4+7 Swap
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Joined: Apr 1999
Posts: 250
From: Iowa
Kicking the dead horse up again,
If you repin the 4 & 7 injectors and swap the two plug wires what is the difference? The O2's, if so, how I'm not understanding how the spent gases sent to the O2's will cause the engine to be off balance?
I'm pretty positive that, there is cam retainer plate milled into the LT/L98 GM roller blocks, so there shouldn't be a need for a cam button. I'm using a standard Roller timing set not an LT-1 timing gear set-up now on my 383.
Does anyone have a viable reason that if you change the injector wires and plug wires, and use the cam retainer plate, why won't it work with out problems???
This has been getting kicked around for a while now I'd hope this can get answered and we can put the 4/7 swap questions to rest. I'd like to do it if it's possible.
Money isn't the issue, so don't respond about the cost of doing it as an answer not too, please.
If you repin the 4 & 7 injectors and swap the two plug wires what is the difference? The O2's, if so, how I'm not understanding how the spent gases sent to the O2's will cause the engine to be off balance?
I'm pretty positive that, there is cam retainer plate milled into the LT/L98 GM roller blocks, so there shouldn't be a need for a cam button. I'm using a standard Roller timing set not an LT-1 timing gear set-up now on my 383.
Does anyone have a viable reason that if you change the injector wires and plug wires, and use the cam retainer plate, why won't it work with out problems???
This has been getting kicked around for a while now I'd hope this can get answered and we can put the 4/7 swap questions to rest. I'd like to do it if it's possible.
Money isn't the issue, so don't respond about the cost of doing it as an answer not too, please.
Last edited by gixxer92; Nov 30, 2006 at 07:35 PM.
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Joined: Jan 2001
Posts: 838
From: ajax ontario canada
I know I went to the graveyard to digup this old thread but I need to know what is needed for this swap
the cam I want to put in is solid roller 264/270 688/660 on a 108lsa with 4/7 swap
thanks
Dave
the cam I want to put in is solid roller 264/270 688/660 on a 108lsa with 4/7 swap
thanks
Dave
Last edited by rock1501; Aug 13, 2007 at 12:23 AM.
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Joined: Apr 2003
Posts: 2,628
From: Pgh, PA
Yea I forgot about the injectors. I got on to post it but you beat me to it this morning Rich.
And, as long as its done right, nothing could happen from doing that. Just use your head, like any other modifications. I would think its probably not worth it. You can make more power going to a custom grind solid roller than an off the shelf 4 + 7 Swap.
And, as long as its done right, nothing could happen from doing that. Just use your head, like any other modifications. I would think its probably not worth it. You can make more power going to a custom grind solid roller than an off the shelf 4 + 7 Swap.
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Joined: Dec 1969
Posts: 10,745
From: Buffalo, New York
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Joined: Jul 2002
Posts: 1,367
From: Burlington, NJ
one of the spike morning shows did this and gained around 117hp. not sure if they swapped over different specs with the cam or just the 4/7 swap, but i remember the numbers because that's what got me interested in the cam.
i want to run the 2/3 and 4/7 on my next cam, which may be coming a lot further away than i had hoped. i keep buying parts for my dang jeep. wheeling is too much fun...street is fun but you can only go straight.
i want to run the 2/3 and 4/7 on my next cam, which may be coming a lot further away than i had hoped. i keep buying parts for my dang jeep. wheeling is too much fun...street is fun but you can only go straight.
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Joined: Dec 1969
Posts: 10,745
From: Buffalo, New York
117 hp from swapping firing order is absolutely impossible. The only believable test results that I know of was reported in Hot Rod magazine: http://www.hotrod.com/techfaq/113_07..._manifold.html As you probably know, magazines tend to emphasize positive results, so the tone is very upbeat. But the bottom line was 2-3hp gain at peak, The article quotes two extremely successful and well known engine builders:
"No one knows why." That was Reher-Morrison Racing Engines' Darrin Morgan when we asked him why 4/7 swaps make power, and sure enough, we ran into a lot of differing opinions from the experts we spoke with. Morgan told us that every Reher-Morrison crate engine above 555 ci uses a 4/7 cam, and that he's used them to prove gains of 4-6 hp on single-four-barrel engines and 6-8 on tunnel-rams, and the gains are everywhere in the curve. The bigger the displacement, the greater the gain of up to 10 hp. He says he has no hard-core evidence as to why the firing order makes power, as he's seen conflicting information from test to test, but he did comment that, "The Corvette firing order has been proven to be more dynamically stable in the crank, but it's not what made the most power for us. The 4/7 is the only one that makes power on every engine we tested, and it's even better with a properly tuned intake."
On the other end of the opinion scale is Tony Bischoff of BES Racing Engines, a winning NMCA and street-car-racing builder. He told us of three separate back-to-back tests with regular cams and 4/7 cams in small-blocks operating above 6,000 rpm. "You're not going to like the answer," he told us, "because I didn't find any power anywhere." After we bench-raced all the theories, he allowed that, "Some people say the power is due to reduced crank bending, so maybe I don't see anything because I always use the best billet cranks. Others say it's in the intake, but any off-the-shelf intake is symmetrical on both ends."
Darrin Morgan sees small hp gains (~0.5%, keep in mind he is talking 555+cu big block race motors). Bischoff sees NO gain. You CAN honestly gain >100hp with a cam swap. But you have to read the fine print. Look at: http://www.kennedysdynotune.com/customcams.htm That is my writing, my cam specs, and my results so I stand by them. But do you see the "fine print"? The switch involved going from a flat tappet to a roller with very different characteristics. Pretty amazing nonetheless, if I do say so myself! But >100 hp from the same cam with the only difference being the 4/76 swap? No way in hell! I suppose you could say "why not" as people aren't reporting losses.
Rich
"No one knows why." That was Reher-Morrison Racing Engines' Darrin Morgan when we asked him why 4/7 swaps make power, and sure enough, we ran into a lot of differing opinions from the experts we spoke with. Morgan told us that every Reher-Morrison crate engine above 555 ci uses a 4/7 cam, and that he's used them to prove gains of 4-6 hp on single-four-barrel engines and 6-8 on tunnel-rams, and the gains are everywhere in the curve. The bigger the displacement, the greater the gain of up to 10 hp. He says he has no hard-core evidence as to why the firing order makes power, as he's seen conflicting information from test to test, but he did comment that, "The Corvette firing order has been proven to be more dynamically stable in the crank, but it's not what made the most power for us. The 4/7 is the only one that makes power on every engine we tested, and it's even better with a properly tuned intake."
On the other end of the opinion scale is Tony Bischoff of BES Racing Engines, a winning NMCA and street-car-racing builder. He told us of three separate back-to-back tests with regular cams and 4/7 cams in small-blocks operating above 6,000 rpm. "You're not going to like the answer," he told us, "because I didn't find any power anywhere." After we bench-raced all the theories, he allowed that, "Some people say the power is due to reduced crank bending, so maybe I don't see anything because I always use the best billet cranks. Others say it's in the intake, but any off-the-shelf intake is symmetrical on both ends."
Darrin Morgan sees small hp gains (~0.5%, keep in mind he is talking 555+cu big block race motors). Bischoff sees NO gain. You CAN honestly gain >100hp with a cam swap. But you have to read the fine print. Look at: http://www.kennedysdynotune.com/customcams.htm That is my writing, my cam specs, and my results so I stand by them. But do you see the "fine print"? The switch involved going from a flat tappet to a roller with very different characteristics. Pretty amazing nonetheless, if I do say so myself! But >100 hp from the same cam with the only difference being the 4/76 swap? No way in hell! I suppose you could say "why not" as people aren't reporting losses.
Rich
Last edited by rskrause; Aug 14, 2007 at 05:13 AM.
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Joined: Jan 2001
Posts: 838
From: ajax ontario canada
since I already have the cam if all I have to do is swap 4/7 plug wires and injector wires thats awesome
5-6 rwhp is cool with me every bit helps
I already have long enough wires anyway because they run all the way to the back of the engine to the distributer(oldskool style)
I was thinking I could change the firing order through my programable digital 7 box but that would only help me with spark and not fuel since the fuel is run still off the stock pcm controlled by the rpm signal from the optical sensor in the opti
I guess I could only change the 2 plugs on the injectors and change the firing order through the msd box right and leave the ignition wires as is right?
thanks for the help guys
Dave
5-6 rwhp is cool with me every bit helps
I already have long enough wires anyway because they run all the way to the back of the engine to the distributer(oldskool style)
I was thinking I could change the firing order through my programable digital 7 box but that would only help me with spark and not fuel since the fuel is run still off the stock pcm controlled by the rpm signal from the optical sensor in the opti
I guess I could only change the 2 plugs on the injectors and change the firing order through the msd box right and leave the ignition wires as is right?
thanks for the help guys
Dave
Last edited by rock1501; Aug 14, 2007 at 11:49 AM.
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Posts: 1,367
From: Burlington, NJ