Why do people hate on stock ls3 castings
04-17-2017, 06:38 AM
#3
TECH Fanatic
Like most things, there aren't very many apples-apples comparisons out there. So, you have the cathedral guys and the square port guys backed into their corners relating to their own single experiences and regurgitating facts they read online.
04-17-2017, 10:44 AM
#4
Don't know. I don't hate on them at all....they're pretty bad-*** IMO.
At the same time, they have big enough intake runners and valves that make them 'not ideal' for strong torque at low RPMs for most applications.
Bottom line.....just like a custom spec'ed cam, they aren't the end-all/be-all for (particularly) a lot of NA, stock displacement applications.
KW
At the same time, they have big enough intake runners and valves that make them 'not ideal' for strong torque at low RPMs for most applications.
Bottom line.....just like a custom spec'ed cam, they aren't the end-all/be-all for (particularly) a lot of NA, stock displacement applications.
KW
04-17-2017, 11:24 AM
#5
TECH Veteran
I think they good in some cases depending on usage/goals.
They are also the most complex head to cam from what I can see. You ever notice the guys that run fast *** times at the track with a LS3 or LS7 head don't share they cam specs?
They are also the most complex head to cam from what I can see. You ever notice the guys that run fast *** times at the track with a LS3 or LS7 head don't share they cam specs?
04-17-2017, 11:46 AM
#6
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They sure look impressive. 20 years ago they would be consider cutting edge. They're a lot like Cleveland 4V heads, only a few know how to make them work to their potential and many that try have less performance than they thought they'd have.
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04-18-2017, 12:40 AM
#12
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In my opinion the reason cathedrals are alive is some darn good porters out there that have done some great work making some serious horse power with them and the fact that they been around a lot longer.
My choice is the port that shapes best to the valve head and that's the rectangular port, the heads had to be redesign to come up with a better shape port to better flow for larger displacements.
While many have no admiration for higher flow numbers I do, the best 255 cc intake port cathedral head will never match the best 255 cc intake port rectangular head in flow numbers or power potential.
The rectangular port is more versatile as well while the cathedral port have to be optimized for a particular displacement a 255 cc rectangular intake port will be perfectly at home in an ls2 but not the case with a 255 cc cath, in fact the ls3 aftermarket 255 cc in my stock block ls3 will be rite at home in an ls7 as well they even flow more than the stock cnc ported ls7 heads with larger displacement ports.
In case you didn't get it a good set of ls3 heads will be great on an ls2 build later if you decide to go bigger like ls3 you can use same heads no need to sell and start over looking for another set of heads and if you decide to stroke it to 416 no problem same ls3 heads are still good.
The ls3 intake manifold is better than all factory cathedral port intakes.
My choice is the port that shapes best to the valve head and that's the rectangular port, the heads had to be redesign to come up with a better shape port to better flow for larger displacements.
While many have no admiration for higher flow numbers I do, the best 255 cc intake port cathedral head will never match the best 255 cc intake port rectangular head in flow numbers or power potential.
The rectangular port is more versatile as well while the cathedral port have to be optimized for a particular displacement a 255 cc rectangular intake port will be perfectly at home in an ls2 but not the case with a 255 cc cath, in fact the ls3 aftermarket 255 cc in my stock block ls3 will be rite at home in an ls7 as well they even flow more than the stock cnc ported ls7 heads with larger displacement ports.
In case you didn't get it a good set of ls3 heads will be great on an ls2 build later if you decide to go bigger like ls3 you can use same heads no need to sell and start over looking for another set of heads and if you decide to stroke it to 416 no problem same ls3 heads are still good.
The ls3 intake manifold is better than all factory cathedral port intakes.
04-18-2017, 12:55 AM
#13
TECH Veteran
http://www.superchevy.com/how-to/engines-drivetrain/1247-626hp-ls3-stroker-build-supersize-me/
This engine made 1.495 hp per cube. It made great power for only a 235 intake duration cam but look at the torque curve on the engine. Looks like a hill.... hard to achieve that flat curve all the way across the graph.
This engine made 1.495 hp per cube. It made great power for only a 235 intake duration cam but look at the torque curve on the engine. Looks like a hill.... hard to achieve that flat curve all the way across the graph.
04-18-2017, 05:49 AM
#14
Your asking a perception question which really means am opinion question. As KCS said depends on application.
My perception of the LS3 is that is just a failed design for the LS7. That comes from the LS3 head design being regarded as a failure at GM in providing air flow for the LS7. A new head had to be designed to meet LS7 requirements in GM's view. I'm sure most people couldn't care less but I find that a big issue for how I view LS3 cylinder heads.
Another part is LS3 heads typically seem to make about 1.75 hp per cfm vs 2hp per cfm which just screams underachieving cylinder head. That underachieving image is supported by various articles like this that have been around for a long time.
http://www.superchevy.com/how-to/ght...-head-to-head/
Cathedral ports are more forgiving of cam selection.
I like some other folks have a lot of cathedral parts that accumulated over the years that are suitable for what we are doing. Example - my 91 Camaro convertible - a stock LS1 or LS2 swap is good enough for a crusier and the LS1/LS2 swap is less expensive than doing an LS3 or LS7.
Cathedral vs LS3 head reminds me of:
Cleveland vs Windsor
Big Block Chevy Oval vs Rectangular
Any of these heads can work very well in the right combo - so a lot of it comes down to just what one wants and is willing to spend $ on.
My perception of the LS3 is that is just a failed design for the LS7. That comes from the LS3 head design being regarded as a failure at GM in providing air flow for the LS7. A new head had to be designed to meet LS7 requirements in GM's view. I'm sure most people couldn't care less but I find that a big issue for how I view LS3 cylinder heads.
Another part is LS3 heads typically seem to make about 1.75 hp per cfm vs 2hp per cfm which just screams underachieving cylinder head. That underachieving image is supported by various articles like this that have been around for a long time.
http://www.superchevy.com/how-to/ght...-head-to-head/
Cathedral ports are more forgiving of cam selection.
I like some other folks have a lot of cathedral parts that accumulated over the years that are suitable for what we are doing. Example - my 91 Camaro convertible - a stock LS1 or LS2 swap is good enough for a crusier and the LS1/LS2 swap is less expensive than doing an LS3 or LS7.
Cathedral vs LS3 head reminds me of:
Cleveland vs Windsor
Big Block Chevy Oval vs Rectangular
Any of these heads can work very well in the right combo - so a lot of it comes down to just what one wants and is willing to spend $ on.
04-18-2017, 06:03 AM
#15
Your asking a perception question which really means am opinion question. As KCS said depends on application.
My perception of the LS3 is that is just a failed design for the LS7. That comes from the LS3 head design being regarded as a failure at GM in providing air flow for the LS7. A new head had to be designed to meet LS7 requirements in GM's view. I'm sure most people couldn't care less but I find that a big issue for how I view LS3 cylinder heads.
Another part is LS3 heads typically seem to make about 1.75 hp per cfm vs 2hp per cfm which just screams underachieving cylinder head. That underachieving image is supported by various articles like this that have been around for a long time.
http://www.superchevy.com/how-to/ght...-head-to-head/
Cathedral ports are more forgiving of cam selection.
I like some other folks have a lot of cathedral parts that accumulated over the years that are suitable for what we are doing. Example - my 91 Camaro convertible - a stock LS1 or LS2 swap is good enough for a crusier and the LS1/LS2 swap is less expensive than doing an LS3 or LS7.
Cathedral vs LS3 head reminds me of:
Cleveland vs Windsor
Big Block Chevy Oval vs Rectangular
Any of these heads can work very well in the right combo - so a lot of it comes down to just what one wants and is willing to spend $ on.
My perception of the LS3 is that is just a failed design for the LS7. That comes from the LS3 head design being regarded as a failure at GM in providing air flow for the LS7. A new head had to be designed to meet LS7 requirements in GM's view. I'm sure most people couldn't care less but I find that a big issue for how I view LS3 cylinder heads.
Another part is LS3 heads typically seem to make about 1.75 hp per cfm vs 2hp per cfm which just screams underachieving cylinder head. That underachieving image is supported by various articles like this that have been around for a long time.
http://www.superchevy.com/how-to/ght...-head-to-head/
Cathedral ports are more forgiving of cam selection.
I like some other folks have a lot of cathedral parts that accumulated over the years that are suitable for what we are doing. Example - my 91 Camaro convertible - a stock LS1 or LS2 swap is good enough for a crusier and the LS1/LS2 swap is less expensive than doing an LS3 or LS7.
Cathedral vs LS3 head reminds me of:
Cleveland vs Windsor
Big Block Chevy Oval vs Rectangular
Any of these heads can work very well in the right combo - so a lot of it comes down to just what one wants and is willing to spend $ on.
Also I keep hearing these talks about it being a lazy head but it seems every engine with those heads outperformas its cathedral counterpart. Even 6.0 engines that came with both make more power and TQ with the ls3 castings.
And as mentioned an ls3 which has 12 more cubes and a similar cam asbolutely dominates the ls2 everywhere in the rpm band. Much more so than a couple degrees on a cam and 12 CI would dictate.
04-18-2017, 06:58 AM
#16
TECH Veteran
Big Hammer, would you find it interesting that the LS3 heads get outperformed (torque production) to 4000 rpm vs a 317 cathedral head even on a motor using a 4.000 inch crank (408ci) ?
04-18-2017, 07:31 AM
#17
Restricted User
Large flow disparity between intake and exhaust ports on an LS3 head. That's why rectangle port camshafts usually have much more exhaust duration than intake. They also make less torque for the first half of the rev range than cathedrals, and they don't work on anything smaller than a 6.0.
When it comes to boost, the extra intake flow from LS3 heads is almost irrelevant.
When it comes to boost, the extra intake flow from LS3 heads is almost irrelevant.
04-18-2017, 08:11 AM
#19
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