Sprint engine tapping noise - Where is it coming from?!

[Galileo]

The old screwdriver trick failed to enlighten me, and it only surfaces audibly during idle and not only that but it's being doing it for about 5000k miles. Now you might ask why I didn't mention this before, and the answer is that I was convinced it was the viscous fan, but having removed it the noise is the same. I'm hoping that someone who has been around Sprints for many years passes by and says "Easy, it's your _____"!

Ah, cannot upload mp3 files...

Oh, nor wav files...

So here is a link to an MP3 on my Google drive!

[Jon Tilson]

Seems to come and go, so rotating worn cam bucket is a possible.

You can try and wiggle them when they are on the back of the cam and see if you can find one that moves more than the others.

Also gives you a change to see if all the rocker finger oil ways are clear.

Jonners

[tony g]

Mine makes the same noise (less than 1500 miles on rebuild ) When I first heard it I ripped the timing cover off in a bad mood thinking this could be the make or break for this engine before Japan takes over. Anyway the chain etc was still good so I put it back together and keep running it. As you said the noise is hard to pin point and I have now put it down to a bucket(s) rotating giving a slight clearance change.

Tony

[Galileo]

I do not like odd noises, more so when they appear to be just coming from the entire engine and I can't narrow it down. Glad no one exclaimed 'good god it's your xyz about to go bang!' that's for sure. I did wonder if it might have been timing chain related, but the sound got no louder at the front.

Cheers for the lead Jon, and the reassurance Tony!

[soe8m]

Valve play. Adjust to .15 in and .20 out and you have a nice quiet engine again.

Jeroen

[Magenta Auto Sprint]

Valve play. Adjust to .15 in and .20 out and you have a nice quiet engine again.

Jeroen

This sounds interesting, it also has the effect of advancing the inlet timing and retarding the exhaust timing? any noticeable change in performance?

Malcolm

[tony g]

Actually itll advance both inlet and exhaust opening times. Not sure Id be going down as tight as Jeroen suggests 6 thou on the inlet as half what Triumph recommend.

Tony

[Jon Tilson]

Clearances go with the cam too....

On mine its 8 inlet and 9 exhaust.

Jonners

[GTS290N]

I read on here a long time ago that the Triumph recommended valve clearances for the slants were based on previous engineering knowledge gained from the ohvs and not the fancy new modern slant engines - I have absolutely no practical input, just thought I'd share that........

[Galileo]

So not 0.018" for both, but slightly smaller for the inlet and bigger for the outlet for a standard cam? Next time I'm doing any work on the car I'll whip off the cam cover and check what they are.

[trackerjack]

Okay I will join this conversation and add my tuppence worth. When I rebuild sprint engines I use Jeroens figures after both consulting with Jeroen (who has mega knowledge of sprint lumps) and reading about all the other engines that use bucket and shim type valve mechanisms for instance Cosworth, Hillman Imp and Ford. So in my opinion if its good enough for them its good enough for me, plus it has the added bonus of making the ticking old Triumph sound like a proper engine.
You might also find a couple of extra horse power in there as well.

[Jon Tilson]

Std cam figures are 16 thou on both IIRC. I can see the logic of going a bit wider on a hotter exhaust valve but does 1 thou on the inlets really make a difference?

Jonners

[mahony]

Std cam figures are 16 thou on both IIRC. I can see the logic of going a bit wider on a hotter exhaust valve but does 1 thou on the inlets really make a difference?

Jonners

There 18 thou on both Jon so 3 thou smaller on inlet and two thou increase on exhaust

[tony g]

Jon, Jeroens figures are metric so .15 is 6 thou, .2 is 8 thou

Tony

[GTS290N]

Jon, Jeroens figures are metric so .15 is 6 thou, .2 is 8 thou

Tony

Of course. doh. I really couldn't work out where the discrepancies were from.