Lunati "4/7" cams
02-23-2004, 09:15 AM
#46
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The comment about cylinder balance was a very good point. Many of us forget that each cylinder makes a little different hp/tq than the other one. With the EFI setup from the factory, care would need to be made in tuning to enrich the cylinder(s) which benefit from this change and make slightly more power. This was brought up a few years back in a wacky discussion about making a cam that had a different profile for different cylinders and the "what ifs" of that.
Obviously optimizing this change would take some serious tuning. Someone with DFI would be much more likely to realize the ultimate potential here. Even so, I'm toying with the idea of trying it w/ the factory PCM...of course I'm toying with the idea of a lot of thing$. We'd all know the an$wer$ to our wilde$t que$tion$ if it wa$n't for one big variable. I've come to the conclusion that if you put the big players on this board together in a room with an endless amount of cash and told them to build a drag-car, the result would be the end of the world. Upon launch of the car (depending on the direction) the earth's movement would either stop or double.....
Obviously optimizing this change would take some serious tuning. Someone with DFI would be much more likely to realize the ultimate potential here. Even so, I'm toying with the idea of trying it w/ the factory PCM...of course I'm toying with the idea of a lot of thing$. We'd all know the an$wer$ to our wilde$t que$tion$ if it wa$n't for one big variable. I've come to the conclusion that if you put the big players on this board together in a room with an endless amount of cash and told them to build a drag-car, the result would be the end of the world. Upon launch of the car (depending on the direction) the earth's movement would either stop or double.....
02-23-2004, 11:55 AM
#47
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Originally posted by LT1Brutus
This was brought up a few years back in a wacky discussion about making a cam that had a different profile for different cylinders and the "what ifs" of that.
That's far from a "wacky" idea. It has lots of merit, and may have been tried once or twice.
I've come to the conclusion that if you put the big players on this board together in a room with an endless amount of cash and told them to build a drag-car, the result would be the end of the world. Upon launch of the car (depending on the direction) the earth's movement would either stop or double.....
This was brought up a few years back in a wacky discussion about making a cam that had a different profile for different cylinders and the "what ifs" of that.
That's far from a "wacky" idea. It has lots of merit, and may have been tried once or twice.
I've come to the conclusion that if you put the big players on this board together in a room with an endless amount of cash and told them to build a drag-car, the result would be the end of the world. Upon launch of the car (depending on the direction) the earth's movement would either stop or double.....
I'm not so sure those kind of brain-storming sessions (with the real folks involved) aren't what happens in the world of Nextel Cup, and other "evolutionary" rather than "revolutionary" engine designs. Example: Rethinking water pumps and associated plumbing helped Cup engines run cooler with fewer H2O pump rpm. Sure that's a couple more hp to the flywheel, but it also allows more tape on the air intake which can help front downforce. So better cooling hardware can speed up the car.
Maybe not stop or double, but there is some very slight change. So should we be running drag strips E-W or N-S to keep from changing the climate or the life of the earth as we know it?
02-23-2004, 12:01 PM
#48
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Need some really big tires to change earth rotational speed.... really really big
As for the 4/7 swap, most custom cam manufacturers charge like $25 bucks extra for it over a standard custom grind, my cam's costing me $320 opposed to $295 with a 4/7 swap and so far I've heard of no down sides whatsoever so its worth a shot right? I doubt it'll lose power. Ofcourse a carb motor doesn't have individual cylinder fueling, so I'm sure an EFI setup would benefit from firing order specific tuning. Perhaps time for the MSD Digital 7+ with ICT
As for the 4/7 swap, most custom cam manufacturers charge like $25 bucks extra for it over a standard custom grind, my cam's costing me $320 opposed to $295 with a 4/7 swap and so far I've heard of no down sides whatsoever so its worth a shot right? I doubt it'll lose power. Ofcourse a carb motor doesn't have individual cylinder fueling, so I'm sure an EFI setup would benefit from firing order specific tuning. Perhaps time for the MSD Digital 7+ with ICT
02-23-2004, 12:22 PM
#49
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SStroker, I know there's some merit....but I want to hear Comp's response when you tell them you want that! What would that go for......$3,000?
You see, we already have someone working on the size tires we need!
SStroker, that IS what happens in Nascar....but they have rules so that they don't go TOO buck-wild
You see, we already have someone working on the size tires we need!
SStroker, that IS what happens in Nascar....but they have rules so that they don't go TOO buck-wild
02-23-2004, 12:47 PM
#50
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Location: Upstate NY
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Originally posted by LT1Brutus
SStroker, I know there's some merit....but I want to hear Comp's response when you tell them you want that! What would that go for......$3,000?
You see, we already have someone working on the size tires we need!
SStroker, that IS what happens in Nascar....but they have rules so that they don't go TOO buck-wild
SStroker, I know there's some merit....but I want to hear Comp's response when you tell them you want that! What would that go for......$3,000?
You see, we already have someone working on the size tires we need!
SStroker, that IS what happens in Nascar....but they have rules so that they don't go TOO buck-wild
Unfortunately, it's VERY hard for a sanctioning body to control the spending. The tighter the rules, the more spending. When 1/2% or less means winning or not, that 1/2% advantage costs huge amounts. That's one reason it was hard to fill the field this weekend at The Rock.
Last edited by OldSStroker; 02-23-2004 at 12:51 PM.
02-23-2004, 08:16 PM
#51
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I suppose the "buck" in buck-wild wasn't taken right. I'm more than aware of the cost to win asymptote theory. I semi-regularly go over to the UCF graduate Engine Optimization program lab that's here in orlando and shoot the breeze with the "Mad Dr." there. Hendricks, Roush, and several other companies enlist UCFs engine lab to do tests on new nascar theory stuff. I think you read a post a ways back (8 months) where I mentioned the head/piston design they were experamenting with that basically put 90% of the combustion chamber volume in the piston....not the head and centered it under the exhaust valve. The theory behind this was that in the super-speedway corners they have always had problems w/ the inner bank running lean and the outer bank running rich. This made it to where NONE of the cylinders wanted to fire @ their designated time....or sometimes @ all. The idea was that the high heat of the exhaust valve would cause combustion one way or another. Lab tests were a major success, even with the motor tilted on its side (special setup). I believe one of the motors picked up over 11 hp. I don't know if track testing has been done yet. ........Anyway, the meaning of that tangent was you DON"T want to know how much those pistons cost!!
02-24-2004, 07:32 AM
#52
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Location: Upstate NY
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Originally posted by LT1Brutus
I suppose the "buck" in buck-wild wasn't taken right. I'm more than aware of the cost to win asymptote theory. I semi-regularly go over to the UCF graduate Engine Optimization program lab that's here in orlando and shoot the breeze with the "Mad Dr." there. Hendricks, Roush, and several other companies enlist UCFs engine lab to do tests on new nascar theory stuff. I think you read a post a ways back (8 months) where I mentioned the head/piston design they were experamenting with that basically put 90% of the combustion chamber volume in the piston....not the head and centered it under the exhaust valve. The theory behind this was that in the super-speedway corners they have always had problems w/ the inner bank running lean and the outer bank running rich. This made it to where NONE of the cylinders wanted to fire @ their designated time....or sometimes @ all. The idea was that the high heat of the exhaust valve would cause combustion one way or another. Lab tests were a major success, even with the motor tilted on its side (special setup). I believe one of the motors picked up over 11 hp. I don't know if track testing has been done yet. ........Anyway, the meaning of that tangent was you DON"T want to know how much those pistons cost!!
I suppose the "buck" in buck-wild wasn't taken right. I'm more than aware of the cost to win asymptote theory. I semi-regularly go over to the UCF graduate Engine Optimization program lab that's here in orlando and shoot the breeze with the "Mad Dr." there. Hendricks, Roush, and several other companies enlist UCFs engine lab to do tests on new nascar theory stuff. I think you read a post a ways back (8 months) where I mentioned the head/piston design they were experamenting with that basically put 90% of the combustion chamber volume in the piston....not the head and centered it under the exhaust valve. The theory behind this was that in the super-speedway corners they have always had problems w/ the inner bank running lean and the outer bank running rich. This made it to where NONE of the cylinders wanted to fire @ their designated time....or sometimes @ all. The idea was that the high heat of the exhaust valve would cause combustion one way or another. Lab tests were a major success, even with the motor tilted on its side (special setup). I believe one of the motors picked up over 11 hp. I don't know if track testing has been done yet. ........Anyway, the meaning of that tangent was you DON"T want to know how much those pistons cost!!
02-24-2004, 08:45 PM
#53
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Join Date: Sep 2000
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Originally posted by LT1Brutus
The comment about cylinder balance was a very good point. Many of us forget that each cylinder makes a little different hp/tq than the other one. With the EFI setup from the factory, care would need to be made in tuning to enrich the cylinder(s) which benefit from this change and make slightly more power. This was brought up a few years back in a wacky discussion about making a cam that had a different profile for different cylinders and the "what ifs" of that.
Obviously optimizing this change would take some serious tuning. Someone with DFI would be much more likely to realize the ultimate potential here. Even so, I'm toying with the idea of trying it w/ the factory PCM...of course I'm toying with the idea of a lot of thing$. We'd all know the an$wer$ to our wilde$t que$tion$ if it wa$n't for one big variable. I've come to the conclusion that if you put the big players on this board together in a room with an endless amount of cash and told them to build a drag-car, the result would be the end of the world. Upon launch of the car (depending on the direction) the earth's movement would either stop or double.....
The comment about cylinder balance was a very good point. Many of us forget that each cylinder makes a little different hp/tq than the other one. With the EFI setup from the factory, care would need to be made in tuning to enrich the cylinder(s) which benefit from this change and make slightly more power. This was brought up a few years back in a wacky discussion about making a cam that had a different profile for different cylinders and the "what ifs" of that.
Obviously optimizing this change would take some serious tuning. Someone with DFI would be much more likely to realize the ultimate potential here. Even so, I'm toying with the idea of trying it w/ the factory PCM...of course I'm toying with the idea of a lot of thing$. We'd all know the an$wer$ to our wilde$t que$tion$ if it wa$n't for one big variable. I've come to the conclusion that if you put the big players on this board together in a room with an endless amount of cash and told them to build a drag-car, the result would be the end of the world. Upon launch of the car (depending on the direction) the earth's movement would either stop or double.....
But, you actually are on something with individual cylinders being set to balance things. A buddy of mine crews a match-race Top Fuel car, and people do in fact change deck clearance, camshaft lobes and other things by the cylinder. I can only imagine what goes in behind-the-scenes professional engine program's R&D departments. Chuck posted about some of the trick stuff a few times. I sure wish that guy would post more.
02-24-2004, 08:47 PM
#54
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Join Date: Dec 1969
Location: Pacific North West
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Not Quite the same but we used to run 1.5-1.75 rockers all on the same motor. I can't remember what the combo was for each cylinder...hell it has been 12 years or so since I circle track raced 
02-25-2004, 11:25 AM
#55
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Join Date: Oct 2002
Posts: 6,518
The chamber being mostly in the piston, check out the story next month on Kaase's EM BBF.
He had a BBF with a 27cc chamber and had a big dish short rod setup. So to get 12:1 in a 468 cube motor you need a -50cc dish! That's a lot of dish!
I think it would be more interesting to see the piston top for that than anything.
Bret
He had a BBF with a 27cc chamber and had a big dish short rod setup. So to get 12:1 in a 468 cube motor you need a -50cc dish! That's a lot of dish!
I think it would be more interesting to see the piston top for that than anything.
Bret
02-25-2004, 05:37 PM
#56
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Location: Donaldsonville,LA
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Guys,
I haven't read the entire post so if I repeat what someone else has already said please excuse me. I race an NHRA Competition eliminator car and Stock eliminator car. The 4/7 swap cams have been out for a long time, probably 10 years or more but are just getting to the general public because it was a big secret within the ranks of Pro Stock down to Comp. for a long time. We run a 4/7 swap cam in both of them and have for 5 years now. There are also a large number of LT-1 stockers running them also. The reason it makes such a significant HP increase is because it balances the efficiency of the motor by seperating the #5 and #7 cylinders on the firing order. These 2 cylinders constantly scavenge each other on a conventional firing order camshaft and always show lean. The reason it is so easy to swap the firing order is because on all SB chevy's there are 2 cylinders on TDC each revolution of the motor. They are 1 & 6, 2 & 3, 4 & 7, and 5 & 8. This allows for any number of firing order changes as long as the cylinders swapped arrive at TDC at the same point. We have run cams with 2 different firing orders, 1-8-7-2-6-5-4-3 which is the same as the LS-1 but the best firing order is the 4/7 swap, 1-8-7-3-6-5-4-2. This has worked on any engine we've tried it on, from 10,000 RPM comp. motors to 7000 RPM stock eliminator motors. The cost on the cams is a little more expensive but it is the cheapest HP you can but. Just my 2 cents feel free to e-mail me anytime if you would like to discuss it further.
I haven't read the entire post so if I repeat what someone else has already said please excuse me. I race an NHRA Competition eliminator car and Stock eliminator car. The 4/7 swap cams have been out for a long time, probably 10 years or more but are just getting to the general public because it was a big secret within the ranks of Pro Stock down to Comp. for a long time. We run a 4/7 swap cam in both of them and have for 5 years now. There are also a large number of LT-1 stockers running them also. The reason it makes such a significant HP increase is because it balances the efficiency of the motor by seperating the #5 and #7 cylinders on the firing order. These 2 cylinders constantly scavenge each other on a conventional firing order camshaft and always show lean. The reason it is so easy to swap the firing order is because on all SB chevy's there are 2 cylinders on TDC each revolution of the motor. They are 1 & 6, 2 & 3, 4 & 7, and 5 & 8. This allows for any number of firing order changes as long as the cylinders swapped arrive at TDC at the same point. We have run cams with 2 different firing orders, 1-8-7-2-6-5-4-3 which is the same as the LS-1 but the best firing order is the 4/7 swap, 1-8-7-3-6-5-4-2. This has worked on any engine we've tried it on, from 10,000 RPM comp. motors to 7000 RPM stock eliminator motors. The cost on the cams is a little more expensive but it is the cheapest HP you can but. Just my 2 cents feel free to e-mail me anytime if you would like to discuss it further.
02-25-2004, 06:50 PM
#57
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Join Date: Feb 2004
Location: Abbeville , LA
Posts: 291
Hi Allen,
your Hydraulic Lifters are working great judging from results.
How much HP did you ever see back-to-back on SBC with 4/7 swap ??
on a Big Block Chevy , it seems to be worth more because of Cyl head's 2 different runner lengths/volume/ and port directions effects
your Hydraulic Lifters are working great judging from results.
How much HP did you ever see back-to-back on SBC with 4/7 swap ??
on a Big Block Chevy , it seems to be worth more because of Cyl head's 2 different runner lengths/volume/ and port directions effects
02-25-2004, 07:19 PM
#58
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Location: smog zone adjacent to a great lake
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Originally posted by MaxRaceSoftware
How much HP did you ever see back-to-back on SBC with 4/7 swap?
How much HP did you ever see back-to-back on SBC with 4/7 swap?
02-25-2004, 07:20 PM
#59
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Join Date: Mar 2002
Location: Baton Rouge, LA, USA
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Glad to see some more La members joining up.
Larry, I'm the guy that contacted you about porting my AFR210's for the supercharged LT1 383.
I ran 10.40 at 133 at NPR last Wednesday.
BTW, Ronnie Rogers at Wall-2-Wall engines has done some before/after dyno testing with this. I believe he found ~15 hp on a 670 hp SUPR motor.
Mike
Larry, I'm the guy that contacted you about porting my AFR210's for the supercharged LT1 383.
I ran 10.40 at 133 at NPR last Wednesday.
BTW, Ronnie Rogers at Wall-2-Wall engines has done some before/after dyno testing with this. I believe he found ~15 hp on a 670 hp SUPR motor.
Mike
Last edited by engineermike; 02-25-2004 at 07:26 PM.
02-26-2004, 10:01 AM
#60
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Location: Donaldsonville,LA
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Larry,
On the only 2 motors I dyno'ed with back 2 back cam swaps the results were as follows:
323" 18* chevy headed comp. eliminator motor- 748HP at peak/ 726 HP avg. from 8200-9800 with conventional cam. With 4/7 swap cam- 767HP peak/ 741HP avg. from 8200-9800.
305" Stock eliminator motor- 378HP at peak/ 352 HP avg. from 5000-7000 with conventional cam. With 4/7 swap cam 392HP peak/ 368HP avg. from 5000-7000.
These are the only ones I dyno'ed back 2 back and after seeing those results we never went back to the conventional cam on any of our other motors. I've only done racetrack testing with the 1-8-7-2-6-5-4-3 firing order cam and it didn't seem to like it. But if you look at a model of what the airflow would be inside the manifold on this type of firing order you would think it would work. I'm in the process of getting a cam ground this way for my new 296" Comp. motor. We've been on the dyno for a month with it and have made 741 at peak/ 712 avg. HP with it so far but we are trying to make around 755. It should still fly at 741 but you know how it is, never can have enough in Comp. Give me a call at (225) 717-1461 sometime if you get free.
On the only 2 motors I dyno'ed with back 2 back cam swaps the results were as follows:
323" 18* chevy headed comp. eliminator motor- 748HP at peak/ 726 HP avg. from 8200-9800 with conventional cam. With 4/7 swap cam- 767HP peak/ 741HP avg. from 8200-9800.
305" Stock eliminator motor- 378HP at peak/ 352 HP avg. from 5000-7000 with conventional cam. With 4/7 swap cam 392HP peak/ 368HP avg. from 5000-7000.
These are the only ones I dyno'ed back 2 back and after seeing those results we never went back to the conventional cam on any of our other motors. I've only done racetrack testing with the 1-8-7-2-6-5-4-3 firing order cam and it didn't seem to like it. But if you look at a model of what the airflow would be inside the manifold on this type of firing order you would think it would work. I'm in the process of getting a cam ground this way for my new 296" Comp. motor. We've been on the dyno for a month with it and have made 741 at peak/ 712 avg. HP with it so far but we are trying to make around 755. It should still fly at 741 but you know how it is, never can have enough in Comp. Give me a call at (225) 717-1461 sometime if you get free.