Hydraulic Lifter Preloading Instructions

[Tim_C.]

Hydraulic Lifter Preloading Instructions

 

Preload Definition: Amount of travel placed on the lifter hydraulic, OFF of the cam lobe, or lash check position of lobe. The lifter hydraulic will travel a maximum of .125”. However, some of that travel is taken up even when the lifter is off of the lobe and on the backside of the cam. The amount of that travel is the “preload” that is always putting pressure on the lifter.

Cam Swap: Use the factory service manual to swap out the camshafts. If you have questions, you can e-mail me, PM me, or post them, and they will be answered.

Rules: These rules are suggestions only. It is my experience that this works best. If you or your machinist prefers to use different figures, then, do what you think works better.

1.      The lifter must never go below .020 preload. Other lifters and engines are different. I have found that the lifters will start ticking across the board under .020. Some machinists say any contact is enough, as long as the preload isn’t lost, or gaps like there is when you adjust the mechanical lash on the solid type rockers. There is no such gap allowed, and again, there must be at least .020 into the travel (.125) of the lifter at all times.

2.      The max safe measurement can be as much as .080 of preload on the lifter. Maybe more, but I have not tested it beyond that figure. I don’t treat that as an absolute either. Middle of this spec is preferred. So, your target tolerance window is .020-.080. That gives at least .045 or so for the hydraulic to do its work. I wouldn’t try to go beyond .080 and expect it to work, as the hydraulic needs room to work with and that gives no room. The valve springs would need to be over 125Lbs at install height to go tight like that on the preload.

Preload Factors: There are several hidden factors in the Mitsubishi preload design, that make a big difference in how much preload you get.

1.      Rocker Arms- the factory rockers will wear over time on the inside of the rocker. The lifters push/smash into the rocker aluminum, thus they don’t stick out of the rocker as much over time. I’ve seen as much as a .032 difference between new & used rockers.  It is well over 50K miles before this becomes an issue. It depends on other variables such as spring pressure, engine health, etc.. Again, the aluminum itself becomes more compacted in the mass of it above the lifter.

2.      Lifter length- the factory lifters are somewhat longer than some aftermarket. I’ve seen some aftermarket lifters to be .020 shorter than OEM. If you order aftermarket lifters, measure their length against OEM. Chances are you will need the factory length if using a reduced base circle performance cam. Slip rocker hydraulic cams will not be affected in most cases. I did notice the Schneider hydraulic 274 cam to have an overly reduced base compared to the size of the grind. Why, I don’t know, but be ready to do some modification if using that cam on stock hyd rockers.

3.      Valve length- there are 2 known lengths of valves for the Mitsu 2.6L. Ones that came on the hydraulic heads, and post ’83 mechanicals. And ones that came on the ’83 model year Starion. The ‘83’s are longer by .080 for all intensive purposes. Actually .078 and .080 Exhaust and Intake respectively, for all youjz retentives out there. They also have different keeper grooves with keepers & retainers unique to that valve. The groove is square. The hydraulic, round groove valves are what most all of us have already. They may be long enough to gain sufficient preload, depending on the other factors. If you are building a head, it would be safer to use the longer valves to insure enough preload without the use of shims. A machinist can work with the longer valve to gain the proper preload. Your call.

[Tim_C.]

4.      Valve depth in the seat: This is where some older heads may have an advantage on newer ones. If the head has had 1 or 2 valve jobs on it, then the valve will sit deeper into the seat than a new head. This will give more preload, because now the top of valve is located closer to the lifter. Some performance cam companies and suppliers require a deeper seat cut to make even their new billets work. Yes, even a new billet performance cam is ground with a reduced base for geometry, and clearance reasons. That makes regrinding the superior alloy stock cam an even better choice.

5.      Base circle size of the cam- this means the amount of metal that was cut off the cam to gain the desired lobe profile. The base circle is the off lobe diameter measurement. Example: The Monsta’ Banshee hydraulic roller cam has .070 removed from the stock base circle. This gives roughly .035 less preload than factory. That’s what it takes to get the performance roller lobe.

6.      Rocker ratio & or type: It has been observed that the greater the ratio, the greater the preload is. This is a new to new comparison that was done once by me. Your findings may be different? That’s why we use the 1.6 ratio rockers, Mitsu #MD195450, or the Melling equivalent #MR925, so we get the most ratio, and preload, so the cam needs ground on less to achieve the lobe desired. Used rockers will lose some of their ratio due to the design issue in item #1 above. It is always best to use NEW rockers. That gives the head combination a better chance at having the proper preload, and rocker arm ratio. The shims help that, but it takes a bigger shim (in some cases), to fully restore the ratio on old used rockers. Measuring the actual ratio of the given rocker is the only way to tell what is lost there. I don’t advise the average person to attempt to get an accurate ratio measurement as the actual ratio is not over the entire swing of the rocker, but only part of the wheelhouse is at the given ratio of the rocker. That’s why you don’t want to shoot the messenger so to speak if you go to measure your valve lift, and it isn’t perfectly on the advertised valve lift. Chances are it won’t be perfect. Chances are it will, since the rated ratio is at the top of the rocker swing, but it doesn’t take much to change that.

Preload Procedure Tips:

1. If you are using old used rockers, on the hydraulic length valves, you will most likely need to use the shims supplied. New rockers on hyd length valves may or may not need the shims, depending on what cam, head, and rocker combo is being used. I would put them in, and see how much the lifter pushes into the rocker when you bolt it on. If it falls into the .020-.080 window, then use the shims. If it falls outside the window, then hopefully it is on the topside, so you can remove the shim, and try that. My shims (that I invented) come out of the package, approximately .035 + or - .005. They can be up to .045, but anything over .040 is rare. I try to check them, but a few thou difference should not matter.

3.      You must use rocker shafts made for the hydraulic set-up. If yours was mechanical before, then you need to see if the oiling hole provision is on the rocker shafts. There are many holes on the mechanical ones too. The holes to look for are the ones that line up with the oil hole inside the rocker where it runs on the shafts. Use your factory service manual to help make sure you have hydraulic shafts.

Shims: The purpose of the shims is mostly to just take up the .035 loss in base circle on the cam. I have had a few people try to blame me for their lifters not preloading properly. The reduction in base on my Monsta Cam is .035 at the rocker. The shims are .035, so you do the math, and see how there would be problems even if the stock cam is used. However, the above-mentioned factors, after assembly, may end up resulting in not needing shimmed? The shims are Stainless Steel. They are very strong, and will not smash inside the rocker with the proper valve springs. They are a #6 (for 6X32 screw) washer that is approximately .75 in diameter. .035 thick, + or - .005. They are not precision-machined shims, but rather off the shelf stainless washers that get the job done cheap. I preform the shims by dropping them inside an old rocker arm, smooth/curved side away from the lifter, flat side toward the lifter. Center them perfectly by eye. Then I drop in an old stuck lifter, and tap the lifter with a hammer so the shim forms up into the cup. It’s that simple. It’s best to have the rocker upside down in a vice, so you know the shim will not move when dropping the lifter in. This has already been done to the shims supplied with my cams. I tried many shims that were regular steel of all kinds. None were strong enough. They will flatten out to less than .010, and become useless. These shims won’t. Just make sure the SHIMS & LIFTERS DON’T FALL OUT OF THE ROCKERS WHEN INSTALLING THEM! Use the fingers cut off of latex rubber gloves to put over the rockers with the lifters in them. This will hold the rockers in. Or, put the empty (no lifters) shaft assembly on, and barely start the cap bolts in place. Then lift the rockers up one at a time, starting at one end, to carefully insert the lifters with shims up into the hole. You will need to turn the engine, and make sure none fall out during the entire process. You can use a dab of grease to keep the shim on the lifter, and be very careful when putting it up inside of the rocker. The shims can be picked up with a magnet if needed. You may think they are not Stainless due to that, but they are. They are small enough that a magnet will still pick them up.

     It is very important to make sure the shims are centered properly inside the curved/cup portion of the rocker. They fit just barely in that cup, so it is really best to put the shims in with the rocker assembly upside down, so you can know for sure they are centered.

[Tim_C.]

New rockers generally give more preload. Again, there is up to .032 lost with used rockers, that I have personally observed. A new head with hydraulic length valves, may or may not need the shims. If you are setting up the head off the car, then you can get the needed preload by manipulating the factors stated above.

Procedure:

     Bolt down the entire, properly assembled rocker shaft assembly, either with or without the shims. Observe closely how much the lifter pushes in when the rocker assy is tightened down onto the head. Of course you must be looking at a rocker that is off of a lobe, and on the backside of the cam. Use a small steel ruler to measure how much the lifter sticks out of the rocker before installing the assembly, and then after tightening the cam caps. Some engines must be measured between the lobe & backside somewhere, but on ours, it doesn’t matter, as long as the roller or slipper is not on any part of the lobe itself/off of lift. Your observation needs to be with a measuring device as simple as a very small ruler that measures down to a 1/32”. Or calipers. If the lifter pushes in between .020-.080, then the preload is good. Do what it takes to get inside that window. Remember, the lifter will bottom out at .125.

Lifter Preparation: This is your preference. Most people prefer to play with the lifter forever with a small pin while it is soaking in oil, to get the air bubbles out. The problem with getting them pumped like that first is they will not want to push in as easy when tightening down the shaft assy. That makes it harder to measure. It is better to not do that in this case. We want a lifter that will push in & out by hand, so you can watch how much it pushes in when the shafts/cam caps are tightened down. I like to soak the lifters in light oil (WD-40 is fine), and then make sure they will squish in with my fingers. Then put them in. A properly pressurized oiling system will pump them up in 2 minutes time. Don’t revv it over 2500 RPM until the ticking stops! Keeping it at less than 2500 will get the lifters pumped in a minute or 2. If you are confident that the preload is correct, then you can go ahead and put the stiff/pumped lifters in to start with them, if that is your preference. I advise against that, but don’t let me stop you from doing it your proven way. Then you might only have one or 2 that tick when you start it. That’s another reason I don’t waste my time with the lifter prep like a lot of people do. It always seems to leave one or 2 that aren’t pumped enough, so they tick for the first couple of minutes anyway.  

If the ticking doesn’t stop, then it is usually one of 3 things:

1.      Not enough preload due to one, or a combination of the factors above aren’t correct.

2.      Defective/old stuck lifters.

3.      Not enough oil pressure to pump them up. Watch the stock gauge to be ½ on the scale. That is enough to pump them up.

There is no break-in period on a roller cam with roller rockers. Just make sure it is getting good oil. There is break-in on a new or reground slip rocker cam that has not been run yet. Run the engine at ½ oil pressure for 15 minutes to ensure a proper break-in.

 

Additional info to know:

Just an FYI for everyone.

It has been the experience of HotrodTSi that the Alabama Cylinder Head, non-jet head will only work with the mechanical rocker shaft assembly. If he found another reason it didn’t work, then I did not get that info from him. As far as I know, the head casting was slightly different, and would not work with even a stock hydraulic set-up.

Their unique casting changes make no difference on a mechanical set-up, but some locations were changed in the cam cap journal boss to valve relationship, that will not preload the lifter, and in fact leave a .080" or so gap on a stock hydraulic set-up. For those who don't understand that, it means no hydraulic set-up will work in that head casting because there must be at least .020" of preload into the hydraulic lifter. A .080" gap means it is .100 too far out to work.

The valves were stock, and only faced to match the new seat, which doesn't take much at all, so it would not be a factor in the .100 discrepancy. Optimal preload is .045 or so, which makes the issue .125 or 1/8" of difference that would need made up in order to work nominally. That is way to far to make up with even a custom valve length, especially if a performance cam is used, since they all have a somewhat reduction in base circle which directly affects this same measurement to make the gap even more.

With all hydraulic initial setting-up factors, there is always a chance the tolerances will be too far out to function properly unless some minor machining is done to the head. Not necessarily special machining, but more so basic machining and clearance checks that need done on any new combination of parts. Be advised that going bigger on the cam specs leaves a smaller tolerance window for the parts to mate up correctly. This window is usually easily hit with basic machining tricks to get it there. On monster huge performance cams, it may take the use of the longer valves, or even custom valves, etc…. I’ve had to go custom length valves, fly-cut the pistons, and grind the valve cover for a large cam to work. It was well worth it to me, but not cheap for sure.