20 replies to this topic

[1293gt]

Hello all,

I have an issue with my 1275 A+ engine where it's nice and quiet when cold but upon reaching temp the top end gets really quite noisy.

I have checked the tappet clearance (twice) and they are fine across the board. The motor is fitted with roller rockers which I have set to 15 thou cold.

Using a piece of wood between my ear and the engine I can tell that the noise is not coming from the engine block and is definitely originating from the rockers, seemingly on the left hand side (cylinder number 4).

My next port of call will be to replace the roller rockers with standard items set to 12 thou cold but I wondered if anyone had ever experienced anything like this before?

Thanks in advance.

Edited by 1293gt, 20 July 2022 - 07:51 AM.

[nicklouse]

Why have you set the clearance to 15?
what ratio or the rockers?

what cam?

What rocker cover?

[red81]

I think I had the same thing with my MG 1500, noise from the top and i checked tappets 3 times before one day the dizzy slipped its clamp and destroyed itself. Just a thought check your timing and clamp tight.

[weef]

It would be handy to pinpoint the problem rocker, if that is what it is.

You can try this method to identify the noisy rocker/rockers.

Start the engine and allow to warm up and the noise appears. Now remove the rocker cover and start the engine, be prepared for some oil splash. With a thin feeler blade, say  5 thou, insert it between the rocker and the valve stem. Move along the rockers and when the noise changes you will have located the offending rocker/rockers. 

If you think it is number four cylinder then start at that end.

This method is a bit messy with oil splash but you can put rags down to save too much mess, it only takes a short time to do this and will ruin the feeler blade. 

Once you find the source of the noise you can investigate the problem and repair from there.

[1293gt]

Thanks very much for the replies people, I shall try the dizzy and the feeler blade.

[1293gt]

Why have you set the clearance to 15?
what ratio or the rockers?

what cam?

What rocker cover?

1. Because a previous post on this forum said so

2. 1.5

3. 276

4. Minispares item specifically for high lift roller rockers.

[Designer]

The only experience I have had of noisy Tappets was recently I checked double checked and checked again the clearances and all was correct but still had one noisy Tappet. I removed the rocker assembly and I discovered that one of the rockers had been worn away by the valve stem to a depth of about 0.5mm. I was getting the correct clearance across the rest of the rocker in relation to the valve stem as the feeler gauge was wider than the stem but the gap between it and the rocker was about 0.5mm greater. Replaced rocker now all quiet.

Edited by Designer, 20 July 2022 - 05:42 PM.

[weef]

When the OHV / pushrod were the norm a popular tool to have in the toolbox was the SPQR Click Adjust. With this tool the locknut was slackened and the screwdriver was used to close the gap between the rocker and the valve stem, then the screwdriver was turned back the desired amount of "clicks" to set the gap and the locknut was nipped up. This type of tool eliminated the problem of worm rocker faces and wide feeler blades.

Probably SPQR are well gone and a distant memory for some but I think the Gunson G4094 is the modern day equivolent.

[nicklouse]

 

Why have you set the clearance to 15?
what ratio or the rockers?

what cam?

What rocker cover?

1. Because a previous post on this forum said so

2. 1.5

3. 276

4. Minispares item specifically for high lift roller rockers.

 

Should be 16 tho. Check the shaft for wear.

[1293gt]

 

 

Why have you set the clearance to 15?
what ratio or the rockers?

what cam?

What rocker cover?

1. Because a previous post on this forum said so

2. 1.5

3. 276

4. Minispares item specifically for high lift roller rockers.

 

Should be 16 tho. Check the shaft for wear.

 

Thanks very much.

Edited by 1293gt, 20 July 2022 - 09:01 PM.

[MiniMadRacer]

I agree with Nick and Weef...one other thing I often check is to slacken the rocker off completely so it is not touching the valve and is free from any spring pressure.. and try to twist it on the shaft.. ie twist the back of the rocker towards 9 oclock and the front towards 3 oclock... and see if it has any perceivable movement..if it has the needle roller on that rocker is prob foo barred...

 

By the way .. needle rollers on a rocker shaft is not a good idea and due to the very short oscillation does tend to wear needle rollers on one part of the circumference only...( I could bore you with why...)... the rocker does not roll through 360 degs

[Earwax]

The above info is good advice - in terms of doing easy, non invasive checks, here are some more ideas.

 

It is worth throwing some new quality oil at it -  Sticky lifters love new oil.. I have seen oil in small amounts tipped directly down the pushrod bore holes then rocker cover back on and normal refill of oil  to test - get the rpm up between 2000 and 3000 to help the lifters move ( ie don't just let it warm at tickover)

 

Just to be thorough, is it an oil pump thing, or lubrication at the top - # 4 being further away from oil feed? - or a pushrod rubbing and or pushrod and ball problem.

 

Without removing the head, i would turn it over for a short time and then remove rocker cover and look for oil - if top looks wet but not flooded and oil pressure gauge isn't doing anything strange then good o. While under there back off adjusters and remove to inspect balls and thread for wear cracks ( i have had a thread going brittle and coming off creating a zone of extra movement... I was surprised as the alloy rocker post threads were fine)  - I would be tempted to move the 7 and 8 adjusters to the other end to see if the noise moves. Using a torch you may be able to see /feel the pushrod bore and or cup condition - if noise still occurs it could be time to pull the rockers and check shaft etc as advised above

[1293gt]

Excellent stuff!

Thanks very much everyone, I shall let you know my findings.

Thanks again.

[Lplus]

When the OHV / pushrod were the norm a popular tool to have in the toolbox was the SPQR Click Adjust. With this tool the locknut was slackened and the screwdriver was used to close the gap between the rocker and the valve stem, then the screwdriver was turned back the desired amount of "clicks" to set the gap and the locknut was nipped up. This type of tool eliminated the problem of worm rocker faces and wide feeler blades.

Probably SPQR are well gone and a distant memory for some but I think the Gunson G4094 is the modern day equivolent.

I still have one of those, but find cut down feeler guages much better for ensuring the clearance is measured on the worn part of the rocker face.

[weef]

The object of this tool was to snug the worn part of the rocker to the valve stem thus eliminating any error with using even a cut down feeler blade.