No compression on cylinder 3, help needed

[Oldiebut goodie]

Agree with replace head.
I would say that those valve seats have been replaced / dropped out and have been held in by the punching around them. That alone would not seal them so I suspect the compression is being lost down the side of the seats. Past resurrection I would have thought, personally I wouldn't bother looking for anything else to blame it on and get another head and start again.

[itchyfeet]

Anybody who bodged that could have bodged tappets also, worth checking while head is off, also check pushrods are straight by rolling on a flat surface.

[CJH]

... personally I wouldn't bother looking for anything else to blame it on and get another head and start again.

If the dodgy looking valve seats were to blame, wouldn't the petrol test have shown that? As well as possibly replacing the head, it seems sensible to keep looking for another culprit - maybe a solid lifter that's been adjusted like a hydraulic lifter so the valve is always cracked open, as has been suggested.

So, once again, took the head off, supported it upside down and poured fuel into the valve seat area to see if there were any leaks, left it ten minutes and nope, no leaks so the valves are sitting firm.

[itchyfeet]

Also remember valves rotate so while it may be fluid tight in one position when rotated it may leak if those valve seats are in wrong.
if it were my engine I'd be changing that head looks very suspect

[CJH]

Also remember valves rotate so while it may be fluid tight in one position when rotated it may leak if those valve seats are in wrong.
if it were my engine I'd be changing that head looks very suspect

I'm struggling to understand how a new, straight valve could seat in one orientation but not in another - a bent valve maybe, but once a straight one is lapped into the seat it should seal in any orientation shouldn't it?

[Oldiebut goodie]

... personally I wouldn't bother looking for anything else to blame it on and get another head and start again.

If the dodgy looking valve seats were to blame, wouldn't the petrol test have shown that? As well as possibly replacing the head, it seems sensible to keep looking for another culprit - maybe a solid lifter that's been adjusted like a hydraulic lifter so the valve is always cracked open, as has been suggested.

It isn't under any compression testing like that!

[itchyfeet]

You may well be right CJH
I wonder if there is play in the valve guide and a wonky seat, is the position at rest under gravity the same as under spring compression which will hold the valve square to head, it's possible I'd think.

 it isn't under any compression testing like that!

very good point obg, compression is in the order of 100+ psi,
a bit of fluid say 5mm deep is in the order of a tiny fraction of one psi

[bobob]

Ok, tomorrow I will pop out the hydraulic tappet and have a look, in the meantime I will start the search for a new head!

At what point do I dig deep and replace the entire lump.....

[Oldiebut goodie]

You really shouldn't talk about your missus like that!

[bobob]

Ha ha, the good old lady has asked what I'll chuckling about..... best keep this one a secret!

[CJH]

Ok, tomorrow I will pop out the hydraulic tappet and have a look, in the meantime I will start the search for a new head!

You'll surely find a better deal on a second hand replacement head, but if you're considering a 'new' purchase, GSF do a decent head by AMC - part number 010VG0150 (strangely it's not showing up on their web page at the moment, but it is on their sister site veewee.co.uk). The next time GSF do one of their 35% discount offers (which seems to be every few days at the moment), that price of £330 should drop to £215, which is good value (Thinks - maybe that's why it's no longer in GSF's inventory. Do GSF discount codes work on veewee I wonder...)

I bought two of these heads at 35% off, and it's quite a luxury to have shiny new castings with perfect stud holes and all new valves and springs.

[ajsimmo]

The cylinder heads disappeared from gsf site straight after we both got that deal, Chris! And yes, I'd seen that they do still have them on VeeWee at full price. The 35% off code doesn't work for me on VeeWee - already tried! Lol.
I would be throwing that head away with the seats centre punched in all around. That suggests to me they were loose and looks a poor attempt at repair.
Not trying to flog my gear, but i have dozens of heads if required.

[CJH]

The cylinder heads disappeared from gsf site straight after we both got that deal, Chris! And yes, I'd seen that they do still have them on VeeWee at full price. The 35% off code doesn't work for me on VeeWee - already tried! Lol.

They've rumbled us! Shame. It's odd though - I bet there are other items on their site that are more expensive, but would still qualify under their '35% off everything' promotions. It might just be an error - the next time there's a 35% off offer it might be worth trying to place an order over the phone using their part number 010VG0150, which is clearly a GSF part number.

[itchyfeet]

Not trying to flog my gear, but i have dozens of heads if required.

I will remember that

bought duffers from traders before but by all accounts you're to be trusted.

[bobob]

Ok it's been decided, I'm changing the entire engine!

After putting it all back together for the third time, and this time with all hydraulic tappets removed, dissembled, checked, reassembled etc etc...... it now runs even worse, and not only that, I've now got water and oil mixing so I think the piston jacket seals have gone too

I've had enough!!!! Towel well and truly thrown in.

Now, where's the engine swapping thread.....