The Triumph Dolomite Club - Discussion Forum

Per other threads I'm finally putting the car back together. Re-grinding the valves has taken a lot longer than I remember last time but then again before I just did it until it looked good whereas this time I did leak tests with petrol !!

https://forum.triumphdolomite.co.uk/vie ... 9&start=15

https://forum.triumphdolomite.co.uk/vie ... =4&t=37524

I've done the valve clearances on the workbench. I've used 10 thou per the camshaft thread and unearthed TriumphTune spec sheet. The head has probably only been skimmed about 20 or maybe 22 thou. I will be using an extra thick head gasket +20 thou so really in terms of valve proximity to pistons these two effects more or less cancel out.

Two questions I'd really appreciate some thoughts/advice on :

1. The head is back together and I just need to source a few different shim sizes to revisit and conclude everything. Current shim sizes varying between 100 and 112. But see photos. I knoooow everything I'm doing around this is merely dealing in thou's and the valve stem length is what it is .... but those valves feel like they are sticking out so far they would surely hit the piston.
Paranoia.
Nevertheless, does this look right?

2. Just two bolts hold the camshaft to the camshaft sprocket. They aren't even very long. This just seems a crazy weakpoint. In my case the bolts are OK. But if I did want to replace them where would I get them and are they some special high tensile spec?
I'm thinking they must be.
I only managed to track down the part number from an old Sprintspares catalogue. SH604041. Is that correct?
So for example this https://rimmerbros.com/Item--i-SH604041 or https://robsport.co.uk/index.php/online ... -1-2%C2%94

But do these meet the spec?

Thanks

Mark

You can add another two bolts to double up the sprocket attachment, Mark.

Disappointingly the new adjustable sprocket I bought only came with two bolt holes,
but I got a machinist at a local factory to accurately add another two, this being a simple task
for them with all the right equipment



Thanks
Ian

Do a dummy dry build.
Putting some plasticine on top of the piston.
A little bit of oil on the head stops is sticking to both parts.
With everything timed up turn the engine over by hand.
Pull the head off and measure the plasticine that will give you your clearance rather than second guessing.

There are more technical ways to do this but I find this is the easiest.

Appreciate the thought but I don't want to get into machining the thing. Its been OK for 40 years with two bolts. I just wanted to know where I could get two more bolts really and whether they were "just bolts" or some specific high tensile spec.?

Regarding the valve protrusion its almost exactly 0.3 inches. I'm interested to know whether that looks right ?

I'd thought about the plasticine test but it means clamping the new head gasket down and then releasing the whole thing, taking it apart, doing the checks and then recrushing the gasket when reassembling. It just doesn't feel like a great idea for the head gasket.

After I ground the valves I re-assembled with the existing pallet shims and the clearances varied between 5 and 10 thou suggesting I had used 10 thou clearance when this work was done years ago. Or at least strongly suggesting I had not used the default 18 thou.

It should all be OK. It's just that I've never really looked at the open valves off the engine.

olr159w wrote: ↑Sun Nov 20, 2022 3:38 am
Regarding the valve protrusion its almost exactly 0.3 inches. I'm interested to know whether that looks right ?

I'd thought about the plasticine test but it means clamping the new head gasket down and then releasing the whole thing, taking it apart, doing the checks and then recrushing the gasket when reassembling. It just doesn't feel like a great idea for the head gasket.

I used an old already compressed head gasket to do the valve clearance test using some blutack. I reasoned it would be a bit thinner than the new one so that would err on the side of caution.
Valves looked like this with my Kent DMS1 cam but I didn't measure the protrusion.



Blutack testing and all looked reassuring

olr159w wrote: ↑Sun Nov 20, 2022 3:38 am
Regarding the valve protrusion its almost exactly 0.3 inches. I'm interested to know whether that looks right ?

I have just measured the Inlet valve protusion off my Sprint project and I get 6.00 mm including the film of carbon. The exhausts look to be a lot less. This is with a standard head / cam / springs / etc.
Tony.

Thanks. I had the same idea also. I realised I still have the old head gasket so I'll use that just to check the clearances.

Based on 0.3 inch protrusion mine would be 7.6mm vs your measured 6mm Tony. However measuring much more carefully with mm scale it looks more like 8.75mm. Half as much again. But........ same cam as before so....?

I would suggest that if the camshaft sprocket set screws are supplied by Rob Sport, then they should be ok, they know what they are doing and race cars too.

The brothers would be questionable, I bought my own to a 12.9 Nm spec, you can also buy 14.9.

Malcolm

Robsport advise they are just regular steel bolts and no need for anything more.

Rimmers similar just describing them as standard grade bolts.

So these HT versions and four bolt modifications not necessary? Does anyone know whether the factory fitted bolts are just regular steel bolts or something higher spec?

thks