Project Resto - Supercharged 1992 LX 'Vert

STI_MECE

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Whole new ball game now. I thought you were working with stud mount adjustable rockers. Those are pedestals you have in your hand. Completely different setup.

Did you gather these parts or was this a functioning assembly to begin with? Im trying to make sure you have all the right compatible parts.
This was the functioning assembly. Ie, these parts, rocker arms, push rods, were all part of the engine when we took it apart.

However, those shims, I am not entirely sure if those were to begin with. My father in law was taking the push rods out and I was holding a shoe box that I labeled to mark where each one came out. He never fully took the rockers off the head. We kept all that on and gave that entire assembly to the machine shop.

But I guess I should call the machine shop. I was going to surprise my father in law that I got all this done while he is on vacation but I need some Intel on this and I do not know the shop he took them too.

Any advice?
 
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John Dirks Jr

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When you are working with pedestal mount rockers, there is no adjusting when installing. When the bolt is torqued to factory spec, the correct amount of lifter preload is supposed to be set. On a factory assembled engine, parts are typically in spec and everything just goes together.

Beyond factory assembled engine in good condition, many things can change the amount of lifter preload you get when torquing down the pedestal mount rockers. The main things that can the preload are worn parts, milled head or milled block deck, differences in head gasket thickness.

To correct for these differences, different things can be done. Using different length pushrods is one way, and a good way if you have a substantial differences across all valves. Another way is using shims under the pedestals. I used shims under my pedestals to fine tune preload.

So, need to figure out where you are. Has the block or heads ever been milled and if so, how much? If you know this info it would be helpful. If not you can still work through it.

What is the part number of the head gaskets and how thick are they?

Are you working with a stock length pushrod or something different?

What cam is in the car and does it have a stock diameter base circle?

See how much of that you can answer first, then ill try and walk you through a solution.
 

John Dirks Jr

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Setting proper lifter preload is your goal. Dont let the term “lash” get the process confused.

Preload is the amount the plunger in the lifter is compressed into the lifter bore while the lifter is resting on the cam base circle.

Now, if you have a lifter on the base circle of its cam lobe, its in position to allow you to check preload.

1. Run the bolt down slowly until you feel the slack gone from the pushrod. At that exact point you have zero lash, but still no preload.

2 . From that point slowly continue to tighten the bolt. As you do this the lifter plunger is preloading (pushing down in the lifter bore).

3. The bolt should bottom out at the specified tq spec within 1/2 to 3/4 turn. If its in that range, thats it youre done. Torqued to spec at 1/2 to 3/4 turn beyond zero lash.

4. If you find the bolt turning beyond 3/4 turn prior to bottoming out at tq spec, you need to add shims. Add shims in the thickness needed to achieve tq spec between 1/2 and 3/4 turn.

5. If you achieve tq spec on a bolt prior to 1/2 turn, you need a shorter pushrod. This can happen with excessive head or block milling or combinations of that and head gaskets that are too thin.

Note, thicker head gaskets can also compensate for excessive milling in the same way shorter pushrods could.
 

STI_MECE

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When you say "feel the the slack gone from the push rod" do you mean I shouldnt be able to lift it up or down, or spin it?

Because right now I tried cylinder one and tried another cylinder on the intake side and when I ran them down, the rocker arm was still able to move freely on its own. As in, I could slide a few feeeler gauges between the roller pin and the top of the valve.

So by that logic, and what your telling me It appears I may have to shuffle those shims.

But I'll need to call the shop on how much they milled. I'll get a part number on the gasket shortly.

I have no idea if this has the stock cam in it or not. And don't think I will unless I pull it out. But I know when it ran , there definitely was no lope to it or not excessive at least.

The push rods should be stock length....not 100% sure.
 

John Dirks Jr

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When you say "feel the the slack gone from the push rod" do you mean I shouldnt be able to lift it up or down, or spin it?
Basically yes, but just barely resisting in the pushrod rotation. As soon as it starts to resist, thats zero.

So you are saying you can run the bolt all the way down and still have slop, cant even get to zero lash?

If so than longer pushrods are probably needed. Its possible that adding shims can get you back in the park but too many shims to het there is not good. Ill have to see if theres a limit on them but basically they're used for fine tuning. Id say that if you have a cam with stock base circle and you have stock length pushrods, those heads must have has a substantial amount of material removed. Perhaps they were already milled before you got them as well.

Use a feeler guage to measure how much it takes to find zero. How ever many thousands that is, add another 40-60 thousands. Thats how thick the combination of shims would need to be for that valve.

Id sort all the shims by size and count how many of each size. Try and divide them into equal combinations of one set for each valve. Im thinking that since you have 60’s and 30’s, maybe they had .090 under each rocker. But you need to check and be sure about the preload. Im just trying to help you figure out how to understand whats going on, and see if shims will even get you back in the game.

You may need custom length pushrods to get you where you need to be. But you want to check length requirement for all valves to see if the discrepancy is uniform across all valves before ordering custom length pushrods.
 

John Dirks Jr

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Long story short, if you can add shims to get 1/2 turn beyond zero to tight down tq spec, your in the game. Increase or decrease shim stack to achieve this.
 

STI_MECE

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you sir have been a huge help. I will have to make more room on my bench and grab my vernier calipers to measure them. Ill lay all the rockers out on the table and go one by one. lol

slow process but needs to be done. So if i have slack in the push rod, then removing a shim will work yes? just want to make sure i have the right mind set in my head before i start thinking about dividing all the shims out.

The info you have been passing along is top notch. I like the detailed info you provide then a synopsis at the end. I love technical details lol
 
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STI_MECE

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my headgasket came from engine tech, F302A-1

going to try an track down the thickness of that gasket....gooing to be burried somewhere
 
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John Dirks Jr

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you sir have been a huge help. I will have to make more room on my bench and grab my vernier calipers to measure them. Ill lay all the rockers out on the table and go one by one. lol

slow process but needs to be done. So if i have slack in the push rod, then removing a shim will work yes? just want to make sure i have the right mind set in my head before i start thinking about dividing all the shims out.

The info you have been passing along is top notch. I like the detailed info you provide then a synopsis at the end. I love technical details lol
I may have been backwards in my previous post so now ive got myself confused too. But i think you are correct. Remove shims to take up slack.

Start with no shims. Take slack to zero. Count turn of tool it takes to tighten down. It it goes beyond 1 full turn, add shims and repeat. 1/2 to 3/4 turn to tight beyond zero is the amount of lifter preload your after.

Again; i may have been backward up there somewhere. But youll figure it out easy with the stuff right in front of you there.
 

STI_MECE

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One other question, is it possible that the intake and exhaust have different base cam circle radi? I was able to snug the exhaust rocker down but not the intake.

Just want to know if it's okay for them to be different
 

John Dirks Jr

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They can be different. Not usual but not unheard of. Other wear and tolerance in the part combination can make it different on any valve, in any engine. So check all 16 and adjust accordingly.

On my 302, one cylinder needed a different thickness shims than the other 7. I double and triple checked, that’s how it was.
 

STI_MECE

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Keeping this here to read later. Last post on thread is helpful....
 

STI_MECE

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anddddd i completely forgot to mention this but the heads had a new intake valve but they reused the exhaust valve. i hope they were competent enough to swap it out with a valve stem of the same length....
 

STI_MECE

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Couldn't fix rotation of image....so the first picture is intake cylinder 1, second is exhaust. I measured the silver pedestal thing and they are the same thing. I KNOW I have the bolt going through the rocker correctly on both. The intake has 3/4inch sticking out, the exhaust has 5/8inch.

I'm lost now lol I'm not sure shims can make up that much difference lol
 

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STI_MECE

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Soo I was taking off the rockers because I noticed some of them were put in upside down....and then I noticed the silver pedestal thing on cylinder 4 exhaust has one crack on each side....

So now what lol
 

John Dirks Jr

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Obviously check all parts for wear and damage and replace as necessary. I had assumed you had already done that. Did these parts go to the machine shop with the heads? If so I would think they would have at least gave them a quick visual for concerns.