We do not stock this item. All Air Flow Research cylinder heads are built-to-order and will take 3-6 weeks, or more, for delivery. Thank you. AFR 300cc Fully CNC Ported Oval Port Magnum BBC Cylinder Heads PN 3670 For the ultimate in "Oval Port" performance, the fully CNC ported AFR 300 has no competition. With flow figures most small to medium sized rectangular port castings would be envious of, these high flowing "Ovals" produce tremendous airspeed and really pack a punch. Ideally suited for 427-540 CID street and strip performance, as well as circle track applications which require strong low and mid-range torque to help accelerate a car coming off a corner. Once again, AFR has included it's trademark 3/4” deck, reinforced rocker stud bosses, and thick rugged castings, so you can own the strongest and most efficient heads on the market today. Premium hardware such as 2.300/1.880 one piece stainless valves, 1.550 double springs, 10 degree locks and retainers, and high quality studs and guideplates all come as standard equipment. Take note the higher flowing exhaust ports and bolt pattern are raised .375 over stock location, this rarely affects chassis fitment. These heads have no EGR and are not emissions legal. Note: Properly selecting the correct aluminum cylinder head for an application depends on a large number of variables. Please consult with one of our sales technicians to help assist you in making the best decision for your particular application. Optional stud girdle available to fit 2° rolled valve angles. 1” longer head bolts needed on four bottom exhaust bolt holes of each head. Longer pushrods might also be required. Fully-Assembled, complete pair of cylinder heads including: ·        1 pair assembled, CNC-ported AFR aluminum heads ·        113cc combustion chambers (can be reduced by AFR to 107cc flat min or 102cc angle min) ·        300cc intake port ·        Angle plugs ·       Stainless steel valves: 2.250" x 11/32"-stem 5.500" OAL intake, 1.880" x 11/32"-stem 5.448" OAL 'Nail Head' exhaust ·      1.550"-dia dual solid roller valve springs (AFR #8001: 250lbs. @ 2.00"; 770lbs. @ 1.200", .800" max lift) (other springs available) ·        10-degree chrome moly retainers std. (Titanium retainers optional for extra $$$) ·        New locks & seals ·        3/8" pushrod guide plates ·        Spring cups ·        Extra thick deck surfaces to resist warpage ·        7/16" screw-in rocker studs ·        Exhaust ports raised 3/8" over stock 300cc BBC Aluminum Cylinder Head Flow Chart Tested on 4.310 Bore   This is just a partial listing. We also offer heads from: Cylinder Head Innovations (CHI), CFE Racing Products, BMF Racing Heads, Dart, Edelbrock, Brodix, GM Performance Parts, RHS Pro Action, and more to work on all engines. Any head combo including 23, 18, 15, 14, 13, and 11-degree valve angles can be custom-tailored to fit your needs. From mild-to-wild, we can put together a package to make your ride scream! We offer UPS Ground shipping to the 48 states. AK, HI, and P.R. shipping extra.   Feel free to call for more info or to customize your kit accordingly. International Shipping may be available for extra cost. Please provide a shipping address for quote. Hardcore Horsepower, LLC Franklin, TN 615/595-0060 10am-6pm Monday thru Friday USA Central Time Check out all of the other great deals available in our eBay Store!!! We Make It Go Fast!!! BBC Cylinder Head Footnotes General special parts/requirements Marine Applications: We strongly recommend Inconel exhaust valves. Boosted/NOS Applications: We strongly recommend upgrading your springs since boosted or NOS applications accelerate the RPM so quickly, additional spring pressure is required. Boosted/NOS Applications: We strongly recommend considering Inconel exhaust valves and AFR's optional intake valve for power adders exceeding 1000HP. Boosted Applications: We strongly recommend increasing your valve spring pressure since boost pressure on the valves reduces your spring tension. For example, 15 lbs on a 2.125 O.D valve reduces the springs closed seat pressure by approximately 40-50lbs. Intake runner volumes can vary 2-3cc from advertized sizes. The reason for this is different combustion chamber volumes require different intake runner length for proper alignment with the intake manifold. For all applications we strongly recommend true roller rocker arms, not just roller tip rockers with stock style bodies. As with all aftermarket heads, a different lenght pushrod might be required. As with all aftermarket heads, your self aligning rockers will no longer be compatible. As with all aftermarket heads, check pushrod clearance with heads placed on the block before final assembly. As with all aftermarket heads, milling the head deck might affect air flow. Flat and angle mills might require a .120 thick gasket. Due to many available factory OEM style/variations your existing stud girdle may not fit. Valve Springs: AFR springs that come standard with our assembled packages are very high quality and are sufficient for most applications. However, forced induction applications and cams with aggressive ramp rates (some cam manufacturers now offer much faster ramp designs and more aggressive cam profiles) may require additional spring pressure. We offer optional valve springs for these types of applications. AFR also recommends the use of billet cam cores which tolerate higher spring loads. Please don't hesitate to contact us directly if you question which spring is more ideally suited to your application. AFR assumes no responsibility for damage if the end user builds an engine without properly verifying he has enough piston to valve clearance (depth and radial clearance both checked). We recommend a minimum depth of .080 on the intake valve and .100 on the exhaust with a radial clearance of .200 minimum around the perimeter of each valve. Clay is recommended to visually verify both depth as well as radial clearance. Just checking depth is not enough...the position of the valve pocket must also be addressed. See below what factory OEM head AFR used for CAD/CAM modeling. Please see footnotes and the specific product page your researching for specific variences from OEM heads. BBC Cylinder Heads Was modeled after the GM LS6 open chamber rectangle port castings. With some domed aftermarket pistons, it may be necessary to slightly clearance or modify the piston due to our more modern (efficient) heart shaped combustion chamber design. Most of the newer manufacturer's dome profiles will clear, however the middle peak or crest of the chamber directly adjacent to the spark plug (between the intake and exhaust valve) is typically the problem area in some of the older piston designs. Note that the typical amount of material needed to be removed is very small usually less than 1 cc of aluminum is removed which only equates to a weight reduction in the piston of one to two grams. If your rotating assembly is already balanced this is a non-event and creates a VERY slight overbalance which in theory brings your engine into a better balance situation at slightly higher RPM. You could easily be off three times that amount by simply setting up your rotating assembly on a different shop's balancing machine. In short, don't worry about the slight removal of material effecting the balance of your rotating assembly. While some of you might be inclined to remove the material from the actual cylinder head, note that all of the combustion chambers shapes are very critical to flow and altering the cylinder head can and will effect flow and power production. We advise and recommend that you remove the material from the piston in the event you have piston dome to head interference. The easiest way to check for this is turning the engine over slowly with the cylinder head installed without the head gasket. AFR's Limited Lifetime Warranty! AFR warranties the aluminum cylinder head casting for the lifetime to the original purchaser with proof of purchase. Additionally, valves, guides, valve seats, valve springs, valve job, retainers, locks, studs, guide plates, valve seals are warranted for two years to the original purchaser with proof of purchase. All returns must have a RMA number in order to be returned, call for a RMA number. Parts must be returned prepaid freight by the original purchaser. When it has been determined, by AFR at its sole discretion, that the product does indeed have a warrantable problem from workmanship, materials or an undetermined cause (mystery failure) AFR will repair at no charge and reimburse UPS ground freight and return UPS ground freight. AFR will repair or replace the casting at its option. This warranty doesn’t cover fitness for purpose and/or merchantability on any product sold by AFR. This warranty does not cover the following: Failure due to improper installation or maintenance, abuse, misuse, unauthorized repairs, modifications, or alterations determined at the sole discretion of AFR. If your machine shop, engine builder or installer performs any unauthorized repairs, AFR warranty is voided and AFR will not reimburse any cost you incurred. Removal or replacement cost. Costs incurred due to down time of the vehicle. Damage to related components. Marine salt water corrosion. Corrosion from not using/refreshing antifreeze. Fitness for purpose or merchantability.