96capricemgr

iTrader: (1)

never mind if the result is poor, look into it. I bet all the LS3 head believers will tell you not to run them with that cam.

Combining mismatched parts due to budget is wasting money not saving it.

Your 243s aren't worth $600 used as some have claimed to sell for, springs should be assumed worn out and not reused so no value there and LS2 had solid valves not the LS6 valves.

Start adding up the costs of rockers, trunnion upgrade, springs, new cam etc and then lowball or better yet leave out your estimates of what you can sell what you have for and see if this still suits your budget. I say lowball or ignore expected sale price of what you have to give some cushion.

speedtigger

iTrader: (16)

I think you will find, that cam on a 110 LSA will make more horsepower and peak torque than the same cam on a 114 LSA even on rectangle port heads if they have the same ICL. I offer that while the rectangle port heads may exaggerate the less desirable effects of overlap at low speed and below peak torque, that will not hold true at and above peak torque.

What I would look at in addition to the overlap, would be the intake valve close event. I don't not see where the OP mentioned the ICL or advance, so it is hard to say how that cam will perform in his application.

If you look around on here, there is a thread where a member was disappointed with the performance of his high dollar cathedral port heads. He removed those heads and his FAST intake and replaced it with STOCK L92 heads, stock LS3 intake and a custom Cam Motion camshaft that was notably smaller. He made more power and had better drivability.

So, I agree that the combination is crucial, but I don't agree with the generalizarion that rectangle port heads "don't like overlap". You have to take into consideration the combination and what the vehicle owner wants his vehicle to do.

thunderstruck507

iTrader: (18)

I looked at doing the ls3 top end back when I found some ported ls3 heads on sale and after looking around a good bit couldn't find anything to convince me it would benefit my application over ported 799 cathedral heads on a stock cube ls2.

I've been very pleased with my previous hydraulic combo and even more so with my new LLSR I'm getting lined out. The off idle response and torque even with a "large" cam are insane. I've seriously driven some big block cars that came through my dad's shop which don't have the low end this thing does.

Really just depends on the application and goals I think.

mchicia1

iTrader: (5)

For what it's worth, I made 460 rwhp on my GTO with a 230/232 114 cam and a fast 102. The 243s were never taken off the car. If I had milled and had AI port them, I have no doubt I would have made 490+ rwhp.

Much easier swapping an intake manifold than removing heads. The big plus for the ls3 swap is you get bigger injectors by default and an intake as good as a fast.

96capricemgr

iTrader: (1)

I am not against overlap, cam in my Caprice is a 108lsa, enough stall/gear/compression and it is fine.

My understanding is the big valves have an effect almost like increasing overlap and they will offer less compression which is often used to tame some of the poor manners of large cams. Basically low speed manners will suffer and so should low speed performance because all tests show that with the rectangle heads compared to cathederal. Is the owner OK with further compromised manners and reduced lowend response? Enough stall/gear to mask it?

Far as the guy swapping to rectangles from high dollar catherderals, there is also a threads about a guy swapping from the "ultimate" high dollar 11 degree cathederal to ported 243s WITH STOCK VALVES and having far better results, only other change was unported FAST since the original FAST runners were ported for the aftermarket casting. Same cam, same tuner etc.

Let's go back to your 35hp proposed gain.

The LS2 intake is crap, now that I have gone looking it seems like it is worse than the LS1 intake even despite the big TB.
http://www.hotrod.com/features/1507-...ifolds-tested/
They found 60hp in LS1 vs. FAST 102 intake and as low as the dyno went no loss down low so if it does lose way down low the crossover is early. Now I don't think the OP car is going to make 590fwhp, but it is a cam of similar duration just on a wider LSA and it is a set of AFRs on an overbored 6.0l block so for argument's sake let's say he only sees half the gain(conservative), 30hp so nearly the same peak you estimate, for similar money, with retained compression and lowend. With lots of room to improve because many vendors offer 243 porting if more budget becomes available.

The big rectangle stuff has it's place but IMO a reasonable rpm street 6.0l isn't it, it is a bandwagon jumped on too quickly based on flowbench numbers primarily and a little bit of peak HP numbers too. Maybe it works for the dragracers who let the engine live at WOT 4500+rpm too but most of us like to drive our cars. I will trade 10hp up top for 10tq down low any day.

MX6.0

Actually, they were sold to a member on this site for $650 shipped. I did include the pushrods and stands though. 8 offset rockers were $80 and the LS3 stands were $15

Totally agree here

Those numbers are really close to what I've made with the LS3 top end. Mind posting your dyno sheet? I'd love to see how much of a "lowend hit" I'm taking?

96capricemgr

iTrader: (1)

As I said 243s with solid valves and used valvesprings are not worth $600. If someone was stupid enough to think used valvesprings made them worth more, then I guess that helped you or maybe they thought they were hollow valves then $650 shipped is still IMO high but not rediculous, if they were new springs then that money should be deducted from sale price. Price has come up on LS3 topend since you bought too, you might not make that choice if starting over now.

Far as lowend hit, not going to see the real picture on a dyno, they don't read low enough. Plus what does it matter with 2400lbs behind 6.0liters, f-bodies are often 3400lbs and the Camaro/GTO/G8/SS/CTS-V are all closer to 4000, and trucks heavier than that yet, the 6.0l trucks often topping 5000lbs. I bring that up because I see too many people want to jump on the LS3/L92 bandwagon with 6.0l without considering such things. Your car weights literelly half or less than half of what most 6.0l OEM vehicles weight, because 3/4ton trucks are the vast majority.

Heck a convertible f-body can weight half again what your car does...

speedtigger

iTrader: (16)

Compression is a mechanical relationship. It is what it is regardless of valve size or overlap. If I understand where you are going with this, you might be implying that overlap diminishes volumetric efficiency ie cylinder filling at low RPM and this is exaggerated by valves with a larger curtain area. I could see that argument. However, once the RPMs get up, I offer that those larger valves and effective overlap can become an asset.

I have heard a lot of anecdotal claims and seen plenty of poor comparisons, but I have never seen what I would consider proof that either port configuration is superior across the board. Rectangle ports and cathedral ports each have some characteristics that are desirable. It just depends on what you are building.

mchicia1

iTrader: (5)

Sure. Also car ran 12.0 at 119 the only pass I ever ran with this setup before I obliterated the rear. I am sure I would have dipped into the 11's at over 120 with more time.

KW Baraka

iTrader: (7)

Dwayne.....you really need to stop saying this.

The 6L80 tranny was introduced in 2006....in cars that did NOT have LS3 engines.

The LS3 and the L92 weren't introduced until 2008.

GM developed this tranny when they needed a 6-speed Auto to give the illusion of keeping up with other car brands that had 6 and 8-speed trannies in their cars.

Why they decided to give it such a low 1st gear versus giving it a bit more on the top end is anyone's guess. But since the 6L80 pre-dates the LS3/L92 rectangular port engines, it's pretty much a stretch to say it was spec'ed to make-up for that engine generation's perceived shortcomings.....

I mean, usually you're right on target. But in this respect.....not so much.

KW

96capricemgr

iTrader: (1)

Remember like a month ago when you said my Caprice had a lot more gear in it than my SS, and I had to point out to you that 4.03/3.27 is actually more gear than 3.06/4.10, so how much thought have you put into it. How objective are you if you can't identify something so blatantly obvious when owning both vehicles yourself so long?

Far as dates the rectangle port debuted in 2006 on the LS7 didn't they? Granted it is not exactly the same head but it was the beginning of rectangle ports in LS engines.

Maybe it is a stretch to say it was designed that way but it is used that way, all the testing we have indicates the rectangle ports hurt down low and the 25% flow advantage only seems to be worth about 7% in peak power. Seems odd to me with such a magical design. That 7% I am deriving from both the GM output of motors and the HotRod article where they test 317s vs. LS3s and in both those cases the rectangles have a compression advantage small but the deck is stacked for them and where we have detailed dyno results the rectangles lose out down low. The 7% real world peak result is pretty well in line with the idea being floated about a 35hp gain too.

Can the extra flow be made to work YES, but people see the huge flow numbers and expect a huge result and they aren't there, and nobody wants to talk about down low, or what kind of result 243s and a FAST would have on a same displacement motor.

Considering
http://www.hotrod.com/how-to/engine/...re-port-heads/ and
http://www.yellowbullet.com/forum/sh...84&postcount=7

Makes one wonder how it would have turned out if HotRod used 243s? The 40hp gap between the 317s and the LS3s would have shrunk up top and the 243s would have widened the cathederal lead down low. Nobody is going to pay for that test though because GMPP isn't selling new 243s, they do however offer new LS3s.

KW you and I have had this argument forever you believe bigger is better and I look deeper for what tangibly works, you ever get you solid roller 396 LT4 to run what my little motor has with ported GM LT1 and a hydraulic cam?

speedtigger

iTrader: (16)

I think a lot of what limits the potential power of the rectangle port heads for many people is the long runner plastic intake manifold. I would like to see a good rectangle port head flowed by itself with just clay and then with an LS3 intake.

thunderstruck507

iTrader: (18)

"Despite additional flow and smaller chambers, the big, rec-port LS3 combo lagged behind the smaller (cathedral-port) 317s up to 4,000 rpm."

That was a stand out line to me. Especially if what Tooley said about the 243 versus 317 chamber is true.

Granted in a drag race scenario the car won't spend any time below 4,000rpm. But the same can't be said for a street car or corner carver. So again, it comes down to application and intended usage (as most things in the engine do).

96capricemgr

iTrader: (1)

Certainly the plastic intakes are a limiter, but most of the cars these motors are in dictate such so that isn't much of an argument, and the trucks with monstrous space are porky and need the lowend.

Are all the rectangle port truck motors VVT?

speedtigger

iTrader: (16)

A lot of truth there. Most of the people I hang out with could give a damn about what goes on below 4000 RPM. They are after average power between 5500-7000+. Really if you think about it, even in a combo with a really tight street converter, the shift drop is about 5200 RPM at the lowest. So, the only time people are below 4000 is leaving from a dead stop when traction is a problem on the street anyway.

96capricemgr

iTrader: (1)

But having something that start making torque 600rpm sooner lets you run a lower stall for more comfort on the street, more responsiveness. My preferred track is 137miles from my current house.................................. and I have never trailered a car to or from the track, and hopefully I didn't jinx myself with that.

speedtigger

iTrader: (16)

LOL! I have always bragged about that. And then, I blew my rear differential apart at the 2015 NMCA event at BMP. I still drive to the track, but maybe not brag as much about it.

MX6.0

Thanks mchicia1.
Other than the cam and FAST 102, I don't know what your other supporting mods are. But since we have about the same peak power, I thought it would be interesting to see both dyno charts together to see the differences in power delivery. I've overlaid both dyno sheets on the same plot. Ignore the blue and green lines. Both are Dynojets, both are SAE 5

speedtigger

iTrader: (16)

Uh oh! That doesn't match up with all the theory.

96capricemgr

iTrader: (1)

Show me a case of just heads changed and things being that similar?
I already posted the HotRod article where they actually tested 317s and LS3s back to back yes the shortblock was larger but was consistent, do you think that overlay trumps back to back testing? No exhaust/header, cam, CAI etc. influence.

Even when they test more similarly sized aftermarket heads in each style they see a torque difference and the extra airflow not turning into the power one would expect.
http://www.superchevy.com/how-to/ght...-head-to-head/