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^^^^^^plastic intakes are about all that fits these cars besides the sniper.
For what 99Black Bird?.....it's a waste of time. With out question the ls3 > cathedral for making all out power.....just as the ls7 > ls3 stuff. This is really no different than the bbc guys arguing about oval ports vs rectangles back in the day. Ovals had a advantage in lower rpm but in order to use the rectangle head like it should be you had to have the valvetrain in place to do it......just like this scenario.
I think you’ve been watching too much Street Outlaws.
Huh... how does anything I posted relate to that show whatsoever? More torque is always good, but more torque at a higher rpm usually means faster. No? Or is that just a street outlaws thing?
To the masters of "what everyone wants with their cars". Actually being "what I like for my cars & everyone else should too". So what is the tq difference between the two heads at say 15-20% throttle at 1500-2500 rpm? Or do you guys just drive on the street at WOT 100% of the time? The masters will shine with this answer..
For me, it would make no difference having 350 ft lbs vs 400 ft lbs at 3500rpm on the street. I don't know about everyone else, but I've never started a street race at 3500 rpm. Why would anyone do that who knows better? Not sure why that extra 50 ft lbs at 3000rpm is so important to pass granny on the highway....? lol
Like underlined. There's no problem with what anyone wants here. And no one knows about everyone else. It seems it's people that just think they know what is the best for everyone & are selfish *** wipes about it.
I've started runs at 3500. Not to my liking but sometimes **** happens. Like a person with different gears/speeds than you & will only go from his speeds. Or you don't hook from speed rpm etc.. I rather run than not run. No big ego like "only run if a sure W" as some are.
I did run a coyote yesterday from a second gear roll at 3000rpm it was really bad for him lol imagine if I would have had another 60 foot pounds there. I was at a severe disadvantage with my mid runner fast and stock ls3 heads/cam for sure.
Here is a comparison you might find interesting. It is a dyno comparison between rectangle port heads and cathedral port heads. It is two different engines, but done on the same dyno at Westech. This test is using two nearly identical engines with the same camshaft (231/247 113+4 .617"/.624") and same Holley Hi-Ram intake.
Cathedral Port Engine
370" Iron Block 4.030 x 3.622
11:1
AFR 230cc cathedral port heads
Rectangle Port Engine
376" Aluminum Block 4.065 x 3.622
11:1
Chevrolet Performance 276cc CNC LS3 Heads
As you can see, with this intake and camshaft, the Chevrolet Performance LS3 heads outperform the AFR 230 CC heads pretty decisively.
You shifted the torque band to the right or to the left. Since hp is a ratio of rpm, higher rpm makes more power. If you put a head on the shifts power to the right and then dont rev of course you will be disappointed.
Torque is more a function of displacement and cylinder fill. At a certain point, a motor will only make so much torque NA regardless of tricks. But the rpm range determines horsepower just as much as torque does. On a 346, that number is about 430-440. If you are set up to make peak torque at 4800, yeah by 6700 its likely done and falling fast.
Cathedrals in general like to peak torque around 4800-5200. That graph in the article is rather unusual in that it peaks at 5200-5500. But the ls3 heads peaked even higher and carried further. That is when port velocity stops mattering and total flow takes over.
At any rate, I would wager you could optimize cams etc to where both engines make the same torque. The rectangles will make more power with same peak torque due to rpm.
But if you are not going to rev, then why bother? Just do what hio did and leave it bolt ons. The whole argument hinges on how you intend to drive the car.
FWIW the 5-sec LS Head was a lsxdr a la ls7 head design by baker before we start googling results for various heads. Fastest LS Head is a ls7 design
Here is a comparison you might find interesting. It is a dyno comparison between rectangle port heads and cathedral port heads. It is two different engines, but done on the same dyno at Westech. This test is using two nearly identical engines with the same camshaft (231/247 113+4 .617"/.624") and same Holley Hi-Ram intake.
Cathedral Port Engine
370" Iron Block 4.030 x 3.622
11:1
AFR 230cc cathedral port heads
Rectangle Port Engine
376" Aluminum Block 4.065 x 3.622
11:1
Chevrolet Performance 276cc CNC LS3 Heads
As you can see, with this intake and camshaft, the Chevrolet Performance LS3 heads outperform the AFR 230 CC heads pretty decisively.
I like this post but that cam is a POORLY SPECCED cam for the afr 230 heads... the AFR heads would do better with a 231/235 duration camshaft. The 231/247 cam is really hurting the intake/exhaust ratio of the AFR heads. Too wide of a split....
^^^^^^plastic intakes are about all that fits these cars besides the sniper.
For what 99Black Bird?.....it's a waste of time. With out question the ls3 > cathedral for making all out power.....just as the ls7 > ls3 stuff. This is really no different than the bbc guys arguing about oval ports vs rectangles back in the day. Ovals had a advantage in lower rpm but in order to use the rectangle head like it should be you had to have the valvetrain in place to do it......just like this scenario.
The LS3 pulls away from an LS1 at 6200 rpm and up. If you are running out to 7800 rpm then the LS3 has the advantage, provided your bottom end can take the abuse. Larger cubes, get real heads like TF 255's.
^^^^^^plastic intakes are about all that fits these cars besides the sniper.
For what 99Black Bird?.....it's a waste of time. With out question the ls3 > cathedral for making all out power.....just as the ls7 > ls3 stuff. This is really no different than the bbc guys arguing about oval ports vs rectangles back in the day. Ovals had a advantage in lower rpm but in order to use the rectangle head like it should be you had to have the valvetrain in place to do it......just like this scenario.
I agree it's very much BBC oval vs rectangular type of discussion.
Plastic intakes are about all that fits 4th Gen's, C5's, 5th Gen's & C6's but the LS world includes a lot of trucks and swapped cars that often have more flexibility with intake selection.
The sort of testing I want to see is objective data / science project type testing. Need to win that $1.6 billion dollar lottery to fund a 1000+ hours for Westech to test all this stuff and publish the results so I read about it while partying in Dubia
There has to be more to it then what we see here. If square ports were so bad under 5000 why would they be put on trucks? I've also seen cathedrals with significantly less flow on paper run just as hard as the larger square ports. I need to research this and find the right people to ask because I want to know if I should put ls3 heads and intake on my 403 or 243s and fast.
What i dont UNDERSTAND is how a guy can put LS3 heads/intake on a 408ci and it only makes 470-490 rwhp then the car cant get past 123 mph running mid 11s. It really leaves me scratching my head.
I've been following that thing. Looks promising for guys that ain't skeered of over 6k rpm.
Originally Posted by wannafbody
The LS3 pulls away from an LS1 at 6200 rpm and up. If you are running out to 7800 rpm then the LS3 has the advantage, provided your bottom end can take the abuse. Larger cubes, get real heads like TF 255's.
not really a bottom end issue. Hasn't been for a long time. It's all about valve control.
Originally Posted by Tuskyz28
What i dont UNDERSTAND is how a guy can put LS3 heads/intake on a 408ci and it only makes 470-490 rwhp then the car cant get past 123 mph running mid 11s. It really leaves me scratching my head.
Well those combos happen quite often. Not go call no names buts its a few on this site.... its not just one guy. I went to LS fest and seen one in person. Nice car and all but it it was 11.4s at 122 with a T56 and a Quick Performance 9 inch on slicks. 408ci with LS3 heads and intake. Car also had some BMR/UMI tubular parts as well. Fast car but slow.....
10-25-2018, 10:47 AM
