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Was wondering if anyone knows if switch from a cathedral port heads/intake to a square port set up worth it price/effort wise. I would like to switch out for something aftermarket Trick, AFR, etc. if I go down the square port route. I have a set of 799 heads on now and I’m wondering if I could get similar results just from sending them out to get worked on. It would be going on a lq4 with ls2 rods and pistons. I also have a BTR stage 4 NA cam and I’m hoping to throw a FAST on it soon depending on what style heads I end up running. I don’t really plan on throwing any kind of boost at it but might run spray at the track if I’m not happy with the ET.
Some one here switched from LS3 heads to ported 799 heads and gained 50 hp along with a different cam. So the combo has to work together and velocity is the key.
Some one here switched from LS3 heads to ported 799 heads and gained 50 hp along with a different cam. So the combo has to work together and velocity is the key.
That guy is me. Best thing i ever done was to get rid of those LS3 heads.
I'm willing to bet that compression jumped up with the cathedrals and not really an apples to apples comparison..What if the LS3's had been ported with the right camshaft stabbed in there with just an LS3 intake? What power gains could have been made from those? Cathedrals known for the quick throttle response but rectangulars are known for making more horsepower and sometimes it's more horsepower that wins the race. Especially if your racing someone who was late on the tree.
I'm willing to bet that compression jumped up with the cathedrals and not really an apples to apples comparison..What if the LS3's had been ported with the right camshaft stabbed in there with just an LS3 intake? What power gains could have been made from those? Cathedrals known for the quick throttle response but rectangulars are known for making more horsepower and sometimes it's more horsepower that wins the race. Especially if your racing someone who was late on the tree.
Bigger valves and bigger intake runner always means more power? Velocity is real.
The 2.16 intake valve is a big *** valve right up against the 4.00 inch bore cylinder wall. That dont helps it at all.
Why would you want to port a head thats already 260cc on the intake runner on a 4.000 inch bore motor thats only 6800 RPM and below ?
Wonder if that really helps airflow? NOPE
The LS3 head needs Lots of RPM, and really a single plane intake to go with the motion.
I have done my home work on this topic. The FASTEST two hydraulic roller stock bottom end LS2 cars have both run cathedrals. One is ZZRacer at 10.2s at 130 plus amd the other car run 9s.
naturally aspirated.
Show me better results and i will swap my top end again.
I get that rectangular port heads aren't ideal for a 4.00 inch bore due to the intake valve being close to the cylinder wall. There's offset dowel pins you could use to shift the head away from the cylinder wall to help with valve shrouding. They were originally designed for a 4.065 bore not a 4.00 inch bore but yet GM decided to run the 823 on a 4.0 in bore hence the L96 which GM claims to make 360hp 380tq comapred to the LQ9 which had 317's and made 300hp 360 tq. So there wasn't much of a gain in the way of torque but a horsepower increase of 60hp. I suspect a ported 799/243 head would be a win win here in the 4.00 in bore as you would gain more compression which equates to more power and torque. Match a ported LS3/L92 head with the right camshaft and intake manifold and it gonna make more power, especially in a bore larger than 4.00 in.
Worth it price/effort wise all depends on what your goals are
Mamo's 12 degree AFR ls3 heads are making excellent power. Check out the thread... "403ci N/A build" in the Gen IV internal forum
@Tony @ Mamo Motorsports Absolutely!! Unless I'm thinking of Tonys LS7 heads, his heads outflow the OEM LS7 heads by maybe 20cfm per port AND do so at a higher velocity. Which is awfully damn hard to do. Tony's heads are one of the few have your cake and eat it, too, scenarios in cylinder heads that I have ever seen.....
Last edited by grinder11; Jan 16, 2025 at 05:28 PM.
Bigger valves and bigger intake runner always means more power? Velocity is real.
The 2.16 intake valve is a big *** valve right up against the 4.00 inch bore cylinder wall. That dont helps it at all.
Why would you want to port a head thats already 260cc on the intake runner on a 4.000 inch bore motor thats only 6800 RPM and below ?
Wonder if that really helps airflow? NOPE
The LS3 head needs Lots of RPM, and really a single plane intake to go with the motion.
I have done my home work on this topic. The FASTEST two hydraulic roller stock bottom end LS2 cars have both run cathedrals. One is ZZRacer at 10.2s at 130 plus amd the other car run 9s.
naturally aspirated.
Show me better results and i will swap my top end again.
IIRC, and I think I do, Alan Futral had a 346 LS1 6 speed in the 9s (first 346 6 speed in the 9s) back in the early 2000s, and in that time period they had to be cathedral. Cathedral ports haven't gotten much love since the LS3/LS7 heads have been released. They can still be a very formidable street/strip weapon.....
I'm sure the camshaft profile between the the two engines that I had mentioned are different and the reason I'm driving this home is that the ported 243/799 heads wasn't the only thing that contributed to the gains made over the LS3's. The Fast 102 intake, a larger throttle body and a more aggressive camshaft to go with the additonal flow those worked over cathedrals offered was the difference.
On a post I read, Pat G prefers Cathedrals on a 4.0 bore. It really comes down to the bore size and overall combo...
Brian Tooley as well. Brian recommended LS3 head for a guy on a budget and TFS 220/225 for a guy that didnt have a budget.
Originally Posted by 01CamaroSSTx
I'm sure the camshaft profile between the the two engines that I had mentioned are different and the reason I'm driving this home is that the ported 243/799 heads wasn't the only thing that contributed to the gains made over the LS3's. The Fast 102 intake, a larger throttle body and a more aggressive camshaft to go with the additonal flow those worked over cathedrals offered was the difference.
I didnt have a poor cam choice with with the LS3 top end on my LS2. The cam was a BTR 229/244 on a 114+3 LSA. Brian Tooley recommended me this cam first hand on the phone.
Yes the cams are different BUT so is the intake/exhaust ratio on the cylinder head.
Martin Smallwood will tell you a LS3 Fast 102mm intake is NOT worth the cost/power vs the GM LS3 intake.
My build is not basic by no means however, ZZracer and I talked on the phone for hours on my car and had a plan from day one. The cam choice for the 799s was talked about BETWEEN us for five days. Attention to detail goes along way not just big CFMs on a flow chart.
Martin Smallwood told me a CID intake with a 1050 Dominator was the way to go if you want the most from rectangular port heads.
I think you guys will appreciate this video. He says every time he uses the Dominator with ls3 heads, he loses power. But he gains when using it with cathedral port heads.
Rick crawford has had the best results with g8s (6.0 with the 823s). He likes to port and rod mod the intake and port and mill the heads. Milling the heads is likely more important than porting, at least with respect to the intake side. Exhaust ports could definitely use more flow as they are only like 190-200 cfm like a cathedral head whereas the intake ports flow like 320-330cfm stock.
Rick's cams are small on the intake and bigger on the exhaust like Brian tooley's, but he uses tighter lobe separations like 111+3. He also likes higher lifts. Minimum of .612 on intake and exhaust or .638 on both if you want to get more aggressive.
He used to use lunati cams but didn't like them as much after comp bought them and now has cammotion grind hus custom lobes. His intake lobes used to have a difference of 50 between advertised and .050 duration. I dont know what it is now with cammotion but i bet very similar.
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Cathedral or Square port Heads 
