the terrible sound of big end knocking or something else

I haven't heard it because I haven't downloaded the software to allow me to see it, but I have one question, auto or manual?
 
If it were the big ends there would be a pronounced knock coming from the bottom, of the engine,this is a light "tap" coming from the top of the engine so is probably excessive valve clearance on one or two valves,or possibly a leak on the exhaust manifold where it joins to the frontpipe,
 
hermione149 said:
If it were the big ends there would be a pronounced knock coming from the bottom, of the engine,this is a light "tap" coming from the top of the engine so is probably excessive valve clearance on one or two valves,or possibly a leak on the exhaust manifold where it joins to the frontpipe,
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That could just be, as Kev says, an exhaust blow. Does not sound serious to me. Compared to a couple of cars we've had recently, it's quiet!

Cheers
Nick
 
its been making this din for a couple of years now so im not convinced its that serious, but aimed for the big ends based on the fact that they are practically service items!

ive just checked the valve clearances and they are the following and i presume I have matched them up with the correct port (through guess work!)
1 - 8 (inlet)
2 - 13 (exhaust)
3 - 11 (inlet)
4 - 13 (exh)
5 - 9 (in)
6 - 13 (exh)
7 - 11 (in)
8 - 14 (exh)

so theres nothing too untoward with he sizes bar a couple of inlets that are a thou too large

ill have a look at the exhaust manifold tomorrow when its light (i ran out of light this evening)

im also going to look at the fuel pump as i dont remember it making the noise prior to replacing the fuel pump, might try blanking it off and then running it gravity fed with fuel to eliminate the pump from my enquiries,

could it be gearbox? my gearbox is bloody noisy and on its way out (a manual btw harvey!). the once a rotation tap was pointing me towards the big ends but as you say its more a tap than a knock.
 
Well ive eliminated the fuel pump from my enquiries as that didn't make a jott of difference, and its not the gearbox as it still makes the noise when the clutch is pressed. Access to the manifold to check for cracks is a bit of an arse, ill try to get it onto a ramp to check the entire exhaust for leaks.

it probably is the slightly over tolerance valve. Clearances and if it is ill leave it, im likely to get the head converted to unleaded at some point so ill get it remedied then.
 
OrganDoctor said:
Big ends banging usually are accompanied by low oil pressure at idle.
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Not necessarily. Worn mains will cause a far bigger drop in pressure than worn big ends.
 
harveyp6 said:
Not necessarily. Worn mains will cause a far bigger drop in pressure than worn big ends.
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How so? It's the same oil way through the whole crank? And the holes look the same size?

Michael
 
redrover said:
harveyp6 said:
Not necessarily. Worn mains will cause a far bigger drop in pressure than worn big ends.
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How so? It's the same oil way through the whole crank? And the holes look the same size?

Michael
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It's not a mistake I'll make again. I bought a Humber Sceptre years back that had a bad knock and I discounted it as a big end because it had superb oil pressure...... A crank grind and rebore (and a severely lightened wallet) later and the knock was gone but the oil pressure was exactly the same. It was a nice engine afterwards though, shame the rest of the car wasn't as good rot-wise.
 
U don't feel that i have low oil pressure at idle, the oil light goes off about .5 of a second after startup and never comes on again even at idle when warm
 
Whitewash said:
U don't feel that i have low oil pressure at idle, the oil light goes off about .5 of a second after startup and never comes on again even at idle when warm
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It's likely your oil pressure is going to be lower than it would be in a rebuilt engine, as the 4-cylinder seems particularly prone to wearing the bottom end, and common consensus seems to be a shell replacement every 40-60k miles, but that entirely depends on the state of the rest of the engine and your driving habits/service intervals as to how accelerated the wear will be. But if you're not getting the oil light at a hot idle on a motorway slipway after a decent 70+ run, you're probably not going to need to worry about it just yet.
In any case, rattling "musical" timing chains is the giveaway of low oil pressure. The "tinkle-tinkle" is the top chain, which is more likely to rattle if the oil strainer beneath the banjo bolt on the shoulder of the cylinder head isn't cleared out at service time, so not too much to worry about there. The "garble-garble" rattle is the lower chain, which is reasonably unequivocally a sign of worn/wearing crank bearings.

But that's off topic... Your engine sounds very similar to mine, which developed a crack in one of the joints of the exhaust headers a few months back. I'd be inclined to agree with the others on that one. I agree it could also be an overly wide valve gap, but your clearances are so far within in tolerance as to be as close to perfect as you can reasonably get on an unconverted engine. I wouldn't worry about that just yet. My cyl 4 exhaust clearance is 20 thou and doesn't rattle once warm. And won't rattle at all in a few weeks... ;-)

Cheers
Michael
 
That is some interesting information about oil pressure and noises. Since my TC is not yet on the road, I haven't been able to evaluate the engine properly. It got new pistons,and bearings, and at first the oil pressure was good enough to come up while cranking, and before start-up. Now it has been run , off and on, as I move it outside for welding and to open the garage for other uses. I added an oil pressure guage (mechanical) and sometimes the pressure seems erratic, shooting up to 80 or better when revving.
I have what sounds like chain noise which occurs as the engine comes down for revving. Sadly, chains were not replaced during rebuild, although the tensioners were.
I expect to revisit valve clearances once the engine has been run in. Also the exhaust manifold will have to come off, as I hear an obvious leak.
When this car was retired it was due to dramatic big end failure during which the oil pressure went down and the oil light came on.
 
OrganDoctor said:
I added an oil pressure guage (mechanical) and sometimes the pressure seems erratic, shooting up to 80 or better when revving.
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I suppose it all depends on the range of the pressure changes, but had you considered the release valve may be sticking slightly? Or the spring may be too strong? IIRC, there are different ratings for the pressure release springs after a series of modifications were made to the valve itself at various points in the mid sixties. Worth looking into if you're worried about it.

Michael
 
That noise sound like its valvetrain related. You don't need much wear on a cam lobe or tappet to make a noise.

Does the noise get louder with increasing engine load?, if not then I can't see it being a cracked or blowing exhaust manifold.

Agree with Harvey re. oil pressure, I've had engines with rumbling bottom ends yet quite reasonable oil pressure. Worn mains do
seem to give more of a drop though, I wonder if its down to their greater surface area, than that of the big ends?
 
robgee1964 said:
Agree with Harvey re. oil pressure, I've had engines with rumbling bottom ends yet quite reasonable oil pressure. Worn mains do
seem to give more of a drop though, I wonder if its down to their greater surface area, than that of the big ends?
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I think it's because on the mains if everything is as it should be then the pressure is retained, whereas on the big ends there's always a pressure drop caused by the take off for the splashfeed for the bores and underside of the piston.
 
Moved the TC out again today as I needed the garage for work. Got to watch the oil pressure guage do its crazy dance. At one point , while idling it went to 70-80. Then it will drop down and stay steady at 50. Very tempted to take adrive in its present state, but the local police are not very understanding.

 
When my TC was like this, and a little more nude without boot and bonnet but also with a full interior, i was driving it around the yard of the paint shop last summer. Well, i don't know how much all the panels weigh, but it felt so much more a lighter car, it was unbelievable. The steering lightness and how it jumped off the line on take off were impressive. It would be rather nice if anyone builds a lightweight P6. The wide arched factory P6 racers must have been a few good steps towards lightness.
 
Demetris said:
When my TC was like this, and a little more nude without boot and bonnet but also with a full interior, i was driving it around the yard of the paint shop last summer. Well, i don't know how much all the panels weigh, but it felt so much more a lighter car, it was unbelievable. The steering lightness and how it jumped off the line on take off were impressive. It would be rather nice if anyone builds a lightweight P6. The wide arched factory P6 racers must have been a few good steps towards lightness.
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I think lightweight doors would be a good start !! Anyone who has removed a door and carried it away can testify that this is most of the weight !!
 
OrganDoctor said:
I think lightweight doors would be a good start !! Anyone who has removed a door and carried it away can testify that this is most of the weight !!
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They may be heavy, but because they are so easy to fit on your own I've never found them to be a problem. I've lost count of the cars I've fitted doors to, balancing the weight of the door on my knee, one hand supporting it in place, while the other lines up the hinge bolts..... P6's are just so easy! Just hang them on the top hinge pin and away you go.
 
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