1998TA__1991RS

iTrader: (23)

will my 98 heads be ok for a good head job untill i get out of school and build my motor(bud has machine shop and can get it done for cheap), or should i get some 241 castings?

JZ'sTA

iTrader: (23)

The 98 heads are fine.
The 241's are better stock for stock, but after they are ported they is nearly no difference. Plus you wont have to change you valve cover's.
Stick with the 98 castings.

JZ'sTA

iTrader: (23)

This should help out.
THANKS JRP.
The important part your looking for is at the VERY BOTTOM.
Enjoy.


Head Casting Info

ALL Gen III heads are interchangable.


Here is a list of a few casting #'s:

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 LS6 aluminum center bolt 5.7
862 and 706 99 and up 4.8-5.3 truck heads
873 99-00 LQ4 6.0 iron center bolt heads
317 01 and up LQ4 6.0 aluminum center bolt heads
035 02 and up LQ9 6.0 aluminum center bolt heads

Even more info:

Casting Number 241
Head: 1997+ LS1 5.7 Litre Passenger Car
Material: Aluminimum
Part Number:
12559806 (1997-98) Chambers = 69cc
12559853 (1999-00)
12564241 (2001-03)
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


Casting Number 243
Head: 2001 LS6 5.7 Litre 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

Casting Number 706
Head: 1999+ LR4 4.8 Litre Truck
1999+ LM4 /LM7 5.3 Litre Truck
Material: Aluminimum
Part Number:
12559852
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

Casting Number 373
Head: 1999-2000 LQ4 6.0 Litre 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
Head: 2001+ LQ4 6.0 Litre Truck
Material: Aluminimum
Part Number:
12572035
Combustion Chamber Volume: 71.06cc
Compression Ratio: 10:1
Intake Port Volume: 210cc
Exhaust Port Volume: 75cc
Intake Valve Diameter: 2.00 inches
Exhaust Valve Diameter: 1.55 inches



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 mille 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.

1998TA__1991RS

iTrader: (23)

ok thanks alot, just what i needed to know, i really didnt want to change the valve covers anyways

Kraest

iTrader: (3)

Best stock head for porting? 243

Mike

slowpoke96z28

iTrader: (2)

you can remove more material from 243 heads befroe you get to water jackets than the 241, from my understanding.

1998TA__1991RS

iTrader: (23)

yea but i dont want to drop that much money on some ls6's, i just want somthing that will get me through the next year to year and a half and when i get out of school get some nice heads for a turbo motor

N4cer

iTrader: (11)

Why not just leave 'em alone and get some thinner head gaskets then?