862 vs 243 heads

Aug 6, 2020 · The 243's have bigger valves which do better on 4.0" and larger bores. On the smaller 3.898/3.78" bores of the LS1/6 & all 5.3/4.8's the 706 are very decent. On a 4.00" bore of an LQ4 though it is splitting hairs. On the same cam, on the same engine, the heads are going to perform within +/- 5hp/5tq of each other, it is almost meaningless.

Why are Chevy 706 Heads better than 317 or 862 Heads? 706 Heads Vs. 317 Heads; Most people tend to prefer 317 heads as they have improved ports, same as 243 and 799 Heads, which are more expensive. However, 317 heads have larger combustion chambers of 71.06cc, which will cost performance, especially on a naturally aspirated engine. This ...1291 posts · Joined 2007. #12 · Feb 3, 2010 (Edited) i purchased at set of 799 heads last summer for $100.00 bucks ,from another member on this forum. keep us posted when this project is complete. im going the budget daily driver route myself. i will be topping mine of with a fast,and a ported throttle body.This results in a slightly higher compression ratio using AFR heads. AFR: 56cc combustion chambers, smaller valves. Trick Flow: 58cc combustion chambers, larger valves. On smaller displacement engines, smaller valves and ports in AFR heads can provide better low-end torque source. The AFR 165, for example, is known for its good torque curve.Office. Aug 3, 2019. #13. There's the #315 head for 64 and 65. There is also a # 080 head for those years. In 66 there was a #178 (early) #234 (late) and also the late #920 head which was used late in 66 and into 67. In 68 when 273's went open chamber and hydraulic cam, they shared the #675 head with the new LA 318.Showing the progress Porting the 862’s for my Turbo 4.8 project. Yes it’s a slow process and I limit how much I can do each day.I’m in the dirtiest portion ...Aug 6, 2020 · The 243's have bigger valves which do better on 4.0" and larger bores. On the smaller 3.898/3.78" bores of the LS1/6 & all 5.3/4.8's the 706 are very decent. On a 4.00" bore of an LQ4 though it is splitting hairs. On the same cam, on the same engine, the heads are going to perform within +/- 5hp/5tq of each other, it is almost meaningless.

So how do 862 heads compare against the factory heads these engines come with? The 5.3L LM7 crate engine from GM trucks feature stock 243 heads. 243 …Here is what it was: -283 bored .060" over to 292. -gm turbo heads fully fully ported. -11.8:1 duffys custome forged pistons. -solid roller cam 276/280 @.050 .670/.630 108* lobe seperation {in an auto or these days it would be a 104-106* lobe center} -edelbrock tunnel ram.In the world of automotive engines, the choice of cylinder heads can significantly impact your vehicle's performance. Two popular options that have gained a lot of attention are the 862 and 317 heads. Each has its strengths and weaknesses, and understanding the differences between them is crucial for making an informed decision. …Unless your building something something over 7000rpm an OEM head is the way to go. People routinely get 1000hp out of them. On 4.8, 5.3, 5.7, NA 6.0 - I always recommend the 243. Maybe even milled a touch if needed. On 6.0+ the 823 variant of the rectangular head is great. 65 Chevelle Malibu 2dr HT LS Swapped.Aug 1, 2023 · The 862 Cylinder Heads. Features and Specifications. In contrast to the 243 heads, the 862 cylinder heads are typically made of cast iron, which makes them heavier but also more durable. They have smaller ports compared to the 243 heads, which can limit airflow to some extent.I know 243's are good but didn't know if 862's are any good when they're right in front of me. They won't flow as good as 243 but you'll have better compression vs 243. You can have them ported for a reasonable price and have a good valve job done on them to make them perform. They'll never be rock stars but they'll do fine with that cam.

GM never made an iron LS1. Look at the front of the block and it will clearly have the displacement cast into it. If it is a 5.3, slap some 243's on it and a punchy mid range cam in it and it'll be a good street brawler. If it is a 4.8, some aftermarket heads with revised valve angles and dual valvesprings (TF Gen X 205 for example) and a cam ...LET'S TALK TECH, ANYONE EVER SEE A SET OF STOCK 243 HEADS FLOW 270+ CFM? WE COMPARED 243 HEADS TO 862 HEADS, PORTED, …With that, we packed up our heads and shipped them off to Lingenfelter Performance Engineering (LPE). Lingenfelter's 243/799 CNC program opens the intake port (left) to 228cc and increases flow at .600-inch of lift to 320 cfm. The exhaust ports get opened up to 84cc, and the chambers stay at 65cc in the off-the-shelf configuration.C5 Tech - 853 heads vs 241 castings - :sadangel:I have an 04 coupe with stock heads but I just purchased a set of ported and polisshed 853 castings. ... For a n/a car, most start with 243 or 5.3l (862 or 706) heads for the compression benefits. Not many mess with modifying LS1 heads anymore, at least not like they did in years past. Reply Like ...

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ported 243s, ls2 stock shorty + cam. procharged. 740~whp. That sounds healthy. If I can pull off 700 rwhp like that through my A4 for the time being with 234's or 317's I think I'll be satisfied. SOFAKINGGR8 said: Numbers in sig, recently made over 700whp a few weeks ago, and have been over 600whp since April.I recently jailbroke my iPhone and now that it's done I'm very overwhelmed by Cydia. I've downloaded a couple apps, but I don't understand most of what I'm looking at. The descript...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 ...Vehicle enthusiasts argue about 243 heads Vs. 799, as well as 243 heads Vs. 862 heads . However, if you desire improved horsepower with excellent power output, the 243-cylinder head is a perfect choice.

Simply put, the .243 Winchester became the darling and the .244 Remington became the goat. The reviews took their toll, and the .244 Remington began to wither. In 1963, Remington made their first attempt at the name game. They revised the rifle and ammunition, equipping it with a 1:9″ twist rate in 1958 and renamed the cartridge the 6mm ...Feb 13, 2020 · The 706 Vortec heads are even slightly superior to the commonly found 862 heads. The reason is that the 706 heads are SPM ... these are basically 243 heads; See All 5 Photos. Vital Specs for 706 ...You will see 50+rwhp probably at same psi. 317/243 heads flow MUCH better than 862 truck heads. flow more at .400 lift than the 862's flow at .550 lift. Boost will also lover the bigger 2" intake valves. 243's with their smaller combustion chambers would be a better match. than the 317's.Jun 11, 2020 · 64nailhead. 4523 posts · Joined 2012. #5 · Jun 13, 2020. Here's your decision - the 317's will work better if you're looking for boosted 1000+ HP, but the 243's will work better everywhere below that. Something to keep in mind, old school SBC and SBF static and dynamic compression ratios do not apply to LS heads.Regarding finish, many reviews say 799s deliver a smoother one than its rival when pitching them against each other. 823 vs 243 Heads. As mentioned about the LS 823 heads specs, its bigger intake port owns a 70cc, whereas the common 243 L6 cylinder heads have basically a smaller volume at 64cc.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.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.Why are Chevy 706 Heads better than 317 or 862 Heads? 706 Heads Vs. 317 Heads; Most people tend to prefer 317 heads as they have improved ports, same as 243 and 799 Heads, which are more expensive. However, 317 heads have larger combustion chambers of 71.06cc, which will cost performance, especially on a naturally aspirated engine. This ...I knew the flow was the same just didn't realize gm put the 243's on the 5.3's. I better look at the driver side because I remember GTO's and vettes with 1 - 799 head and 1 - 243 head on the other side. My LS6 has 10.5:1 with 243's and I love it. The 09' has great response also eventhough I haven't tuned it yet. 97 GMC, 2002 LS6.Aug 2, 2010 · Compression Ratio & Combustion Chamber Size. I'm looking to install a set of 243/799 heads on my 5.3. The stock heads have a combustion chamber volume of 61.15cc, and 243/799 heads have a volume of 64.45cc. My stock compression ratio is 9.5:1. I already know that I need to mill the heads .007" to lose 1cc of volume.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.

Are the 799/243 that much better ported , then the 862 ported with bigger intake valves? Heads are for a turbo car running M1. Thanks Mike. in this thread in this sub-forum in the entire site. Advanced Search Cancel ... 862 5.3 heads. Jump to Latest Follow 1 - 3 of 3 Posts ...

Here’s a quick data sheet on the specs of 799 heads. Due to the similarity, 243 heads should follow the same characteristics in normal situations: Combustion chamber volume: 64.45cc. Intake port volume: 210cc (sometimes seen as 209cc too) Exhaust port volume: 75cc. Intake valve diameter: 2.00 inches.320. Exh. 111. 153. 193. 209. 219. 221. Our fully CNC'd 243 heads give your choice in stock 2.0intake/1.550 or upgraded 2.02Intake/1.600 exhaust with an intake flow of 320cfm and an exhaust flow of 221cfm.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. These 706 heads for sale are perfect for your 5.3L V8 engine, offering enhanced power and efficiency.The combustion chamber diameters can play a big role in hindering flow and performance. The 706/862 combustion chamber diameter measures out at around 3.670" and the 243/799 combustion chamber messages out at around 3.880” and giving the fact that the LM7 5.3L engine bore is 3.780" this more than likely has something to do with the power loss ...RPO L99 and LS3 cylinder heads are aluminum with 68cc combustion chambers, rectangle intake ports with 257cc runners, D-port exhaust with 87cc runners, 2.165˝ intake valves and 1.590˝ exhaust valves. These heads can be CNC-ported to improve on flow and milled for higher compression. These heads are almost the same, but the L99 heads used a ...The 862 heads have a smaller combustion chamber size than the stock 243 heads. The chambers measure 61cc, which bumps static compression over 10:1 with a standard 3.622″ LS crankshaft. This can improve the power output and durability of the engine.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.

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Location. Nebraska. Feb 15, 2009. #6. I have a 6-284 and my idiot ex-hired man had a 243 AI and they both shoot well. My 6-284 is on the edge with high BC bullets and is very picky. I have suspected that that the 6-284 would be better suited to lighter bullets with a slow twist.The first has to do with port shape. The LS6 and the later LQ9-LQ4 heads used reshaped intake ports and D-shaped -- as opposed to oval-shaped -- exhaust ports for better flow: 200 cfm intake and 70 cfm exhaust for the 241's, and 210 intake and 75 cfm for the 243's. The second major difference is that the LS6 heads used hollow, sodium-filled ...Our 706 & 862 ported heads include: Our in house CNC port. PCD surfaced to your desired chamber size. Proprietary competition valve job. Hand blended valve job. ***This is our most common setup, but if this doesn’t meet your needs please call us so we can get you set up to your needs***. Intake valve: 2.02 Exhaust: 1.57.706 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 ...Regarding finish, many reviews say 799s deliver a smoother one than its rival when pitching them against each other. 823 vs 243 Heads. As mentioned about the LS 823 heads specs, its bigger intake port owns a 70cc, whereas the common 243 L6 cylinder heads have basically a smaller volume at 64cc.The L33 is an example and the its pistons are 4.8l piston, same part number BTW. All the later 5.3l's have flat tops and 243 heads. So the blocks are the same. The rods and crank are the only differneace. Use the crank and rods from the 5.3L and use 243 heads and have the 5.3L H.O. or L33 (well an iron block version at least).Find Chevrolet Performance LS3 Cylinder Heads and get Free Shipping on Orders Over $109 at Summit Racing! Fit any LS engine with Chevrolet Performance LS3 cylinder heads. Manufactured from aluminum alloy, these GM stock replacement heads are assembled with intake and exhaust valves, stem seals, retainers, springs, and locks. Great cylinder head airflow has always supplied the LS Series with ...If you are just installing stock heads with no work, forget the 5.3 heads and just get a set of decent 243 heads which will still bump CR up 1/2 point on the LS1 (64cc combustion chambers compared to 66 CR of the 241 heads). 2004 torrid red with red interior A4 GTO (1 of 499)The depth of the Columbia River ranges from 20 feet to 170 feet at various points along its route, and its total length is 1,243 miles. Locks, dams and reservoirs built on the Colu...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 head? Engine is stock other than cold air intake. ….

To help your comparison a little more, the ported 241 castings flow a max of about 295-300 CFM and are 215 CC's after porting. The ported 243's flow a max of 315-320 CFM and are 225 CC's after porting. In our experience, apples to apples the ported 243's are worth about 20 RWHP over ported 241's (with a similar torque curve down low).By Paul Johnson - March 9, 2016. This article applies to Chevrolet Camaro and Pontiac Firebird (1998-2002), as well as all LSx engines. The cylinder head (or "head") has several main functions. Its first order of business is sealing the top of the cylinder (the piston seals the other end). The second order of business is to provide a way for ...So what the difference between some milled 862s and some stock 243s? Also how big of a difference would the 243s and a nnbs intake do on a 2003 4.8? 862 s Vs 243 s.....Sort by: Add a Comment. J8ke_Stampede. • 1 yr. ago. There's no debate, it's been proven the 862/706 heads will make more power than the 317's. 317's and 241's are the worst factor LS heads. It's also not only because the chamber size and compression ratio either. 862/706 heads have higher velocity and better coefficient of discharge. 8.243 04 up LS6 aluminum center bolt 5.7 ***These castings were also used around 05 in truck applications*** 862 99 and up 4.8-5.3 Truck heads 706 99 and up 4.8-5.3 Truck heads 799 05 and up 4.8-5.3Truck heads ***reportedly came on a few corvette's too*** These are basically 243 Heads 873 99-00 LQ4 6.0 Iron center bolt headsThe 243 and 706 heads are the exact same. The only difference is that on the ls6 specific 243s, the exhaust valves were sodium filled to make them ever so slightly lighter. The 243 heads and 799 heads are the same. The 706 heads are the same as the 862 heads. Yep I'm dumb.5.3 vs Vortec 350 in a Jeep; Changed direction on project. A1000 fuel regulator questions; Fuel boiling.... Breaking up at 5k and above RPM; ... 862 vs. 243 Heads; Holley Tunnel Ram; Easiest way to rig starter? perf rpm; 5.3 teardown/build; started my swap; Help with Rad Fans; FYI for Performer RPM users!!862 Vs 243 Heads . One of the first things that you need to consider when building a performance engine is what heads to use. There are many different options on the market, but two of the most popular choices are 862 castings and 243 castings. So, which one is better? The 862 heads were originally designed for high performance applications. 862 vs 243 heads, 243 cylinder heads have cathedral-shaped intake ports and a D-shaped exhaust, which helps to enhance air and fuel intake, smooth combustion, and quicker exhausting. This …, The 243 heads have larger intake and exhaust ports than the stock heads, allowing for an improved airflow that increases torque and horsepower. With this increased airflow comes a greater capacity to burn fuel efficiently, giving you better performance overall. Additionally, these upgraded 243 heads are designed with a higher-lift camshaft so ..., 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 jumped to 468 hp at 6,800 rpm and 413 lb ..., 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., Showing the progress Porting the 862’s for my Turbo 4.8 project. Yes it’s a slow process and I limit how much I can do each day.I’m in the dirtiest portion ..., stock 243 chambers are ~64.5cc but they're going to vary a bit from head to head. Think the original LS2 head gaskets had a compressed thickness of 0.055", but the newer replacement LS2/LS3 head gaskets are 0.051". 2006 GTO, 6.2L, XAIR, Stage II Formato Intake & TB, P&P 243's, 228r cam, UDP, Kooks SS LT, Catted Mids with factory cat-back ..., I wonder if the Edelbrock head was an LS1 or a 5.3L specific head. The bore difference of the LS6 to the 5.3 liter motors is 99mm vs 96.01. 3mm diameter is only 1.5mm smaller from the wall to the valve. I know it will shorud but the test showed it worked. The engine ran on an engine dyno and ran well., The LQ9 is a 6.0L Gen. 3 small block engine used in GM trucks between 2002 and 2007. For marketing purposes, it was also known as the Vortec HO 6000 or VortecMAX. The information listed here is for the stock engine. Mechanically similar, General Motors' LS and LS-based Vortec engines wound up on almost every branch of the GM family tree ..., In contrast to the 243 heads, the 862 cylinder heads are typically made of cast iron, which makes them heavier but also more durable. They have smaller ports compared to the 243 heads, which can limit airflow to some extent., The engine also had 799 or 243 casting heads which are closely related to the LS6. The engine has flex-fuel capability. In 2010, the LC9 gained VVT as well as pistons with valve reliefs, and compression dropped from 9.9 to 9.6:1. … For LC9 engine specs, read this: LC9 5.3L Engine Specs: Performance, Bore & Stroke, Cylinder Heads, Cam Specs ..., The best factory cathedral port heads (243, 799, and 317 castings) flowed near 250 cfm, which represented a huge step up from the conventional small-block heads that preceded them. However, the ..., 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., The 799 and 862 heads have their own pros and cons. While the 799 heads offer better flow and performance, the 862 heads offer better combustion chamber design and improved efficiency. Ultimately, the choice depends on the specific needs and goals of the engine. Pros of Using 862 Heads. Cons of Using 862 Heads., 243 04 up LS6 aluminum center bolt 5.7 ***These castings were also used around 05 in truck applications*** 862 99 and up 4.8-5.3 Truck heads 706 99 and up 4.8-5.3 Truck heads 799 05 and up 4.8-5.3Truck heads ***reportedly came on a few corvette's too*** These are basically 243 Heads 873 99-00 LQ4 6.0 Iron center bolt heads, 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..., 317's would kill your compression, get the 243's. The 243 chambers will make more power than the 241's or 317's, even if flow and chamber volumes are the same. You are correct, the 317 has a bigger chamber than the 241 & 243, thus dropping compression ratio. That being said I have seen a few 5.7's with 317's, and worked quite well., The reason is simple: The more you squeeze the air and fuel mixture in the combustion chamber, the more power you can create. In theory, forcing air and fuel in as small a combustion chamber as possible (measured in volume) will yield maximum engine compression and horsepower. There are a number of ways to accomplish the task., 2005 GTO QSM, 418" NaturallyAspirated ,Bullet Racing cam, 243 heads, 6speed, Kooks 1-3/4" headers w/cats ,matchported FAST 102,NW 102mm, 3.73 gears PB in 1/8th 7.76@97 on Firestones with 1.97 60'. Tick Performance tuned., Are you looking for a new shaver head for your Norelco electric razor? If so, you’ve come to the right place. In this article, we’ll provide you with all the information you need t..., 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 ..., The cam used was a 231/231 (LSL lobes) on a 114+2. No ported 243 head at 1500 will get you much over 470rwhp and even that will be with a huge cam that most wouldnt want to live with. A Trick Flow 225 with a mid 230's cam has the H/C 1/4 mile record in an LS2 and it isnt a crazy overlap cam., The 799 heads will need to be milled a bit to get the compression ratio back to where it needs to be. That will determin what pushrod to go with. The stock heads should be something like 61.15 cc. The 799 heads should be 64.45. . 1994 SFBD extcab longbed 20/22 406sbc . Project thread., One popular option for 383 strokers is aluminum heads. They offer several benefits, such as being lightweight. This results in reduced overall weight, which enhances performance. Additionally, aluminum dissipates heat well, allowing the engine to run cooler., 706 vs 862 heads - Thoughts on port/polish? My current LS is a stock LM7 out of a '05 Silverado with about 130k'ish miles on it (112k when pulled; about 20k on the swap). Only major change is the Holley Mid-Mount kit on the front and some generic block-hugger headers. Otherwise running stock 706 heads and stock truck intake with DBW throttle body., Street Performance of The 706 Head. It’s worth noting that the 706 heads have a larger combustion chamber than the 862 heads, which measures at around 71cc. While this might sound like a disadvantage, it can actually be helpful for engines running on lower-octane fuel or those using forced induction., 3012 posts · Joined 2008. #1 · Apr 14, 2012. I have a 2004 Aluminum 5.3 with 70k miles that has 862 heads on it. I also have a set of 243 heads off of a 2009 Aluminum 5.3. Which heads should I use? I've been told the 243's flow better and the 862's supposedly raise compression .5 a point., The 243 Heads are cast iron cylinder heads that have been CNC-machined to create larger intake and exhaust ports. The combustion chambers have also been machined to be smaller, which increases the compression ratio. While the 243 heads are not the newest or best option out there, they offer a great value for the price., For the price you pay for us to port 241s they will flow the same numbers as a stock 243 head." ... but I just noticed that Ai's 706/862 5.3 heads flow tremendously especially on the exhaust CFM (269CFM at .600). I just don't know how I could really benefit more from such a high exhaust CFM vs. having a higher intake CFM on TSP's 2.5 LS6 ..., hivoltagedriver. Port and polish on a set of 243's is usually ~20hp. A set of ported 243's on your LS1 should make a sizable difference, especially with a cam. '09 PSM G8 GT w/ Premium & Sport packages. Go: Kooks 1 7/8" LTs, catless mids, Corsa, VCM OTRCAI, Rick C. AirRam intake and ported TB, tuned by me., 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 jumped to 468 hp at 6,800 rpm and 413 lb ..., Aug 24, 2022 · The 862 head is commonly utilized in high-performance cars, racing, and sports cars. It’s also found in some luxury and sports cars. The 862 is a 12-valve design that utilizes two intake valves per cylinder and one exhaust valve per cylinder. The combustion chamber volume is 84cc for the 862S, 83cc for the 862C, 84cc for the 862F, 82cc for ..., For the 862 heads, the intake valve size is 1.89 inches and the exhaust valve measures 1.55 inches. The 706 heads, however, feature an intake valve size of 2.00 inches and an exhaust valve size of 1.55 inches. In terms of port volumes, the 706 heads have larger intake ports., May 7, 2023 · Street Performance of The 706 Head. It’s worth noting that the 706 heads have a larger combustion chamber than the 862 heads, which measures at around 71cc. While this might sound like a disadvantage, it can actually be helpful for engines running on lower-octane fuel or those using forced induction.