Loss of compression

[oslo triumph]

I have posted this on a big saloon Facebook group, but it idoesn't appear to be the right place for the answers I'm after.

Lost all compression on cylinder 1 and after taking off the cylinder head it seems that the valve seat has disappeared from the exhaust valve, the inlet valve doesn't look right either. This is a big valve 218225 head, did they have valve seat inserts from new?

I have a 219016 head as spare but the question is can I run this in standard form with the 2000 block I have? Block is ML547HEA and has +.030 flat top pistons.

[thescrapman]

No valve seat inserts on any 2000 head as standard.

A 2.5 head on a 2000 needs dome top pistons unless it has been skimmed.

there is dimensions out there for thickness of head for each application.

.... found them ... 219016 is 75 thou thicker. 3.475 against 3.400 for you other head.

[RobPearce]

None of the pushrod Triumph engines had valve seat inserts from new, with the possible exception of some US market TR6s. However, that doesn't usually cause any problems - my GT6 has done four Round Britain Reliability Runs since leaded petrol disappeared and shows no sign whatever of valve problems. The only car I have had serious VSR on was a Toledo in which I tackled RBRR with a faulty float valve, so it was running piss weak and got mercilessly thrashed to compensate for the lack of power. You should check why your cylinder 1 has suffered.

The 219016 head is for a 2500S - it's a low compression head on that, it will be very low on a dome-top 2000 and almost none (OK, I exaggerate but...) on a flat-top like yours.

If it were my car, I'd take the existing head to Ivor Searle for "unleaded conversion", since that fixes the recessed valve seats. I guess you're not as close to them as I am, though.

[glang]

None of these heads had valve inserts from new so maybe yours is badly burnt? If the other cylinders are ok I can only think this exhaust valve wasnt closing fully (although of course then it wouldnt have run very well) but that wouldnt affect the inlet valve.... And being a 2000 its not a PI is it?

According to the Chris Witor page those two heads have different ex valve sizes, are different heights and use different length push rods.....

[oslo triumph]

It is strange as all the other vavles are OK, just cylinder 1

I have no history of the car but seeing that it has oversized pistons it could well have had work done on the top too.

I can't seem to post pictures here on the forum?

[glang]

I think just members can now post pics on here.....

The change of piston size would most likely just be from a rebore that was necessary due to wear or bore damage and not for tuning purposes as this normally needs a much bigger increase to achieve anything worthwhile.

What does the no1 sparkplug look like?

[oslo triumph]

Oh yeah, I agree. There is no way this engine was put togheter with performance in mind considering all the different parts they used.

2000 block, mismatched head and pistons, HS4 SU carbs on a short manifold with needles from a 2500TC, amazing it ran at all really.

The spark plug was actually not too bad, this was a sudden compression loss so it was running OK before i heard the bang from the engine.

[glang]

sounds interesting, pity cant see a photo! Could it have had a valve seat insert which has somehow gone somewhere? Is the any damage to piston or exhaust valve?

[oslo triumph]

seems like the best I can do are these links..

https://i.imgur.com/lrzFSpO.jpg
https://i.imgur.com/Tbn02BX.jpg
https://i.imgur.com/mS6F78Y.jpg
https://i.imgur.com/Iuy2Ky7.jpg
https://i.imgur.com/vlsCtXs.jpg
https://i.imgur.com/IDUzW8B.jpg
https://i.imgur.com/APmLhUL.jpg
https://i.imgur.com/fxPYexZ.jpg
https://i.imgur.com/zvjx2w7.jpg

[glang]

They are interesting! Could an insert have been fitted to the inlet maybe as an attempt to repair a crack between the two valves (they are prone to it) but where is the exhaust valve seat? Surely it couldnt have been left like that as theres no bevelled edge or maybe its been severely burnt.

Theres also a chunk missing of the inlet valve guide but maybe thats old damage....

[RobPearce]

I'd say that's had some highly incompetent "work" done on it. Probably suffered a valve failure in the past and the PO had it "repaired" by a machine shop who couldn't be bothered to put in the inserts it needed because they'd taken too much metal away. Also, they didn't replace the broken valve guide that caused it, judging by the first photo.

[oslo triumph]

Yes all a bit of a mystery, I guess we will never know the cause for certain but it seems likely that the valve inserts are to blame if ever they were properly installed in the first place.

The long and short of it is that I have a 2000 block in my 2500TC that I don't trust now, with the wrong pistons for the cylinder head I had and that head is probably not worth fixing. 😫 

Time for a re-think.

I have a 2500 block and head that came with the car but it is completely stripped down to it's bare components and I have no idea why it was taken out in the first place. It is going to need assesing by an engine spesialist and that will mean great expense here in Norway. Plus I really want this car back on the road ASAP.