust you're using. Best to try and match up the gasket to your header or exhaust manifold
Head Gasket: Felpro 1017-1 for Mark V & VI blocks, or our PC-5211 MLS head gaskets for Mark V or earlier blocks.
Flow, Exhaust: BBC-50 Head bolts, or ARP 135-3607 Head bolts or our BBC-75 Head stud kits.
Manifold: Most any oval port style intake will work. Our oval port aluminum intakes fit very well.
Milling: Max. .060 Scroll down to see info in this listing for details on this.
Pistons: Most stock or aftermarket pistons. Our Wiseco pistons combine perfectly with these heads.
Push Rod length: 7.800 intake side, 8.600 exhaust side We have the correct pushrods needed. See our other listings.
Push rod Guide Plate: We strongly recommend Dart adjustable guide plates. Not included. # BBC-ADJ-GP. See our other listings
Rocker Arm studs. ARP 100-7101 Do not use off-shore rocker arm studs. ARP only. Not included. See our other listings.
Retainers: Steel 10° Comp brand machined locks are used on all of our heads.
Spark Plug: Straight, .750" reach, gasket, Autolite 3923 or NGK 4544 for one step lower heat range. See our other listings for these.
Spring Pockets: 1.550" OD (.030" deeper max)
Springs: Melling brand 1.46 outer diameter. Dual spring for hyd.
roller cams. Single for those running a hyd. flat tappet cam.
Valve Length: .250 over intake valves, .100 over exhaust valves.
Valve Stem Dia: .3415" - 11/32"
Valve Train: STD BBC 7/16" stud mount
Valve Guides: 1/2" OD Int = Mag-bronze Exh = Phos-bronze (.002" press)
Valve Guide length:
Valve Guide clearance: .0014" - .002" (with our .3415 dia. valve stem)
Valve Guide Spacing:
Valve Seats: Hardened Ductile Iron, .006" press
Valve Seat dim. Standard
Valve Seat angles: Int = 32° - 45° - 60° - 70° Exh = 37° - 45° - radius
Torque: Head Bolts = 65-70 ft/lb
Rocker Studs = 50 ft/lb
Manifold = 35 ft/lb
Block Use: Any BBC, GM OR DART Iron or Aluminum
Weight: 70-72 lbs fully assembled pair.
Below is an excerpt from our 496/505 engine ad that uses the Procomp heads. This can give you an idea of what these heads are capable of on a common 496 engine build, set up to run on pump gas, with a compression ratio of approx. 10.4:1 These cams have been very popular for us, and are perfect for most 496 builds. We have sold approximately 500 of our 496-505 engines with these heads, and approx. 200 of the larger 540/555 engines. The 320cc rectangular port version of these heads coupled with a single plane intake have shown to make up to 680 horse power at 5900 rpm on a pump gas 555 engine with 10.5:1 compression ratio, using a new special custom grind cam that is only 615 lift. We are in the process of updating our line of bbc cams to the special grind numbers that are highly suitable for the Procomp heads for use in street rods. The oval port heads would still make close to this, but it's fair to say that due to most people running a dual plane intake with the oval port heads, the power would drop by approx. 35-40 hp.
This recent testing we have done with our special grind cams has proven that the Procomp heads have the ability to make huge horse power numbers with the use of streetable cams, and safe compression ratios for use with pump gas. We recommend checking out our BBC engine ads for the full story on what to expect from these heads. We use the Procomp heads on all of our 496/505 and 540/555 engines.
Cam Choice # 1
PART # 120335-10 retro style, roller cam for use in non-roller blocks.
If you require the oe step nose version of this cam the part number is # 126736-10
Int. .612/Ext. 612 lift
Duration @0.050": INT .251 / EXT .255
Lobe Separation Angle: 110º
When used in a 496 build, this cam has a peak horsepower of approx. 600, coming in around 5,850 rpm when using a single plane intake with the rectangular port 320cc Procomp heads. Max torque of 600 pound feet of torque produced at around 4600 rpm. A 2800-3500 stall converter is recommended when using this cam and a final gear ratio ratio of approx. 3.55. This cam produces an aggressive/lopey sound at idle, or may we say that it beats the ground with no mercy in a 496 engine. This is the perfect cam for those building a 496 for use in light to medium weight cars. Drivability is decent if the car is setup properly. We find this cam to be overly aggressive for use in 454/468 engine builds, with the exception of those building what is referred to as a pro-street setup. It is strongly recommended that you use our Howards Max Effort tie bar lifters or our Comp short travel tie-bar lifters with this cam. We have had outstanding results with these lifters on engines running hyd. roller cams in this lift range. We have achieved approx. 35 more horse power with our new special grind cam that is near identical in lift and duration. Those cam profiles will soon be published.
Cam specs. Cam choice 2
Part number, 120246-10 oe roller style for use in roller blocks.
We also have this cam available in retro style for non roller blocks part # 120245-10
Lift Intake 567"/ exhaust .578"
Duration @ .50 225/231 @ .050" 110+4L/C
Cam choice # 2 offers increased drivability and improved low end power when used in a 496 engine build, with a slight sacrifice of the max power as compared to cam choice # 1. The torque numbers are slightly less but peak numbers come in much sooner at around 3800 rpm compared to cam choice # 1. Valve train stability is greatly increased with this cam. BBC engines that run a hyd. roller cam with 600 lift or greater and producing rpm numbers in the 5850 range or more are nearing the point of valve train instability due to the heavy valves used in BBC engines and the geometry of the valve train. This cam is actually the perfect choice for those wanting the best balance between power and drivability when used in a 496 engine build. This cam has less lift and duration than cam choice 1 and will increase drivability in the lower rpm range by a noticeable amount, but we do recommend you choose the oval port heads and a dual plane intake when selecting this cam for a 496 engine build. You do not need the expensive short travel race grade lifters with this cam, but we do recommend a good set of USA made tie-bar lifters.
By using cam choice # 2, your valve train will be much better off and longevity/reliability is certainly improved. Cam choice # 2 will allow you to run a near stock stall converter (2200-2500) with a reasonably tall gear ratio, (3.23) and overdrive is more of a possibility when used a 496 engine build. Mileage with taller gearing is also a plus. This cam would be more suitable in heavy vehicles weighing over 3600 lbs and a must for those in the range of 4200-5500 lb range. This cam is not recommended for heavy towing or in very heavy trucks such as a 4x4, 3/4 or 1 ton dually quad cab. We would use a special order cam in such heavy trucks that may possibly be used for towing.
Cam specs. Cam choice 3
Part number, 123516-10 oe roller style for use in roller blocks.
We also have this cam available in retro style for non roller blocks part # 123515-10
Lift Intake 555"/ exhaust .555"
Duration @ .50 219/227 @ .050" 110+4L/C
This cam has a slight reduction in lift and duration from cam choice 2 and will help increase bottom end torque. This is a good all around choice when used in a 496 engine build, giving you decent power and increasing valve train stability to a very reasonable level. When used in a 454/468 build, this cam would be somewhat radical.
Cam specs. Cam choice 4
Part number, 120236-10 oe roller style for use in roller blocks.
We also have this cam available in retro style for non roller blocks part # 120235-10
Lift Intake 510"/ exhaust .538"
Duration @ .50 213/221 @ .050" 110+4L/C
When used in a 496 engine build, this cam would produce huge amounts of torque in the very low rpm range. Excellent for a heavy car or truck. Mid range power would come in low, max power would finish out at around 5200 rpm. Excellent for use in the heaviest pickup trucks, and towing would not be problem. Compression ratio requirements in a 496 build could be low as 9.0:1 with this cam, and it is also ideal to keep compression ratio low in very heavy vehicles especially when towing. When running this cam in a 454/468, compression ratio should be in the 9.4:1 range or more. This cam could also be used in a daily driver street rod with a stock or near stock stall converter, and tall gearing is not problem. Overdrive cruising in the 1800 rpm range is for sure possible with this cam in a 496 build. If you're building a 454/468, things will change a bit but this cam would still be excellent for producing low end power and having outstanding drivability. We would recommend a 2200-2500 stall and gearing should be in the 3.23 range or higher. Valve train wear would be virtually non-existent with this cam. It would make sense to stay with the oval port heads rather than our rectangular port version using this cam, and you would want to run the small runner dual plane intake manifold. Edelbrock calls this intake the Performer, and our version of it would be the Cyclone. These intakes make power right off idle very well, yet produce very decent power in the upper mid range. This intake matches up well with this cam.
We are not responsible for collateral damage caused by the use of this product.