Rocker Shims

[JD1964]

In my engine upgrade process I'll be installing Ford Racing pedestal type 1.7 roller rockers. The GT40 heads will also be milled .030 so I think I want to shim the rockers when I install them.

The kits I see available have 32 shims including 16 .030 and 16 .060. Is this basically my only choice or are there kits with other size shims also available?

I know there is a certain amount of tolerance and variance in the lifter pre-load on hydraulic lifters. What is the acceptable range of pre-load?

I know this aint rocket science but I don't wanna take it apart a second time (at least not for a while anyway). After all, when do we ever stop taking thing apart again?

 

[revhead347]

Shimming the rockers will throw your geometry off. With the heads milled, the relation of the tip of the rocker to the valve will be the same. In order to correct the valve geometry for a milled head, you need to get shorter pushrods, not bring the rocker up. The preload range is actually pretty large. What I would do is assemble the engine first, then do a geometry test to see if it is off. If it is, then order the correct pushrod length to correct it. Shimming the rocker up will definitely not fix the problem, it will only make it worse.

Kurt

 

[mikestang63]

Shimming of pedestal rockers is used when you can't get proper preload within lets say a 1/2 turn after zero lash, not to adjust the height or acheive proper geometry or swipe You can try using a thicker head gasket, but as Kurt said you should get a pushrod length checker. That will ensure proper geometry. Then if needed, add shims for proper preload.

 

[JD1964]

I will put it together and see how things size up. I would be using the shims to adjust preload (if needed) as directed in the instructions that came with the rocker arms. I'm using a stock cam so I doubt a .030 shim is going to change the geometry enough to cause a problem. After all, why would the instructions written by Ford Racing indicate that shims may be needed. Milling the head is going to add lifter preload to a pedestal type rocker setup. As noted in the instructions, the shims are used to correct excessive preload.

Here are the instructions that came with the kit. These rockers are sold as direct replacements for stock pedastal type rockers. Look at step 6 and 7 for the shim instruction.

 

[mikestang63]

John, you essentially confirmed what I said, in that the shims are used to adjust preload. You removed .030 of material from the head surface, so to ballpark that would require .030 shorter pushrod or as I said a thicker head gasket to keep the same geometry.

Have you checked the swipe on the valve tip with the stock pushrods?

 

[JD1964]

John, you essentially confirmed what I said, in that the shims are used to adjust preload. You removed .030 of material from the head surface, so to ballpark that would require .030 shorter pushrod or as I said a thicker head gasket to keep the same geometry.

Have you checked the swipe on the valve tip with the stock pushrods?

No but worth noting. Not back together yet.

But again, the instructions that came with the rockers say to use shims to correct preload if needed. They dont say anything about the shims affect on geometry. If it were a critical thing in the intended application of the part, why would they not mention it?

 

[stykthyn]

They were likely assuming all things being equal that the builder has covered all ptv issues including push rod length. The shims are merely there to ensure proper preload as said previously.

 

[jrichker]

Michael Yount’s valve adjustment procedure

Here's an easy way to determine this. Start with the #1 cylinder. Rotate the engine with a ratchet on the crank bolt clockwise. Watch the #1 pushrods. First the exhaust pushrod will rise and fall signaling what would be the exhaust valve opening and closing if the rocker were on. As it closes the intake pushrod will rise -- keep rotating clockwise until the intake pushrod falls and is level with the exhaust pushrod - both at the same height. Both lifters are now on the base circle of the cam - both valves would be closed if the rockers were on.

Now, install both rockers. Tighten the bolts with one hand while rocking the rocker with the other hand - continue until you reach the point where you can't 'rock' the rocker any more because there's no gap on the valve stem end or the pushrod end. You are at zero lash - i.e. - no gaps. Stop tightening just as you reach this point.

Now, put your torque wrench on the bolt and tighten it to 18-20 ft-lbs while counting the number of turns it takes to reach the torque. You should hit the torque within 1/4 to 1 turn of the bolt. If it takes more than 1 turn, use a shim to raise the rocker -- each .030" shim will reduce the number of turns to torque by about 1/4 turn. If you reach the torque in less than a 1/4 turn, or you have trouble reaching zero lash even at full torque, then you'll either need longer pushrods, or to CAREFULLY remove some material from the bottom of the rocker fulcrum. Using the procedure described above, you will work through the remaining 7 pairs of rockers. If you follow the firing order, it will minimize the manual cranking you have to do to get the lifters on the base circle of the cam prior to installation of the next pair.

When I first went through mine, 13 of them took no shims; 3 of them took 1 .030" shim. Upon cranking it up, one or two of them sounded a bit noisier than I thought was right, so with the engine hot, I pulled the upper off, and the valve covers, and went through the installation procedure again. That time, 11 of them took no shims; 4 of them took one .030", and one of them took one .060" shim. And they were very quiet running.

Good luck with it.
__________________
Michael Yount - K'ville,TN 82 Volvo 242w/5.0L; 2000 Suzuki Bandit 1200

 

[JD1964]

Michael Yount’s valve adjustment procedure

Here's an easy way to determine this. Start with the #1 cylinder. Rotate the engine with a ratchet on the crank bolt clockwise. Watch the #1 pushrods. First the exhaust pushrod will rise and fall signaling what would be the exhaust valve opening and closing if the rocker were on. As it closes the intake pushrod will rise -- keep rotating clockwise until the intake pushrod falls and is level with the exhaust pushrod - both at the same height. Both lifters are now on the base circle of the cam - both valves would be closed if the rockers were on.

Now, install both rockers. Tighten the bolts with one hand while rocking the rocker with the other hand - continue until you reach the point where you can't 'rock' the rocker any more because there's no gap on the valve stem end or the pushrod end. You are at zero lash - i.e. - no gaps. Stop tightening just as you reach this point.

Now, put your torque wrench on the bolt and tighten it to 18-20 ft-lbs while counting the number of turns it takes to reach the torque. You should hit the torque within 1/4 to 1 turn of the bolt. If it takes more than 1 turn, use a shim to raise the rocker -- each .030" shim will reduce the number of turns to torque by about 1/4 turn. If you reach the torque in less than a 1/4 turn, or you have trouble reaching zero lash even at full torque, then you'll either need longer pushrods, or to CAREFULLY remove some material from the bottom of the rocker fulcrum. Using the procedure described above, you will work through the remaining 7 pairs of rockers. If you follow the firing order, it will minimize the manual cranking you have to do to get the lifters on the base circle of the cam prior to installation of the next pair.

When I first went through mine, 13 of them took no shims; 3 of them took 1 .030" shim. Upon cranking it up, one or two of them sounded a bit noisier than I thought was right, so with the engine hot, I pulled the upper off, and the valve covers, and went through the installation procedure again. That time, 11 of them took no shims; 4 of them took one .030", and one of them took one .060" shim. And they were very quiet running.

Good luck with it.
__________________
Michael Yount - K'ville,TN 82 Volvo 242w/5.0L; 2000 Suzuki Bandit 1200

Thanks for the extra info and I totally understand the procedure.

 

[JD1964]

They were likely assuming all things being equal that the builder has covered all ptv issues including push rod length. The shims are merely there to ensure proper preload as said previously.

If custom length push rods were part of an engine build and done correctly, there should be no need for shimming to correct lifter preload on pedestal stlye rockers.

I still do not agree that shimming these pedestal style rockers as instructed by the part manufacturer is going to mess up the valve train geometry. Remember, I'm running a stock cam and replacing stock pedestal rockers with pedestal roller rockers. Shimming .030 to compensate for .030 milling isn't going to hurt a thing in my opinion.

 

[stykthyn]

Only one way to find out

 

[84Ttop]

If custom length push rods were part of an engine build and done correctly, there should be no need for shimming to correct lifter preload on pedestal stlye rockers.

I still do not agree that shimming these pedestal style rockers as instructed by the part manufacturer is going to mess up the valve train geometry. Remember, I'm running a stock cam and replacing stock pedestal rockers with pedestal roller rockers. Shimming .030 to compensate for .030 milling isn't going to hurt a thing in my opinion.

I really think you are completely discounting all of the good advice from above. It seems to me that you have made up your mind about the best way to go about things so why bother even asking for everyone's opinion? I don't mean to sound brash here but if you don't intend on heading the advice from other members then don't bother asking questions when you may not like the answer you recieve.

 

[JD1964]

I really think you are completely discounting all of the good advice from above. It seems to me that you have made up your mind about the best way to go about things so why bother even asking for everyone's opinion? I don't mean to sound brash here but if you don't intend on heading the advice from other members then don't bother asking questions when you may not like the answer you recieve.

I just got back from dropping the heads off at a well know area machine shop to be milled. The experienced engine builder shared the concern about how milling the heads changes things. He asked a few more questions about my intentions including what cam I would be running. I told him the cam would remain stock but I was adding the 1.7 pedestal roller rockers. I told him I would be shimming the rocker arms to ensure proper lifter preload and he agreed with my plan.

You said why bother asking a question if I don't like the answer? First of all, how would I be able to agree or disagree with any answer unless I first asked a question? Second, if you go and read my initial post, you will see I did not ask a question about valve train geometry or how shimming might affect it. I asked what shim kits are available and what is acceptable lifter preload range.

The persons who responded took the thread in a different direction. Don't get me wrong because if someone thinks I'm about to make a big mistake, I appreciate their opinion. In the case of this discussion (which went in a different direction - not by me), I just happen to disagree that shimming to ensure proper lifter preload is going to cause a problem in my application.

I thank all who respond to my posts and take no offense to differing opinions.

 

[madspeed]

View: https://www.youtube.com/watch?v=6zXDo4dL7SU

 

[84Ttop]

How very dramatic @madspeed lol