hahaha quote of the day

sorry,,, i can`t believe i missed the insert ring in the pic,,, i must have been pretty tired, it was pretty late

but now that you`ve mentioned it, & i`ve spotted in the pic,,, well well well,,, there isn`t much of a recess for the insert to grab onto

was the head chambered out quite a bit after the insert was fitted (IE: chamber roof lifted) ???

or was the machinist who fitted the insert just a dumb nKut????

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

I don't know who by or how your inserts were fitted, but it's a worry how some people (in UK) suggest it's easily done with just a shouldered punch and a BFH...
IMO the only proper way (if you must have them) is to shrink fit the buggers.
But I agree with Matt, there ain't much of a recess there.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

there is more of a recess than it looks in the picture, it's pissing down rain so I'm not going to take another...

they were shrink fit, and have been in there 6 years or so, but yeah, it might not have been the best job in the world - I guess they shouldn't ever come out, should they!

Have you recently had the head serviced? If so did they re-cut the valve seats? I might be grasping at straws, but as you said it does seem strange that it would just drop out like that...

Hahahahah... Matt, you funny funny bugger... glad you were around to clear that up for me

nah, not since January - probably 5000k's - maybe it's just cos it was the first time it got a decent run after I put the blower on it

Increased pressure/ increased valve temps / valve seat has to work harder to transfer heat to cylinder head/ more thermal expansion....

Which cylinder was it again? The one closest to the radiator or the one furthest away?

It is difficult to tell from the photo, (and also because of the awesome carnage ) but the recess for the incert does not appear overly deep... when you press an incert into a recess like that, it puts a degree of load on both the parent material and the incert. When you cut (or grind) the incert, you are relieving some of that tension.... and If there is insufficient purhcase, and you take too much, it is possible for the incert to have insufficient loading to hold itself in place... it might stick for a while but with time and fatigue it could work loose...


Again, I might be grasping at straws. I have not experienced this personally in an cylinder head application, but have experienced it in others.

<edit> and certainly as Morris1100 has suggested, heat wouldn't help either if what I am suggesting is the case

yep, #4 - always the hottest end

The seats have actually been cut 2-3 times since they were inserted, so yeah, there would have been some stress relieving going on. The seats weren't peened over either. I'd suggest that even if I hadn't put the blower on, it might not have lasted the summer

I'll take a photo of something else (probably unrelated) in the head that might have you scratching yours

You can't peen cast iron over anything, it is too brittle. It breaks long before it bends. Aluminium- sure, no problem.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

and good luck tying to pein a high nikel or Chromium content steel incert,,

Might be able to pin it in place though

either that insert was not pressed hard on the shoulder or it had dropped a little going by the amount of carbon build up on the shoulder face.
I have seen it happen in big diesel heads and as the carbon builds up with the acid corrosion in the fuel it eats away behind the seat and bingo, one dropped valve.

So Simon looks like a rebore and a big head job [excuse my pun]

So when you get around to it I will knock you up a set of these, 36inlets and 31 exhausts [or 38's and 32's if you have big balls]
They are a bit stronger than the S ones with 8mm stems.


did a set for Mick for his baby 295 head [not 36/32's]

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Research is the difference between speculation and investment. Anyone who copys some one else will always be second
www.minisprintgt.com

wooo, shiny! pm sent

more pist'n broke pictures






and here's the seat insert step - a bit over 4mm, should have been enough to hold it in

That looks nasty...is that chunks taken out of the seat also..looks like something has been rattling around for a bit

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Stop Licking the Dog...I Don't Care Who Started It

yeah, the edge of the seat cut has taken a big hit - I'll see what the guru at my machinist says about it



not that long... the engine was turning over for at least 10 seconds after it happened, and it happened at 4000rpm - 10 seconds at 4000rpm is 670-odd revolutions. So 10 seconds could easily do that much damage