Rocker Bridge studs

[reb]

Hey there, I'm new to the forum, but I've been reading for a while. Anyhoo, I have a 1984 station wagon that pisses oil from the back of the valve cover. Turns out the gasket is blown back there next to that bolt that only a child with miniature hands could access. Also turns out that the PO put one of those aftermarket chrome covers on, and to do so... wait for it... ground off the studs on the rocker bridges. I found this out AFTER I bought one of the plastic "original" replacement covers.

So my question is this: since I don't want to return the plastic cover (and I like the concept of "stock") I went ahead and ordered a couple replacement studded bridges from Morris. BUT (and I totally apologize if this is a stupid question) do the nuts holding down the bridges have anything to do with valve adjustment? Put another way, when I swap out the bridges will I have to re-adjust my valves?

Thanks!
Reb

[85AmCfreak]

Reb
         Ok first of all welcome to the forum.
When replacing the rocker arm bridges there is no adjustment to the valves. Actually there is no adjustment period. They are hydraulic lifters. The bridges (if I recall) are to be torqued to 20 ft lbs.  Why do you want the plastic valve cover? I understand you want to retain the stock look but, they were a terrible design from the start always leaking and warped due to heat. I own 3 eagles and my 85 has been in the family since we walked off the dealer lot with it in 85. The plastic covers were recalled for leaking gaskets when the car was new. My suggestion is to keep the aluminum valve cover and replace the gasket. The instructions suggest to only use a cork gasket but I've been using the FEL-pro VS50244R which is a Cork/Lamb composite and it works very nicely. I haven't had any trouble and it's been about 2 1/2 yrs since I did them. It's an Amc inline 6 cyl. It's going to leak oil. Better get used to that lol. As for that bolt in the back near the firewall. Remove the wiper motor assembly and drill a hole large enough to get a 1/4 inch drive socket and extension just above and inline with the bolt. That should end your troubles dealing with that ridiculously placed bolt. I deff do not suggest using that plastic cover, get your money back.

[mudkicker715]

With proper extensions u joints and tools period that rear bolt is the easy bolt. Trust me on this. I have gotten that bolt off in seconds. Also go to an aluminum aftermarket cover. Also welcome to the forum

[AMC1]

I've used a 1/4" drive flexible extension on that bolt & it works OK. Interesting though I didn't know there was a recall on the plastic valve cover for '85. I have '83s & never heard a word.

[2xEaglewagons]

Hello
I have bought Smith brothers. adjustable pushrods for a few different engines.
They will custom make pushrods for you.
There is a preload spec. for  hyd lifters.
Maybe someone here knows what that spec is for an AMC lifter?
Depends on the machining of your engine,head or and block work,gasket thickness,or a solid lifter.
If your engine is factory stock dont worry about it
An adjustable valve train could be handy for H.P.
I have also just used 1 adjustable pushrod to measure what size was needed,then ordered a set of that length.
I am not a machinist but think out loud a lot
Randy(wants a decent idle)H.
Mission B.C.Can.

[85AmCfreak]

No disrespect 2x (it's good to know someone will make custom pushrods) but what does that have to do with his valve cover and gaskets?

[2xEaglewagons]

Hello
I reread the post and saw this question...
>
" BUT (and I totally apologize if this is a stupid question) do the nuts holding down the bridges have anything to do with valve adjustment? Put another way, when I swap out the bridges will I have to re-adjust my valves??
>
I figured i got help here and would like to help someone else if i could.
I tend to work long hrs and may ramble on at times,,age .
Randy H.
Mission

No disrespect 2x (it's good to know someone will make custom pushrods) but what does that have to do with his valve cover and gaskets?

[amcfool1]

no

[85AmCfreak]

Ok 2x now I understand where you were coming from. Amcfool what's the no for???

[amcfool1]

hi, the question was do the plastic valve cover hold down studs on the rocker bridges affect valve adjustment, no, they do not.
Also, unless one is doing a full race motor with roller rockers, high lift cam/springs, etc, custom pushrods are NOT needed. good luck, gz

[2xEaglewagons]

amcfool1
I was just thinking as a rule of thumb after even basic machine work on block,heads,valves.
Are there after market head gaskets avail for 258s? how thick?
With even a mild street cam,checking preload on lifters would be the norm?
So i went and found this..
>>
>
.The function of any lifter, hydraulic or mechanical (solid) is to ride the eccentric slope of the camshaft's lobes and effect the opening and closing of the intake and exhaust valves. Hydraulic lifters have the ability to automatically adjust themselves and maintain zero clearance in the valve train by supporting the pushrod plunger on a small chamber of pressurized oil, regulated by a precisely controlled oil bleed rate. Valve train noise is prevented because the lifter is preloaded, eliminating any clearance.

Hydraulic lifter preload is the distance the pushrod plunger is depressed below the retaining lock. Preload should be between .020"-.060" for the lifter to perform properly. With too little preload, the valve train will be noisy and the retaining lock may fail (break or pop out) due to excessive hydraulic force against the retainer. Conversely, too great a preload (more than .060") will produce excessive lifter pump-up, causing the valves to open longer and lift higher, drastically reducing cylinder pressure and hurting engine performance. The engine will also have very low vacuum, causing it to idle very poorly.If preload needs to be adjusted, there are several different avenues the engine builder can travel, each dependent upon what type of mounting the rocker arms use.
Probably one of the simplest ways to change preload is to change pushrods.
A longer pushrod increases preload and a shorter pushrod decreases preload. Adjustable pushrods are also available.
When should hydraulic lifter preload be checked? Something as simple as changing a camshaft or installing thinner (or thicker) head gaskets may affect lifter preload. Other engine machining operations such as valve grinding, decking the block, or milling the heads will, for sure, have a serious effect on preload. A good rule of thumb is that any time a cylinder head has work done, or has new components installed, is a good time to check and adjust preload.
 >>>>>>>>
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I read back and saw why i started the adj push rod talk.
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>Posted by: 85AmCfreak
« on: October 19, 2016, 03:56:43 AM » Insert Quote
Reb
         Ok first of all welcome to the forum.
When replacing the rocker arm bridges there is no adjustment to the valves. Actually there is no adjustment period. They are hydraulic lifters.
>>>
>>
>
Randy(thinking out loud again)H.

hi, the question was do the plastic valve cover hold down studs on the rocker bridges affect valve adjustment, no, they do not.
Also, unless one is doing a full race motor with roller rockers, high lift cam/springs, etc, custom pushrods are NOT needed. good luck, gz