Square Port heads vs. Cathedral Port heads
10-13-2020, 07:38 AM
#301
Playing devils advocate here Bort, but when in your mind will Cathedrals not be the answer? I dont wanna hear just dedicated top end racecar niether. Cuz GM didnt design the Z06 to just beat up on COPOs, Hellkitten redeyes, etc in a 1/4mile race. Again, not argueing, just playing devils advocate. I simply dont know or understand the clean cut hate on ls7 heads.
Last edited by rkupon1; 10-13-2020 at 07:45 AM.
10-13-2020, 07:56 AM
#302
Playing devils advocate here Bort, but when in your mind will Cathedrals not be the answer? I dont wanna hear just dedicated top end racecar niether. Cuz GM didnt design the Z06 to just beat up on COPOs, Hellkitten redeyes, etc in a 1/4mile race. Again, not argueing, just playing devils advocate. I simply dont know or understand the clean cut hate on ls7 heads.
Maximum rpm 6-6500rpm
.595 lift and broad torque band.
The fit for this requirement is a cathedral head.
When someone want to rev to at least 7000rpm or if they want less torque and hp below peak then an ls7 head might be the answer.
Or if the engine is large.
How much lift is wanted, etc
A lot of variables.
Even Smoke said cathedrals and he is a square port head man.
Look at Darth's combination as an example.
It's purpose built and a cathedral is not the right head for his goals.
Different Rpm and power targets etc.
I'm the type of person who likes looking at the tradeoffs and deciding what to prioritise.
10-13-2020, 08:02 AM
#303
Exactly the kinda answer I was looking for. Thanks. I just wanted to clear up some confusion in my mind. Seen alotta Cathedral luv n ls7 hate lately. Im guessing maybe its because Cathedrals still fit the bill for majority of builds on here? I dunno, when I think ls7, i think z06 and pure bad assery of a car designed to do it all!
10-13-2020, 08:13 AM
#304
I'd like to tack on a question.....has anyone ever done a street car rec port build that targeted mid-range torque and max rpm of 6500? Would it be that much worse than a cath port if it was designed to run in that rpm range? Most here shoot for north of 7k with rec port's, but I don't recall ever seeing someone do a build that was setup for low-end with a rec port.
10-13-2020, 08:24 AM
#305
10 Second Club
Personally for the weight of the car and goals posted a simple stage 1 ls3 cam with stock ls3 heads and ls3 intake is all it would need. Not sure where all this off idle laziness is, but my stock ls3 with bolt ons at his weight went mid 10s and got 28mpg (went 11.0 with 100% stock exhaust). My fat gen went mid 11s at 120 with the same set up. Having 427ci in a 3rd gen I would imagine 10s in the configuration i mentioned above would be a cake walk and still get 25+mpg.
10-13-2020, 08:34 AM
#306
I'd like to tack on a question.....has anyone ever done a street car rec port build that targeted mid-range torque and max rpm of 6500? Would it be that much worse than a cath port if it was designed to run in that rpm range? Most here shoot for north of 7k with rec port's, but I don't recall ever seeing someone do a build that was setup for low-end with a rec port.
https://ls1tech.com/forums/dynamomet...3-434-a-2.html
10-13-2020, 08:35 AM
#307
10 Second Club
I'd like to tack on a question.....has anyone ever done a street car rec port build that targeted mid-range torque and max rpm of 6500? Would it be that much worse than a cath port if it was designed to run in that rpm range? Most here shoot for north of 7k with rec port's, but I don't recall ever seeing someone do a build that was setup for low-end with a rec port.
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rkupon1 (10-13-2020)
10-13-2020, 08:41 AM
#308
Okay, let's talk about my next project . . . 1989 Camaro / 4L85E / 12-Bolt . . . Cam Undecided, Heads Undecided, Torque Converter Undecided ( want Lock-Up ), Gears Undecided.
Engine : 427 Stroker / Dart LS Next SHP Short Block ( Flat-Top pistons -12cc ) . . . Dynamic Compression Ratio 8.5:1, for 91 Octane Pump Gas ( 9:1 for 93 Octane )
https://ls1tech.com/forums/generatio...ification.html
Goals :
( 1 ) Smooth Idle, High Vacuum at Idle, Broad Torque Band . . . ( Fuel Economy, if possible )
( 2 ) Maximum 6000 - 6500 RPM.
( 3 ) Durability / Longevity - Daily-Driver . . . Some Drag Strip.
( 4 ) Camshaft - .595" Max lift ( easier on valvetrain ) . . . Zero or Negative Overlap. Cam Specs - To be determined
( 5 ) Cylinder Heads - Undecided whether Cathedral Port or Square-Port . . . Same for Intake Manifold.
( 6 ) Exhaust will be Headers, High-Flow cats, Crossover, Walker / Dynomax Super Turbo Muffler, Part # 17739 ( I want it "QUIET" ).
So, CATHEDRAL or SQUARE PORT heads & what INTAKE MANIFOLD ?
Thanks !
Engine : 427 Stroker / Dart LS Next SHP Short Block ( Flat-Top pistons -12cc ) . . . Dynamic Compression Ratio 8.5:1, for 91 Octane Pump Gas ( 9:1 for 93 Octane )
https://ls1tech.com/forums/generatio...ification.html
Goals :
( 1 ) Smooth Idle, High Vacuum at Idle, Broad Torque Band . . . ( Fuel Economy, if possible )
( 2 ) Maximum 6000 - 6500 RPM.
( 3 ) Durability / Longevity - Daily-Driver . . . Some Drag Strip.
( 4 ) Camshaft - .595" Max lift ( easier on valvetrain ) . . . Zero or Negative Overlap. Cam Specs - To be determined
( 5 ) Cylinder Heads - Undecided whether Cathedral Port or Square-Port . . . Same for Intake Manifold.
( 6 ) Exhaust will be Headers, High-Flow cats, Crossover, Walker / Dynomax Super Turbo Muffler, Part # 17739 ( I want it "QUIET" ).
So, CATHEDRAL or SQUARE PORT heads & what INTAKE MANIFOLD ?
Thanks !
Last edited by Che70velle; 10-13-2020 at 12:56 PM.
10-13-2020, 09:02 AM
#309
Exactly the kinda answer I was looking for. Thanks. I just wanted to clear up some confusion in my mind. Seen alotta Cathedral luv n ls7 hate lately. Im guessing maybe its because Cathedrals still fit the bill for majority of builds on here? I dunno, when I think ls7, i think z06 and pure bad assery of a car designed to do it all!
He makes some interesting points but they have some advantages also over the older style cathedral.
As I said it depends on what you want to prioritise.
10-13-2020, 09:04 AM
#310
TECH Enthusiast
To All,
I was thinking about Cathedral port heads, but the Square-Ports are "seductive". The Low-Rpm, long-runner, intakes for square port heads ( Stock LS3, for example ) flow much better than the ones for Cathedral ports do ( LS6, for example ).
Virtually all of the aftermarket intakes have short runners and benefit a high-RPM motor, while killing low RPM performance. Spending almost $1000 on a "plastic" FAST manifold seems a waste for the small gains.
Basically, my car will be a "sleeper" . . . I want it to drive like "stock", but take full advantage of the extra cubic inches.
Dead Smooth idle, QUIET, full exhaust system, economy, & great durability / longevity . . . Basically, "the wrong car to pick on at a stoplight" - LOL !
I was thinking about Cathedral port heads, but the Square-Ports are "seductive". The Low-Rpm, long-runner, intakes for square port heads ( Stock LS3, for example ) flow much better than the ones for Cathedral ports do ( LS6, for example ).
Virtually all of the aftermarket intakes have short runners and benefit a high-RPM motor, while killing low RPM performance. Spending almost $1000 on a "plastic" FAST manifold seems a waste for the small gains.
Basically, my car will be a "sleeper" . . . I want it to drive like "stock", but take full advantage of the extra cubic inches.
Dead Smooth idle, QUIET, full exhaust system, economy, & great durability / longevity . . . Basically, "the wrong car to pick on at a stoplight" - LOL !
Last edited by ez2cdave; 10-13-2020 at 09:15 AM.
10-13-2020, 09:09 AM
#311
TECH Enthusiast
Since the consensus seems to be Cathedral heads, the question is WHICH Cathedral heads ? ( remember the RPM range & intended usage )
Looking at the short block, I believe that I will need a 72cc chamber, +/-, and don't want to spend a small fortune on heads.
Maybe ported 317's ? ( send in heads that I buy ) https://store.katechengines.com/cnc-...pair-p589.aspx
Also, any intake manifold suggestions ?
Looking at the short block, I believe that I will need a 72cc chamber, +/-, and don't want to spend a small fortune on heads.
Maybe ported 317's ? ( send in heads that I buy ) https://store.katechengines.com/cnc-...pair-p589.aspx
Also, any intake manifold suggestions ?
Last edited by ez2cdave; 10-13-2020 at 09:24 AM.
10-13-2020, 09:17 AM
#312
With that rpm range you are wanting he 235cc head might be the hot ticket.
You would have crazy response off idle and in the mid range with big torque and will be perfect for your powerband requirements. That 235cc head will be in it's element.
The 245 will also work and be about 25hp higher at peak.
Will still be snappy off idle but you will be able to cam more with the smaller head and still have that smooth idle you are wanting due to the high air speed you would be generating through the ports.
if you were wanting a 6500-7000rpm power band I would definitely suggest the 245cc head like mine.
10-13-2020, 09:23 AM
#313
10 Second Club
That's easy.Either an AFR or trickflow casting with a fast 102mm intake and you are good to go.
With that rpm range you are wanting he 235cc head might be the hot ticket.
You would have crazy response off idle and in the mid range with big torque and will be perfect for your powerband requirements. That 235cc head will be in it's element.
The 245 will also work and be about 25hp higher at peak.
Will still be snappy off idle but you will be able to cam more with the smaller head and still have that smooth idle you are wanting due to the high air speed you would be generating through the ports.
if you were wanting a 6500-7000rpm power band I would definitely suggest the 245cc head like mine.
With that rpm range you are wanting he 235cc head might be the hot ticket.
You would have crazy response off idle and in the mid range with big torque and will be perfect for your powerband requirements. That 235cc head will be in it's element.
The 245 will also work and be about 25hp higher at peak.
Will still be snappy off idle but you will be able to cam more with the smaller head and still have that smooth idle you are wanting due to the high air speed you would be generating through the ports.
if you were wanting a 6500-7000rpm power band I would definitely suggest the 245cc head like mine.
10-13-2020, 09:31 AM
#315
My build is pretty close to that. Its a 434 with ported ls3 heads and a mild cam. Here's a link to the dyno thread
https://ls1tech.com/forums/dynamomet...3-434-a-2.html
https://ls1tech.com/forums/dynamomet...3-434-a-2.html
I've seen some similar graphs. The 350@2500 is pretty typical but the 400@3500 is excellent. You've got a light clutch/flywheel setup right? Be cool to see what that is worth on the dyno either way.
10-13-2020, 09:36 AM
#316
10 Second Club
You do realize he has a car that is less than 32xx pounds right? I cant believe GM didnt slap cathedrals on the ole LS7 for GRUNT and fuel economy lol With budget in mind please tell me how a stock ls3 head and intake cant keep up with the cathedral/fast set up you mention utilizing the parameters he has set for us.
10-13-2020, 09:39 AM
#317
TECH Enthusiast
10-13-2020, 09:47 AM
#318
10 Second Club
What is your budget sir? In all seriousness a 427 will motivate your car with about any top end you slap on it. You are the one who ultimately has to be happy with it. Realistically with a stock LS7 cam and a decent bolt on package you could have a very simple, docile, reliable yet mean as heck 3rd gen that would punk a lot of people. Its a shame the stock LS7 heads were such a catastrophe but the LS3 heads would get the job done.
10-13-2020, 10:23 AM
#319
10-13-2020, 11:01 AM
#320
You do realize he has a car that is less than 32xx pounds right? I cant believe GM didnt slap cathedrals on the ole LS7 for GRUNT and fuel economy lol With budget in mind please tell me how a stock ls3 head and intake cant keep up with the cathedral/fast set up you mention utilizing the parameters he has set for us.