Hydraulic lifters

[HeleneCillie]

My husband had his J160's SB8 done, requiring the new hydraulic lifters with hollow push rods etc.

 

After doing the first cylinder head bolt torque he also checked the lifters for clearance. With the engine turned so that the cam lobes facing away from the nr 1 cylinder (valves fully closed) he compressed the lifter by pushing with his thumb hard on the bottom of the tappet. After about 10 sec. the tappet had about 1mm play between the valve and tappet. He then checked all the valves the same way by rotating the engine and compressing the lifters.

 

All the inlet valves had zero play - so no compressing the lifters and were solid against the valves. He also found one exhaust valve without any play. Can this be correct? It seems as if the push rods are to long....

 

(I hope I explained correct!)

 

 

[facthunter]

There should be 2 figures applying. A max and a min. clearance that is the acceptable range. When the lifters are new you can bottom them out and check this. It's much harder to bleed them down after they have oil in them. If they are not in the right range they have to be corrected.

 

Before you start your engine it is a good idea to pressurise the oil galleries to reduce the time before the "lash" goes. Nev

 

 

[Louis Moore]

There needs to be some clearance but it sounds as though you might be doing the checks with the lifters filled with oil!

 

 

[geoffreywh]

I found the same problem when rebuilding the top end of a 3300. Converting the engine from solid push rod to oil feed pushrod I had zero clearance on several valves. Solution? shorten the offending valves...easy....

 

 

[David Isaac]

There should be zero clearance on hydraulic lifters ... its called pre-load. If you have clearance with hydraulic lifters there is a BIG problem. There are various techniques for checking pre-load on hydraulic lifters and one method is a tool that collapses the lifter and the clearance measured as pre-load.

 

 

[facthunter]

WARNING!. Shortening your valves changes the angle the rocker makes with the valve stem end. It should be 90 Degrees with the valve half open. You will have rapid wear of the guides if the geometry is not right. Nev

 

 

[geoffreywh]

This is, of course, an absolutely unnecessary WARNING. Shortening the valve by a millimeter and a half will change the rocker angle by tenths of a degree of angle. This will have no measurable effect on the life of the guide. The top end will wear out long before the "extra" wear on the guide takes effect. I.e. look at the wear on the rocker shafts, mine were ruined by 240 hours!. geoff

 

 

[RKW]

The valves have friction welded hardened tips. Shorten them at your peril! I believe you can get shorter pushrods.

 

 

[facthunter]

WARNING...That's completely incorrect, geofreywh. You would want them within 1/2 mm. of correct. or spot on. Valve guide wear in these engines is a problem. If the relationship of the end of the rocker and the valve stem is out at all there will be an unnecessary sideload on the valve stem.. Nev

 

 

[David Isaac]

I Find it staggering that we are talking of this type of modification to valve length on a supposedly certified engine. What on earth is anyone thinking here. We would be asking serious questions about doing this on an auto engine. Something must be seriously wrong with the valve trane geometry if this seen as necessary. Either the valves have stretched beyond spec or the valve seats have receded or the cylinders have been machined short or the heads had too much machined off.

 

Are we that unprofessional that we are serious about such a suggestion. There must something seriously wrong with this engine design to be having all these valve trane problems. First we hear valve guides, then valves and now valve rocker gear failing at 250 hrs. What the .....

 

 

[facthunter]

I think it is the rocker bush that he is talking about David. I think some of them had some non metallic coating.(teflon or something). think they use bronze mostly.

 

Anytime you remachine valve faces or recut the seats the valve will end up futher into the port. Unless you shorten the valve stem to compensate for it, you will alter the geometry of the valve action remembering that the end of the rocker is moving through an arc of a circle and the valve stem is moving up and down, the contact point of the rocker on the end of the valve should be tangential at the 1/2 open position. This is so as to minimise side loads on the valve. It's not a particularly easy thing to check, but should be checked anytime the head is worked on.

 

I wonder how good they are at original assembly. with CNC techniques they should all be the same. If you have a lot of valve guide wear, the head of the valve may eventually detach ( which they do) and the inlet guide will allow a lot of oil down it. which can cause detonation and/or short out plugs. The anti friction additives in modern oils will short out plugs. Nev

 

 

[geoffreywh]

So here is the whole story. Updating the 3300 engine to hydraulic lifters after top end failure ( shattered/broken rings, sticking valves, worn guides, burnt valves, badly worn cylinders, galled rocker shafts ) I find that the (new) valve/ lifter combination has insufficient clearance with the lifters empty.( Everybody checks this right?) Seats VERY lightly cut....... A call to Rod and find this is not unusual. Solution is to shorten the valves (They DO NOT have hardened welded on tips, what nonsense is this?) The shortening is quite usual among engine builders There is a special jig on my Warren Brown valve grinder for this very purpose....The shortening does alter the valve/rocker relationship, BUT by such a small margin I think it would be difficult to measure. Plus other factors will probably stop the engine BEFORE any additional wear will make its presence felt...Like I said the rocker shafts were galled to hell and back in 240 hours. ( HOW does a bush get "splash" lubrication ? answer, it doesn't) .THat wear alone will alter the valve/rocker angle relationship!....Later I hear that there may now be shorter pushrods....I work on the engine with MORE than 50 years of documented aircooled (endurance/ speedway/ drag racing ), engine building experience so Dont tell grandad how to suck eggs....I believe that the engine components are from water cooled engines running in an air cooled environment ,s so many of the clearances are too tight . As an aside I only chose to change to hydraulic lifters to get the positive rocker feed.....Solid lifters are much more appropriate as any noticed change in the clearance will be identified before its too late.....PM me if you want to know how I got the 3300 to work reliably. Geoff

 

P.S. I believe that the engine people at Jabiru are struggling with a whole swag of problems mainly due to overheating. They are curing the problems but it is taking a LONG time..When it's running properly it's a Great Engine.

 

 

[facthunter]

Well I certainly got up your nose. I'm not the one telling people that the length of the valve doesn't matter . You are. We would probably agree on most of this, with you but you chose to chip in and contradict me. You wouldn't know me from a bar of soap so forget the suck eggs bit. . I thought I put out a warning that was valid, and I stick to it. . Nev

 

 

[geoffreywh]

You are right in theory, The length of the valve is , of course important..........,. sorry if I got on my horse.

 

 

[facthunter]

. I just hate it when this happens. I get funny about what goes out there, because it gets a life of it's own. I'm over cautious, in these things, I know that.. My apologies for any upset . I don't want to pointscore.. Nev

 

 

[Wynand]

Can one not shorten the pushrod a tad?

 

I also found an exhaust valve with the hydraulic lifter bottomed out. On inspection I found the pushrod was 0.4mm longer than the others. Fortunately I had a spare of the correct length and that sorted out the problem.

 

 

[RogerLewis]

My husband had his J160's SB8 done, requiring the new hydraulic lifters with hollow push rods etc.After doing the first cylinder head bolt torque he also checked the lifters for clearance. With the engine turned so that the cam lobes facing away from the nr 1 cylinder (valves fully closed) he compressed the lifter by pushing with his thumb hard on the bottom of the tappet. After about 10 sec. the tappet had about 1mm play between the valve and tappet. He then checked all the valves the same way by rotating the engine and compressing the lifters.

All the inlet valves had zero play - so no compressing the lifters and were solid against the valves. He also found one exhaust valve without any play. Can this be correct? It seems as if the push rods are to long....

 

(I hope I explained correct!)

Your husband should have 'charged' the hydraulic lifter before re-assembling the head. When that is done he should have used a tool to compress the valve springs so as to make the installing of the easier engine. If you are following what I am saying the you will realise there will be no play when the head is fully assembled.