Strange top end rattle?

[Simon says]

spend said:

TVR Beaver said:

looking good there... does it rattle on over-run ....

Just getting back to Chatter.... Chris52 did his cam and fitter genuine Land-Rover ones... and his is a quiet as a mouse... Just goes to show... But he did also machine his pedastals to get a bit more pre-load... I may try this over winter

Was suggested last night (in the pub).. that synthetic oil can glaze bores... and then you can get piston slap on the 500's due to the shorter skirt?....
But in my mind it's a hard metal noise... I sticking with the lifters I think.
.
Only problem is.. to get new lifters will mean another new cam as I'm sure putting new lifters onto a bedded cam will be a no-no..

500's don't have a shorter skirt? they are just 4.2 pistons with a little relief for clearance around the bottom bits, just like some of the block needs a bit of grinding away. It's nothing at all really in the scheme of things IYSWIM.

The tolerances of lifters and bores has to be a big concern I would say. The actual tolerance of the manufacturing OD of lifters, how big the oil band (the wasted bit in the middle) so how much actual bearing surface they have left must also vary from brand - brand. Neither overlooking wear on the block lifter bores or whether they were perfectly aligned to start with, as well as the old chestnut of ham-fisters knocking out damaged / mushroomed lifters upwards? There is also the odd predicament of all bearings being fed from the O/S gallery and the N/S gallery only feeding the N/S lifters so I don't expect you will get the equal pressure you expect ~ and your pressure gauge is just a spot reading after the pump that is ALL (the fact your kitchen tap works fine doesn't mean the cloakroom in the loft tap will flow the same if you follow the analogy). st load simpler to check bores & fit solids IMHO, there seems to be a lot of assumptions about pressure & hydraulic lifters that never quite rings true to me?

Have not studied the oiling on the RV8 but after reading this feel that consistent pressure across the lifters is not on the cards then great Dave did you receive my last reply?

[spend]

Simon says said:

Have not studied the oiling on the RV8 but after reading this feel that consistent pressure across the lifters is not on the cards then great Dave did you receive my last reply?

Yes, I think that may be a crucial point in that some lifters need continual pressure others stay pressurized - ie how quickly they pump up / bleed down? So when it comes down to it some brands / batches may work

got last 1 at 16:51 yesterday?

[TVR Beaver]

spend said:

Does make me wonder if some of this could be the weird dislike your motor took to Robs cam?

Okay.. get you now.. and bleed down on differant makes etc.. the original TVR ones were fine.. .but the ones I had with the Stealth did it.. and the Power ones I have now do it a tad more...

I'm not sure how it could tie in with the cam bit?.. it ran the 435 before great.. and the 885 I have in now is very good (just needs re-maping at some point as it's running the Stealth map so very rich)... how could the two be linked in any way?..

[spend]

TVR Beaver said:

I'm not sure how it could tie in with the cam bit?.. it ran the 435 before great.. and the 885 I have in now is very good (just needs re-maping at some point as it's running the Stealth map so very rich)... how could the two be linked in any way?..

These cams are cunningly fiendish devices that make use of opening valves very slightly to start flow early as well as taking advantage of aggressively quick openings maximising the area under the timing/lift curve. The greater you try & leverage these features I would imagine the more you are dependant upon the lifters making sure all 8 cylinders get the same treatment. ISTR all your problems were under light load at which time overall pressure is generally lower and maybe the oil is bleeding out too fast / pissing down the bores instead of in the lifter and some are collapsing, hence less lift. Could be like a cam with completely different timing / duration on each pot I guess?

In fairness once the lifters are initially filled with oil they are supposed to stay there & in an operational state. I just personally have my reservations that they don't work as well as they are supposed to, and that many of the suppositions folks hold that everywhere inside the engine sees the pressure you see on the gauge is just plain flawed. Always seems to me that to avoid the headaches and have the extra power you get with a solid cam/lifters for the small extra cost of having to check the clearances occasionally is an obvious trade-off to make?

[Alexdaredevilz]

spend said:

In fairness once the lifters are initially filled with oil they are supposed to stay there & in an operational state. I just personally have my reservations that they don't work as well as they are supposed to, and that many of the suppositions folks hold that everywhere inside the engine sees the pressure you see on the gauge is just plain flawed. Always seems to me that to avoid the headaches and have the extra power you get with a solid cam/lifters for the small extra cost of having to check the clearances occasionally is an obvious trade-off to make?

I agree with you Spend...... for once

[TVR Beaver]

I had issues up to about 3 1/2 to 4 K where it was lower torque than it should be... but get your point... you could be right but guess we'll never know... it's long gone...

solids do sound the best option if you don't mind a bit of setting once a year...

food for thought....

[WokingWedger]

I had a theory that it may be due to sticking/ slugish oil pressure relief valve, that had opened at high revs but is a bit slow in shutting so that when the revs dropped oil was still being diverted and not feeding the lifters.

I took my relief valve out at the weekend and it certainly wasnt stuck and the spring measured 60 mm as it should.

As an experiment I added a 0.9 mm washer behind the spring, but it made no difference except the pressure at hot idle is higher ( now 30 PSI according to gauge). Why at idle ? Surely it should only effect pressure at revs ?

[spend]

I don't think of it like the valve just pops open & stays open at high observed pressure, but that it can continually regulate (slight flutter of seat only) the 'sinusoidal ?' pressure peaks of the individual paddles at each pump action IYSWIM.

Things can often look quite different from the big picture when you break them down in detail I'm a strong supporter of using screw in adjusters to set the oil pressure relief valve tension.

[TVR Beaver]

You hear of people using double springs etc.. so I'm supprised 0.9mm made any diferance at all...
Are you tempted to up it at all and try again?

[WokingWedger]

spend said:

I don't think of it like the valve just pops open & stays open at high observed pressure, but that it can continually regulate (slight flutter of seat only) the 'sinusoidal ?' pressure peaks of the individual paddles at each pump action IYSWIM.

I am not sure I understand that.

Sureley the spring needs a certian force to compress it, and until sufficient pressure exists to do this it will remain shut. When the pressure reaches this level the valve will open and when it is reduced the valve will close.

Any pulses from the pump would be at very high frequency 14 teeth at 1000 rpm =14000 pulse per minute = 233 per sec. I cant imagine the valve reponding to that.

[spend]

Maybe try thinking of it the other way round? The spring creates a force to close the plunger / tadpole on the seat, but that has a layer of oil under pressure keeping it partially open? Just because the frequency of the pump is high doesn't mean the force is ignored the fluid dynamics & the damping effect of the spring just smooth it out. Hence my comment/reference to thinking of the mechanism as a regulator as much as a relief valve IYSWIM?

[WokingWedger]

Hmmmm

So at say even 1000 rpm a certain percentage of oil was bypassing the engine by being recirculated( I assume thats what happens.

Actually thinking about it adding the washer should do nothing at all as the spring rate remains constant. It will still require the same force to compress the spring by the same ammount as its a linear spring.

Only if the spring had lost its 'set' would the washer be of benefit( to make up the distance so the spring is in contact)

I think I may just remove it.

I am not sure why I noticed an increase in pressure at idle though !

[TVR Beaver]

By putting the washer in, you will have compressed the spring more... so have indeed increased the force now needed to move it (but only a little)....
.
Are we sure it's more pressure we need at this RPM on overrun... I'd like to get mine on a mechanical gauge and reduce the pressure as much as I can and see what that does.. .I still think the caps may be floating on pressure in the system on over run... although with mine its temperature related (not a sound when cold)... so may be does point more to blead down as the oil gets thinner or things expand?
.


Tell you what.. It was 24 deg the other day and it was quite noisey... just been out in it today at 14 deg and its much less?... Suppose that could point to two things... Oil temp lower (so would an oil cooler help)... although sat on my drive reving it would have increased the temp... but then the fan's kick in... so could this cool it down again??...

Or Air temp in the fuel / air on top of the piston... could 10 deg in out side air temp make the small ends expand / contract more..... It's certainly quieter today???

What ever it is it's very marginal if a 10 deg fluctuation makes a differance...

Edited by TVR Beaver on Monday 8th August 11:36

[WokingWedger]

TVR Beaver said:

By putting the washer in, you will have compressed the spring more... so have indeed increased the force now needed to move it (but only a little)....
.
Are we sure it's more pressure we need at this RPM on overrun... I'd like to get mine on a mechanical gauge and reduce the pressure as much as I can and see what that does.. .I still think the caps may be floating on pressure in the system on over run... although with mine its temperature related (not a sound when cold)... so may be does point more to blead down as the oil gets thinner or things expand?
.


Tell you what.. It was 24 deg the other day and it was quite noisey... just been out in it today at 14 deg and its much less?... Suppose that could point to two things... Oil temp lower (so would an oil cooler help)... although sat on my drive reving it would have increased the temp... but then the fan's kick in... so could this cool it down again??...

Or Air temp in the fuel / air on top of the piston... could 10 deg in out side air temp make the small ends expand / contract more..... It's certainly quieter today???

What ever it is it's very marginal if a 10 deg fluctuation makes a differance...

Edited by TVR Beaver on Monday 8th August 11:36

If Spend is right then even at tickover the force is sufficient to overcome the preload without the washer, perhaps the extra 0.9 mm is sufficient that tickover now dosnt quite lift it, hence the higher pressure. Once lifted, say at 3000 rpm the washer should make no difference. And that is what I am seeing.

I also noticed the noise the other day with a cold engine in a warm ambient.

Edited by WokingWedger on Monday 8th August 12:28

[TVR Beaver]

On a cold engine but high ambient... ???

ambient does make a big differance... and I've noticed how it's fueled in the past has changed it also (so guess that tie in a bit?)

So would going to 2mm hold it down further up the RPM band?... may be worth a try... are we just seeing ageing oil pump springs loosing their presure?

Wonder if Peter (haircutmike) actualy measured the small end / holes in the piston?... The pin to piston should be a tight press fit but this is where Rob says it comes from... How can something with a press fit become loose enough to rattle?... wonder how much they expand with temperature.... this area may be more prone to being affected by air / fueling temps??

[haircutmike]

Didn't actually measure, but there was no play in this instance.

[WokingWedger]

TVR Beaver said:

are we just seeing ageing oil pump springs loosing their presure?

wonder how much they expand with temperature.... this area may be more prone to being affected by air / fueling temps??

I cant see it being the spring aging as mine was the right length (maybe even 1 -2 mm over) and the oil presure was always normal even before the noise started.

I cant imagine 14 to 24 deg ambient having any effect on temperatures deep inside the engine, unless you are suggesting the temp may rise due to fueling changes which in turn is caused by ambient temperature changes.

Do you think if there is not enough preload there is a chance the pushrod cup could make contact with the spring clip (sort of circlip)

[carsy]

Interesting thread. Could be the best theory yet.

[chris52]

As John has already mentioned mine does not make this noise, but this is an interesting thread so I will try throw some sugestions into the pot.
From what I have heard on Johns car this noise only apears on over-run. I would have thought that if there is any play in the small end or anywhere else you would here it at other times especially under load not just over-run.
So what is different on over-run? the only thing I can think of is that the throttle is closed causing a larger vacuum in the plenum chamber and less air(lower compression) in the cylinders. So the vacuum advance on the dissy is at full pelt due to the large vacuum in the plenum also the car will be fuelling to allow Idle there will be some air in the plenum aswell, could this be some kind of detonation/pinking happening in the cyliders that is giving this noise?

Chris

[v8 racing]

So just curious, if it was down to oil pressure? why does this not happen on all of the pre serps that have a much lower oil pressure than the serps? and why does it not do it on idle where oil pressure would be at its lowest?, as for pre load on the tappets, why would a certain rpm (very small rpm band) cause this issue?? so the tappets are fine at 1600rpm, they all collapse at 1400rpm and are then fine again by tickover?