Assessing an unknown engine

[hot66]

Rob if you get stuck there is Bob near Hinckley that runs the Machine Shop. Which you can turn up and use the machine and welders. For a very small fee Bob I'll weld it for you or teach you how to do. He is pretty good with a Tig welder. Ex Triumph and TT mechanic.

https://the-machine-shop.co.uk/

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That looks a great set up

[RobFrost]

Sadly there won't be any more welding for a little while because all the gases in my bottle Argon.

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[RobFrost]

This arrived today, the wait for which has been holding up the cylinder heads.



Before reaming the valve guide bores, I eased off the edges just to help it go in straight.



I think that's more necessary when machine-reaming but it can't do any harm.

You may recall the oversize valve guides are 13.26mm and require 0.05mm interference so I'm shooting for a 13.21mm bore, so this reamer will leave 0.01mm for me to hone out to size.

The bores are at around 13mm now, exactly the right size for the reamer to start with.

I must admit this was a Chinese reamer, no more than say £30, hence the wait. But I had read the reviews and other buyers claimed the products were straight and to size, and performed well. Nevertheless it was with a little trepidation I cut the first bore.



But I needn't have worried. The ball gauge came out bang on 13.20mm and was equally snug all the way down the bore.



I reamed each one in two cuts, with plenty of cutting oil, removing the reamer once to blow away the swarf.



Not honed yet but five heads done tonight.



One thing that's consistently surprised me through this process so far, is what consistent levels of accuracy can be achieved with very basic workshop tools, a little care and some accurate measuring.

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[RobFrost]

I practiced the tig welding in the week. Slowly getting better.



And again this Friday, preparing to build up the casting on a half kilo aluminium ingot I bought. In so doing, I began to appreciate just how much energy I'll have to put into the case. The welder had to come up to 105 amps which is way more power than I've ever used before. Amazingly the ingot was still turning water to steam half an hour later.



I honed the valve guide bores in the five cylinder heads. Very satisfying job this for some reason. It takes a bit of willpower to stop after just four or five passes of the hone.



All looking good and measuring up nicely for the guides.



But why only five? I've heard it said that a shop will charge you £x to do a job, or £3x if you've tried to do it yourself first. Sadly, the sixth cylinder head is going to be a case in point. I reamed the cylinder heads with a hand reamer, after an engineer on Pelican Parts forum told me to make sure I do so. Sadly, I had a machine reamer in hand and did not see his message until after I had attempted one of the heads. The taper is too steep on a machine reamer for it to straighten itself as it goes in.



So that is going to need to go out another couple of tenths of a mm and have a wider guide in. You live and learn, I guess. I'm happy so far with the mishap frequency, based upon doing a lot of jobs in unknown territory.

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[RobFrost]

Finishing off the oil bypass mod requires a 1/4 bsp plug in this little hole here, preventing bypass oil from returning to the crankcase. Access is a bit tricky, and at first I thought the tap was too fat for the hole. But checking the facts, I found 1/4 bsp requires an 11.8mm drill and I measured the hole at 11.94mm so as near as dammit to spot on. So with added confidence, I placed a plastic lever behind the head of the ratchet to apply a little inwards force, and sure enough, it was soon cutting nicely.



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[RobFrost]

That will go in for proper when I have the thread lock open.



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[neilbardsley]

Nice job. How where you reaming by hand? What tool did you use to turn the reamer?

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[911hillclimber]

Reaming seems an art form almost. I've a few and use them in the lather where things are steady.

[RobFrost]

Nice job. How where you reaming by hand? What tool did you use to turn the reamer?

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The hand reamer itself has a much longer taper on it than a machine reamer, meaning as it's inserted it centres itself before it starts cutting. There was still a little freedom to wiggle at the top as it first started, so I carefully assessed the movement and made sure it was placed centrally. But by its nature having eight flutes, it would cut equal amounts all round even if not entirely straight at first. But definitely better to start it straight. I was reading that a machine reamer will definitely give a more accurate cut but hand reamers are perfectly acceptable.

As for what I turned it with, ironically, in a mixed auction lot I came by a massive tap wrench which would probably have been useful for this. I gave it away to a mechanic friend of mine, joking that he would NEVER ever use it.

Rooting around I found a box of these long square drive spanners and one was a perfect fit. The length was helpful as it obviously amplified any lateral movement, making it easier to be aware of and keep central.

You're only removing a minimal amount of material and it's aluminium so the forces aren't huge.

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[RobFrost]

My home made drift will come in to service again to drive the new valve guides in. The guides are exactly 9mm internal but that could come in a bit as they're driven in due to the 0.05mm interference. So to prevent the drift getting stuck, I've reduced it to about 8.92mm. In theory the internal diameter could reduce by more than .05mm although i don't think it will, so that should allow plenty. I don't want to come in too much as the drift supports the guides and prevents them distorting.



It was an oven-baked sausage roll for lunch today, which led to my covert valve guides in the freezer being discovered. So I was sent to the naughty step.

I don't think the cold will make a huge amount of difference and the video I saw on t 'tube drove them in warm. He said it would take "medium force" which I was prepared to mean potentially quite a lot of force.

I gave the bores one final clean with carb cleaner, greased the valve guides and, with the head sat in a rubber mat, drove the first two in with a medium hammer.



They have a shoulder so you can see when to stop.

Medium force turned out to be quite a lot of force (as expected) so I'll have to keep an eye on my makeshift drift and make sure it's holding up.

I measured these two internally, just a quick measure out of curiosity and they're still close to 9mm - haven't narrowed much at all. That may mean new valves all round as I was hoping the narrowing would take in some of the play, but I'll reassess accurately later as I can't remember the valve stem diameters or the correct clearance just now.


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[RobFrost]

All 10 guides went in without problem, consistent force needed. It's really satisfying to have everything looking new, although the sixth head is a bit of a fly in the ointment.

I checked the valves and they fit really nicely except for one guide in which any valve I try is tight.



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[RobFrost]

Valve stem to guide clearance should be 0.03mm to 0.05mm for intake valves, and 0.05mm to 0.07mm for exhaust valves.

There's up to two hundredths of a mm of wear in these valve stems, leaving the narrowest one 8.93mm at its narrowest point versus 8.95mm when it was new.

Measuring the guides, they have indeed come in narrower than 9mm upon driving into the head, and can all be reamed to 8.98mm which will leave every valve within spec. so I've an 8.98mm hand reamer on order.

With respect to the sixth cylinder head: Given the mess I've made of the bores I don't trust a hand reamer to self-centre correctly. So for that one I'm planning to ask a machine shop. I'll take them one of the good heads with which to set the angles, then they can swap over to a reamer and drill out the bores straight. I already have a pair of oversize valve guides which will be turned down on the lathe to match the bore (plus interference), whatever that bore needs to be in order to cut away the mess I made. I was expecting a few tenths of a mm by eye, but having had a bit of a measure it's hard to be sure but could be as much as a 14mm or 15mm bore required. I don't see a problem with that. Only thing is I wondered if it might warrant increasing the interference by a mm.

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[RobFrost]

Here are the two reamers. The delay in writing this up was waiting for the hand reamer to arrive in the hope of having something relatively successful to write up.

Note the taper in the first inch or so of the hand reamer, whereas the machine reamer only has slightly chamfered corners at the end.



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[911hillclimber]

My small reamers are hand type, 15mm or so taper on a 5/16" dia.

With head #6 I would be going to the guys in Nantwich to sort it out. The danger here is the guide centre line being some way off the truth of the valve seat centre line so making lapping the valve/seat really hard or impossible. Cylinder Head people will machine, re-guide, ream and reseat the valve to the seat in one precise go.

They have the jigs for the heads rob.

[RobFrost]

Here's the broken off engine mount stud the welding practice is for.



I've been looking forward to taking out the cam box oil jets. Because they have a large inlet, and only little jet exits, they're where debris often accumulates if it circulates the engine.

I'm expecting this to tell me whether material really did circulate the engine, as opposed to it running dry of oil due to e.g. a split oil pipe or simply not being topped up.

On first opening it looks clean.



There's a tiny flake of aluminium on the end of this nut. Maybe that's a sign of more to come.



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