862 ls heads

Otherwise running stock 706 heads and stock truck intake with DBW throttle body. I have a spare LS short-block that is also an LM7 (I think) with 862 heads and no intake on it. My plan is to rebuild the spare block from the inside out with all new bearings, BTR "Torque" cam, Weiand aluminum intake, and then port/polish the heads.

862 ls heads. Precision Race Components Customer-Supplied 4.8L/5.3L/LS1/LS2/LS6 Cylinder Heads Fully CNC Ported & Assembled With Choice of Your Stock or Stainless Steel 2.02" Intake Valves, 1.575" Exhaust Valves, & Optional TSP Dual Valve Spring Kit with PAC Valve Springs & Titanium Retainers. Kit Also Includes TSP Hardened Pushrods & Your Choice …

863. Rectangle. 4.750" +- 0.003". 12604861. 12610716. 12675872. Share this article. We've tried to boil down the GM part numbers, casting numbers and other LS cylinder head information into an easily usable (and ideally definitive) cross reference. Note that we're not perfect and some of this data may not be perfect so use it for what you will.

[Editor’s Note: This LM7 engine upgrade guide is part of a series of LS engine upgrade guides assembled by a team of LS experts at Summit Racing that we are sharing at OnAllCylinders. For a primer on the entire LS engine universe, read LS Engines 101: An Introductory Overview of the Gen III/IV LS Engine Family.]. Intro to LM7 Engines. Meet …16 Jul 2021 ... Texas Speed F-35 Cam going into a Mega Truck Bog Brook Auto 207-261-1341.Receive notifications when cylinder heads are in stock and ready to ship. First Name. Last Name. ... FED LS1/2/6 Cathedral 862 Stage 1 $ 2,074.96. Fresh off the assembly bench and available. Orders placed before 3PM ship same day. GM Stock Intake and Exhaust Valves, 1.890″ / 1.550″ ...In terms of cylinder heads, we included the 706 small-valve 5.3L heads, the 241 (LS1), 317 (6.0L truck), and 799 (as a stand-in for the hallowed 243) heads. The idea was to flow and measure each ...Our Performance Rebuild option includes our high end CNC'd valve jobs, precision valve grinding, milling to any chamber volume, cleaning, inspection, and professional assembly. Typical gains are 10-20rwhp. 226cc Full CNC Porting Package. The go-to head for 450-500rwhp 5.7/6L's. Our high end machine work applied to GM's best cathedral head ...243 heads are commonly found in LS-based engines, including the LS1, LS2, and LS6. Their design is optimized for high-revving applications, making them a favorite among racers and performance enthusiasts. If you are looking to squeeze every bit of power from your LS engine, the 243 heads are a solid choice. The 862 Cylinder Heads863. Rectangle. 4.750" +- 0.003". 12604861. 12610716. 12675872. Share this article. We've tried to boil down the GM part numbers, casting numbers and other LS cylinder head information into an easily usable (and ideally definitive) cross reference. Note that we're not perfect and some of this data may not be perfect so use it for what you will.Watch in HD!!Another segment on putting together my cylinder heads.Took a different approach to installing my seals after doing some searching on the forums....

In this story, we will dyno test three new LS cylinder heads and perform a camshaft swap on a 6-liter naturally aspirated LS Gen III (an LY6 truck engine).Curious on what factory head would be better on my 2002 4.8. Factory has the 862 heads. I’ve been offered a 5.3 block with 243 heads on it for $300. Would the stock 243 heads work better on it than the 862 heads? Obviously they need to go to the machine shop to be looked over but without any alterations to the stock form, which is the better ...[Editor’s Note: This L33 engine upgrade guide is part of a series of LS engine upgrade guides assembled by a team of LS experts at Summit Racing that we are sharing at OnAllCylinders. For a primer on the entire LS engine universe, read LS Engines 101: An Introductory Overview of the Gen III/IV LS Engine Family.]. The Gen. 3 aluminum block …Description: 99-06 Chevy 5.3L V8 706/862 Aluminum Cylinder Head. Upgrade your Chevy 5.3L V8 engine with our Remanufactured 99-06 Chevy 5.3L V8 706/862 Aluminum Cylinder Head (Part#: ALL-20314). To ensure a high level of performance, these Chevrolet heads are built to exceed OEM specifications. ... Whether you're into 5.3 Vortec heads or 706 …Apr 4, 2019 · The minimum recommended clearance is 0.035-inch, so you should be able to deck most blocks 0.010-inch without a problem, but be sure to check the piston protrusion before you install the heads. If ...

16 Jul 2021 ... Texas Speed F-35 Cam going into a Mega Truck Bog Brook Auto 207-261-1341.No 243s or 799 have the casting defect that I've heard, it was pretty isolated to the castech only 706's on gen III 4.8/5.3's. There are 2 other sets of 706's that are not affected. The early sand cast heads come as 862s and 706's, and a die cast 706 that isn't made by castech. 16 posts.If you have a Gen IV short block (no heads), you can find an equally cheap set of 862 heads and do a valve job and port job to get both compression and airflow. …Sep 21, 2015 · These large-runner heads have a 12-degree valve angle, like stock, and are compatible with factory LS7 rocker arms and stands. The heads can accommodate 1.625-inch-diameter springs, and several are available. A 4.125-inch-or-larger bore is required. Base price is $1,130 each, fully assembled, through Summit Racing. GM 4.8 5.3 V8 C#706, 862 Assembled Cylinder Head. $499.99. Quantity. Add to Cart. This Chevy GMC Head is a new and improved casting. The cylinder head is either sold complete with all new parts or bare. This is OEM replacement quality at a fraction of the cost. This Cylinder Head has an industry leading 2-year Warranty. I’ve had some emails and messages, on the SierraC3TV Facebook page, making arguments against using 706 heads on my 6.0. In this episode, I give my reasons wh...

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Oct 24, 2023 · The 243 heads have a D-shaped exhaust and cathedral-shaped intake ports. The cylinder heads combustion chamber is smaller than the earlier cylinder heads fitted on LS1 engines. 243 is also more efficient than the earlier heads found on LS1. What do stock 243 heads flow? The GM stock 243 heads are designed to boost flow by up to 32.2 cfm and 28. ... The LS engines with 799 heads are 5.3L and 4.8L. The sophisticated architecture, cathedral-shaped port, and smaller combustion chamber work amazingly on these truck engines. The smaller combustion chamber with a higher compression ratio offers increased power output. The 799 LS heads boost horsepower up to 25 hp.Oct 24, 2023 · The 243 heads have a D-shaped exhaust and cathedral-shaped intake ports. The cylinder heads combustion chamber is smaller than the earlier cylinder heads fitted on LS1 engines. 243 is also more efficient than the earlier heads found on LS1. What do stock 243 heads flow? The GM stock 243 heads are designed to boost flow by up to 32.2 cfm and 28. ... 18 Jul 2016 ... Disassembling the 862's for clean up and port work. Heads will be ported to either a 205-210cc intake port and an 80cc exhaust port.Feb 8, 2022 · I flow a stock 706, 862, and 317 LS Head and share the numbers.

Suicidal Racing. 862 are for my ls1 an will make it around 11.9-1 compression and my lq9/ls3 combo will be around 13.5-1..the extra compression going from 10.2-1 on my ls1 to the 11.9-1 should be worth 30hp,the motor has a big cam (243/251 with 23 degrees of overlap) so it really needs the extra compression.The 862 heads are an excellent choice for any GM vehicle with an LM7 engine. Although the design is meant for high-performance settings, it performs well in the Avalanche, Express, Silverado, Sierra, Yukon, and other trucks or SUVs from the late 1990s to about 2007. You know if you’ve got an LM7 engine by looking at the eighth digit of the ...Nov 9, 2009 · The 2007 year had three 5.3L motors offered. The 2007 Classic (still a NBS) had the 5.3L with either the L59 (flexfuel version) or the LM7. The 862/706s are on the 99 and up 4.8/5.3L motors. The only difference about the L59 motor was the injectors. 2005 and up motors had the factory electric fans and electric TB. To get the best bang for your buck gen 3 lq4 + 862 Heads will give you a 10.5:1 compression ratio with smaller combustion chamber with a more responsive per...Summit 8702 stage 3 cam. Summit trunion upgrade, trick flow double springs, hardened pushrods. Stock 862 heads ( small chamber same as 706). Ls7 lifters. LS 9 head gaskets. Melling hp oil pump, summit double roller chain, vic jr intake, 750 or 850 dbl pumper, msd 6014 controller. Nos cheater plate.This test was a simple one involving a 5.3L LM7 equipped with the stock cam and factory 862 heads. To establish a baseline, we equipped the engine with a dual-plane Holley intake, a 650-cfm ...Mar 8, 2018 · [Trying to find an LS or LS-based Vortec engine for a swap or build? Check out Part 1 and Part 2 of our LS Spotter’s Guide.] … Upgrading LM7 Cylinder Heads. The stock heads can be CNC ported for more airflow and milled up to .030 in. for more compression. Flow numbers can be as high as 325 cfm at .600 lift. Run with the 317 heads, the modified 5.3L produced 448 hp at 6,800 rpm and 398 lb-ft of torque at 5,000 rpm. After installation of the 706 heads, the power …

The 862 head is a popular choice for both drag and road racing applications, as it boasts an efficient airflow and a small combustion chamber size, which can provide higher compression ratios and improved power and torque. ... LS 706 Head Specs [Features & Comparison with Other Cylinder Heads] Connect with Us. X social media …

In a nutshell, the LS 862 heads are the best-performing, affordable, and ported 5.3 heads that will best suit your car. If you are looking for a high-performing cylinder head at an economical price, then …18 Jul 2016 ... Disassembling the 862's for clean up and port work. Heads will be ported to either a 205-210cc intake port and an 80cc exhaust port.What is the difference between 862 and 706 LS heads? So, while the 862 heads and 706 heads look virtually identical at first glance, they have one major difference: their make. The 862 heads are sand cast while the 706 heads are semi-permanent mold. This means that, ...MLS Head Gasket for Notched 853, 862, 806 LS Heads Fits 1997-2013 4.8L 5.3L 5.7L LS-Based V8 Engines These gaskets are specifically designed for the 2001-earlier LS1, 4.8L truck and 5.3L truck heads that have a "notch" in the cylinder head deck, preventing them from sealing with a conventional MLS gasket. Can also be used on the …[Editor’s Note: This LM7 engine upgrade guide is part of a series of LS engine upgrade guides assembled by a team of LS experts at Summit Racing that we are sharing at OnAllCylinders. For a primer on the entire LS engine universe, read LS Engines 101: An Introductory Overview of the Gen III/IV LS Engine Family.]. Intro to LM7 Engines. Meet …LSXceleration Stainless Steel 8mm x 2.000 LS Intake Valve Set 15-22000-8 Stainless Steel LS Valves 2.165" Head x 8mm Stem x 4.870" OAL x 0.160" Tip x 45 degree seat angle Features: Hardened Stem Tip Chrome Plated Stem Fully Machined Surface Swirl... 15-22165-8 $96.00 Add to Cart Compare. Add to Cart Compare. Dart Stainless Steel GM …MLS Head Gasket for Notched 853, 862, 806 LS Heads Fits 1997-2013 4.8L 5.3L 5.7L LS-Based V8 Engines These gaskets are specifically designed for the 2001-earlier LS1, 4.8L truck and 5.3L truck heads that have a "notch" in the cylinder head deck, preventing them from sealing with a conventional MLS gasket. Can also be used on the …Apr 4, 2019 · The minimum recommended clearance is 0.035-inch, so you should be able to deck most blocks 0.010-inch without a problem, but be sure to check the piston protrusion before you install the heads. If ...

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A good shower doesn’t just get you clean; it also relaxes and refreshes the body and spirit. If your shower isn’t blissing you out, perhaps it’s time to upgrade to a shiny new show...You could also mill the heads. It takes .007" milling to remove 1cc from an LS1 head. If you have a stock 66cc chamber and you want to get down to 63cc chamber, 66-63 = 3 (you'll have to remove 3cc's).007 x 3 = .021" So to get your 66cc chambers down to 63cc you'd have to mill .021"#862 LS HEADS REBUILT PAIR. Heads have been cleaned Pressure tested. Guides checked and or replaced, valve seats cut on rottler head shop, surfaced .030 assembled with new seals and valve springs, This is for a pair of matching heads complete Shipping is for the pair No core charge or need to return any ...The LS3 was run with a Holley HP management system and FAST injectors. With stock heads, the modified LS3 combination produced 552 hp at 6,400 rpm and 513 ft-lbs of torque at 5,000 rpm. After installation of the TFS Gen X 255 heads, the power numbers jumped to 571 hp at 6,500 rpm and 525 ft-lbs of torque at 5,200 rpm.$149.99. custardcoresupply (2,999) 99.1% Buy It Now. +$25.00 shipping. 5 watchers. 862 LS2 LS1 Gen III Gen Cylinder Head W/ Valves & Springs 5.3 / 4.8 LS1. GOOD USED …Despite numerous differences the Gen III LS Engine and Gen IV LS Engine cylinder blocks share a lot of the same traits. 4.400 Bore Spacing (same as the original SBC) Deep Skirt Block with Six Bolt Cross Bolted Main Bearing Caps (reminiscent of the old Ford side oilers, FE, and some early hemi blocks) Center Main Thrust Bearing. 9.240 …227cc SBC LT4 Race Cylinder Head. AFR's 227cc "Race Ready" and "Competition" LT4 heads feature 100% CNC ported intake, exhaust & chambers, A356 aluminum castings and high quality components throughout. This head features 60/40 valve spacing and requires shaft mount rocker arms for optimum valve train geometry (can be used with .050 offset ...LSA and LS9 heads were basically an improvent on the LS3 head, but for emissions and improved driveability they have a flow vane in the intake port. These heads can be CNC ported to remove the vane … ….

862 is a 5.3 liter head. Smaller combustion chamber (61.5CC), increased CR. 241 is a 5.7 liter head. Larger combustion chamber. Gains from a higher ration rocker arm (1.8 vs 1.7) are going to be minimal. Expect approximately 10 peak HP. IMO, if you have any plans of adding a aftermarket camshaft later down the road, pass on the 1.8 ratio rockers.[Trying to find an LS engine for a swap or build? Check out Part 1 and Part 2 of our LS Spotter’s Guide.] … Upgrading LR4 Cylinder Heads. Casting number 862 or 706 heads were used and sported a 61cc chamber but had tiny 1.890 intake valves. The stock heads can be CNC-ported for more airflow and milled up to .030 inch for more compression.Swapping in 243 heads will increase flow a little, but unless you mill them first, you'll lose compression. If anything, you want to raise compression. For just a basic bolt-on 5.3, the 862 heads will do a decent job. Texas Speed has ported 5.3 heads for a reasonable price if you want more flow.Most importantly, 862 LS heads provide a lot of power at a cheap rate. Moreover, hundreds of thousands of old 862 heads built in 1999 are available in the exhaust port volume ranging from 4.8 to 5.3 L, often meant for truck heads. Why Casting 862 Heads Is A Great Choice? Casting 862 heads could be a great idea because of the following reasons:NEW ONLINE STORE!!!https://lsnasty.comhttps://lsnasty.comFollow The LS NastyChannel: http://youtube.com/lsnasty @ls.nastyLS Nasty700 N 13th StErwin NC 28339S... Small Block Chevy LS Cylinder Heads by Casting Number 10215339 – LS Small Block V8 1997 346, LS1, aluminum, 68cc chambers . 12480005 – LS Small Block V8 2000 LS1, GTZ, aluminum, 38cc chambers, 2.125/1.625 valves, angle plugs . 12556743 – LS Small Block V8 1999 325, 5.3L, aluminum, truck, van . 12558806 According to the trusty flow bench, the chamber work did indeed improve the flow rate of our 706 heads, with the largest gains coming at 0.200 lift for the intake and 0.400 lift for the exhaust ...189 posts · Joined 2010. #1 · Jun 13, 2016. I've read a dozen posts about cracked LS heads between the valve seats, specifically 317 casting heads. This has got to be a very common problem, as I have six 317 head cores here and five of them are cracked between seats on atleast once cylinder. All of these heads were just cores pulled from …Mar 8, 2018 · [Trying to find an LS or LS-based Vortec engine for a swap or build? Check out Part 1 and Part 2 of our LS Spotter’s Guide.] … Upgrading LM7 Cylinder Heads. The stock heads can be CNC ported for more airflow and milled up to .030 in. for more compression. Flow numbers can be as high as 325 cfm at .600 lift. 862 ls heads, [Trying to find an LS engine for a swap or build? Check out Part 1 and Part 2 of our LS Spotter’s Guide.] … Upgrading LR4 Cylinder Heads. Casting number 862 or 706 heads were used and sported a 61cc chamber but had tiny 1.890 intake valves. The stock heads can be CNC-ported for more airflow and milled up to .030 inch for more compression., American Airlines is reinforcing its position at the top of the pack in Hilton Head, South Carolina, with new flights to Chicago, Dallas/Fort Worth and Philadelphia next spring. Am..., The 241 heads were used on 5.7L LS1 applications and are considered by many to be just a minor step up in performance from the 706. In terms of peak flow, the 241 heads offered 242 cfm at 0.700 ..., 706 heads tend to be more popular than 243 heads with those who run naturally aspirated engines. While they don’t have the same size combustion chamber they also don’t have the tendency to lower the compression ratio and reduce horsepower. When looking to replace your heads, they offer a high degree of consistency since they are ..., Our Performance Rebuild option includes our high end CNC'd valve jobs, precision valve grinding, milling to any chamber volume, cleaning, inspection, and professional assembly. Typical gains are 10-20rwhp. 226cc Full CNC Porting Package. The go-to head for 450-500rwhp 5.7/6L's. Our high end machine work applied to GM's best cathedral head ... , Sep 6, 2017 · 706/852/862 '99-up 4.8L-5.3L truck heads 61.15cc. ... L92 heads (often referred to as LS3 heads) moved to a rectangular port and are some of the best LS heads ever made, far outflowing their ... , May 21, 2023 · 863. Rectangle. 4.750" +- 0.003". 12604861. 12610716. 12675872. Share this article. We've tried to boil down the GM part numbers, casting numbers and other LS cylinder head information into an easily usable (and ideally definitive) cross reference. Note that we're not perfect and some of this data may not be perfect so use it for what you will. , No 243s or 799 have the casting defect that I've heard, it was pretty isolated to the castech only 706's on gen III 4.8/5.3's. There are 2 other sets of 706's that are not affected. The early sand cast heads come as 862s and 706's, and a die cast 706 that isn't made by castech. 16 posts., Katech CNC Porting LS1/Truck 862, 706 Cylinder Heads (PAIR) In Stock (0) Reviews: Write first review. Description: CNC Porting Service Item #: KAT-M7107. Condition: New. Price: $534.99. ... Description: For LS heads with dual springs and OEM or most bronze guides Item #: KAT-7536. Condition: New. Price: $7.99. Qty: Add to Cart, According to the trusty flow bench, the chamber work did indeed improve the flow rate of our 706 heads, with the largest gains coming at 0.200 lift for the intake and 0.400 lift for the exhaust ..., The 243 heads came on the powerful LS6 engines from 2001 to 2006. Although the heads were initially made for C5 Corvettes, they later found their use in engines like the truck-spec LQ9 and LQ4. The LQ4 and LQ9 had 6 cc larger combustion chambers. LS6 was also used in some Camaros and Pontiac GTOs. The 243 heads are …, 18 Jul 2016 ... Testing the strength of the Easy Off oven cleaner on dirty aluminum. Test heads 110k heads with full grime, carbon, oil etc., Check out Part 1 and Part 2 of our LS Spotter’s Guide.] ... behind top intake on block it has 12559767 on rear of block behind fly wheel is 12551358 with 862 heads. Mexican build gm plant motor, which is it , 4.8 or 5.3. Reply. Kerry D Browning says: December 14, 2023 at 11:35 am., Great cylinder-head airflow has been a key enabler of the LS-Series’ exceptional performance. Chevrolet Performance delivers those power-building attributes to you with a range of production-style aluminum heads — from the LS6 heads for smaller-displacement engines to LS7 style heads for 427-inch-and-larger combinations, our aluminum heads …, 243/317/799 LS6/LS2, 241/853/806 LS1, 821/LS3 & LSA/9, 823/L92, 706/862/5.3 LS1, 8452/LS7. GM 243, 799, & 317 LS2/LS6 Options: Performance Rebuild Package ... Our most powerful GM casting based LS head. Typical stock short block LS7's manage 590-640rwhp SAE with daily drivable hydraulic cam grinds. Proven capable of supporting …, These large-runner heads have a 12-degree valve angle, like stock, and are compatible with factory LS7 rocker arms and stands. The heads can accommodate 1.625-inch-diameter springs, and several are available. A 4.125-inch-or-larger bore is required. Base price is $1,130 each, fully assembled, through Summit Racing., 706/862 LS CNC Ported Heads. Speed Works has teamed up with Wilkes Performance to bring you the most powerful heads available. We have a few options you can purchase …, Dec 24, 2017 · The 241 heads were used on 5.7L LS1 applications and are considered by many to be just a minor step up in performance from the 706. In terms of peak flow, the 241 heads offered 242 cfm at 0.700 ... , Small Block Chevy LS Cylinder Heads by Casting Number 10215339 – LS Small Block V8 1997 346, LS1, aluminum, 68cc chambers . 12480005 – LS Small Block V8 2000 LS1, GTZ, aluminum, 38cc chambers, 2.125/1.625 valves, angle plugs . 12556743 – LS Small Block V8 1999 325, 5.3L, aluminum, truck, van . 12558806, GM LM4 / LM7 / LR4 4.8L 5.3L Cylinder Heads PAIR # 862 w/ rocker arms OEM. $649.99. Free shipping. Check the item description to confirm this fits your vehicle. Hover to zoom., 373/873 LQ4 iron heads - 71.06cc. 706/852/862 '99-up 4.8L-5.3L truck heads - 61.15cc ... L92 heads (often referred to as LS3 heads) moved to a rectangular port and are some of the best LS heads ..., Nov 27, 2017 · Our fellow tech writer and dyno-flogger Richard Holdener reports a gain of roughly 15 hp with stock 5.3-liter heads on a 6.0-liter. Our 5.7-liter head test bumped the average power by 9 hp but ... , Cylinder Heads & Camshaft Packages. Add 100+ horsepower to your GM LS or Gen 5 LT engine with a Texas Speed & Performance cylinder heads and camshaft package! Our packages will include cathedral port, square port, and rectangular port cylinder heads to accommodate LS1, LS2, LS3, L99, LS6, LS7, LSA, LQ4, LQ9, L83, L86, LT1, and more! …, The L59 engine is a 5.3L Gen. III iron-block engine used in GM trucks and SUVs between 2002 and 2007. It is essentially the flex-fuel version of the LM7 . For marketing purposes, it was also known as the Vortec 5300. The engine specs and information listed here is for a stock L59 engine. Mechanically similar, General Motors’ …, Great cylinder-head airflow has been a key enabler of the LS-Series’ exceptional performance. Chevrolet Performance delivers those power-building attributes to you with a range of production-style aluminum heads — from the LS6 heads for smaller-displacement engines to LS7 style heads for 427-inch-and-larger combinations, our aluminum heads …, Which factory LS cylinder head works best with a turbo, 706 or 317? It's the age-old comparison, airflow vs compression. This LS head shoot out between the s..., Part 6 of the LS 5.3L Build will cover Installation of the 862 Aluminum Heads, Lifters, Pushrods, and Rocker Arms. Project Rowdy is a restoration on a 1979 J..., In terms of cylinder heads, we included the 706 small-valve 5.3L heads, the 241 (LS1), 317 (6.0L truck), and 799 (as a stand-in for the hallowed 243) heads. The idea was to flow and measure each ..., Heads-up displays (transparent displays that let drivers see data without looking down) are built-in on some modern luxury cars, but if you're not lucky enough to have one, here's ..., The 2007 year had three 5.3L motors offered. The 2007 Classic (still a NBS) had the 5.3L with either the L59 (flexfuel version) or the LM7. The 862/706s are on the 99 and up 4.8/5.3L motors. The only difference about the L59 motor was the injectors. 2005 and up motors had the factory electric fans and electric TB., Microsoft Excel features alignment options so you can adjust the headings in your worksheet to save space or make them stand out. For example, if a column heading is very wide, cha..., GM LS1 Gen IV Cylinder Head 862 BIG VALVE LS3 Spring Milled 025 High Performance. Opens in a new window or tab. Remanufactured. $679.99. teauran_0 (515) 100%. or Best Offer. Free shipping. 1999-2008 Chevy Reman Cylinder Head casting #862/706 5.3 4.8 Pair (Both) Opens in a new window or tab., Oct 24, 2023 · The 243 heads have a D-shaped exhaust and cathedral-shaped intake ports. The cylinder heads combustion chamber is smaller than the earlier cylinder heads fitted on LS1 engines. 243 is also more efficient than the earlier heads found on LS1. What do stock 243 heads flow? The GM stock 243 heads are designed to boost flow by up to 32.2 cfm and 28. ...