4-7 lobe swap
Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
Gkull isn't supposed to be easier on the crankshaft its main contributing factor. Besides rollers I noticed comp cams makes off the self solid flat tappit cams with 4/7 swap.
Last edited by Little Mouse; Apr 4, 2009 at 11:04 AM.
Racer
Joined: Feb 2009
Posts: 343
Likes: 0
From: San Diego CA
While it's an interesting application, and I laud those who ground the cams & tested this stuff out, on the SBC motors it's not a winner. Perhaps other motors but not ours.
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
According to my understanding, here is the reasoning behind my choosing to go with a 4/7 swap in my new 427 BB build...
1) Better balance of peak loads on the crank journals; the 4th main having much higher loads than the 2nd in the 1-8-4-3-6-5-7-2 order, but the difference between the two is said to be significantly less with the swap. This supposedly also improves integrity of the oil films on the mains.
2) Improving A/F mix distribution to 7, which tends to be lean (especially with 180* manifolds), which should reduce the need for staggered jetting.
3) Having 4 & 2 exhaust events together apparently doesn't pose as large an issue as does having 5 & 7 together, as the former cylinders typically run cooler given they're closer to incoming coolant.
Given these and other lesser potential benefits, I really don't care if it makes any more torque or power. My $.02.
TSW
1) Better balance of peak loads on the crank journals; the 4th main having much higher loads than the 2nd in the 1-8-4-3-6-5-7-2 order, but the difference between the two is said to be significantly less with the swap. This supposedly also improves integrity of the oil films on the mains.
2) Improving A/F mix distribution to 7, which tends to be lean (especially with 180* manifolds), which should reduce the need for staggered jetting.
3) Having 4 & 2 exhaust events together apparently doesn't pose as large an issue as does having 5 & 7 together, as the former cylinders typically run cooler given they're closer to incoming coolant.
Given these and other lesser potential benefits, I really don't care if it makes any more torque or power. My $.02.
TSW
Thread Starter
Drifting
Joined: Nov 2003
Posts: 1,874
Likes: 7
From: l In
According to my understanding, here is the reasoning behind my choosing to go with a 4/7 swap in my new 427 BB build...
1) Better balance of peak loads on the crank journals; the 4th main having much higher loads than the 2nd in the 1-8-4-3-6-5-7-2 order, but the difference between the two is said to be significantly less with the swap. This supposedly also improves integrity of the oil films on the mains.
2) Improving A/F mix distribution to 7, which tends to be lean (especially with 180* manifolds), which should reduce the need for staggered jetting.
3) Having 4 & 2 exhaust events together apparently doesn't pose as large an issue as does having 5 & 7 together, as the former cylinders typically run cooler given they're closer to incoming coolant.
Given these and other lesser potential benefits, I really don't care if it makes any more torque or power. My $.02.
TSW
1) Better balance of peak loads on the crank journals; the 4th main having much higher loads than the 2nd in the 1-8-4-3-6-5-7-2 order, but the difference between the two is said to be significantly less with the swap. This supposedly also improves integrity of the oil films on the mains.
2) Improving A/F mix distribution to 7, which tends to be lean (especially with 180* manifolds), which should reduce the need for staggered jetting.
3) Having 4 & 2 exhaust events together apparently doesn't pose as large an issue as does having 5 & 7 together, as the former cylinders typically run cooler given they're closer to incoming coolant.
Given these and other lesser potential benefits, I really don't care if it makes any more torque or power. My $.02.
TSW
Will let you all know how I come out.
Thanks for the replies
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Instructor
Joined: Mar 2007
Posts: 153
Likes: 0
From: London
Safety Car
Joined: Oct 2004
Posts: 3,926
Likes: 739
From: Youngstown Ohio
Personal observations show it be lopey at idle but smooth at the same time if you can understand what I mean....sort of wicked....gobs of torque from idle through 7000 rpm. Not radical duration, but lots of lift.
I don't know how much horsepower is added because of the swap, but I'm well satisfied with its behavior. See dyno sheet.....
Hear it run....
Le Mans Master
Joined: May 2003
Posts: 8,877
Likes: 3,556
From: Fernandina Beach FL
2023 Restomod of the Year finalist
2020 C3 of the Year Winner - Modified
According to my understanding, here is the reasoning behind my choosing to go with a 4/7 swap in my new 427 BB build...
1) Better balance of peak loads on the crank journals; the 4th main having much higher loads than the 2nd in the 1-8-4-3-6-5-7-2 order, but the difference between the two is said to be significantly less with the swap. This supposedly also improves integrity of the oil films on the mains.
2) Improving A/F mix distribution to 7, which tends to be lean (especially with 180* manifolds), which should reduce the need for staggered jetting.
3) Having 4 & 2 exhaust events together apparently doesn't pose as large an issue as does having 5 & 7 together, as the former cylinders typically run cooler given they're closer to incoming coolant.
Given these and other lesser potential benefits, I really don't care if it makes any more torque or power. My $.02.
TSW
1) Better balance of peak loads on the crank journals; the 4th main having much higher loads than the 2nd in the 1-8-4-3-6-5-7-2 order, but the difference between the two is said to be significantly less with the swap. This supposedly also improves integrity of the oil films on the mains.
2) Improving A/F mix distribution to 7, which tends to be lean (especially with 180* manifolds), which should reduce the need for staggered jetting.
3) Having 4 & 2 exhaust events together apparently doesn't pose as large an issue as does having 5 & 7 together, as the former cylinders typically run cooler given they're closer to incoming coolant.
Given these and other lesser potential benefits, I really don't care if it makes any more torque or power. My $.02.
TSW
The Chevy guys are doing it now (and have been for 12 years) w/ the LS motors.... And I don't think the cam pricing is anymore expensive.
