Tappit Clatter....

[pfgiz]

not overly the correct place for this as the car in question is my Spitfire but I need to tap into the wealth of knowledge regarding general engines that resides on this forum... So here we go.....

I have a tappit clatter, it's not there for the first 20 or so seconds but once it starts it doesn't go away. I've recently had to swap engines, long story the moral of which is when changing a gearbox make sure the flywheel is held on by the correct sized bolts. Since then I've had a clatter, I've reset the gaps many times but don't really seem to be making any difference... Either I have a set of feelies that are out or the engine may have been fitted with a different cam at sometime and this has put the gaps out...
My question is this, does the 'quiet for 20 seconds and then noisy' mean the gaps are slightly too big or small, in other words should I set the gaps a size up or down? I'd do a trial and error but don't want to damage the engine if I get it wrong.

Many thanks for any help in advance.....

[bmcecosse]

Well - you are not going to do any damage - but are you SURE the noise is from the valve train - and not piston slap or big-end bearing knock ? If you 'lean' on each rocker in turn using a length of timber - can you isolate the noise down to one rocker assembly ?

[williamraff]

Hi, I don't mean to hijack the post but can you explain the leaning on the rocker witha piece of wod technique, I have not heard of that one before and would like to try it on mine.
Thanks,Will.

[bmcecosse]

Just to kind of 'feel' the movement and to take up any slack in the valve train - if the noise disappears when gently 'leaning ' on a particular rocker - you have narrowed down the problem!

[mike.perry]

I have got a noisy tappet but your solution is a bit difficult on a side valve

[bmcecosse]

Ahh - now you genuinely HAVE 'tappets' - the OHV engine of course don't have any tappets! It does have cam followers - and push rods - and rockers instead.

[williamraff]

Gotcha!

[pfgiz]

Thanks for all the comments, I've been buzy fitting new suspention to the Spit so have lived with the clatter but now have an update...

As I'd never used the 'bit of timber' technique, although I've seen my Dad use it on more that one occation, I went for the 'slightly larger, slightly smaller gap' trial and error technique... Well the manual says it should be 10Thou, so I set them all to 11 at which point the engine wouldn't turn. 9 was less noisy and 8 has been less still, 7 tomorrow if I get enough time to do it before needing to move the car. This is to ensure that the engine is cold when setting the gaps, as this is the way the manual advises, but how cold should cold be? Stone cold or just not burning hot???

Just to recap the timber technique, I take a piece of wood and lean it hard against the rocker, which end, adjuster or valve? and see if it amplifies the rattle, or removes it? Should have taken more notice of Dad when he was bradishing a length of broom handle or a screw driver at different parts of his engines......

[bmcecosse]

I don't understand you saying the 'engine wouldn't turn' at 11 thou gap........ Why not ?? The official BMC figure is 12 thou inlet and exhaust - but with modern hotter burning unleaded fuel I urge all to set the exhausts to 15 thou, which is in fact the official figure given by MG/Rover for the later A series cars anyway. Don't run the inlets with any less than 12 thou. The temperature actually doesn't matter all that much - because pretty much everything expands/contracts at similar rates. The push rods are a bit longer than anything else (valve stems/cylinder head etc) and so they will expand slightly more than the other bits when hot - but then the exhaust valve stems get much MUCH hotter - and so they expand more because of this - hence the need for larger gap to ensure the valve always has clearance to get down on it's seat. If it doesn't seat properly - the seat and/or valve will be burned away in minutes.

[pfgiz]

What I mean is the starter was very lumpy and didn't want to turn the engine over, like the whole thing was preasureised an no valves were opening.

I have mentioned that this is for the Spitfire, just tapping the 'general engine' knowledge on this forum as it greatly out strips any other I know of, hence why my quoted sizes are smaller than those on an A series.

Here's the funny one... Set the gaps to 8, ran the engine until the rattle started and, after stopping the engine but while still warm, check the gaps, they were nearer 11..... Something is not expanding uniformly.......

[MarkyB]

"the starter was very lumpy and didn't want to turn the engine over,"
This sounds a lot like the timing is too far advanced.
This could also cause a rattle, try retarding it a bit.

[bmcecosse]

Ahh sorry - didn't realise Spitty engine. However - tiny adjustments like that to valve gaps are not going to make ANY difference - and certainly won't affect 'engine turning over'. The advice to not run with tight valve gaps still stands.

[pfgiz]

Thanks for everything, setting them to 7Thou this morning, when very cold, removed the clatter. Interestingly when warmed up the gaps are 10Thou, as recommended for that engine....
The timing has been set using a strobe and the engine runs very well normally just with an annoying clatter. Just didn't want to turn over at 11Thou, as if the valves were not opening and the pressure was on all of the cylinders together.
Makes me start to wonder if my feeler gauges are accurate, guess I'll need to check them against my micrometer...

Cheers again for all your help...

[Alec]

Hello Peter,

a few points, worn rocker tips will give a wider gap than the feeler gauge you are using. Worn rocker bearings will make the valve train noisy and finally are you getting any oil to all of the rockers?

Alec

[bmcecosse]

Seriously - 4 thou difference in the gap won't make the engine 'not turn over'!

[pfgiz]

Seriously - 4 thou difference in the gap won't make the engine 'not turn over'!

Which leads me to disbelieve my feeler gauges... I hear what your saying....

Also, I've checked the flow of oil and it's getting to each rocker...