Engine Noise. Piston Slap? Herald 13/60 1968

[Kev]

Pete, one thing you mentioned... the diaphragm. It does seem baggy and bigger and does not sit snug in the carb. Clean it in petrol to return it to its new shape?

I just checked the valve and it is not sticking at all. I have two fuel filters to catch any debris from the hoses. I may put new hoses on again anyway.

Thanks.

[Pete Lewis]

yes just give it a splashing 

the rubber criters hide at the back/behind the float needle  need to unscrew to find them

let a few good squirts into a jar to flush the pipes,

crafty little sods , every time you pop hose off/on you can make more  

pete

[Kev]

So I cleaned the carb, again, and made sure no little criters were hiding and refitted. The engine is still reving up and down on its own. After a few days it came to me. Maybe the manifold gasket I fitted was not sealing properly in the air intake part. The exhaust part is sealed. Maybe air is getting inside causing the fluctuations in the revs? So I went online and found an older unused manifold gasket (Payen JA 469) and bought that. It is actually thicker than the new one I recently put in. Will try this one and see what happens!

Thanks, Kev

[Pete Lewis]

can you test  the pump output   ???   volume and pressures      

subjective  ie thumb over pipe and good squirts  dont need any special gauges

Pete 

[Iain T]

I assume the air piston falls with a clunck on the bridge? I had one new diaphragm that actually stopped the piston from dropping to the bottom. The jet was centred but it still held the piston off 1-2mm off the bridge. Couldn't get the engine to tick over properly so I replaced the diaphragm and cured the problem. 

Iain 

[Patrick Taylor]

Your first pic shows a hose to the rocker box breather, but it isn't there on the video. I'm not sure what the arrangement is for a Stromberg, but does it need connecting to the inlet manifold? This will affect tickover (although SU's run better with it disconnected!).

[NonMember]

48 minutes ago, Patrick Taylor said:

Your first pic shows a hose to the rocker box breather, but it isn't there on the video. I'm not sure what the arrangement is for a Stromberg, but does it need connecting to the inlet manifold? This will affect tickover (although SU's run better with it disconnected!).

No, the 13/60 breather arrangement is rather crude. The missing hose goes to the air filter box at atmospheric pressure, so its absence won't cause a problem.

[daverclasper]

1 hour ago, NonMember said:

The missing hose goes to the air filter box at atmospheric pressure, so its absence won't cause a problem.

My Vitesse was like this. Converted back to original PCV arrangement. Has been easier to set up carbs mixture (I think). Cleaner air filters as well.

One thing I was wondering about, before, a bit of oil smoke used to come out of rocker cover if filler cap removed, at idle (was this excessive blow bye?).

With the PCV fitted, it now has a fair bit of suction at filler hole, therefore no smoke.

Cheers, Dave

[Patrick Taylor]

22 hours ago, NonMember said:

No, the 13/60 breather arrangement is rather crude. The missing hose goes to the air filter box at atmospheric pressure, so its absence won't cause a problem.

Ah, OK. The Mk3 Spit engine in my Bond from the same era feeds the oily fumes into the manifold via a flashback arrester. Same principle, different method.

[NonMember]

37 minutes ago, Patrick Taylor said:

The Mk3 Spit engine in my Bond from the same era feeds the oily fumes into the manifold via a flashback arrester.

It's not a "flashback arrester" but a flow / vacuum regulator valve. This is called "Positive Crankcase Ventilation", where a controlled partial vacuum is applied to the breather system. The Herald one is technically not PCV as it's atmospheric.