Cathedral Port Vs. Rectangular Port
Launching!
Joined: Oct 2003
Posts: 267
Likes: 14
From: Chicago
Lt 1 was a bad boy...
I am really talking big blocks here.
A Buick 455, or a poncho 455. Produced more low end torque than the 454 engines. Even though the buick head flowed way less. I was making a point that head flow, is not the only thing to consider.
Buick stage 1 motors, where even hemi killers. Consistently beating Chevy, and those 440 six packs motors where also.
I am really talking big blocks here.
A Buick 455, or a poncho 455. Produced more low end torque than the 454 engines. Even though the buick head flowed way less. I was making a point that head flow, is not the only thing to consider.
Buick stage 1 motors, where even hemi killers. Consistently beating Chevy, and those 440 six packs motors where also.
The turbo TA was one of the quickest cars GM ever built.
The 370hp 350 was in a corvette much lighter than any mopar it would have faced. The Chevy small block won lots of races due to weight, not output. Otherwise, we wouldn't be putting LS's into older cars.
A 340 six pack putting down 400+? At the crank MAYBE.
Now, back to the thread. Square port heads are great when the engine is drawing 300+ cfm. Most of the time, your engine isn't breathing that hard, so port velocity becomes more important than total flow capability. This is what gives air momentum to continue filling cylinders past TDC. Also the reason cathedrals can tolerate bigger cams
The 370hp 350 was in a corvette much lighter than any mopar it would have faced. The Chevy small block won lots of races due to weight, not output. Otherwise, we wouldn't be putting LS's into older cars.
A 340 six pack putting down 400+? At the crank MAYBE.
Now, back to the thread. Square port heads are great when the engine is drawing 300+ cfm. Most of the time, your engine isn't breathing that hard, so port velocity becomes more important than total flow capability. This is what gives air momentum to continue filling cylinders past TDC. Also the reason cathedrals can tolerate bigger cams
Launching!
Joined: Oct 2003
Posts: 267
Likes: 14
From: Chicago
The LT-1 came in the much heavier Z28 too....and it was just as fast as a 340 6 pack....no doubt it's no LS, but that was 45 years ago...of course 45 years of engine development is gonna result in more HP. Anybody replacing a factory LT-1 with a LS is a fool as they are desirable collector cars! My old man sold his 71 stingray convertible 4spd LT-1 for TRIPLE what he paid for it in the late 80s...
Lt 1, dz 302, 340 6 packs... Are worth their weight in gold now.
Only reason I mentioned the 340 is, we just finished a 7 years resto on a rare white TA challenger. 100 percent numbers matching. It has 2 miles on it. And the dyno time.
I can't speak for others. But those numbers I posted are truthfull. 1250 cfm is the carberation, on it! We had the carbs super tuned also.
The main problem with the carbs, is if you use too much duration, they won't function as intended. Because they work off vacuum.
Very hard set up to dial in. But once dialed, these carbs, make the motor scream.
Our car is very rare, and prob never see a track. But the numbers I posted are no joke. I was pleasantly surprised. I knew it would make good power, but it was the tq that really impressed me.
But regardless, it's a trailer queen, prob never see real street duty. Not by us anyways.
, and having a blueprinted engine; well that's a loose definition of "stock"....in reality it means you've got a "ringer"! LOL Not unlike the "stock" 389 GTO tempest Car and Driver tested in 1964 that ran 4.6 0-60....http://www.caranddriver.com/reviews/...ad-test-reviewI'm sure they were ALL that fast back then....
Launching!
Joined: Oct 2003
Posts: 267
Likes: 14
From: Chicago
Hold on, remember these cars, had Polyglass tires.. Most Muscle cars where deep in the 12s, with carb tuning. In 71 the ho 455, did 13.8 at 107, on 8.5 points of compression. 107...
The hemi, was like 13.8... Even though the motor was good for the 10s, with a cam change.
The 440 six pack cars, actually ruled...
The 440 6 pack cars where king of the street back then... Doing 12.20, all day long, with a only a jet change. The Buick's also, where doing that. The 70 Buick stage one, won motor trend car of the year... It did have 400 Rw...
Now, on the 340 6 pack cars, it came with special heads, special race block... And a de-tuned .424 inch cam, the regular 340, got a .474 inch cam. I did nothing to the heads, only changed the cam, but used a 70 stock regular 340 cam. Tell you the truth, I wish, I did a copy of the z06 cam, at .550 lift.
Look, some Ls1's run 13.8 stock. And some 12.60s stock. My bros stripper Z, ran 12.60, at 108..
There are freak cars...
The hemi, was like 13.8... Even though the motor was good for the 10s, with a cam change.
The 440 six pack cars, actually ruled...
The 440 6 pack cars where king of the street back then... Doing 12.20, all day long, with a only a jet change. The Buick's also, where doing that. The 70 Buick stage one, won motor trend car of the year... It did have 400 Rw...
Now, on the 340 6 pack cars, it came with special heads, special race block... And a de-tuned .424 inch cam, the regular 340, got a .474 inch cam. I did nothing to the heads, only changed the cam, but used a 70 stock regular 340 cam. Tell you the truth, I wish, I did a copy of the z06 cam, at .550 lift.
Look, some Ls1's run 13.8 stock. And some 12.60s stock. My bros stripper Z, ran 12.60, at 108..
There are freak cars...
Last edited by stage274; Jun 17, 2015 at 09:34 PM.
Launching!
Joined: Oct 2003
Posts: 267
Likes: 14
From: Chicago
No...
My olds w-30 car was an 11.80 car in the late 90s. With a factory 305 duration race cam, 474 lift. From the factory. All I had is 10.5 inch tire. A Buick with a tire would run the same, if not harder.
The guys running stock class are 10 sec cars. Factory cams, heads, and rockers. They are bad *** cars man..
Here is a little 340 TA spanking a newer challenger, running anywhere from 14.00 to 11.90 at 115.
When he can shift.. .. That is z06 mile an hour.. Its more like its an 11.50 car. People are complaining its not stock. That is not true.. Stock heads and block. So what if he has a cam. All new cars have cams, over 550 inch lift, my little 340 has a .474 lift.
The heads on the TA challenger are special fast burn heads. If the 340 had the same cam as the ls6, it would put way more power down, and torque, than a 347 ls6. My 340 did it, with a .474 lift cam, mild duration.
Why, is it making so much power, it is because, it is the same heads, that ran the Trans am series. 500 hp 302s in the trans am cars. OK... The TA heads and Block, where the best factory small block race heads and block, ever to come out of Mopar.
My olds w-30 car was an 11.80 car in the late 90s. With a factory 305 duration race cam, 474 lift. From the factory. All I had is 10.5 inch tire. A Buick with a tire would run the same, if not harder.
The guys running stock class are 10 sec cars. Factory cams, heads, and rockers. They are bad *** cars man..
Here is a little 340 TA spanking a newer challenger, running anywhere from 14.00 to 11.90 at 115.
When he can shift.. .. That is z06 mile an hour..
The heads on the TA challenger are special fast burn heads. If the 340 had the same cam as the ls6, it would put way more power down, and torque, than a 347 ls6. My 340 did it, with a .474 lift cam, mild duration.
Why, is it making so much power, it is because, it is the same heads, that ran the Trans am series. 500 hp 302s in the trans am cars. OK... The TA heads and Block, where the best factory small block race heads and block, ever to come out of Mopar.
Last edited by stage274; Jun 17, 2015 at 09:31 PM.
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The LS6 cam in your 340 COULD do even better, but it also would with a big aftermarket LS cathedral head type cam and fuel injection. Your point about vacuum affecting carbs was spot on. In the end, I have no nostalgia for the older engines. The mopars to me were the best of them. I hated that rear mounted Chevy distributor. I hated screwing with points, and I hated trying to tweak timing with the distributor twisting and vacuum controlling everything. I hated screwing around with the choke every time the weather changed. I hated re-jetting to make the car act differently.
Admittedly, there is still nothing that sounds like a 426 hemi, but nobody listens to my car and says it sounds weak. What you can do now on these motors - make 500+horsepower daily drivable on the street, tell the computer when and how much to inject and when to fire, etc - I would never go back.
Admittedly, there is still nothing that sounds like a 426 hemi, but nobody listens to my car and says it sounds weak. What you can do now on these motors - make 500+horsepower daily drivable on the street, tell the computer when and how much to inject and when to fire, etc - I would never go back.
There is one point you made that is relevant back to the thread. Power is made in the heads, and those fast burn heads were the shiznit. When it comes to cathedral vs square, it's a choice between top end airflow and low end port speed.
The port speeds of the cathedrals allow air to develop momentum and continue to fill the cylinder after BDC far better than the squares. Makes them easier to cam, tolerate bigger cams, feel more responsive in the middle.
The squares flow more air, but at lower engine speeds, the air moves slower. Results in shorter intake durations on the cam and shorter overlap periods. They are not bad heads, but they make power differently.
If I'm building a street car, I would go to really good cathedrals, even if they are more expensive than squares. If I'm planning a max effort, 8000 rpm, big cube monster, then squares all the way. If I'm only chasing dyno numbers, I'd go squares.
Still need to be honest with how you want to use the motor
The port speeds of the cathedrals allow air to develop momentum and continue to fill the cylinder after BDC far better than the squares. Makes them easier to cam, tolerate bigger cams, feel more responsive in the middle.
The squares flow more air, but at lower engine speeds, the air moves slower. Results in shorter intake durations on the cam and shorter overlap periods. They are not bad heads, but they make power differently.
If I'm building a street car, I would go to really good cathedrals, even if they are more expensive than squares. If I'm planning a max effort, 8000 rpm, big cube monster, then squares all the way. If I'm only chasing dyno numbers, I'd go squares.
Still need to be honest with how you want to use the motor
Launching!
Joined: Oct 2003
Posts: 267
Likes: 14
From: Chicago
The LS6 cam in your 340 COULD do even better, but it also would with a big aftermarket LS cathedral head type cam and fuel injection. Your point about vacuum affecting carbs was spot on. In the end, I have no nostalgia for the older engines. The mopars to me were the best of them. I hated that rear mounted Chevy distributor. I hated screwing with points, and I hated trying to tweak timing with the distributor twisting and vacuum controlling everything. I hated screwing around with the choke every time the weather changed. I hated re-jetting to make the car act differently.
Admittedly, there is still nothing that sounds like a 426 hemi, but nobody listens to my car and says it sounds weak. What you can do now on these motors - make 500+horsepower daily drivable on the street, tell the computer when and how much to inject and when to fire, etc - I would never go back.
Admittedly, there is still nothing that sounds like a 426 hemi, but nobody listens to my car and says it sounds weak. What you can do now on these motors - make 500+horsepower daily drivable on the street, tell the computer when and how much to inject and when to fire, etc - I would never go back.
I agree... 100 percent, even though our car is orginal, we put a modern distrib on it. The hell with points. Also, this is why I am driving a 383 ls6 computer car. These old orginal cars are museum pieces, to be enjoyed for a stroll around town. And they are investments, not to be drag raced anymore. The ones we see on the track, are the ones that lost their orginal equipment years ago.
And that was my point also, when comparing the 340 small port fast burn heads. It's offered better drivability and tourqe over the big square port counter parts. Flow numbers are not everything, it's how they flow for the set up, which is important.
The hemi was a pure race motor, stop light to stop light, the 6 pack cars rulled. And was just more enjoyable to drive all around.
So yes, I would also rather build a modern car, GM with cathedral ports.
I also posted this, because people dog on the muscle cars. Because of advertised numbers, and times they actually ran in the day. But add a set tires, a new ignition system, jet them right. They become just as capabale as the modern egines. The engineers back then, also knew what it took to win, they also had flow benches, with dynos to test combos.
Tell you the truth, I think the cars now, are getting way too heavy. The hell cat is 4500 lbs, the camaro is coming in at 3800 lbs.. The new mustang is 350 lbs heavier. It looks like this trend wont change anytime soon. This is why, I like my 02 bird, and prob hang on to that for a long time. I think it's a pig even at 3500 lbs.
I agree... 100 percent, even though our car is orginal, we put a modern distrib on it. The hell with points. Also, this is why I am driving a 383 ls6 computer car. These old orginal cars are museum pieces, to be enjoyed for a stroll around town. And they are investments, not to be drag raced anymore. The ones we see on the track, are the ones that lost their orginal equipment years ago. And that was my point also, when comparing the 340 small port fast burn heads. It's offered better drivability and tourqe over the big square port counter parts. Flow numbers are not everything, it's how they flow for the set up, which is important. The hemi was a pure race motor, stop light to stop light, the 6 pack cars rulled. And was just more enjoyable to drive all around. So yes, I would also rather build a modern car, GM with cathedral ports. I also posted this, because people dog on the muscle cars. Because of advertised numbers, and times they actually ran in the day. But add a set tires, a new ignition system, jet them right. They become just as capabale as the modern egines. The engineers back then, also knew what it took to win, they also had flow benches, with dynos to test combos. Tell you the truth, I think the cars now, are getting way too heavy. The hell cat is 4500 lbs, the camaro is coming in at 3800 lbs.. The new mustang is 350 lbs heavier. It looks like this trend wont change anytime soon. This is why, I like my 02 bird, and prob hang on to that for a long time. I think it's a pig even at 3500 lbs.
My 99 hawk will never leave my possession
This is how the debate should go: stock LS3s with mild port work are the best budget option for the 402/408/416 strokers and stock LS3 motors. Whereas the cathedral port setups are better on LS2/LS3 strokers in terms of overall output - they do cost more, but are more capable with more cam options. LS7s for 427+ motors.
Stock LS3 heads with the hollow-stem valves and exhaust work are very strong heads. They don't need any intake work - as most of the time that picks up very little on those heads. Even the aftermarket TFS heads don't pick up a ton. So, the LS3 is a cheap way to make big horsepower with an LS3 manifold. You can do well over 500 in a 376 with LS3 heads. They can do 550 with the right sorts of mods and especially with more cubes.
The issue is, so can cathedral ports with smaller ports and intake valves. They do cost more. Especially when you put FAST 102s on top. However, the TFS and AFR/MMS heads can do well over 550 in optimized 408/416s combos. Frankenstein ported TFS heads have done 600 through 402s and 416s alike. Vengeance has done 600 with 440s and TFS 245s with an awful lot of torque (560). They are good for powerbands close to what we see on cammed LS1s with lots and lots of torque.
LS7 with it's raised port works better on the 427+ sized motors. It's one of the few ways to carry power past 6500 on those big motor. Even the FAST LS7 flows damn good and will help support 650+ at the wheels.
Stock LS3 heads with the hollow-stem valves and exhaust work are very strong heads. They don't need any intake work - as most of the time that picks up very little on those heads. Even the aftermarket TFS heads don't pick up a ton. So, the LS3 is a cheap way to make big horsepower with an LS3 manifold. You can do well over 500 in a 376 with LS3 heads. They can do 550 with the right sorts of mods and especially with more cubes.
The issue is, so can cathedral ports with smaller ports and intake valves. They do cost more. Especially when you put FAST 102s on top. However, the TFS and AFR/MMS heads can do well over 550 in optimized 408/416s combos. Frankenstein ported TFS heads have done 600 through 402s and 416s alike. Vengeance has done 600 with 440s and TFS 245s with an awful lot of torque (560). They are good for powerbands close to what we see on cammed LS1s with lots and lots of torque.
LS7 with it's raised port works better on the 427+ sized motors. It's one of the few ways to carry power past 6500 on those big motor. Even the FAST LS7 flows damn good and will help support 650+ at the wheels.
Launching!
Joined: Oct 2003
Posts: 267
Likes: 14
From: Chicago
I ran the stock type 317 heads on my 383 ls6 block. They where so cheap to run at the time, and I still see them fairly cheap.
So, on 9.1 compression, my motor dyno'ed 450s hp, and 494 ftlbs, its a 383, with the stock zo6 cam. I only had a 200$ bowl clean on the heads, and running Manley sever duty valves.
I just bought an F1A pro-charger, I am upgrading up, from my p1sc-1. Its going on the car soon.
I really think, this set up, is good for at least 800 rear wheel, at least. I also hope, the torque numbers, is, not trialling ,to much down from the hp numbers when I dyno it. I would like to see equal numbers honestly, will see. I am kinda sacred, at 6500 RPM, the blower is at 67k rpms. 74k is the limit, on this blower. At 7k, the blower is at 72k.
I am thinking I might get around 20 lbs of boost.
Since I have the CBR 8.65 crank pulley, I can run a huge blower pulley. My pulley size, is 4.5 inch. This is the pulley maxing it out...
I am thinking this is too much, my bro told me, dont worry, you will be fine with that pulley, just shift at 5k rpm for driving. I am thinking a 5in pulley, and spraying it 100 shot.
So, on 9.1 compression, my motor dyno'ed 450s hp, and 494 ftlbs, its a 383, with the stock zo6 cam. I only had a 200$ bowl clean on the heads, and running Manley sever duty valves.
I just bought an F1A pro-charger, I am upgrading up, from my p1sc-1. Its going on the car soon.
I really think, this set up, is good for at least 800 rear wheel, at least. I also hope, the torque numbers, is, not trialling ,to much down from the hp numbers when I dyno it. I would like to see equal numbers honestly, will see. I am kinda sacred, at 6500 RPM, the blower is at 67k rpms. 74k is the limit, on this blower. At 7k, the blower is at 72k.
I am thinking I might get around 20 lbs of boost.
Since I have the CBR 8.65 crank pulley, I can run a huge blower pulley. My pulley size, is 4.5 inch. This is the pulley maxing it out...
I am thinking this is too much, my bro told me, dont worry, you will be fine with that pulley, just shift at 5k rpm for driving. I am thinking a 5in pulley, and spraying it 100 shot.
Staging Lane
Joined: Feb 2014
Posts: 68
Likes: 0
From: south jersey
hahahaha WHATS A CARB?? lol isnt it the thing on the side of a bong? luckily ive never had to deal with that, and i couldn't imagine, having to mess wit a carb all the tie, or god forbid the POINTS ****... thank god for fuel injection, first motor i messed with was a tbi 350 in a silverado, and made 450 street able hp with vortech heads, cam, carb style intake, custom made tb adapter, and 454 throttle body, and a tune.. full exhaust and gears to.. it was reliable as hell and sounded great.. i know we have been gettin off topic here so ill continue on!! i love old cars but, with NEW style engines if im messing with them
Launching!
Joined: Oct 2003
Posts: 267
Likes: 14
From: Chicago
hahahaha WHATS A CARB?? lol isnt it the thing on the side of a bong? luckily ive never had to deal with that, and i couldn't imagine, having to mess wit a carb all the tie, or god forbid the POINTS ****... thank god for fuel injection, first motor i messed with was a tbi 350 in a silverado, and made 450 street able hp with vortech heads, cam, carb style intake, custom made tb adapter, and 454 throttle body, and a tune.. full exhaust and gears to.. it was reliable as hell and sounded great.. i know we have been gettin off topic here so ill continue on!! i love old cars but, with NEW style engines if im messing with them
Actually carbs are awesome when dialed in. They make more power if tuned right, because, the intake has a wet cool charge. Racing quadrajets, acted like a fuel injection actually, ran on the small primary, unitll you hammer it wide open, then the huge secondaries would open, and pull the front wheels up, that was on my Oldsmobile set up. I was destroying all the built LT1 cars in the day, late 90s. They underestimated the set up. These where factory race cars..
I am not that old, I am 40... But ran carbs all my life on my race cars, till my GN, then my LS6 bird. No doubt, fuel injection is where its at. But carbs, are a wonder of mechanical engineering actually.
That little 340, has 1250 cfm.... When dialed in, that system screams, it was made for the drags... I cant believe they actually had such system. This is why, these cars demand the money today.
Its not that big of deal to tune, especially with the quadrajet, the jets rods, took seconds to remove, and put back in.. Holley carbs suck thou... They would always blow the power valve.
Staging Lane
Joined: Feb 2014
Posts: 68
Likes: 0
From: south jersey
well yea, there is nothing wrong with carbs, but same time, nothing wrong with the new technology, and plenty of HP to go around, i like the easier tunability and gas mileage. just a little more reliable to..
but many people still use carbs and they will use them forever. I haven't had to and may not ever have to. but i can never say never, i may one day do an LS carb setup, because i would like to try one, sometime so i can say i did and learn something!!
ps nice mopar man! they are pretty damn cool man, love them old mopars!!
but many people still use carbs and they will use them forever. I haven't had to and may not ever have to. but i can never say never, i may one day do an LS carb setup, because i would like to try one, sometime so i can say i did and learn something!!
ps nice mopar man! they are pretty damn cool man, love them old mopars!!
Teching In
Joined: Nov 2001
Posts: 45
Likes: 0
From: MCCALLA,ALABAMA
well for our build efi is just not the way to go. Cause efi full out race car stuff is 3x the cost of stuff for a street car.and I am old school guy but do like the new age stuff but it just don't work in all areas.
Launching!
Joined: Oct 2003
Posts: 267
Likes: 14
From: Chicago
I love both, and it depends on the car...