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Those 706 heads made 2 hp more than the 243 heads. I think that was on a 5.3 engine. The 243 have more potential with additional mods.
There were a few tests on both the 6.0 and the 5.3. You are looking at at one point on the 5.3 graph. You need to look at the whole curve. Its not a "2 HP difference". You have much more average HP across the whole RPM band with the 706's. I'm seeing a 10-20 jump in hp/tq in several places.
Curious why you say the 243's have more potential? I'd argue that the 706's have more potential, esp. per $. You are starting out with a dirt cheap head and can easily add a larger intake valve AND do a performance valve job and port cleanup done to them for roughly the same cost as the 243/799 untouched.
There is much more meat on the smaller 706 ports/runners. So they can be shaped into a race port more easily. On the 243/799, they have to remove and add material to to get the ports shaped ideally. Head porters I've spoke with prefer the 706's for that reason.
I'm not saying 706's (esp. in their stock form) are some perfect BA race heard. They are far form it. But the 243/799 is VERY overrated IMO and not a worthwhile upgrade for guys with under 470chp or so NA.
There were a few tests on both the 6.0 and the 5.3. You are looking at at one point on the 5.3 graph. You need to look at the whole curve. Its not a "2 HP difference". You have much more average HP across the whole RPM band with the 706's. I'm seeing a 10-20 jump in hp/tq in several places.
Curious why you say the 243's have more potential? I'd argue that the 706's have more potential, esp. per $. You are starting out with a dirt cheap head and can easily add a larger intake valve AND do a performance valve job and port cleanup done to them for roughly the same cost as the 243/799 untouched.
There is much more meat on the smaller 706 ports/runners. So they can be shaped into a race port more easily. On the 243/799, they have to remove and add material to to get the ports shaped ideally. Head porters I've spoke with prefer the 706's for that reason.
I'm not saying 706's (esp. in their stock form) are some perfect BA race heard. They are far form it. But the 243/799 is VERY overrated IMO and not a worthwhile upgrade for guys with under 470chp or so NA.
Well, the big one is that the 706 head is prone to cracking and I'd imagine a ported one would be even thinner in places. The 853/241 head has a larger chamber and a poor short turn radius. The 243 can be ported to roughly 225cc intake runners. I'm not sure how big the runners are on a ported 706 head.
Well, the big one is that the 706 head is prone to cracking and I'd imagine a ported one would be even thinner in places. The 853/241 head has a larger chamber and a poor short turn radius. The 243 can be ported to roughly 225cc intake runners. I'm not sure how big the runners are on a ported 706 head.
The cracking thing was specific to 1 year and not all heads form that year had the issue. I believe it was 2006. GM had a service bulletin about those heads. They have what looks like a battery emblem on them, and not all with the battery casting were bad, just some. To say all 706's are prone to cracking is incorrect.
243/799 def flowed more and had larger runners, no argument there. They just don't perform as well due to the larger CC. If you were to mill a 243/799 to 61cc they would def out perform the 706's easily. But Then you've lost a lot of deck strength and spent what amounts to entry level aftermarket head prices. Esp. if you choose to port and work the head any beyond milling. You can easily be into a set of milled/ported 243's for more than the cost of the entry level aftermarket heads with much thicker decks that flow better. So I guess my point is the small chamber stuff has the best bang for your buck on super mild NA builds around 400-470chp. And if you want a performance head, you'd be be better off buying aftermarket than modifying the 799/243.
I spend around 900 on my 243's, that's cnc port & polished and milled 30 thousands that's including .660 dual spring kit from cam motions. My heads supposedly had all this done when I bought the truck and when I pulled my heads it had the springs with the wrong retainers and no porting or anything was done so calhoun motorsports got me all the right parts and did all the port, polish, n mill work for that price, I didn't feel that was a bad price, idk what you guys are paying your way but here that's a relatively cheap job to get done, then might I add my old tuner ended up over boosting the truck and it ran hot on me and ended up breaking a rod where it connects to the piston and destroyed one of the heads so I brought them back and these guys found me another head and put all new parts in the one head and went back over the other one to make sure everything was OK and milled the one good one 10 thousands more and the new head 40 thousands so I'm now at 40 and they charged me 350 for that and that included the purchase of the new head. If that gives you an idea of what it cost. Honestly it's not much here and I would assume you guys have similar prices.
I'll just say this- E85 exists due to, and for the benefit of, the corn lobby. That's it!
I live in a corn state and you aren't wrong, but I do love me some ethanol in my procharged gto. Makes tuning so much easier and everything seems to stay so much cooler under the hood helping make even more power.
I live in a corn state and you aren't wrong, but I do love me some ethanol in my procharged gto. Makes tuning so much easier and everything seems to stay so much cooler under the hood helping make even more power.
we do have plenty corn here in Louisiana but my truck definitely loves the e85
I live in a corn state and you aren't wrong, but I do love me some ethanol in my procharged gto. Makes tuning so much easier and everything seems to stay so much cooler under the hood helping make even more power.
My brother lives in NW Iowa, so that's where I get my corn info, LOL!
The cracking thing was specific to 1 year and not all heads form that year had the issue. I believe it was 2006. GM had a service bulletin about those heads. They have what looks like a battery emblem on them, and not all with the battery casting were bad, just some. To say all 706's are prone to cracking is incorrect.
243/799 def flowed more and had larger runners, no argument there. They just don't perform as well due to the larger CC. If you were to mill a 243/799 to 61cc they would def out perform the 706's easily. But Then you've lost a lot of deck strength and spent what amounts to entry level aftermarket head prices. Esp. if you choose to port and work the head any beyond milling. You can easily be into a set of milled/ported 243's for more than the cost of the entry level aftermarket heads with much thicker decks that flow better. So I guess my point is the small chamber stuff has the best bang for your buck on super mild NA builds around 400-470chp. And if you want a performance head, you'd be be better off buying aftermarket than modifying the 799/243.
The smaller chamber is the main advantage. Still on a LS1 the 243 heads give a 10:5 to1 compression ratio.
I have an LQ4 with 706 heads in a 2006 Silverado 1500 2wd crew cab. Measured CR is 10.4. It has a 210/216 114+4 .550/.550 camshaft. Tuned by Geoff Skinner. It gets 16-19 MPG and it runs great but, I am not blown away. Has good power if you lay into it but, underwhelming/soggy at part throttle. Takes a lot of pedal and a drop in gear. It has a 3.73 gear, 31.5” tire and a 4L60e.
i was thinking of going to flat top pistons, 317 heads, and a smaller cam as I spend 99% of my time below 3000 rpm.
As is, it’s only slightly better than the 5.3 LM7 I pulled out below 3000.
Last edited by Jake Wade; May 21, 2024 at 09:33 AM.
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