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Topic Review (Newest First)

  • 01-25-2008, 09:55 PM
    Rocket-J

    .009 short

    If your rocker height is too high or too low you will not get the full use of your 1.7:1 ratio. Only at a right angle to the valve will you achieve the full throw. Good luck. Al
  • 01-13-2008, 05:42 PM
    Hass828
    Quote Originally Posted by steelcomp View Post
    The cam card should have a lobe lift no. You can check that at the lifter. The gross lift will be the lobe X whatever ratio the rocker is. The net lift will be that number less the lash, so make sure you have that number right. Rockers are seldom exactly what they say they are. When I did my BB Chev, the cam card said a net lift of .717/.663 w/ 1.7 rocker, but when I checked everything, I was geting about .030 more. I checked the lobe on the cam and it was dead on, so it could only be the rocker ratio. It was supposed to be 1.7:1 and was stamped as such, but actually measured out to be 1.73:1. (Crane Golds)
    Studs aren't going to flex that much.
    I checked the gross lift by setting up a dial indicator on the end of the pushrod and the lift at the cam was exactly what the cam card said. Figuring for the lash I'm still .009 short at the valve , guess it must be these rockers as it seems to be the same on intake and exhaust both. By the way you were correct as I was about .200 to short on the ex and .100 to short on the in when I checked at midlift after reading the miller web site. thanks for the info.
  • 01-13-2008, 05:27 PM
    scott foxwell
    Quote Originally Posted by Hass828 View Post
    I also checked the lift at the valve and am still coming up short .009. So I pulled the rocker and checked from the end of the pushrod and multiplied by 1.7 rocker ratio and the cam is providing the proper lift. All I can figure is the ratio of the rockers must be off a little. I checked Intake and exhaust both and they are off the same amount. I'm running a set of crower stainless rockers. I'm checking this without the stud girdle in place so it may be flexing the rocker stud enough to cause the problem. Springs are 240 on the seat and 660 over the nose. Thanks Hass
    The cam card should have a lobe lift no. You can check that at the lifter. The gross lift will be the lobe X whatever ratio the rocker is. The net lift will be that number less the lash, so make sure you have that number right. Rockers are seldom exactly what they say they are. When I did my BB Chev, the cam card said a net lift of .717/.663 w/ 1.7 rocker, but when I checked everything, I was geting about .030 more. I checked the lobe on the cam and it was dead on, so it could only be the rocker ratio. It was supposed to be 1.7:1 and was stamped as such, but actually measured out to be 1.73:1. (Crane Golds)
    Studs aren't going to flex that much.
  • 01-13-2008, 04:48 PM
    Hass828
    Quote Originally Posted by steelcomp View Post
    .030".
    Glad the info was helpful to you, and you were able to use it. Now as far as the valve train is concerned, you'll be getting all you can from your cam. Lots of guys leave lots of HP on the table by not taking the time like you did.
    I also checked the lift at the valve and am still coming up short .009. So I pulled the rocker and checked from the end of the pushrod and multiplied by 1.7 rocker ratio and the cam is providing the proper lift. All I can figure is the ratio of the rockers must be off a little. I checked Intake and exhaust both and they are off the same amount. I'm running a set of crower stainless rockers. I'm checking this without the stud girdle in place so it may be flexing the rocker stud enough to cause the problem. Springs are 240 on the seat and 660 over the nose. Thanks Hass
  • 01-12-2008, 08:36 PM
    scott foxwell
    Quote Originally Posted by Hass828 View Post
    I need to thank you boys for the info as you were exactly correct on the pushrod length information, its amazing that that many cam companys are incorrect about the proper way to find the correct pushrod lengths. That miller site rocks, full of good info. Like so many others I never thought about the job of a rocker arm to enough depth. With that being said, know that I have the correct pushrods in my own engine, what would you consider as the bare minimum rocker arm to valve spring retainer clearance? Thanks for the help , Hass
    .030". If you can find a piece of wire near .030" dia. you can use it as a gauge. Stainless safety wire is what I use. Just bend it so you can slide it between the retainer and rocker like a feeler gauge. It goes, or it dosen't.
    Glad the info was helpful to you, and you were able to use it. Now as far as the valve train is concerned, you'll be getting all you can from your cam. Lots of guys leave lots of HP on the table by not taking the time like you did.
  • 01-12-2008, 05:53 PM
    Hass828
    I need to thank you boys for the info as you were exactly correct on the pushrod length information, its amazing that that many cam companys are incorrect about the proper way to find the correct pushrod lengths. That miller site rocks, full of good info. Like so many others I never thought about the job of a rocker arm to enough depth. With that being said, know that I have the correct pushrods in my own engine, what would you consider as the bare minimum rocker arm to valve spring retainer clearance? Thanks for the help , Hass
  • 01-07-2008, 09:24 PM
    scott foxwell
    Quote Originally Posted by Ken N View Post
    Since I am changing the heads and cam at the same time, I was trying to set up the rocker geometry to get the proper push rod lenght when I install the new heads.
    MM is exactly right, Ken. There's no shortcut to doing this, and I can tell you with exact certainty that PR length and valve train geometry is one of, if not the most critical things to get right on an engine if you want the most out of the money you are spending.
    We're here to help.
  • 01-07-2008, 07:26 PM
    motormonkey
    Ken, for what its worth you need to put the head on the motor with the head gasket and bolt down snugly. Lube the cam and install.Lube and slide in the first set of lifters. Put in your low tension checker springs. Put in your adjustable checker push rod and screw down the rockers your going to use snugly. Now you would be closer to be ready to check some stuff. Read the mid lift info from the link and it will guide you step by step to check things out. If you dont have a degree wheel, dial calipers, and a dial gauge with a mag base nows the time to buy. I hope it helps you some and theres smarter people around here that could help more. Have fun and let us know what you found.
  • 01-07-2008, 02:50 PM
    Ken N
    Since I am changing the heads and cam at the same time, I was trying to set up the rocker geometry to get the proper push rod lenght when I install the new heads.
  • 01-06-2008, 07:33 PM
    Ken N
    I Have a new set of Iron Eagle 308 heads siting on my work bench.
  • 01-06-2008, 05:01 PM
    Jim W
    Quote Originally Posted by Fiat48 View Post
    Yes...trust nothing to these boat web sites. They seem to "vanish" without notice.
    Years of tech and links at HB.....most likely gone.
    I thank God every night that Fiat sent me his E-mail address just a few days before HB crashed and burned......

    Whewwww that was a fuKKin close one!!!!!

    Be good, Jim
  • 01-06-2008, 04:39 PM
    motormonkey
    Why would you setup your rockers with the head off.
  • 01-06-2008, 02:55 PM
    scott foxwell
    On a stud mount rocker, the rocker is going to fall where it falls, depending on many things. If you know your exact net valve lift, then yes, you can determin where your rocker will be with the head off. Install a valve with a test spring, set the rocker over the stud and compress the valve one half your net lift. Then hold the rocker so the imaginary line that passes through the center of the trunion, through the center of roller tip, is at 90 deg. to the valve stem. (proper geometry at mid-lift) This is where your rocker will sit on the stud. If you have shaft rockers, you can do the same, but you're not going to know what the PR end geometry is, and that's adjustable with shaft rockers. Note that all this should really be checked fully assembled for a final check, and preferably with your actual springs installed.
  • 01-06-2008, 02:04 PM
    Ken N
    I think it is called Stack Height. Adjusting the rocker's axes below the roller tip.
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