ls3 heads or 243
01-11-2011, 04:40 PM
#1
ls3 heads or 243 I have a lq9 6.0 With truck intake and heads and a small cam. I am ready to step it up a notch and don't know whether I would be better off with ls3 heads and intake or do the 243 with a ls6 intake. Either way I go I will get a custom cam. The cost seem close as the ls3 heads are more expensive but the intake is cheaper.Which intake flows better? Any input is welcome.
01-11-2011, 05:06 PM
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LS3 heads and intake flows a ton better than the ls6 parts. They actually flow better than most aftermarket heads. The only thing about the ls3 heads is you have to have the 8 offset rocker arms.
The LS3 setup with a decent cam and a good tune will get you atleast 450rwhp. You might be able to reach 400-410rwhp with the ls6 setup and a lot bigger cam. If you look around ls3 parts are actually cheaper too. L92 heads are the same except for the valves.
One more thing....if you go LS3, research cams. The grinds that are making the most power are a lot different than the LS1/LS6 grinds.
The LS3 setup with a decent cam and a good tune will get you atleast 450rwhp. You might be able to reach 400-410rwhp with the ls6 setup and a lot bigger cam. If you look around ls3 parts are actually cheaper too. L92 heads are the same except for the valves.
One more thing....if you go LS3, research cams. The grinds that are making the most power are a lot different than the LS1/LS6 grinds.
01-12-2011, 11:48 PM
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i have an Ed C cam for my 402 ls2 with ls3 heads, should be 500 hp 500 tq, ported heads but a pretty mild cam for the cubes/heads, my 347 with 243s its got pretty radical heads, and a slightly more choppy cam is good for 460 ish; with afrs 205s it made 430 
01-13-2011, 12:58 AM
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L76/L92/GMPP LS3's all the way. Mast has sweet LS 3 heads too and scam proven to make tons of power with them. Break down and get a FAST 102. Intake Restriction is a bitch on these LS engines.
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01-14-2011, 06:15 AM
#10
Thanks guys keep em coming. So would it be safe to say I would make a conservative 430 ish with the 243 and mabee 470 ish with the ls3 heads? If its as simple as that and that big of a power difference I'm sold. Guess a couple of my concerns were compression ratio and limited cam size because of the big valves and the flat top pistons I have. The beauty is I don't own anything so the heads will be decked per cam guys advice and I wouldn't be totally against notching the pistons if needed.
01-14-2011, 08:26 AM
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Yes you're going to make tons of more power with LS3's period. Especially with a big cam I've seen a handful go OVER the 500 mark. But they're at sea level which makes a big difference.
01-14-2011, 09:30 AM
#13
I went and reviewed the Oct. '07 and Nov. '07 issues of HotRod. If you compare test D against test N, you find that just switching from #317 heads and LQ9 intake and cam, with Dynotech headers, to #364 L92 heads with L76 intake, costs 26.9 ft-lbs down at 1600 rpm. And the L92 heads continue to give less torque on up to 4300 rpm.
If you're running a 4,000 stall converter, then this means nothing. But if you have a pickup, in which the stock converter seems to be a 1,400 stall, then the cathedrals are the only way to torque.
In the October issue, test D was nearly identical to test N, with the fewest parts changed, just intakes, rockers and heads, nothing else. Test D was the truck intake, test N was L76. Test E added catalytic converters, which seem to have stayed on for tests F, G, H, and I, but come back off by test N. Test E kept the truck intake. F was the Ls1 intake, G was LS6, H was LS2, and I was F.A.S.T. 90mm. The 90 was down by 4.3 ft-lbs at 1600, but even so, theL92 heads still cost 22.6 ft-lbs.
If you're running a 4,000 stall converter, then this means nothing. But if you have a pickup, in which the stock converter seems to be a 1,400 stall, then the cathedrals are the only way to torque.
In the October issue, test D was nearly identical to test N, with the fewest parts changed, just intakes, rockers and heads, nothing else. Test D was the truck intake, test N was L76. Test E added catalytic converters, which seem to have stayed on for tests F, G, H, and I, but come back off by test N. Test E kept the truck intake. F was the Ls1 intake, G was LS6, H was LS2, and I was F.A.S.T. 90mm. The 90 was down by 4.3 ft-lbs at 1600, but even so, theL92 heads still cost 22.6 ft-lbs.
01-14-2011, 10:16 AM
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I went and reviewed the Oct. '07 and Nov. '07 issues of HotRod. If you compare test D against test N, you find that just switching from #317 heads and LQ9 intake and cam, with Dynotech headers, to #364 L92 heads with L76 intake, costs 26.9 ft-lbs down at 1600 rpm. And the L92 heads continue to give less torque on up to 4300 rpm.
If you're running a 4,000 stall converter, then this means nothing. But if you have a pickup, in which the stock converter seems to be a 1,400 stall, then the cathedrals are the only way to torque.
In the October issue, test D was nearly identical to test N, with the fewest parts changed, just intakes, rockers and heads, nothing else. Test D was the truck intake, test N was L76. Test E added catalytic converters, which seem to have stayed on for tests F, G, H, and I, but come back off by test N. Test E kept the truck intake. F was the Ls1 intake, G was LS6, H was LS2, and I was F.A.S.T. 90mm. The 90 was down by 4.3 ft-lbs at 1600, but even so, theL92 heads still cost 22.6 ft-lbs.
If you're running a 4,000 stall converter, then this means nothing. But if you have a pickup, in which the stock converter seems to be a 1,400 stall, then the cathedrals are the only way to torque.
In the October issue, test D was nearly identical to test N, with the fewest parts changed, just intakes, rockers and heads, nothing else. Test D was the truck intake, test N was L76. Test E added catalytic converters, which seem to have stayed on for tests F, G, H, and I, but come back off by test N. Test E kept the truck intake. F was the Ls1 intake, G was LS6, H was LS2, and I was F.A.S.T. 90mm. The 90 was down by 4.3 ft-lbs at 1600, but even so, theL92 heads still cost 22.6 ft-lbs.
01-14-2011, 10:16 AM
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Perfect example of Hot Rod using the wrong cam for the L92's. Properly cammed they will not lose any torque "down low" to a cathredal port. If they are bad for trucks why does GM put so many of them in trucks?
01-14-2011, 10:20 AM
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I have a lq9 6.0 With truck intake and heads and a small cam. I am ready to step it up a notch and don't know whether I would be better off with ls3 heads and intake or do the 243 with a ls6 intake. Either way I go I will get a custom cam. The cost seem close as the ls3 heads are more expensive but the intake is cheaper.Which intake flows better? Any input is welcome.
01-15-2011, 09:24 PM
#17
Yea it is going in my truck. I should have mentioned that. I do use it as a truck and haul mulch and crap, but I also like the drag strip. Right now it has the stock convertor and 3.44 gears. I will do what ever covertor the "cam guy" recomends but I would like to keep it tight as possible. I would rather do a steeper gear to get away with that if needed. A while back I read a similar thread where a vender recomended 243s over the new heads for the higher compression ect. Also we have 93 octain here if that matters.
01-19-2011, 12:07 AM
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The LS3 is a 4 bolt head pattern block from GM.
Some aftermarket ls3 heads are 6 bolt (but they are made to go onto the LSX blocks).
Going with a set of cnc'd ls3's and a l76 truck manifold along with a cam designed for low end torque, good midrange tq & hp, and decent hp in the 6000 to 6500 rpm shouldn't be a problem (will mainly depend on the cam and bolt-ons to achieve it though).
FYI... Going to a Fast 102 manifold (truck or car version) probably would not show enough gains compared to gm's l76 truck or l76/ls3 car manifold on a 6.0L engine (ie small gains for close to a grand).
Now if you were going to stroke the 6.0L from the 364cu in up to say a 408 then a fast 102 would show better results but from what you mentioned about mainly using the truck to haul stuff with some run's at the track every now and then... the fast probably wouldn't be worth the cost.
A cost effective setup would probably be something like PRC LS3's with .650" springs, custom cam, headers, ported gm manifold (fasterprom's usually has a good price) a retune on the ecm along with cold air kit for said manifold and a converter to match the cam.
Oh and maybe some shocks, springs, and a stronger pumpkin head for the rear so you don't send the gears out the back...
Thats my 2 cents anyway.
01-19-2011, 12:15 AM
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Yeah, id say the cams are comparable size (or at least both in the smaller side of the spectrum), but the AFR cam was more lift while the 243 cam has more duration.. This is off the shelf afr 205s vs 243s that have flow numbers that match/beat every cnc-only head ive seen (not that flow numbers are everything 
). This is also 430/405 dyonoed hp/tq vs ~460 hp through a 6 speed approximated by the porter (both on my 347)
Here are my claimed flow numbers for both my setups; i cant vouch for the accuracy (as neither of my new setups has been dyonoed), but fwiw, here are my ls3s to compare to the 243. Obviously these wont work on a 347, and are on my 402:
LS3:
Intake Exhaust
.200 159.9 129.9
.300 237.1 180.1
.400 291.2 226.0
.500 330.8 255.9
.600 365.9 268.1
243s:
0.200 144 112
0.300 205 170
0.400 264 203
0.500 294 224
0.550 310 228
0.600 318 233
AFR no longer has flow numbers on their site, but the 215s are pretty close to these 243s if memory serves
). This is also 430/405 dyonoed hp/tq vs ~460 hp through a 6 speed approximated by the porter (both on my 347)Here are my claimed flow numbers for both my setups; i cant vouch for the accuracy (as neither of my new setups has been dyonoed), but fwiw, here are my ls3s to compare to the 243. Obviously these wont work on a 347, and are on my 402:
LS3:
Intake Exhaust
.200 159.9 129.9
.300 237.1 180.1
.400 291.2 226.0
.500 330.8 255.9
.600 365.9 268.1
243s:
0.200 144 112
0.300 205 170
0.400 264 203
0.500 294 224
0.550 310 228
0.600 318 233
AFR no longer has flow numbers on their site, but the 215s are pretty close to these 243s if memory serves