red hot exhaust manifold - lt40 2.4 petrol/lpg

hmmm, that doesnt look particularly good. They arent deep gouges though, just scuff/burn. When my seat is in different position (further back i think) sometimes I operate the clutch differently and my clutch control goes out the window....perhaps this is the result of all that snatching...

Cyl5:

Cyl6:

This is obviously where it gets expensive :( but never mind...might as well suck it up and have nice reconditioned engine now i've come this far. This time, I'm getting a flash lube installation and will add a dose of 2 stroke oil to my petrol tank to keep the carb lubed.

and then giving each of the main faces a good rub down with a mixture of the sanding block, scotchbrite and the abrasive stone.

Sump side:

Head side:

Flywheel end:

Pully end:

and then had the cylinders honed roughly so we could more clearly see the nature of the wear:

Close up of the wear:

Score marks:

You can see a fair amount of wear across all of the cylinder but number 2 and 6 were by far the worst:

And then, a quick look at the little water pipe fitment casting that attaches to the head which had suffered from a bit of nasty corrosion. The new one has been cast from lycoming aircraft engine pistons melted down and reformed:

Really excellent job and these ones have got a bit more meat on them so they hopefully last a tad longer than their predecessors. Here is the milled face before the neck is shaped and the holes drilled:

The other issue i wanted to look at was the oil pressure. Im pretty sure it was running a bit high and despite changing out the pressure sensor it never stopped the light coming on so I tested the pressure with one of them screw in pressure testers for a while (before the rubber hose on it rotted away due to being left sitting for a couple of years without use while i was travelling) and it measured quite high oil pressure.....i can't remember exactly what the pressure reading was but it was close to the pressure that the relief valve is meant to kick in at. I've looked at the relief valve and the oil pump and the oil pick up assembly and can't see any defunct or blocked parts so it still needs looking into. I've got a nice shiny new digital pressure reader that I'm going to wire in when its ready to run again but hope to find some anomaly that might have been causing higher than specified pressure before all the work has been done bolting it back together.

Need to find the right clutch kit for it. Theres a lot of price variation on the ebay for these 3 piece kits and want to find the good one with matching original quality. 

Not sure If I should re-use the old conrod bolts or not. I know that mine are the original type and not the new stretch bolt style that would surely then have to be replaced.

So yes its been a while since my last postings. I've really struggled to get these pistons so have opted, to order some custom oversize (+0.5mm) pistons from JE in the states which have been ordered today and should be here just before xmas hopefully. 

To everyone who helped me look for existing stock, thank you. I appreciate it. Couldn't find them anywhere though so am sucking up the cost of some custom pistons. 

We had the crankshaft back on with one piston properly in place and discovered that there is roughly 4.3mm of clear space between the piston crown and the top of the bore. So as they are being totally made up new, I have asked JE to add 1.3mm to the crown height and reposition the top ring a tiny bit higher. The maths says it'll give a significant improvement to the compression ratio which is currently 8.1:1 with the increase bringing it to roughly 9.5:1.  Prob could have added a touch more but didnt want to be greedy. currently, it should still be valve safe with 1mm + gasket for clearance if anything went disastrously wrong.

ALso, I have been talked into replacing the exhaust valve seat inserts with super tough nickel based alloy ones, at ridiculous expense. Having mulled it over I can't help but agree it is the way to go with all this other work thats gone into getting it fixed up. It'll love that LPG by the time i'm finished with it!!!

Main reason for this unexpected addition was that we tested the camshaft back on with one of the valve sets put back together and discovered that the old seat inserts had really receded and the exhaust valve wasnt closing properly. We could have looked at taking a bit off of the valve stems but as it's gonna run on lpg, and because we've now got time on our hands waiting for the pistons.... :)

We measured the first seat with the old insert still in there and got the outer diameter right first time but the feckin engineering place i got them from still sent me inserts that were identical in size to the hole they had to go back into. Now have had to order some slightly larger ones and will machine some off accurately when they arrive. 

Heres the process so far:

So.....having already skimmed the head...there's only a fraction left that can be re-skimmed if this goes wrong so I'm nervous of the whole process. Lots of heating and cooling to undergo now we've decided on new high temp inserts. Here is the nicely skimmed head all masked up to stop as much welding splatter as poss.

Welding the first seat to create a lip which can be used to then slide hammer the old seat out.

and the gentle slide hammering:

I've been reliably informed that the process of welding a ridge onto the inner diameter of the seat inserts is known in the trade as "Welding a cat's bum" onto it....

Here is an example of said anatomy, which split in two and had to be welded twice. Also the first of the wrongly sized new nickel inserts that has now been sent back while we wait for larger ones to arrive:

The measurements for these are as follows:

Outer diameter of insert:

Inner diameter of seat insert:

Depth measurement of seat insert:

and the corresponding bore diameter on the head:

Apparently the ideal interference between the outer diameter of the bore and the edge of the insert should be between 0.0015in and 0.0019in...which should hopefully be just enough once the new inserts are frozen and the head baked, to allow them to drop in with minimal pressure exerted on the head. 

As you can see, the new inserts were a tiny little bit too small. I'd have used them, as it seems the old inserts outer diameter is identical to the new ones but my exceptionally particular engineering buddy has told me off....What do i know...:

Fingers crossed!!!!

The lovely new water pipe attachment finished and bolted on:

and the dirty sump before I got fed up of wire brushing and had it blasted and zinc coated:

Well, having seen how much stuff needed attention, i'm sure lots of things led to it being in such bad condition but with this particular issue, i think micro welding might be the fault (due to everything being a bit hotter with the lpg and no upper cyl lubricant). 

So apparently as the valve contacts the exhaust valve seat insert at 1000s rpm, the contact between the two can remove some microns of seat insert material(unless they are hardened to cope), is more prevalent with hotter burning fuels and lean mixtures and effectively slowly reduces the seat insert height and closes the clearances up so much that the whole lot goes out of time and roasts itself. 

The exhaust clearance was practically zero and so the cams will have opened and closed the valves at the wrong time in relation to the ignition, flames will have been continually leaping into holes that they shouldn't under high pressure for a long long long long time....while the exhaust continued to glow....and while i adjusted any number of unrelated and probably damaging things....remember this initial glowing exhaust s**t started in 2013! :)

If it hadnt come apart when it did, i'd have been on the side of the road somewhere very soon afterwards, extremely pissed off.

My good fortune really!