MGA MGA Engine Rattle

[MartinMGA]

Hi All,
Just trying to trace an annoying engine rattle. The car has been laid up for 18 months. Hopefully the attached youtube link works but the rattle, difficult to hear, happens at light to hard acceleration. Other than that the engine works fine and has done for a number of years.
I first looked at pre ignition so tried the timing at various points at 1000rpm from 2.5 - 10 degrees.
The fuel tank has 97 octane fuel in it and has run happily on it in the past
The timing advances to 20 degrees at 4000rpm, so I have ruled this out for the time being although I am aware that I put a new electronic distributor on before the car was laid up so may come back to it. The engine is a 1622cc with some mild tuning and has run perfectly well up untill now.
The rocker shaft clearances were all good.
The head gasket and clearances were good.
Compression 200-210 PSI on all cylinders when hot, 217-232 with oil squirted in the bores when hot.
Oil pressure is 60 PSI when running and 40 PSI when hot on tick over.
The car has had a rebuilt gearbox fitted and the rattle was there before and after.
I am in the process of stripping the engine down and have found.
The main bearings are good as is the oil pump.
The cylinder bores look good with no steps at the top.
Camshaft end float is .012" so will need adjusting. The camshaft is halfway out as I need to jack the engine up a touch to get it out the rest of the way but the half that I can see is OK.
My next job is to pull the pistons out and check the big ends, little ends (wrist pins) and the rings.

Does anyone know of anything else that I need check while the engine is in a thousand pieces?

Kind Regards, Martin

 

[bobhustead]

Timing chain?
Bob

 

[DrEntropy]

Martin, BEFORE you have the engine in pieces, have a look at the FAN. There are rubber grommets between the fan mounting holes and the sleeves the bolts go into, to thread into the water pump. If the grommets wear through a fairly frightening rattle on acceleration is a result. Worth a look.

 

[MartinMGA]

Martin, BEFORE you have the engine in pieces, have a look at the FAN. There are rubber grommets between the fan mounting holes and the sleeves the bolts go into, to thread into the water pump. If the grommets wear through a fairly frightening rattle on acceleration is a result. Worth a look.

Thanks for the response. Unfortunately, all is good in the pulley area.

 

[DaveA0524]

I'm not sure what I was hearing in the video. I had an annoying rattle/tinkle on my 59 1500 that turned out to be the bendix on the starter motor. Replaced the starter and all went away. Did you set the advance to 20 degrees at 4000 as a test? That seems quite retarded timing.

 

[MartinMGA]

I'm not sure what I was hearing in the video. I had an annoying rattle/tinkle on my 59 1500 that turned out to be the bendix on the starter motor. Replaced the starter and all went away. Did you set the advance to 20 degrees at 4000 as a test? That seems quite retarded timing.

Hi Dave, There is a higher pitched "tinkle/knock" on acceleration (10secs in on the video is most prevalent). I set the ignition timing using a strobe at 1000rpm at 2.5 degrees, 5 degrees and 10 degrees and had the same issue at all three settings. I also plotted a rough curve to get the 20 degrees although it's a new Alden distributor (I haven't ruled this out as the problem yet). I am committed to getting the pistons out at the weekend to rule them out. I did find some slight pitting on one of the tappets, so will check the cam out as well.
I did look at the starter bendix and can confirm that it returns OK, although I am not currently sure how slack/tight the spring should be, so I will do some more checking in this area.
Thanks for the comments! Regards., Martin

 

[DrEntropy]

Now that Dave mentions it, I recall the Bendix rattle. BMC set up a "fix" through the dealer network to install a "Wobbly Washer" at the spring, putting a bit of tension on it. I did that in '69 in my first MGB. Had forgotten all about that.

 

[MartinMGA]

Now that Dave mentions it, I recall the Bendix rattle. BMC set up a "fix" through the dealer network to install a "Wobbly Washer" at the spring, putting a bit of tension on it. I did that in '69 in my first MGB. Had forgotten all about that.

Thank you. Definitely on my list to check!

 

[Ed Foster]

Not trying to be a smart-a, but check your hub caps. I've known buddies to put a pebble behind the hubcap for a little fun.

 

[NutmegCT]

Martin - what's the latest? Any progress on eliminating the rattle?

One thought - the rattle occurs under acceleration. Rapid acceleration often causes the engine to "twist/rotate" a bit. Is there anything (frame, firewall, etc.) that's very near the engine, engine mounts, lines, etc. that might contact something else only during slight rotation of the engine?

Tom M.

 

[LarryK]

Tinkle/rattle on acceleration? Pinging?