Follower bleed down rate

[wokingwedger]

I have been doing a bit of experimenting with preloads, trying to get rid of a 'rattle on over run' that I, and approx 50% of 5.0 litre TVR RV8s appear to have.

I have adjustable pushrods and set all preloads to 50 thou, but due to limited adjustment on the pushrod had to use a 35 thou shim under the pedestal. The rattle was still there (1200 rpm only as previously)

There may be other reasons for the noise but as I say I have been trying different preloads.

Question for all those in 'the know' :-

I have removed the shims thus increasing preload to approx 100 thou.
How long will it take for the lifters to evacuate their excess oil and settle at their new compressed height. Will each one do it whenever the engine is turned off and each lifter is left in its compressed state. I have barred the engine over a few turns, leaving a hour or so in between.

Before having the cam changed I noticed that when trying to measue lift at the rocker arm , the dti kept winding back, presumably due to bleed down of the lifter.

The noise is still there, but I without an answer to the above I am not sure things are operating as I intended. The car is running superbly by the way !

[DEVONMAN]

Hi, At 100 thou preload you are probably getting close to the point where the follower is solid and the valves may be kept off their seats.
Me, I would not risk 100 thou preload.

My 5.0 tvr lump makes several unusual noises. I believe one noise/rattle come from the pistons because with the 90mm stroke, short rods and relatively large compression height, the skirt of the piston almost leaves the bore on full drop and tends to wobble as it returns into the bore.
On strip down, I noticed a wear mark on the piston skirts which coincided with the botton of the cylinder liner with the piston at the bottom of it's stroke.

Cheers Denis

[wokingwedger]

Hi, At 100 thou preload you are probably getting close to the point where the follower is solid and the valves may be kept off their seats.

Denis

I am not sure what you mean.

The followers are capable of a good 5mm plus compression, so at 100 thou are about halfway.

Am I missing something

[kiwicar]

Hi
Are you sure it is followers and not piston slap?
Mike

[wokingwedger]

Hi
Are you sure it is followers and not piston slap?
Mike

It could be piston slap, but I thought that tended to happen when an engine is cold and it really sounds like lifters (sort of hardened metal chatter)

Will 100 thou pre-load cause a problem ?

Surely valve movement will remain the same, its just that a there is a different amount of oil in the lifter.

[kiwicar]

Hi
100 thou of preload I think will lead to burnt valve seats and bent valves if you rev it certainly the lifters will pump up leading to loss of power at higher revs. I would be sure what the problem is before you try and fix it, exhaust gasket leak can sound metalicky, piston slap can occour on a warm engine (go stand near a Honda twin cylinder motorcycle engine if you want proof) and at prectically any revs. Remember these engines are designed to work quietly and reliably within a set of specifications and 98% of the time they do when put together by unskilled assembly staff. Going outside those limits to solve a problem probably means that you are not actually on the right track and you need to see if you are chasing the wrong fault.
Best regards
Mike

[dbv8]

A leaky exhaust manifold gasket or (common to TVRs) a leak in the manifold where the primaries meet may be the problem.
It sounds almost exactly the same as the tappet noise we all love to hate.

[wokingwedger]

Hi
100 thou of preload I think will lead to burnt valve seats and bent valves if you rev it certainly the lifters will pump up leading to loss of power at higher revs.

Mike, I am not sure why valve lift will change.

The cam lift is the same the raio of 1.6 is the same,

I have just lowered the rockershaft and the push rod and top of the lifter.

Are you saying they will pump up more because there is less oil in them ?

I assume there is less oil in them, or it will be compressing the valve spring.

[wokingwedger]

A leaky exhaust manifold gasket or (common to TVRs) a leak in the manifold where the primaries meet may be the problem.
It sounds almost exactly the same as the tappet noise we all love to hate.

Derek, no its not that, you may have seen the thread on Pistonheads Griiff forum 'Strange Top end Rattle ' started by TVR Beaver.

Mine has been diagnosed by various respected TVR garages and Rover V8 builders as :-

1) lifter rattle due to loss of pressure due to crankshaft/brg design tolerances
2) Rod chatter due to 2 con rods sharing one journal
3) Pin to piston wear

[mgbv8]

Hi
100 thou of preload I think will lead to burnt valve seats and bent valves if you rev it certainly the lifters will pump up leading to loss of power at higher revs.

Mike, I am not sure why valve lift will change.

The cam lift is the same the raio of 1.6 is the same,

I have just lowered the rockershaft and the push rod and top of the lifter.

Are you saying they will pump up more because there is less oil in them ?

I assume there is less oil in them, or it will be compressing the valve spring.

The lifters (if working ok) should pump up solid at X rpm. The lifters dont maintain the pre load gap when running fast.
This gives you the full lift from the cam at higher rpm. My Rhodes lifters pump up hard at around 3000 rpm. You can see this in a torque spike at that rpm on the dyno.
The pre load gives you more clearance (bigger tappet gap) at low rpm when the lifters cant pump up fully.

So its cam lift x 1.6 = ?? at low rpm for valve opening.
And Cam lift + your 100 thou x 1.6 at higher rpm for max valve lift.

Too much pre load can lead to bent push rods if you havent got all the clearances set right.

[SuperV8]

Mine has been diagnosed by various respected TVR garages and Rover V8 builders as :-

1) lifter rattle due to loss of pressure due to crankshaft/brg design tolerances
2) Rod chatter due to 2 con rods sharing one journal
3) Pin to piston wear

I'm not sure I understand, (not for the first time ) If you already have a 'trusted' diagnosis of three causes why aren't you investigating them further?

Tom.

[wokingwedger]

Hi
100 thou of preload I think will lead to burnt valve seats and bent valves if you rev it certainly the lifters will pump up leading to loss of power at higher revs.

Mike, I am not sure why valve lift will change.

The cam lift is the same the raio of 1.6 is the same,

I have just lowered the rockershaft and the push rod and top of the lifter.

Are you saying they will pump up more because there is less oil in them ?

I assume there is less oil in them, or it will be compressing the valve spring.

The lifters (if working ok) should pump up solid at X rpm. The lifters dont maintain the pre load gap when running fast.
This gives you the full lift from the cam at higher rpm. My Rhodes lifters pump up hard at around 3000 rpm. You can see this in a torque spike at that rpm on the dyno.
The pre load gives you more clearance (bigger tappet gap) at low rpm when the lifters cant pump up fully.

So its cam lift x 1.6 = ?? at low rpm for valve opening.
And Cam lift + your 100 thou x 1.6 at higher rpm for max valve lift.

Too much pre load can lead to bent push rods if you havent got all the clearances set right.

Ahh, so if they pump up every time its revved, they also bleed down every time the revs drop, so I should have the reduced amount of oil and increased pre comperession I expect (for good or bad) as its been revved a few times.

So are you saying that when revved the lifter will fill until the spring clip stops it ?

[wokingwedger]

Mine has been diagnosed by various respected TVR garages and Rover V8 builders as :-

1) lifter rattle due to loss of pressure due to crankshaft/brg design tolerances
2) Rod chatter due to 2 con rods sharing one journal
3) Pin to piston wear

I'm not sure I understand, (not for the first time ) If you already have a 'trusted' diagnosis of three causes why aren't you investigating them further?

Tom.

I never mentiond 'trusted' !

Seriously, I do actually trust that they have given the best diagnosis they can , but clearly 2 of the 3 are wrong.

Items 2 and 3 are very expensive to 'investigate', in fact once the engine is removed and stripped down, you may as well just replace the parts.

If Item 1 is correct then rectifying the root cause is also very expensive, but as all the 'respected' experts say its nothing to worry about, a lot/most do that, I am trying to minimise the symptom.

[kiwicar]

Hi
I referre back to my earlier post,
1/ I would be certain what the problem is before you try to fix it
2/ I would make sure anything you do is within standard specifications for the engine.
I would also add that It would be a very good idea to be sure you understand how somthing works before you change it's operating peramiters drastically.
A hydraulic tappet relys on the fact that the oil has a certain viscosity for it to operate properly, that viscosity along with the preload dictates the operating "height" of the lifter throughout the rev range and as Perry and I have already said the lifter will Pump up giving excess lift above certain revs so be carefull if you decide to change things that you won't have unforseen consiquences (ie piston/valve collision).
I really think your first action should be to find out what the problem really is, not just try to "fix" the easiest "possible" problem. Ask yourself how are you certain that it is not exhaust gasket, get an engine stethascope and see where the noise is truely comming from, is it the valley or the bore area or from the crank, you can check this without any disassembly and that way you will be on your way to finding out the problem without any cost. The 5 litre rover is along way from the original engine design, however it was designed to be assembled to a set of peramiters, check them as far as you can and return any to specification. Take the sump off (with the engine in situe) and shine a torch up into the bores, look for signs of skirt to bore contact, stick a feeler gauge between the bores and the pistons and find out what the clearance is, is it to spec, likewise check the clearances between the rods on the common big ends, all have specs and tolerances all can be checked without any major dissasembly and without replacing anything.
Sorry to go on but you seem to be going about "fixing" thinga at random and guessing at solutions without actually answering simple questions for yourself.
Best regards
Mike

[wokingwedger]

Hi
I referre back to my earlier post,
1/ I would be certain what the problem is before you try to fix it
2/ I would make sure anything you do is within standard specifications for the engine.
I would also add that It would be a very good idea to be sure you understand how somthing works before you change it's operating peramiters drastically.
A hydraulic tappet relys on the fact that the oil has a certain viscosity for it to operate properly, that viscosity along with the preload dictates the operating "height" of the lifter throughout the rev range and as Perry and I have already said the lifter will Pump up giving excess lift above certain revs so be carefull if you decide to change things that you won't have unforseen consiquences (ie piston/valve collision).
I really think your first action should be to find out what the problem really is, not just try to "fix" the easiest "possible" problem. Ask yourself how are you certain that it is not exhaust gasket, get an engine stethascope and see where the noise is truely comming from, is it the valley or the bore area or from the crank, you can check this without any disassembly and that way you will be on your way to finding out the problem without any cost. The 5 litre rover is along way from the original engine design, however it was designed to be assembled to a set of peramiters, check them as far as you can and return any to specification. Take the sump off (with the engine in situe) and shine a torch up into the bores, look for signs of skirt to bore contact, stick a feeler gauge between the bores and the pistons and find out what the clearance is, is it to spec, likewise check the clearances between the rods on the common big ends, all have specs and tolerances all can be checked without any major dissasembly and without replacing anything.
Sorry to go on but you seem to be going about "fixing" thinga at random and guessing at solutions without actually answering simple questions for yourself.
Best regards
Mike

Mike, I have a stethascope (this is why I bought it) and brilliant though it is at magnifying sound, it is still not easy to pin point the noise source.

I do believe the 3 TVR experts would have diagnosed a blowing manifold and I am sure if just listening was sufficient there opinons are better than mine.

Removing the sump may be next on the agenda, but I was trying easy to access items first (I have no pit or ramp).

I beleive that many RV8s are assembled and running fine, without any consideration to pre load at all, so my thinking was lets try a little more preload, as at least I know the starting point of mine. I did measure amount of available travel in the lifter and check that valves dont contact pistons (by rotating by hand).

It hasnt made any difference so I shall revert back to 50 thou (or try 20)

I would value your comment on what has been posted on Pistonheads in the thread started by TVR Beaver (Griff forum) entitled 'Strange Top end Rattle' 10th July this year. There is a sound recording on there (not mine but exactly the same)