Cathedral or Square port Heads
10 Second Club
Joined: Aug 2010
Posts: 4,465
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From: Harford Co. Maryland
LY6 Engine Ratings Compression Ratio 9.6:1 Horsepower Rating 364 hp Torque Rating 383 ft.-lbs.
LQ4 Engine Ratings Compression Ratio 9.4:1 Horsepower Rating 300-330 hp Torque Rating 360-370 ft./lbs.
Wonder why GM would do this then ?
And 3Pedals made just shy of 650 with a cam and spring swap on a LY6 ?
DMMizel 9.8-10.0's...LY6
And others.
Just asking, not here to argue.....
LQ4 Engine Ratings Compression Ratio 9.4:1 Horsepower Rating 300-330 hp Torque Rating 360-370 ft./lbs.
Wonder why GM would do this then ?
And 3Pedals made just shy of 650 with a cam and spring swap on a LY6 ?
DMMizel 9.8-10.0's...LY6
And others.
Just asking, not here to argue.....
TECH Apprentice
Joined: Feb 2010
Posts: 370
Likes: 138
VVT on the LY6
LY6 4600 rpm HP peak 4400 TQ peak tiny bit more compression. Makes sense because of port size. Both look to be on the same cam.
LQ4 4400 HP peak 4000 TQ peak
I’m guessing the VVT makes a small difference.
Along with the compression bump.
Id imagine GM switching to square port across the board was money saving issue not try to squeeze 100% performance from the engine.
that video his cam selection favors a square port head better. The decision of what’s best for yourself seems to be intended use.
LY6 4600 rpm HP peak 4400 TQ peak tiny bit more compression. Makes sense because of port size. Both look to be on the same cam.
LQ4 4400 HP peak 4000 TQ peak
I’m guessing the VVT makes a small difference.
Along with the compression bump.
Id imagine GM switching to square port across the board was money saving issue not try to squeeze 100% performance from the engine.
that video his cam selection favors a square port head better. The decision of what’s best for yourself seems to be intended use.
TECH Senior Member
Joined: Jun 2016
Posts: 22,291
Likes: 3,616
From: Central Cal.
The LQ4 was a Gen III engine aimed at 3/4 and 1 ton truck usage and used cathedral heads (all there was then), a very mild cam, initially the same one used in 5.3s (191/190. .457/.466, 114LSA), then the one used in the LQ9 (196/207, .467/.479, 116LSA)
The LY6 was a Gen IV engine with the same target usage but upped the game with rectangular heads but a cam very close to the LQ9/late LQ4 (196/208, .467/.479, 116LSA) but with VVT.
So why would GM do WHAT?? They got more HP and torque at the possible expense of low end response.
The LY6 was a Gen IV engine with the same target usage but upped the game with rectangular heads but a cam very close to the LQ9/late LQ4 (196/208, .467/.479, 116LSA) but with VVT.
So why would GM do WHAT?? They got more HP and torque at the possible expense of low end response.
10 Second Club
Joined: Aug 2010
Posts: 4,465
Likes: 192
From: Harford Co. Maryland
The LQ4 was a Gen III engine aimed at 3/4 and 1 ton truck usage and used cathedral heads (all there was then), a very mild cam, initially the same one used in 5.3s (191/190. .457/.466, 114LSA), then the one used in the LQ9 (196/207, .467/.479, 116LSA)
The LY6 was a Gen IV engine with the same target usage but upped the game with rectangular heads but a cam very close to the LQ9/late LQ4 (196/208, .467/.479, 116LSA) but with VVT.
So why would GM do WHAT?? They got more HP and torque at the possible expense of low end response.
The LY6 was a Gen IV engine with the same target usage but upped the game with rectangular heads but a cam very close to the LQ9/late LQ4 (196/208, .467/.479, 116LSA) but with VVT.
So why would GM do WHAT?? They got more HP and torque at the possible expense of low end response.
TECH Veteran
Joined: Sep 2014
Posts: 4,893
Likes: 703
From: Mississippi
The LSA ALONE CAN control how productive a engine is UNDER THE CURVE.
For ***** and deep thoughts lets talk bore sizes and valve sizes. My 3/4 ton squarebody big block is 454ci have a 4.250 inch bore. The valve size of the peanut port head is 2.065 valve size. A Popular mod in the big block community is going up to a 2.19 intake valve. Let that sink in for a second guys.
2.16 valve on a 4.00 bore...
(LS motors)
Also some guys that run big blocks have a notch cut in the top of the bore to help the big valves.
For ***** and deep thoughts lets talk bore sizes and valve sizes. My 3/4 ton squarebody big block is 454ci have a 4.250 inch bore. The valve size of the peanut port head is 2.065 valve size. A Popular mod in the big block community is going up to a 2.19 intake valve. Let that sink in for a second guys.
2.16 valve on a 4.00 bore...
(LS motors) Also some guys that run big blocks have a notch cut in the top of the bore to help the big valves.
Here was a comparison on a 427. Some real world numbers right there.
https://www.enginelabs.com/news/vide...le-port-heads/
My 99 car has an LS370 with LS3 intake and NW92, Cam Motion 238/246 111+3, 823 heads with Ferrea valves and a set of TSP 1 7/8 long tubes. Don't know what it's making for power yet but once all is said and done I might just get my hands on a Fast 102 and have a set of cathedrals ported out and go get it dynoed to see if it's worth it but my guess right now is that it wouldn't be.
https://www.enginelabs.com/news/vide...le-port-heads/
My 99 car has an LS370 with LS3 intake and NW92, Cam Motion 238/246 111+3, 823 heads with Ferrea valves and a set of TSP 1 7/8 long tubes. Don't know what it's making for power yet but once all is said and done I might just get my hands on a Fast 102 and have a set of cathedrals ported out and go get it dynoed to see if it's worth it but my guess right now is that it wouldn't be.
Last edited by 01CamaroSSTx; Jan 18, 2025 at 09:03 PM.
TECH Veteran
Joined: Sep 2014
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From: Mississippi
And yet to this day the fastest hydraulic roller LS motors uses cathedrals. We cant race dynos but in that case i made 480 to the tire on a 48 inch drum on PUMP GAS with a ganster torque curve. I could easily clear 500 rwhp on a happy 24 inch drum dyno that gives off a higher output number.
TECH Regular
Joined: May 2023
Posts: 417
Likes: 138
From: Franconia, PA
And yet to this day the fastest hydraulic roller LS motors uses cathedrals. We cant race dynos but in that case i made 480 to the tire on a 48 inch drum on PUMP GAS with a ganster torque curve. I could easily clear 500 rwhp on a happy 24 inch drum dyno that gives off a higher output number.
https://ls1tech.com/articles/worlds-fastest-motor-g8-rick-crawford-racing-10-59-130/
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Joined: May 2023
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From: Franconia, PA
Very fast but a 7.0L vs a 6.0L is not a fair comparison. I think we can admit that all things being equal (stock vs stock, cnc vs cnc, aftermarket vs AM) rec port heads have the advantage up top and cath port have the advantage down low and typically with compression.
I also think with your current cam, you would have had better gains with your rec heads than you did with the other. Its just a better cam.
I also think with your current cam, you would have had better gains with your rec heads than you did with the other. Its just a better cam.
Last edited by Abs; Jan 19, 2025 at 03:32 AM.
I would have liked to have seen LME's test on the 427 with a set of MMS 295cc cathedral heads. I don't think the AFR 245 heads used was a fair comparison since those are better suited on a 4.00 inch bore.
And yet to this day the fastest hydraulic roller LS motors uses cathedrals. We cant race dynos but in that case i made 480 to the tire on a 48 inch drum on PUMP GAS with a ganster torque curve. I could easily clear 500 rwhp on a happy 24 inch drum dyno that gives off a higher output number.
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Joined: May 2023
Posts: 417
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From: Franconia, PA
Weve been down this road here soooooooo many times. No matter what I post, or you post, or anybody posts…it will all be argued and end up a big mess.
Everyone knows cathedrals own.
Everyone knows square ports own.
I say…because I’ve done this crap since the early 90’s in the Cup engine world, that it boils down to the combination. We made 825 in 1993? with a sbc…
That’s my answer and I’m sticking to it…
Everyone knows cathedrals own.
Everyone knows square ports own.
I say…because I’ve done this crap since the early 90’s in the Cup engine world, that it boils down to the combination. We made 825 in 1993? with a sbc…
That’s my answer and I’m sticking to it…
TECH Resident
Joined: Jun 2011
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The VVT still makes it more responsive even at part throttle. With the exception of some steady state cruise areas of the map (which aren't active if the truck is loaded), the cam stays advanced until 3500rpm.
Which is better depends on the bore size, cubic inches, compression and cam. For a street cars cathedral are probably better. For a strictly drag car the rec ports should make more power above 6000 rpm.
TECH Regular
Joined: May 2023
Posts: 417
Likes: 138
From: Franconia, PA
TECH Regular
Joined: May 2023
Posts: 417
Likes: 138
From: Franconia, PA
Weve been down this road here soooooooo many times. No matter what I post, or you post, or anybody posts…it will all be argued and end up a big mess.
Everyone knows cathedrals own.
Everyone knows square ports own.
I say…because I’ve done this crap since the early 90’s in the Cup engine world, that it boils down to the combination. We made 825 in 1993? with a sbc…
That’s my answer and I’m sticking to it…
Everyone knows cathedrals own.
Everyone knows square ports own.
I say…because I’ve done this crap since the early 90’s in the Cup engine world, that it boils down to the combination. We made 825 in 1993? with a sbc…
That’s my answer and I’m sticking to it…
i never knew there was a divide over this topic. I always figured that it was a given that the bigger rec ports flowed better at higher rpm, but had less velocity through those big ports and thus less power at lower rpms.