Discussion Forum - Northstar Chevelle Club

It is interesting, I never knew they made a steel casting, looks like they were on 99-00 LQ4 motors.   The easiest way to ID the LS heads is the 3 digit casting number on the spark plug side of the head.  Bryan's list has part numbers, and several part numbers were made from the same casting.   The 243 or 799 casting are the most popular Gen 3 head.  

Here's more reading than you ever cared to do on LS heads:


933 97 aluminum perimeter bolt 5.7
806 97-98 aluminum perimeter bolt 5.7 
853 99-00 aluminum center bolt 5.7 
241 01-03 aluminum center bolt 5.7 (some late MY00 cars got 241 castings)
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 
317 01 and up LQ4 and LQ9 6.0 aluminum center bolt heads 
035 01 - 04 LQ9 6.0 aluminum center bolt heads 

Even more detailed info: 

Casting Numbers 241, 806, 853 
Head: 1997+ LS1 5.7 Liter Passenger Car 
Material: Aluminimum 
Part Number: 
12559806 (1997-98) Chambers = 69cc
12559853 (1999-00) 
12564241 (2000-03) 
Combustion Chamber Volume: 66.67cc 
Compression Ratio: 10.1:1 
Intake Port Volume: 200cc 
Exhaust Port Volume: 70cc 
Intake Valve Diameter: 2.00 inches 
Exhaust Valve Diameter: 1.55 inches 

Stock Head Flow Numbers 
Chamber 66.67 cc------0.100--0.200---0.300---0.400---0.500---0.550--0.600 
Intake 200 cc------------67----122-----178-----215-----219-----223---227 
Exhaust 70 cc------------52-----97-----133-----156-----170-----76----180 


What you need to know: 
The standard issue LS1 heads is best all-around head for the street / strip engines . A thorough porting and millimg job plus a valve upgrade on these will really wake up your engine.The heads have undergone only minor revisions since their introduction in 1997 , most notably a switch from perimeter to center valvcover bolt configuration for the 1999 model year. Each style has its own dedicated valvecovers and coilpacks mounting apparatus.



Casting Number 243
Head: 2001 LS6 5.7 Liter Passenger Car 
Material: Aluminimum 
Part Number: 
12564243 
Combustion Chamber Volume: 64.45cc 
Compression Ratio: 10.5:1 
Intake Port Volume: 210cc 
Exhaust Port Volume: 75cc 
Intake Valve Diameter: 2.00 inches 
Exhaust Valve Diameter: 1.55 inches 

Stock Head Flow Numbers
Chamber 64.45 cc-------0.100---0.200--0.300--0.400---0.500---0.550---0.600 
Intake 210 cc------------62------126----184----224-----251----256----257 
Exhaust 75 cc------------57------108----143----163-----176----180----183


What you need to know: 
The LS6 cylinder heads is essentially a tuned-up version of the LS1 head. At 65cc, the combustion chamber is slightly smaller and more efficient than the LS1. The more efficient design shortens burn times and ultimately means less ignition timing advance is required to produce the same power. And because less timing allows more efficient combustion, the Ls6 heads allow the engine to produce more torque. The exhaust port is a unique D-shape that improves flow. LS6 heads are the best choice only when all-out power is needed. Be prepared for a big price tag at the dealer or steep core charge from your head porter.



Casting Number 706 and 862
Head: 1999+ 4.8L / 5.3 Liter Truck 
Material: Aluminimum 
Part Number: 
12559862 
12561706 
Combustion Chamber Volume: 61.15cc 
Compression Ratio: 9.5:1 
Intake Port Volume: 200cc 
Exhaust Port Volume: 70cc 
Intake Valve Diameter: 1.89 inches 
Exhaust Valve Diameter: 1.55 inches 

Stock Head Flow Numbers
Chamber 61.15 cc----0.100--0.200--0.300-- 0.400--0.500---0.550---0.600 
Intake 200 cc----------63 ---128----179-----210----218----221-----226 
Exhaust 70 cc----------54 -- 93 ----121----145-----163----168----174 


What you need to know: 
These small combustion chamber truck heads offer no advantage over an LS1 head except the smaller combustion chamber. This along with milling of the deck surface will allow a slightly higher compression ratio to be achieved. Because of the smaller intake valve installed in these heads a valve upgrade is practically mandatory.



Casting Number 873
Head: 1999-2000 LQ4 6.0 Liter Truck 
Material: ***Cast Iron***
Part Number: 
12561873 
Combustion Chamber Volume: 71.06cc 
Compression Ratio: 9.5:1 
Intake Port Volume: 210cc 
Exhaust Port Volume: 75cc 
Intake Valve Diameter: 2.00 inches 
Exhaust Valve Diameter: 1.55 inches 

Casting Number 317, 035 
Head: 2001+ LQ4 and LQ9 6.0 Liter Truck 
Material: Aluminimum 
Part Number: 
12562317 -LQ4
12572317 -LQ9
12572035 -LQ9
Combustion Chamber Volume: 71.06cc 
Compression Ratio: 10:1 LQ9 Flat top pistons
Compression Ratio: 9.6:1 LQ4 Dish piston
Intake Port Volume: 210cc 
Exhaust Port Volume: 75cc 
Intake Valve Diameter: 2.00 inches 
Exhaust Valve Diameter: 1.55 inches

Stock Head Flow Numbers
Chamber 71.06cc----0.100---0.200--0.300--0.400--0.500--0.550--0.600 
Intake 210cc-----------66-----142-----196---228----236---238-----240 
Exhaust 75cc----------59-----104-----137---155----167---173-----177 



What you need to know: 
The LQ4 head received aluminum heads starting in models year 2001. All other features are the same as previous years iron heads. This is the workhorse head for street / strip turbo and blower cars. They offer a large combustion chamber that lowers compression ratio making them perfect for a forced induction application. Swapping on the LQ4 head drops the compression ratio of a typical LS1 engine to 9:5.1 
The Cast-iron casting are heavy!

So you want to figure out how much to mill:

It takes about .005" milling of the block deck to remove 1cc of volume. It takes .007" milling to remove 1cc from an LS1 head 

Simple Milling Math:

You have a stock 66cc chamber and you want to get down to 63cc

66-63 = 3. You have to remove 3cc's

.007 x 3 = .021. So to get your 66cc chambers down to 63cc you'd have to mill ~.021.

You can also do the reverse, say you want to mill a head .030 to figure out how many CC's that removes you take .030 / .007 = ~ 4.28. Milling a stock 5.7 head .030 puts your chamber at ~ 62.



241 cast heads were Die Cast which is a process that smooths up the ports a bit compared to the Sand Cast procedure that was done on the 806 and 853 heads. Once ported any "advantage" the 241 cast had is moot.

Same Info applies to the: 
4.8L/5.3L Truck 862 and 706 Head castings
While the 706 Heads are a SPM = Semi Permanent-mold And considerd to be a more consistant head casting then the 862 wich are Sand cast, Once ported There Is no difference.

--------------------------------------------------------------------------------
799 Vs. 243 Info Copied From pillboxesghost Post's in ths threadhttp://www.ls1tech.com/forums/conver...l#post10241473

This appears to be one of the common misconceptions about heads having the 243 casting no. -- they are not necessarily LS6 head assemblies. The LS2 heads (243 or 799 casting) have the "heavy" standard LS1 valves. However, they do have the LS6 springs.

Only the true LS6 engine heads have stainless steel (not titanium) hollow stem valves (the exhaust stems are sodium filled). These valves are slightly longer than LS1 valves too.

The LS7 heads do have titanium valves.

New LS2 heads are about half the price of new LS6 heads (check sdparts.com). GM is "really proud" of those hollow stem valves!

Oh, if you have the 799 castings -- the only thing "Corvette" about them is the valve springs/retainers! Still a desirable set of LS1 heads though!

Supposedly, the 243 mold was done at GM Research, the 799 mold furnished to other vendors. The same vendor may have the 243 and 799 mold. 

Both heads have identical sized intake and exhaust valves