Engine rattle

[k. rogers]

Having now more or less sorted the slow-running problem on the Javelin I (bravely or stupidly) took it on a 40 mile round trip to a 'do' for drive it day. This was the first longish trip I have done so I was a bit apprehensive. All was well to begin with until the engine got a lot warmer, then I noticed quite a harsh rattle developing on a light throttle which wasn't there under load or on the overrun. I would say this rattle got worse as the journey went on. There was no significant loss of oil pressure compared to previous short runs though it isn't as high as I would like (50lbs cold and 40lbs when hot) though I am assured by those more knowledgable than I this is quite acceptable!
Does this sound like main bearings or could it be play in the camshaft. This engine has only done about 5000 miles since a rebuild back in the eighties before being laid up 15 years ago. I've run the engine without the fan belt to eliminate problems with the fan or pump but the noise is still there.
Any comments will be welcome, I just hope it isn't too serious.

[Forumadmin]

The rattle may be pinking or pinging caused by an over advanced ignition. Dizzie may have turned or a spring come off a dizzie weight. Or it could be something coming loose or touching ..

[k. rogers]

Thanks Keith, I will double check the timing tomorrow evening and other aspects of the distributor.

[k. rogers]

Checked the ignition timing and have retarded a little to just after TDC (about 1/4 inch on the flywheel). Checked nothing loose. Checked distributor weights and springs - all ok. Balanced carbs with synchronometer kindly lent by David Morris, so now idling smoother, though mixture is still weak on nearside carb (air mixture screw all the way in!). Road tested car and though performance has improved, the rattle is still there when slightly depressing throttle though not quite as loud. This may also be due to the cam end play screw which seemed to be right up against the end of the cam so I released it slightly to give a little clearance. I have also taken each plug lead off in turn to eliminate problems such as small ends, etc but it didn't make any difference to the sound. At this stage I feel it may be cam knock perhaps due to worn bearing surfaces - Is there a way of determining this without a strip down?

[David Morris]

Hi Ken,

Glad you received the Synchronometer alright and that it helped with the slow running. Thinking about your 'rattle' my first stop would be the camshaft end float, but you mentioned that you have adjusted the camshaft peg. I expect you know that you must only move this with the engine stationary, and the correct adjustment is to do it up tight and back-off by one flat.

I had what may be a similar rattle a couple of years ago. I just could not pin it down, but it showed itself soon enough! The rattle became a serious loss of power and what had sounded like a 'rattle' was actually an exhaust valve leaking and eventually burning out. We had to limp home and ended up changing the off-side head to cure the problem.

I suggest you might want to check the compressions in the cylinders? Around 120 to 140psi is healthy. You could also check the valve clearances. We suspect that wear in the camshaft journals and the shaft bearing surfaces allows the camshaft to 'flex' and twist as it rotates and give false readings for the clearances. I may well get told off for this, but many old hands set the push rods so that they can just rotate with the engine cold, rather than the factory settings, to minimise noise. The theory is that as the engine heats, the aluminium crankcase expands and if the push rods are set as per the book when cold, they will be well out with the engine hot.

I hope you find the cause.

All the best,

David

[k. rogers]

Thanks David, I have already set the cam end float peg as suggested. I will check the valve clearances again, just in case one of the valves is tight, in view of your experience! Would this type of fault not present itself as a type of misfire, though?

[Forumadmin]

Valve clearances are quite easy to set up wrongly and tapping noises will come well before a misfire. There are two main methods for setting up clearances but you can get easily confused with either. The important thing is to get the valve to be adjusted on the heel or base circle of the cam.

[Drummond Black]

Ken, the experts have covered the all the usual areas that are checked when investigating Jav / Jup engine rattles mainly stemming from the valve gear.
There are a few additional areas that I always investigate, which does require a bit of dismantling.
I take the rocker assemblies off to check the wear on the valve stems, each rocker stem area that bears on the valve, the wear on the rocker shaft / bushes and to check if any of the push rods are bent.
The maintenance manual explains how to remove the rocker assemblies. You MUST be very careful when working in this area, especially when touching or removing push rods that you do not pull the cam follower out of its location bore. If this happens you have the additional work of removing the tappet cover to replace them.

Areas to look at are :- If the rocker tip area is worn this can cause the rocker to move slightly away from the pedestal when the valve is depressed and BANG back against the pedistal when the valve is released. If there is severe wear on the rocker shaft a similar situation can result. If you suspect a bent push rod then it is easily checked by turning it between two ball recessed centres ( I have a jig that checks them ).

I build worn rocker tips up with Stellite 6 and grind and polish back to the correct contour. The shaft and bushes can be renovated by using rocker shafts that are 0.002 inch oversize and reaming out the bushes, pedistals and oil banjo to suit. Sounds complicated but have been doing this repair for nearly 10 years now. ( Just finished a set for Martin's engine )

Davids point on setting the valve clearances by just managing to rotate the push rod is the method I have used since the Seventies. Some rattles you just NEVER get rid off but the engine runs well.

[Forumadmin]

Another possibility is around the clutch area. A worn set of fingers or depressed ball can cause the clutch housing to hit the actuator or the actuator hit the clutch housing. This can happen either when depressed or off.

[k. rogers]

Drummond - thanks for this advice some of which I have done already, albeit with a bit of a calamity on the way! While setting the tappets a while ago I noticed there was still one making a noise and on closer examination found the rocker for that valve was repeatedly moving back and forth from its rest resulting in a noise akin to a loud tappet, as you have described. So I removed the rocker shaft and found the surface of the rocker in question to be quite uneven. I therefore ground the surface lightly to the correct contour and put it back together. However, what I didn't realise was that the pushrod for that valve had indeed pulled out of the seat of the cam follower and I must have had the pushrod pushed onto the casing instead resulting in a bent pushrod. As if that wasn't enough the bronze part of the cam follower promptly dropped out into the tappet chamber! I was not pleased. If only I was aware of the danger you so rightly warn of at that time! I stole a replacement pushrod off my dad's spare engine and all seems well again. Is it possible I may have done some damage in the process resulting in this rattle?
Keith - is there an easy way to check if this part may be causing the problem?

[k. rogers]

Further to my last post, I'm thinking more about this pushrod episode - at the time I couldn't understand why it was so easy for the pushrod seat to drop out yet seemingly difficult to get it back in, also once it was in it didn't seem to be as free moving as it should. Firstly, is it possible the follower was damaged in some way and secondly, are the followers removable via the tappet case so maybe I could examine things more closely?

[David Morris]

Hi Ken,

Following your recent post, yes the followers are removable via the tappet chest. However, Jowett's must have realised that their first version of solid tappets were tricky to get the push rod to locate easily. They altered the bronze cup end, to create more of a 'funnel', so that when you are trying to get the ball end of the push rod into the tappet, it is easier to get it in the right place.

I had hoped to attach a couple of photos that show the two types, but JowettTalk can only handle small photos and mine are too big. I used to be able to downsize them, but the software tool I used has been deleted. Never mind, I'll send them to you on a seperate e-mail. However, in both types the steel tappet body was left unaltered and as you can see, the wall of the tappet is quite thin. Maybe you have a burr on the edge of the steel tappet, causing the 'stiffness' that you mention?

If you need a replacement tappet, do let me know?

Another thought has occurred to me...have a look at the washers under the two nuts holding down the rocker pedestals to the heads. It is easy to fit washers here that are too large in diameter and they will foul the adjacent rocker arms, or at least affect the smooth action of the rocker arms.

Do hope you find the problem?

All the best,

David

[Forumadmin]

If using Windows, Paint will do the resizing job.

Lots of scope for misunderstanding in that last sentence .

It is best if you get under the car with a lift to check the clutch. If you still have the lower cover on then take it off and look to see if the operating lever is rattleable (new word that). If it does there could be wear on the finger tips or the ball is seating too far down into the gearbox. (note there are at least two different sizes of ball and you might have the wrong one for the housing).

If the rattle occurs when the pedal is depressed (with the engine turning) then it may be the clutch plate is worn and the operating lever is hitting the clutch cover or clutch plate springs. This can also occur if a non-standard (I think Mazda) clutch plate has been used as well. You should see some shiny bits if this is happening.

The operating lever may also be able to hit the clutch housing in the trapezoidal slot that it enters through , causing a rattle. Once again, wear is the cause.

[k. rogers]

There has been a further development! I have used David's and Drummond's advice and set all tappets to a nominal clearance in the hope that if the cam is indeed worn this might eliminate some of the noise if it is coming from there. No change in the noise. Following advice from Geoff Wills, tried removing the automatic advance pipe which goes to the carb and manually activated the choke on the nearside carb to compensate for the weak mixture in that carb in case it is a detonation problem - still no difference to the noise!

However, while at the front of the engine trying all the above I noticed a sharp, intermittent tap coming from the timing case on tickover which wasn't there before. Completely undid the cam end float peg this time (without engine running!) so there was no contact and the tap was still there. Is it possible that whatever is causing this noise is what is causing the rattle at higher revs? Any ideas what it might be? It doesn't sound like a worn chain.

[Forumadmin]

Loose (worn) timing chain or timing sprockets?

Or improbably loose sprocket wheel.

It might even be a broken link on the chain although I have never seen that on Jowett.