Noise from the engine area

[alan.barker]

Hi Hiro,
The only way is like i said you remove gaskets to check.
Why not and cheaper than diving into head problems.
Your choice.
Alan

[512BB]

When I need them Hiro, I buy my engine parts from QED, here in the UK. Look up QED Motorsport. Your profile does not say where you are in the world, but I am guessing Japan.

My memory is clearer now about the ticking on the engine I was talking about. The crack in the manifold was where the Y piece came down to the V, not at the flange. You could not feel any exhaust being emitted and nor was there any tell tale soot, but because the head had just been overhauled, the ticking could not have been coming from there, and on removing the manifold, a crack was observed.

In your case, you say that the engine has not been rebuilt recently, so basically, the ticking could be coming from several places. But as Monsieur Barker says, the cheapest possible fix could just be that you replace the manifold gaskets first, and that could be it.

I have another car, where the motor ticks away from the top end quite happily, 90k odd miles. It obviously needs some attention, and I will get round to it as time permits, but it still runs fine.

Keep us posted of your progress and what you find.

Leslie

[alan.barker]

Merci beaucoup Lesie,
It seems a cheap thing to do "avant de casser le tir lire" ( piggy bank for uk).
I have also had a "Y" piece in stainless which had never been welded correctly from new.
Many stainless exhaust manifolds don't have the flanges inline and need adjusting.
Good luck
Alan

[LCRJ]

Hello Alan and Leslie.

Thank you for your time.
I would try to remove the exhaust manifold next weekend.
and let you know if I find anything.

I would appreciate any advice from your experience.

Kind regards,
Hiro

[512BB]

My only advice re exhaust removal is to separate the back box, intermediate pipe and Y piece as a unit, whilst the manifolds are still attached to the engine, much easier that way.

Then you will have to raise slightly and chock the engine on the LHS, and remove the engine mount and dynamo. The manifold is then easily extracted. If the exhaust studs have been in the head for years, and look a bit munchy, I replace them as a matter of course. With the correct item, obviously.

Lets hope you find a small split somewhere, or a gasket leak, as that will be a much easier fix than any head work.

A cautionary tale. Years ago, I was meeting a friend up at Silverstone to go to the Coys auction. We were both in Sprints, naturally. On arrival, he complained that his engine had just started to make a horrible noise, so switched off. On examination in the car park, it appeared that one bucket had disintegrated whilst running...............horrible mess.

The cause was never established, but Mick Miller sorted it out after the head was sent to him. Thats how long ago it was.

Quote: 'I have also had a "Y" piece in stainless which had never been welded correctly from new.
Many stainless exhaust manifolds don't have the flanges inline and need adjusting.

You can say that again Alan. There is always some filing to do on a manifold, be it smoothing the pipes inside the flanges so the gases flow better, or just cleaning up crap welding.

Leslie

[alan.barker]

If you remove exhaust studs please remember when refitting to put some "copperslip" on the threads going into the head. Plus brass nuts and new spring washers.
Check before refitting that flanges are all nice and inline with a straight edge.
Sorry if it seems i am telling you how to "suck eggs".
have fun
Alan

[alanr]

Having listend to the video's a few times I will very surprised if that tapping/clicking noise is an exhaust manifold leak.

The noise to my ear is definitely coming from the valve train, i.e.cam follower/sleeve/spring/tappet shim etc.
Have you checked the valve clearances recently.?..It might give you a further clue or point to which valve or valve area it is coming from and then you can maybe make a judgement call on how deep in to the top end head off strip you want to go, or not go.
Personally if it were my car I would just leave it for a while and see if the noise gets worse and noiser as time goes by which then will give more idea on which way to proceed.

Just my thoughts,

Alan

[rgh0]

Hi Hiro
Replacing the exhaust gaskets and bolting the manifold up correctly is good advice and a good and relatively easy first step.

The noise I hear does not sound particularly bad or different from many Twincams I have listened to over the years with worn followers and sleeves or with a small exhaust leak but hard over a phone recording and YouTube recording to replicate what you hear in real life

After doing the manifold if the problem is not fixed the next step is to remove the cams and pull the followers and check their dimensions. Unfortunately not really possible to check the sleeves without pulling the head and removing the valves and springs.

The chance of a follower fracturing is small unless you have extreme wear in the follower or sleeve in which case rocking the follower in the sleeve will reveal significant movement.

cheers
Rohan

[LCRJ]

Hi all,
Progress report and what I find!
The engine has been removed and checked in order to resolve the noise.
The problem still seems to be the cam follower clearance. #3 on the exhaust side seems to be large.
So my question is.

1, What is the correct clearance? IN/EX
2, What are the sizes of the original standard cam followers?
Diameter OD/ID, Total length, Thickness at shim face, Weight

I will keep post to you.
Hiro

[rgh0]

Standard Valve Clearances
In 0.005 to 0.007 inch
Ex 0.009 to 0.011 inch

Standard Follower
Sleeve Bore - 1.3750 to 1. 3756 inch
Follower O/D - 1.3742 to 1.3745 inch
The follower fit in the bore should be a close sliding fit with no detectable rocking of the follower in the bore

Length - 0.880 inch ( as measured not in manual)
Pad thickness 0.218 inch (as measured not in manual)

cheers
Rohan

[LCRJ]

Hi Rohan,
Thank you for replying with information at all times.
It is very helpful.
Your post on Lotus Twincam Engine Modifications is also very helpful, I have one question and I will post it there. Can you tell us from your experience.
Best regards, Hiro

[rjaxe]

I had a similar tapping sound experience a few years back. The noise was cyclic, repeating in intensity over a 20/30 second period. After much fiddling with valve shims etc to no avail I found that the cam bucket bores had previously been honed out to 0.001" oversize but only three oversize buckets were fitted. I replaced the incorrect standard one with an 0.001 oversize one from QED, I think, problem solved.
When I detail measured the incorrect bucket it was oval only by a few tenths but perhaps this could explain the cyclic nature of the noise. As the bucket rotates in the bore it could find a position where the max clearance and highest load coincided and creating a loader noise- perhaps?
None the less the clearance in this area of the engine build is quite critical.

[rgh0]

Yes the followers are designed to rotate slowly in the bore due to slightly offset cam loads from their centre line to ensure even wear on the cam and follower. An oval follower would certainly make more tapping noise when the smaller axis was sidways to the engine and in line with how the cam wipes across it pushing down first on one side and then on the other causing the follower to rock.

I have noticed similar cyclic tapping in some twin cams and never really thought about why but your explaination makes sense to me.

cheers
Rohan