You Guys Are Killing Me With This Shimmin RockersThing
#378154
07/17/09 02:26 PM
07/17/09 02:26 PM
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Joined: Jul 2008
Posts: 403 NE Ohio
JG71B
OP
mopar
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OP
mopar
Joined: Jul 2008
Posts: 403
NE Ohio
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I have a stock 71 383 HP motor,the 346's on it are milled .030,and I'm using a .020 steel gasket. I am using the factory cam(for now),and all the factory rockers,etc. After reading some posts on here,I am uncertain if I have to do this "shim the rockers" thing. I did speak to Dave at Hughes,and from what I gathered(unless I'm a retard,still),unless the base circle of the cam is different than factory,he says,"why would you need to shim the rockers?". He says that there is a major common misconception for the reasons for doing this. C'mon guys,my turn,enlighten me. I only want to do this once! DO I NEED TO DO THIS? Pleeeaaase,helpful and positve posts only if you could. I am sure youre all sick of hearing about it,just once more and I'll never speaks it's name again!
FJ6 '71 Charger SE 383HP
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Re: You Guys Are Killing Me With This Shimmin RockersThing
[Re: JG71B]
#378155
07/17/09 02:45 PM
07/17/09 02:45 PM
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Joined: Jan 2003
Posts: 75,274 A gulag near you.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 75,274
A gulag near you.
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Shims go between the ROCKER SHAFT AND THE ROCKER STAND (head) , when you deck a block or heads are you CUTTING THE ROCKER STANDS ???? If the answer is NO then why would a person shim the rocker shafts to make up for decking the heads and block ? Why , because they are a And I think you misunderstood Hughes or he misspoke , changing the base circle of the cam is NOT changing rocker to valve tip geometry , again , the base circle change does not change the height of your rocker stands so it will NOT effect rocker to valve tip contact. the fix there is a LONGER PUSHROD. If your rocker to valve tip geometry were off and required a LOWER rocker stand postion to correct it the same line of thinking as ADDING shim under the shaft would be to just run a SHORTER pushrod ? NO , you would have to MACHINE the rocker stand shorter. What you have done MAY require a SHORTER PUSHROD , PERIOD , END OF STORY . MP sells ADJUSTABLE length pushrods , why , to FIX the above scenerios , except for lowering the shaft ....
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Re: You Guys Are Killing Me With This Shimmin RockersThing
[Re: JG71B]
#378156
07/17/09 02:46 PM
07/17/09 02:46 PM
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Joined: Jan 2003
Posts: 9,982 Ansonia, CT
CJK440
master
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master
Joined: Jan 2003
Posts: 9,982
Ansonia, CT
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Bring the engine to TDC of #1.
Pull off the drivers valve cover and remove the rockershaft assembly. Strip off all the rockers except for #1 int and ex.
Reinstall shaft and finger tighten the adjacent hold down bolts until any pushrod lash is gone.
Lay a straightedge on the valve cover rail and lightly scribe a line on the 2 pushrods.
Tighten the bolts down completely and rescribe.
Remove the rocker shaft and measure the distance, thats your actual lifter preload.
That will tell you if your pushrods are the right length.
2017 Contusion Blue Challenger T/A 392 M6 "BLKNBLU"
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Re: You Guys Are Killing Me With This Shimmin RockersThing
[Re: mark7171]
#378159
07/17/09 02:50 PM
07/17/09 02:50 PM
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Joined: Jan 2003
Posts: 75,274 A gulag near you.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 75,274
A gulag near you.
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Quote:
appearently to change the rocker arm geometery. Side to side trying to keep it on the stem tip.
Agree with Dave, why would you?
That's a different shim and they doesn't effect the rocker to valve tip geometry either , those center the tip on the stem .
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Re: You Guys Are Killing Me With This Shimmin RockersThing
[Re: stumpy]
#378160
07/17/09 02:53 PM
07/17/09 02:53 PM
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Joined: Jan 2003
Posts: 25,200 Upper Midwest
MoparforLife
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 25,200
Upper Midwest
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Quote:
YOU DO NOT NEED SHIMS. Is that good enough for you?
Short, sweet, and to the point. No you will not need a shim band aide. Also listen to Dave and Kevin at Hughes, they have forgotten more than most here will ever know or learn.
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Re: You Guys Are Killing Me With This Shimmin RockersThing
[Re: MoparforLife]
#378161
07/17/09 03:06 PM
07/17/09 03:06 PM
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Joined: Oct 2006
Posts: 4,765
quick77rt
Parts Problem
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Parts Problem
Joined: Oct 2006
Posts: 4,765
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Only dealing with small blocks Ive never had to shim anything, but then again why do they make shims if there is no real world use for them? This is sorta like the lash cap issue it seems, some use them some dont...some say there is never a need but they still make them. But isnt a lash cap also a shim of a sort? Its pretty simple to know how and where your rocker tip needs to be on the valve so I say do what you got to do it make things correct.
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Re: You Guys Are Killing Me With This Shimmin RockersThing
[Re: quick77rt ]
#378164
07/17/09 03:56 PM
07/17/09 03:56 PM
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Joined: Jan 2003
Posts: 16,123 Grand Haven, MI
patrick
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
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Quote:
Only dealing with small blocks Ive never had to shim anything, but then again why do they make shims if there is no real world use for them?
This is sorta like the lash cap issue it seems, some use them some dont...some say there is never a need but they still make them.
But isnt a lash cap also a shim of a sort?
Its pretty simple to know how and where your rocker tip needs to be on the valve so I say do what you got to do it make things correct.
yes, a lash cap effectively lengthens the valve stem, so does sunken valves, or running longer valves. if these instances occur, you may need to shim up the rocker arm shaft to correct the valvtrain geometry's relationship between the shaft and the end of the rocker to minimize side loading on the guide (which will cause excessive guide wear and valve stem wear).
if your problem is too much preload, you need shorter pushrods.
1976 Spinnaker White Plymouth Duster, /6 A833OD 1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!*** 2011 Toxic Orange Dodge Charger R/T 2017 Grand Cherokee Overland 2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
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Re: You Guys Are Killing Me With This Shimmin RockersThing
[Re: CJK440]
#378165
07/17/09 03:57 PM
07/17/09 03:57 PM
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Joined: Jan 2003
Posts: 25,200 Upper Midwest
MoparforLife
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 25,200
Upper Midwest
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Quote:
Bring the engine to TDC of #1.
Pull off the drivers valve cover and remove the rockershaft assembly. Strip off all the rockers except for #1 int and ex.
Reinstall shaft and finger tighten the adjacent hold down bolts until any pushrod lash is gone.
Lay a straightedge on the valve cover rail and lightly scribe a line on the 2 pushrods.
Tighten the bolts down completely and rescribe.
Remove the rocker shaft and measure the distance, thats your actual lifter preload.
That will tell you if your pushrods are the right length.
Just because there may or may not be exactly the preload you are looking for it can vary slightly as there is a H of alot of forgiveness built into the hydraulic valve lifter. Which in the case of street driven engines leaves a lot of room with out fear of damage. Personally I have taken up to .070 off heads and still had plenty of plunger travel. Granted that is pushing it but .030 - .040 will under most conditions be no problem.
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Re: You Guys Are Killing Me With This Shimmin RockersTh
[Re: 64Post]
#378167
07/17/09 06:26 PM
07/17/09 06:26 PM
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Joined: Jul 2008
Posts: 403 NE Ohio
JG71B
OP
mopar
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OP
mopar
Joined: Jul 2008
Posts: 403
NE Ohio
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Alright guys,it ends here. I'll bother you no more about it. I'm boltin' 'em on,no shims. I will check pre-load,etc to make sure of things. Thanks all!
FJ6 '71 Charger SE 383HP
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Re: You Guys Are Killing Me With This Shimmin RockersTh
[Re: JG71B]
#378168
07/17/09 07:35 PM
07/17/09 07:35 PM
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Joined: Aug 2003
Posts: 8,716 Baltimore/Denver
64Post
master
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master
Joined: Aug 2003
Posts: 8,716
Baltimore/Denver
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Quote:
Alright guys,it ends here. I'll bother you no more about it. I'm boltin' 'em on,no shims. I will check pre-load,etc to make sure of things. Thanks all!
Don't stop on my account. We're all here to learn. Some things have to be in harder than others...
This internetS thing sure is entertaining though...
Here's my take on the geometry issue and, generally, just about everything else. If your stem-rocker contact is poor it usually means your valves are sunk from a crappy/incorrect/short-cutted valve job. You could have a bad rocker or two, but that is usually not the case. The seats ought to be replaced and recut to correct the issue. Shimming the shafts are a band aid. Yes, an incorrect contact pattern will wear the guides faster, but so what? The rest of the head is crap anyway. If you're not conscientious enough to do it correctly at the basic level, then why bother sweating other minor issues? Right...?
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Re: You Guys Are Killing Me With This Shimmin RockersThing
[Re: BigTerry]
#378172
07/17/09 09:17 PM
07/17/09 09:17 PM
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Joined: Jan 2004
Posts: 27,347 Today? Who Knows?
1_WILD_RT
Management Trainee
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Management Trainee
Joined: Jan 2004
Posts: 27,347
Today? Who Knows?
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Quote:
isn't the ideas to have the rocker tip center on the valve stem hence the needs for the shim when you shave the head too much?
How does shaving the head effect valve to rocker relationship?... Valve stem height effects it & there is a specicfied height for them... The distance from the C/L of the rocker pivot to the point it contacts the valve effects it... But milling the head or deck surface doesn't... Again I'll post this picture which shows what shimming the rocker shaft effectively does...
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Re: You Guys Are Killing Me With This Shimmin RockersTh
[Re: BigTerry]
#378173
07/17/09 09:52 PM
07/17/09 09:52 PM
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Joined: Aug 2003
Posts: 8,716 Baltimore/Denver
64Post
master
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master
Joined: Aug 2003
Posts: 8,716
Baltimore/Denver
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Quote:
isn't the ideas to have the rocker tip center on the valve stem hence the needs for the shim when you shave the head too much?
Noooooo !!!
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