0Mike Yeager@Eastcoast Performance

Hey guys, I have alittle tech question about the 243 heads...I was told that they only come 2 ways from GM, when they are put on motors like the C5 LS6's, C6 LS2's and the 5.3L Silverado Truck motors.

The question is this, do they all come from GM with the same SIZE valves and the same combustion chamber size!!!

tsts

Can't provide an answer to your exact question but have some related information that might be useful.

When ECS built my GM block (LS7 - 427), they used #243 heads which had larger valves and enlarged combustion chambers to accept the 427's pistons, work done by TEA.

~Josh

243 heads were only available on the LS6 and LS2 engines.

The valves are the same size from the factory. Intakes are 2.0 and exhausts are 1.55

The 2001 Zo6 had solid valves just like the LS2 cars, but the 2002-2004 Zo6 got sodium filled (lighter) exhaust valves.

ExTurbo

I have seen 5.3's with 243 castings

But yes the size of the valves dont change from one to the other, and unless they are milled/ported the combustion chamber would be the same.

AU N EGL

Are you sure ?


243s come with Ti intake and Sodium exhaust valves, Ti retainers on the LS6

on the LS2 the valves are Stainless Steel

now there is a 243 head by LPE

~Josh

Casting Number 806 or 933
LS1 (Perimeter Bolt)
97-98 5.7L Passenger Car and Corvette
Material: Aluminum
Combustion Chamber Volume: 66.67cc
Intake Port Volume: 200cc
Exhaust Port Volume: 70cc
Intake Valve Diameter: 2.00 inches
Exhaust Valve Diameter: 1.55 inches

Casting Number 853 or 241
LS1 (Center Bolt)
99-00 5.7L Passenger Car and Corvette (853)
01+ 5.7L Passenger Car and Corvette (241)
Material: Aluminum
Combustion Chamber Volume: 66.67cc
Intake Port Volume: 200cc
Exhaust Port Volume: 70cc
Intake Valve Diameter: 2.00 inches
Exhaust Valve Diameter: 1.55 inches

Casting Number 243
LS6/LS2
01+ 5.7L Corvette/05-07 6.0 Corvette
Material: Aluminum
Combustion Chamber Volume: 64.45cc
Intake Port Volume: 210cc
Exhaust Port Volume: 75cc
Intake Valve Diameter: 2.00 inches
Exhaust Valve Diameter: 1.55 inches

Casting Number 706
LM4 / LM7
99+ 5.3L Truck
Material: Aluminum
Combustion Chamber Volume: 61.15cc
Intake Port Volume: 200cc
Exhaust Port Volume: 70cc
Intake Valve Diameter: 1.89 inches
Exhaust Valve Diameter: 1.55 inches

Casting Number 852
LR4
99+ 4.8L Truck
Material: Aluminum
Combustion Chamber Volume: 61.15cc
Intake Port Volume: 200cc
Exhaust Port Volume: 70cc
Intake Valve Diameter: 1.89 inches
Exhaust Valve Diameter: 1.55 inches

Casting Number 317 or 035
LQ9
01+ 6.0L Truck
Material: Aluminum
Combustion Chamber Volume: 71.06cc
Intake Port Volume: 210cc
Exhaust Port Volume: 75cc
Intake Valve Diameter: 2.00 inches
Exhaust Valve Diameter: 1.55 inches

~Josh

Just to clarify... the LS7 (C6Zo6) heads have titanium intake valves, sodium filled exhaust valves and titanium retainers all around...

The LS6 head is as stated in my first post.
Solid all around in '01 Zo6 and LS2 cars
Solid intakes with Sodium filled exhausts on '02-04 LS6
Regular steel valve retainers all around every year.

Y2Kvert4me

Yes, the 243 and 799 heads are now being used on later model (05+) 4.8 and 5.3 truck engines.

Reason being is they changed from dished to (now) flat top pistons in those engines, which required the larger head chamber to keep compression ratio about the same.

The "old skool" 5.3 heads - 862 and 706 castings, were the smaller 61cc chamber heads used on older 4.8/5.3s with the dished pistons.


And to the OP - yes, the 243s are all 64cc chambers, with 2.00/1.55" valve sizes.

~Josh

Wow, I learn something new here everyday!

Never knew about the 05+ trucks.

Well, I guess the whole story has been told.

lucky131969

I believe the valve length in the Z06 heads starting in 2002 is longer than the valves in 2001 as well.

SDPC

Your answer is they do only come in two varies, standard valves and hollow stem/sodium filled valves. Yes, they have the same size valves and same combustion chamber.

Not part of your question, but discussed here, is what vehicles they came in. That list is more vast than it's getting credit for. It includes but is not limited to

FWD vehicles with the LS4
TBSS
05-06 GTO
Hummer
01-04 Z06
05-07 C6
SSR
CTSV
05+ trucks NOT limited to 4.8 and 5.3 but also found on the 6.0


They are even on some of the 5.3s in the Trailblazers and Buick Rainier. The list is REALLY expansive.

~Josh

^ I thought the '02+ cores are still on the same smaller base circle (compared to LS1) and the pushrods stayed the same.

The LS2 cam is the '01 Zo6 unit
The LS3/LS9 cam is the '02 ~ '04 unit

I'd guess that GM would keep the geometry the same through the years, no?

tail_lights

SDPC

Only the LS6 cars with hollow stem/sodium filled valves have a smaller base circle cam. All other 243s have standard valves and standard base circle cams, this includes the 01 Z06

~Josh

Whoa! Good to know!