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Heavy Engine "Rattle"


GHILA
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I have just put my Spitfire 1500 on the road since buying in November and restoring. I have notice a "Heavy Rattle" when the revs reach around 2500. Which is not nice to hear, I am from an engineering background and don't like knocking noises. From your extensive experience is there anything which immediately comes to mind. This does not seem to happen when standing still and lifting the revs. this is definitely an engine noise.

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"This does not seem to happen when standing still and lifting the revs"  but is "definitely an engine noise".

That does not compute, Captain.

Do you mean it only happens when the car is moving?   In which case this is transmission or suspension, not engine.

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15 minutes ago, JohnD said:

Do you mean it only happens when the car is moving?   In which case this is transmission or suspension, not engine.

Well, probably, but not absolutely. It is possible that it's an engine noise that only happens under load, so you get it when driving but not when revving gently at idle.

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has all the sounds of the the exhaust system is in close contact and when power is applied the tilt of the engine under torque gets the 

exhaust with a  small clearance to make contact somewhere along its route   it can be quite horrific

thats where i would look this could be a cheap noise rather than 1500 with the big ends shot 

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is it just revs or is it more pronounced under heavy throttle. Big end will knock (if worn) when you put your foot down under load but not when revved not in gear. I would first check the end float by trying to move the crank pulley forward and back, more than a couple of thou would indicate a worn engine and is easy and free to check. All of the above suggestions are also possibilities and much cheaper to fix!

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Thank you everyone for your replies but I believe that i have found the cause. I noticed that the stay bar securing the radiator was not securely fastened and after tightening up the nut/bolt. the noise disappeared. Result cost free fix.

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33 minutes ago, GHILA said:

Thank you everyone for your replies but I believe that i have found the cause. I noticed that the stay bar securing the radiator was not securely fastened and after tightening up the nut/bolt. the noise disappeared. Result cost free fix.

Good stuff, a great example of looking for the simple fix rather than over-thinking, well done :) 

....... Andy 

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On 11/06/2021 at 22:26, DanMi said:

I would first check the end float by trying to move the crank pulley forward and back, more than a couple of thou would indicate a worn engine

I gathered, that there was a always few thou of play intended, maybe around 4thou?. 

Also, a view that the outer limit of play specified, can be exceeded to some point?, with no harm to piston alignment, or risk of thrusts dropping out, as long as this play is monitored, so doesn't get excessive?.

Interested in this, if anyone has any thoughts?.

Dave     

Edited by daverclasper
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My Vitesse manual says 6 - 8 thou and Id imagine this is pretty standard. Reckon it has to be quite a bit more before the thrusts can drop out or damage occurs!

Once set correctly you can get a feel for it by moving the pulley and then just recheck it by eye every so often. Unless the clutch has been ridden a lot its most likely the thrusts will not need changing until other work, like big end bearings, needs doing on the crank....   

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end float you must check the workshop manual as there are differing figures for end float even on similar engines 

a 2.5 is less than a 2ltr  for what ever reason  but never guess the spec 

0.002" is  too tight   some ae up to 0.012"

they only fall out when the float exceeds the size of the lump on the bearing cap that retains it 

Pete

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I don't!! First time I ever changed those was on a GT6 engine which seized on first turn of the key. Seized solid after thirty seconds! We had just fitted a replacement gearbox, mate inside the car with a socket and me outside with a spanner for the other end of the bellhousing bolts. After a lot of headscratching a mate told me to whack the pulley with a lump of wood... and that freed the engine. It turned out the gearbox and crank weren't compatible - too long of a shaft tip for the end of the crank - so when they wouldn't join up completely the mate inside the car decided to pull them together by tightening the bolts. All that did was push the crank forward and immediately banjax the thrust washers.

I removed the engine, turned it upside down and slid various sizes of thrust washers in and out until I reckoned I couldn't squeeze another one in. That was as precise as measurements got.

We also cured the gearbox by cutting the end off the shaft with an angle grinder. It ran well until I upgraded both engine and gearbox about two years later.

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i couldnt fit the thickness needed as the back to front thrusters had worn a good radius in the journal face this restricts the thrust fit

ie why wont the thing go in ...argh    its the way the crank face had been worn 

and getting the sump off on a 2000 is lot less faf than in a Vit/Gt6

hence the idea was get a new thrust beaded in and fit to size on the none thrust side thats been fine for 3 years now 

Pete

 

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Agreed a small amount of end float beyond the factory spec on a used engine is no issue but if we are talking a couple of mm that would indicate a very worn engine, hence that coupled with a "rattle" at revs could indicate a bottom end issue. If they do fall out and that has happened twice for me, then it possibly can be fixed, but better to rebuild before they drop out.

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When I bought my GT6 I discovered  the oil was turning to jelly within a month, then I noticed it had a massive end float 1/8" or thereabouts. Because the pistons are held vertical by their bearings as the crank moves back and forth, there is wear to the big ends, crank and piston bores. I replaced end floats, mains and big ends, but too late. The bores had worn in an elongated "S" shape which needed  20 thou re-bore plus the crank re-ground. 

So, don't leave it too late! :lol:

Doug

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6 hours ago, dougbgt6 said:

When I bought my GT6 I discovered  the oil was turning to jelly within a month

I guess that's an exaggeration Doug?, though did all that fine, though plenty of, metal wear make it loads thicker?

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New oil got very thick and grey very quickly, I though exhaust was getting into the oil via the strangely worn bores. But no, not set jelly that you would accept on a plate! Perhaps thick milk shake or smoothie consistancy.

Doug

 

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Good morning Gentlemen, well I thought that I was lucky but alas NO. Still wasn't happy with engine so under I go. Result after removing Main bearing cap is bearing material gone and through to copper. The journal itself looks good, next step pull the caps off the big ends to see what they look like. Hoping to replace just shells if I am lucky. Does anyone know if the Main shells can be removed with engine in situ. Using copper pin in oil hole perhaps and rotating crank to push out shell ??. Once again replies appreciated.

 

IMG_20210617_171337.jpg

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