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Author
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Topic: preload question
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capri man
Gearhead Posts: 6652
From: doerun, ga.
Registered: Nov 2000
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posted 08-10-2003 01:51 PM
   
ok i just put another complete engine in my race car. 51099 lunati hyd. roller cam. adjustable crane roller rockers. the engine ran great in the other car. iafter putting it in my car i decided to check the preload on the lifters. the lifters were pumped up. there was about .010-.012 lash on the valves. so i snuged them up my fingers just to where i just could turn the pushrods with my fingers. i then tightened them 1/4 turn more. now the car spits, backfires, pops fire through the headers etc. acts like the valves are not closing all the way.
i checked compression and had 1 about 150 lbs. i backed off on the adjustors till i had a few thousands lash and the comp went up to 180 lbs. has anyone ever heard of a hyd cam that used lash like a solid lifter one. any ideas??------------------
mike r
racing is real
everything else is just a game.
81 capri-7.51 @89mph 1/8
1.54 60 ft.
http://prestage.com/site/site_display.asp?SiteID=141
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MidLifCrisis
Gearhead Posts: 508
From: Frederick County, MD
Registered: Oct 2001
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posted 08-10-2003 03:34 PM
I am by far no expert, but I was recently educated by the local machine shop about the lifters I am using from Compcams. They apparently have larger bleed holes than OEM, so that they don't fully pump up at idle. This lowers lift and/or duration at low RPM, so that the engine runs more smoothly at idle and provides vacuum for accessories like power brakes. Upon acceleration, they pump up to provide full lift/duration and ful power. Thus, if the rockers are adjusted too tight, you lose cam lift, and in extreme cases compression. Your situation may be similiar. Maybe someone with more experience can confirm. Alex would surely know. Charlie
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mvierow
Gearhead Posts: 209
From: Bay Area, Ca
Registered: Apr 2001
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posted 08-10-2003 04:35 PM
I always hear this technique of removing lash by tightening the retainer until the pushrod stops spinning. Wouldn't there be a difference in adjustment if there were oil or assembly lube on the ends of the push rods, or nothing at all for that matter? The technique taught to me was to simple tighten the nut until all vertical movement is removed, then applying the additional 1/4 turn or whatever amount is required. I've never had problems with this in the past, but it would be good to know the 'right' method for sure.
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Buster
Gearhead Posts: 1466
From: Hurricane alley
Registered: May 2002
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posted 08-10-2003 05:10 PM
I use a dial indicater on one rocker and see how much of a turn is .050" into the plunger... then do the rest with out it.[This message has been edited by Buster (edited 08-10-2003).]
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Helping Hands
Journeyman Posts: 41
From: Salem,OR
Registered: Jul 2003
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posted 08-10-2003 07:28 PM
MidLifCrisis,Are you using a Comp XE cam and lifter kit?
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capri man
Gearhead Posts: 6652
From: doerun, ga.
Registered: Nov 2000
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posted 08-10-2003 07:50 PM
no, its a lunati 51099 special grind and i dont have a clue on the lifters. all i know is that they have "SD9" stamped on the side of them. thanks------------------
mike r
racing is real
everything else is just a game.
81 capri-7.51 @89mph 1/8
1.54 60 ft.
http://prestage.com/site/site_display.asp?SiteID=141
IP: Logged |
Buster
Gearhead Posts: 1466
From: Hurricane alley
Registered: May 2002
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posted 08-10-2003 08:58 PM
MidLifCrisis, I think your referring to the Rhodes style lifters. You needed to be real careful with them. Checking your piston to valve clearance at zero rather then .050? in the plunger. Because they would not compress into the plunger and under higher oil presser could cause piston to valve clearance problems.
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