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1.6 rockers

 
zman123
Everything in my driveway’s a Chevy
Posts: 537
Joined: 06/08
Posted: 07/20/13 07:21 AM

I just installed 1.6 rockers in my 355, comp XE270HR cam, I know the lift went from .501 to .534 but how does the change effect the duration of the cam? Advertised duration is 270 degrees with 215 degrees @ .500 lift. I know there are a couple of cam geniuses out there.  

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redneckjoe69
I mow my lawn and find Chevys
Posts: 2337
Joined: 03/10
Posted: 07/20/13 07:32 AM

oh man, thats been a highly debated subject, lol.    

  IIRC, the major effect on duration is between mid lift and mid closing?    the over-all duration doesnt really change.    its going to reach mid lift numbers quicker and take longer to reach half way down the closing ramp.    so the mid lift duration will be a little bit bigger.     i hope that makes some sense?

   the cam may feel about 2 degrees "bigger".  

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zman123
Everything in my driveway’s a Chevy
Posts: 537
Joined: 06/08
Posted: 07/20/13 07:50 PM

I figured there wouldn't be much if any change. I searched the subject and found so many posts and threads on here on the subject. I looked at a couple of them but most seemed to change subjects after several posts. I'm not "sensitive"enough to feel a couple of degree change. I talked to my friend that has an engine dyno and builds stock car engines, he said I'll probably see a 12-15 HP increase though.  

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redneckjoe69
I mow my lawn and find Chevys
Posts: 2337
Joined: 03/10
Posted: 07/21/13 07:17 AM

it wouldnt surprise me to see that kind of increase on the dyno.    your buddys probably right.  

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busterrm2013
V-6 Camaros rule!
Posts: 46
Joined: 07/13
Posted: 07/23/13 09:37 PM

It really depends on what lift range your heads flow their best at, meaning the 2-3 degrees difference in duration is negligible, but the lift change will add more. Your going to .534 lift, if your heads flow best between 500 and 550, you will see a very noticeable increase.
I will use my Dart SHP 400 as a example, my cam runs 224 duration at 050, so it will probably go to 226-7 on duration. My lift is 525, with the 1.6 rockers it will increase to 563. My heads are RHS 200 pro action 1, they flow their best between 550 and 600. That is the reason I used 1.6 rockers, I wanted a shorter duration for good street manners but with 400 CI I need it to breath more, so I put on 200cc heads to get more fuel. My software told me it will increase my HP by about 21- 24.  

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zman123
Everything in my driveway’s a Chevy
Posts: 537
Joined: 06/08
Posted: 07/24/13 07:47 AM

That sounds right, I have driven the car about 100 miles since the change and it seems to run a little better at cruising speed (2000 RPM) I have Edelbrock Performer RPM heads on it with MSD Atomic fuel injection so the added lift lets it breathe a little better.  

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68scott385
I mow my lawn and find Chevys
Posts: 1994
Joined: 10/09
Posted: 07/24/13 08:16 AM

In your case the added lift is right in the sweet spot for the Eddy heads. The thing to keep in mind is not just the maximum lift but the time the valve spends at mid lift is twice what it spends at max lift. Sounds like you have a package that should work very well together. I mean your heads aren't overkill for your cam, and your cam isn't overkill for the rest of the motor.  
68scott385 68scott385 68scott385

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