Compression VS cam
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Senior User
Joined: Dec 2007
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Compression VS cam
Hello,
As i read and read and read, i get the intension that when the compression differs (low VS high/really high) the cam also should be different.
Is this correct?
reason i ask: I have installed a Melling FT-2 cam in my 400 with stock compression (a RV cam). Now, when i want to raise CR with, for instance a aussie head, do i have to swap the cam again becouse of the higher CR?
And, is it better, or is it really nesceserely?
maybe someone can explain it a bit?
Thanks.
As i read and read and read, i get the intension that when the compression differs (low VS high/really high) the cam also should be different.
Is this correct?
reason i ask: I have installed a Melling FT-2 cam in my 400 with stock compression (a RV cam). Now, when i want to raise CR with, for instance a aussie head, do i have to swap the cam again becouse of the higher CR?
And, is it better, or is it really nesceserely?
maybe someone can explain it a bit?
Thanks.
Posting Guru
Joined: Jan 2005
Posts: 1,299
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From: The Vieux Ford, Kansas
A big cam will keep the intake valve open after the piston reaches the bottom of its stroke so you are not compressing any thing with the intake valve open you are bleeding off some of the compression. This gets really complicated really fast and I really am not an expert on the topic but I think that is basically how a bigger cam lowers you dynamic compression and a smaller cam will raise it. I do know that it is really easy to run into detonation problems with 400s. It all depends on your setup but unless your motor has zero deck pistons you will run into detonation before you see any quench out of the aussies.
-Johnboy
-Johnboy
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Joined: Aug 2001
Posts: 4,270
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From: Delaware
A big cam will keep the intake valve open after the piston reaches the bottom of its stroke so you are not compressing any thing with the intake valve open you are bleeding off some of the compression. This gets really complicated really fast and I really am not an expert on the topic but I think that is basically how a bigger cam lowers you dynamic compression and a smaller cam will raise it. I do know that it is really easy to run into detonation problems with 400s. It all depends on your setup but unless your motor has zero deck pistons you will run into detonation before you see any quench out of the aussies.
-Johnboy
-Johnboy
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well, like i said in another topic:
I have bought a completely fresh and new rebuilt 460EFI with a E4OD tranny (also new) to be installed in my car. It takes a month, maybe uop to 6 weeks, before it's here, and i go on vacation with this car, so i cannot make the swap before that, as it's not a stock OUT-IN swap...
When i'm back end of august, i want to start with the swap.
Before that, i have to do 2000-2500 miles on vacation with a trailer behind the car, so i need some tocrque and fuel efficiency.
Thats why i don't want to spend too much on the heads: its temporarily...
On the other hand however, i have 3 of these cars, and i can swap a good rebuild 400 into one of the other 2...
choices, choices...
I have bought a completely fresh and new rebuilt 460EFI with a E4OD tranny (also new) to be installed in my car. It takes a month, maybe uop to 6 weeks, before it's here, and i go on vacation with this car, so i cannot make the swap before that, as it's not a stock OUT-IN swap...
When i'm back end of august, i want to start with the swap.
Before that, i have to do 2000-2500 miles on vacation with a trailer behind the car, so i need some tocrque and fuel efficiency.
Thats why i don't want to spend too much on the heads: its temporarily...
On the other hand however, i have 3 of these cars, and i can swap a good rebuild 400 into one of the other 2...
choices, choices...
