I guess it could be lots of things on a refurb’d engine. Assuming it’s all in order, when setting the valve gaps you’re definitely starting on #1 when pulley is a TDC and the piston is at the top of the cylinder? I always work from #1 turning the pulley anti-clockwise 180deg to #2, then again to 3 then 4. Just a thought. Hope you get it sorted!
1500 sp Help needed.
I have a refurbished engine and I have set the valve clearances as per the manual- ie position of rotor, TDC on pulley wheel. When the engine gets hot the noise from the tappets is horrendous. I have removed the rocker covers when the engine is hot to find the valve clearances are huge-hence the noise. What am I doing wrong?
TIA
TIA
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Possible mix up of metric and imperial measurements with your feeler gauges ?
Are you using stock valve train parts ? Steel pushrods for instance expand differently when hot than the stock aluminium ones.
Something coming loose somewhere ? rocker shafts loose on the heads ? Rocker side play not shimmed up right esp if using bolt up rocker shafts, or wave spring washers / clips not assembled correctly or coming loose on a stock setup ?
Let it all cool down and re-check when cold. Don't forget there are TWO TDC's in the four stroke cycle, you need to be setting the valve clearances when the piston is at TDC AND the rotor arm is pointing to that cylinder's spark plug lead. As a double check if you rock the engine backwards and forwards a few degrees either side of TDC, assuming you're setting no.1 valves, the valves for no1 cylinder should not be moving but the valves for no.3 (Opposite cylinder) should both be rocking up and down. That's a double check to make sure you have the right TDC. Whichever valves you're adjusting, the valves on the opposite cylinder should both be rocking when you swing across TDC.
Also as a quick sanity check, just look at all the protruding valve screw adjusters. They should all look roughly the same. If any have been set much further in or out than the rest then that should raise a red flag.
Has this engine been running OK in the past or is this a first time run since a rebuild ?
Dave.
Are you using stock valve train parts ? Steel pushrods for instance expand differently when hot than the stock aluminium ones.
Something coming loose somewhere ? rocker shafts loose on the heads ? Rocker side play not shimmed up right esp if using bolt up rocker shafts, or wave spring washers / clips not assembled correctly or coming loose on a stock setup ?
Let it all cool down and re-check when cold. Don't forget there are TWO TDC's in the four stroke cycle, you need to be setting the valve clearances when the piston is at TDC AND the rotor arm is pointing to that cylinder's spark plug lead. As a double check if you rock the engine backwards and forwards a few degrees either side of TDC, assuming you're setting no.1 valves, the valves for no1 cylinder should not be moving but the valves for no.3 (Opposite cylinder) should both be rocking up and down. That's a double check to make sure you have the right TDC. Whichever valves you're adjusting, the valves on the opposite cylinder should both be rocking when you swing across TDC.
Also as a quick sanity check, just look at all the protruding valve screw adjusters. They should all look roughly the same. If any have been set much further in or out than the rest then that should raise a red flag.
Has this engine been running OK in the past or is this a first time run since a rebuild ?
Dave.
Hi Dave, its been running ok-ish but has recently become noisy. I'ts only done 500 miles.Possible mix up of metric and imperial measurements with your feeler gauges ?
Are you using stock valve train parts ? Steel pushrods for instance expand differently when hot than the stock aluminium ones.
Something coming loose somewhere ? rocker shafts loose on the heads ? Rocker side play not shimmed up right esp if using bolt up rocker shafts, or wave spring washers / clips not assembled correctly or coming loose on a stock setup ?
Let it all cool down and re-check when cold. Don't forget there are TWO TDC's in the four stroke cycle, you need to be setting the valve clearances when the piston is at TDC AND the rotor arm is pointing to that cylinder's spark plug lead. As a double check if you rock the engine backwards and forwards a few degrees either side of TDC, assuming you're setting no.1 valves, the valves for no1 cylinder should not be moving but the valves for no.3 (Opposite cylinder) should both be rocking up and down. That's a double check to make sure you have the right TDC. Whichever valves you're adjusting, the valves on the opposite cylinder should both be rocking when you swing across TDC.
Also as a quick sanity check, just look at all the protruding valve screw adjusters. They should all look roughly the same. If any have been set much further in or out than the rest then that should raise a red flag.
Has this engine been running OK in the past or is this a first time run since a rebuild ?
Dave.
Waited until cold and re-checked everything. I set the clearances slightly tight at .003 thou. Ran it up until warm and then checked clearances again. The exhaust clearance on No 3 cylinder is almost 025 thou!! How?
Don’t trust the mark on the distributor. The drive gear might be fitted in the wrong position, shifting the rotor arm at no#1 TDC
Had it all cooled down when you checked it again or was it still warm ?Waited until cold and re-checked everything. I set the clearances slightly tight at .003 thou. Ran it up until warm and then checked clearances again. The exhaust clearance on No 3 cylinder is almost 025 thou!! How?
And I assume you mean 3 thou and 25 thou (Imperial)
If it was cold again when you checked for the second time then something is amiss. Are all cylinders / valves showing the same issue or is it limited to a certain cylinder or valve ?
Dave.
You might have set that now big tappet clearance with the pushrod not fully seated in the follower. Or the cam lobe or follower has a problem. Or bent pushrod, or worn rocker arm cup. Reset it and try again
Please post a photo of No. 3 Exhaust clearance. not that we don't believe you, just in case there are other things affecting it which someone may be able to spot.Waited until cold and re-checked everything. I set the clearances slightly tight at .003 thou. Ran it up until warm and then checked clearances again. The exhaust clearance on No 3 cylinder is almost 025 thou!! How?
Hi Dave, I am using imperial as per the manual. I've let it cool down and started again. I checked the compression on all cylinders both cold and warm and they are all almost identical [ I thought it might be a bent valve ]. Re - set the clearances and again as soon as it gets warm the clearances on number 4 cylinder have enlarged. I noticed that with No4 at TDC the clearance on the inlet valve on number 3 is also large.Had it all cooled down when you checked it again or was it still warm ?
And I assume you mean 3 thou and 25 thou (Imperial)
If it was cold again when you checked for the second time then something is amiss. Are all cylinders / valves showing the same issue or is it limited to a certain cylinder or valve ?
Dave.
So is the problem with cyls 3 & 4 but 1 & 2 are OK ? If so, first check the rocker shaft for 3 & 4 is torqued up to spec.
If not that, remove the pushrods from the affected cylinders and check them for straightness by rolling them on a sheet of glass. Visually inspect the ends and also the rockers on the shaft whilst you have that off the car.
Photo anything suspect and post it up here.
Dave.
If not that, remove the pushrods from the affected cylinders and check them for straightness by rolling them on a sheet of glass. Visually inspect the ends and also the rockers on the shaft whilst you have that off the car.
Photo anything suspect and post it up here.
Dave.
When you set the clearance on the back of the cam lobe, at no other point in the cycle should the clearance get bigger (unless the camshaft is destroyed). I’d suggest you Redo one cylinder & then rotate the engine through 2 revolutions, checking the clearance at 180 degrees intervals.Hi Dave, I am using imperial as per the manual. I've let it cool down and started again. I checked the compression on all cylinders both cold and warm and they are all almost identical [ I thought it might be a bent valve ]. Re - set the clearances and again as soon as it gets warm the clearances on number 4 cylinder have enlarged. I noticed that with No4 at TDC the clearance on the inlet valve on number 3 is also large.
At this point, do it as Slowest Coach says. You only really need concentrate on the 1 large tappet clearance.
I removed the rockers and shaft together with pushrods and nothing seems untoward.
If there is nothing worn on the pushrods, rocker assembly, nothing loose, refit it, reset the tappets, try again, if problem appears again on the same cylinder, I'd be leaning towards a cam follower or cam lobe issue, hopefully this isn't the case.
I am not a stranger to engines-the last one I built raced in the Classic TT on the Isle of Man and I rode it in a couple of meeting at Olivers Mount and various sprints and it still together but this one has me baffled. I set the valve clearances with valves hot and today when cool the inlet valve had no clearance.If there is nothing worn on the pushrods, rocker assembly, nothing loose, refit it, reset the tappets, try again, if problem appears again on the same cylinder, I'd be leaning towards a cam follower or cam lobe issue, hopefully this isn't the case.
You've no cold gap because the engine has cooled off and got smaller, thus closing the hot valve gap. E.G On a vw aircooled with steel pushrods, the trick is to set the valve lash at zero clearance, but still allowing for the pushrods to swivel. When the engine is hot quite often a 6 thou feeler will fit. When it cools off, back to zero lash. Always do valve lash cold. It's good you know your way around engines.
Apart from doing aircooled motors I also work in a machine shop, building anything from Skyline motors to 20 hp Rolls Royce engines.
P. S Steel pushrods run noisy when motor is hot
Apart from doing aircooled motors I also work in a machine shop, building anything from Skyline motors to 20 hp Rolls Royce engines.
P. S Steel pushrods run noisy when motor is hot
Hi, these pushrods are aluminium but some of the noise seems to come from crankcases ie possibly the camshaft. This noise has only just appeared but the engine has always run lumpy. When you say set the valve lash are you talking about valve clearance?
Yeah lash is clearance.
If clearance keeps growing with no signs of anything wrong, then it's possibly the cam follower face getting a deep groove cut into it by the cam lobe, which increases the valve clearance.
If clearance keeps growing with no signs of anything wrong, then it's possibly the cam follower face getting a deep groove cut into it by the cam lobe, which increases the valve clearance.
I think you'll end up taking motor out, remove heads and pistons, then look inside with a torch at the condition of the cam lobes. You might be able to see the cam follower faces too.
1 - 20 of 25 Posts
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