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Old 18-08-2008, 07:41 PM   #1
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need info please valve lifters

i have stripped down a 7.4 mercruiser and replaced lots of new parts.but when replacing the rocker lifters what tension should they be tightend up to as the valve is starting to open. ive been told that there could be oil in the lifters we also have not replaced the inlet manifold yet .
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Old 18-08-2008, 07:43 PM   #2
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valve lifters

sorry rocker lifters
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Old 18-08-2008, 09:42 PM   #3
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You have to set the camshaft on the base circel(not on the ramp ) turn the rocker bolt/stud down until you can,t move the pushrod anymore up and down,make sure this is done very accurate ,then turn 3/4 turn down as a preload .
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Old 18-08-2008, 10:44 PM   #4
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If you haven't pre-filled (primed) the lifters, you'll still be able to spin the pushrods with the lifter partly compressed.

So,
You need to establish the point in the process of tightening the rocker nut where there is no longer any backlash (ie, you can no longer rattle the rocker arm) but it hasn't yet begun to compress the piston within the lifter (whilst on the dwell of the cam)
Then, as AJ says, 3/4 of one turn more. This places the lifter roughly 50% through it's self adjusting travel.

You must prime the lifters before fitment, otherwise they can jam at the bottom of their travel before engine oil pressure fills them.

To prime, get a tupperware container or similar, put 3 inches of engine oil in the container (enough to cover a lifter standing in the tub) put a lifter in and use some sort of rod, or screwdriver or similar to 'pump' the inner portion of the lifter, you'll see bubbles appear as the air within is dispelled and it fills with the oil. As this process happens, the travel of the piston will become limited, this is what you're trying to achieve. (obviously you need to do all 16)
Make sure that whatever you 'pump' it with is nice & clean, you don't want any dirt or shite in the lifter.

Use assembly lube between the cam and mating face of lifter when assembeling (Molybdomen Disulphide grease) and when you start the motor for the first time, you MUST imediately take the motor up to between 1500 and 2000 rpm and hold it there for a minimum of 20 minutes. failing to do this will result in very early cam/lifter failure. (as in minutes, not hours)
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Old 18-08-2008, 11:16 PM   #5
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Its not really necesary to pump the lifters with oil ,even when empty ,the spring inside will press the piston up ,and when the pre lift is set ,its ok when the lifter sets itself with oil press

What we normally do is a mix from what John says and me ,when we put the engine together ,we take the distributer out ,and put a sawed off distributer in where we connect it with a drilling machine ,that way we build 50 psi oil pressure in the engine ,while looking for leaks etc the lifters are filled with oil ,just like the oil cooler /hoses ,filter etc etc ,then we set the pre lift ,and start the engine .

The thing John mentioned with rev the engine +1500 rpm when start up first is russian roulette when you do not ....the camshaft lobes are not press lubed but from oil drops that are flying around

If you have had a few eaten up camlobes/lifters when breaking in,you find it time to throw those flat tappeds as far away as you can ,and install a roller lifter type
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Old 18-08-2008, 11:27 PM   #6
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If ya don't prime em you'll end up thinking the motor is about to shit its innerds on the first start.

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Old 18-08-2008, 11:32 PM   #7
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I too always pre lube the motor using a cordless drill and dummy dizzy drive shaft. I have a converted cam>oil pump drive shaft/housing with the helical gear teeth ground off and an extended shaft for doing the same job on the GM diesel V8s (obviously no dizzy) the primer shaft for petrol V8's are available at any good speed shop.

The reason I always prime the lifters is, I once saw one jam, which I put down to the cylinder wall of the lifter body not being parallel right to the bottom of the lifter, maybe through the end of the hone, or whatever tool is used for boring the lifters to size being blunt or worn at the end. Anyways, the inner portion of the lifter jammed at the bottom of it's travel and didn't want to budge. So I reckon it's easier to be sure than pulling it down again when one won't free up.
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Old 18-08-2008, 11:46 PM   #8
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I had a Gen 6 block for my boat ,several years ago when the gen 6 was just out ,we installed a flat tapped hydraulic (high lift cam with heavy springs ),and it eat up a few lobes ... installed a new one ,this time with stock springs (less pressure on the lobes ),still eat up the lobes ...we measured the lifter bores ,and found the bores are all off , this engine was originally designed for a roller cam,where its not that important where the bores are .

installed a roller ,and it was fine ,I know of a guy that had all the bores bored out ,and installed bronze bushins that were indexed again to the exact place where the bores must sit at

Don,t know if that was a structural thing from GM,or just my block
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Old 18-08-2008, 11:54 PM   #9
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Lifter bores 'Off' as in off centre, or out of line? I take it you don't mean tight.
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Old 19-08-2008, 12:06 AM   #10
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Out of line ,so some lifters would not turn properly,while stay in the same positions they where food for the camshaft.

I don,t fully understand what you did to the V8 diesel to prime it ?
And like to know a little more about how you did those mods.
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Old 19-08-2008, 12:32 AM   #11
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On the V8 diesel, the location of the oil pump and way it's driven is exactly like the gas V8's, however, as there is no distributor, the drop in assy looks like a dizzy, up to the point where the fork clamp holds a gas V8 dizzy in.

It's just a cast drop in bearing assy, with 2 bearings on a shaft and the helical gear that meshes with the cam and a shaft that drives the oil pump (just like a gas V8). On my modded one, I took the blanking cap out of the top (where the upper part of the dizzy would be) and welded a an extension shaft to existing shaft. Then, ground off the helical teeth on the shaft so that it can turn independantly of the cam. I pop the assy in, connect the cordless drill and pump.

The reason for doing all that rather than just having a shaft in a drill that locates on the oil pump is that an oil gallery runs across the block casting where this assy drops in, the assy has two 'O' rings that seal against the block containing the oil as it passes through. So, if the modded assy was not used, all the oil pressure just leaks out of the open gallery and you don't get to force feed the oil system.
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Old 19-08-2008, 08:12 AM   #12
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Smile lifters

thanks everyone gonna try today
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Old 20-08-2008, 03:07 AM   #13
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For priming a big block chevy, you can either buy a tool that fits in where the distributor goes, or, find a junk distributor, strip it of its cam gear, rotor, etc, put it in place, and chuck your drill unto the rotor shaft. You can now prime the engine.
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