Hillman imp + Honda flat 6. Musical engine swap game..

[biturbo228]

Now isn't that a dead smart way to join a driveshaft together! Shall keep that in mind. Will you do any welding on it at all or is the press fit sufficient?

Very neat work on the fuel tank as well.

Mar 18, 2024 6:56:02 GMT ravioli said:

...bogged down in lots of stuff saying you have to have two uj's or two cv's due to uj resonance issues...

Yeah I went round that circle a while back, coming from the perspective of looking at Triumph 2000 and Spitfire/GT6 propshafts being completely out of whack straight from the factory and no-one whinging about those.

From what I can gather, the advice mostly comes from people in the US running big torque V8s through long propshafts to live axles. If you get UJs out of sync (either by just having one, or having two but on different planes), it sets up a pulsing effect where the shaft (and everything else downstream of it) varies in speed like a sine wave. This causes two different things that we can notice.

1. Slightly choppier/harsher power delivery, including when just cruising along
2. A variation in the torque components like the diff or driveshafts see

I figure that the harshness is quite easily lost in general harshness of old, small cars which is why no-one really notices the prop angles in Spitfires. I do wonder how bad this ends up being, considering the T2000 is awful as well and journos still descried it as 'turbine smooth' at the time...

Variation in torque is more interesting I think. If a component is fairly marginal (like the diff in a GT6 with a 2.5l swap), then it's possible that the fluctuations in torque delivery push it past what it can cope with. I do wonder if this is a contributory factor to 2.5l Spitfires eating diffs (and, presumably, hopped up American cars lunching their diffs on a hard launch as their rear end squats and pushes any existing misalignment even further out.

tl;dr if your downstream components are beefy enough for a given engine, and you're not going for super smoothness, you're probably alright with a bit of misalignment.

[yoeddynz]

No welding needed. They won't be separating. I think something else will break* before they ever even give a hint of moving.

*like the traction on my 175mm tyres

[jamesd1972]

Apr 9, 2024 8:54:14 GMT yoeddynz said:

No welding needed. They won't be separating. I think something else will break* before they ever even give a hint of moving.

*like the traction on my 175mm tyres

Tyres are cheaper than gearboxes.....

Plus smoke !

James

[yoeddynz]

As per the title this next stage of building the exhaust silencer/muffler/back box/ take your pick has taken much more time and effort than I had always expected.

I started by taking the blue imp apart. To Woolf valley garage I went....



..where I removed (rusty mild steel) exhaust, bumper and rear valance..



Popped it onto rusty imp shell...



Now I knew exactly how much room I have to play with.

Whatever I was going to build had to work with several things.

I wanted the box to be mounted higher than the existing one behind the Datsun engine as I was sick of scraping it on steep driveway exits.

It had to be built completely of stainless steel, no exceptions. No more corrosion.

It had to look tidy and fit within the bumper line, tailpipes excluded.

The tailpipes were to be twin centre exit. I had a very specific look in mind and they have to be just right.

It had to be quiet enough and yet still sound sporty. This last one is tricky and will most likely need modifications to get right hence the last design point...

It has to be modular, easy enough to disassemble and repack with sound deadening (most likely glass fibre)

Now I knew the size I could build it to I started by making some flanges. This so I can unbolt the flexible sections between the V clamps and the box. Made to suit the 44mm tube as per the tube off the V clamps.



Lifted the big folder we'd made onto the bench top and folded up some 1.2mm stainless. Although heftier than I could have used I've gone with this thickness to helped avoid the tinny sound thin stainless boxes can make.



I wanted perforated stainless tube but couldn't find any within NZ. Got some perforated sheet instead - again 1.2...



Which I cut strips from and formed up into tubes as such...





Welded...



Now I had the start of a box and some tube. I could sit down and nut out a design. I have had some basic ideas for ages on how it might look inside but it was really good to sit down and see how it might work. Drew some ideas up..



Nutted out something I think would work well and be easy enough to change if need be. Time to commit. I had to cut some blue steel. First actual act of modification to the imp in my quest to plonk a flat six in it.



Now I could double check box sizing and weld the flanges in place.



Folded up the second box side..



Complete with captive nuts to suit a lid..



Tail pipe time. I almost went with twin 2" exits but they were just a tad too big. Settled on twin 45mm.

Tacked them to yet another stainless pair of flanges to work with the modular design aspect. Happy with the look I then fully welded them on the inside. The flanges will be sealed with a soft copper gasket.



Happy I had the look right I cut the centre top from the box, created a recessed bit and carefully welded in the second threaded flange.

So now I have inlets and outlets where I want them and just have to connect the dots.

Ideally a nice long a route to dampen sound while keeping it as smooth flowing as possible.

Plus, as per original brief, it has to allow for easy disassembly and re-packing.

There was quite a bit of head scratching with this bit of the build but eventually I sorted a design out.

I cut various bit of sheet and put big holes in them with a nice brand new holesaw set.



Made little boxes with more big holes...



Shaped bits like a heart...(#putmyheartandsoulintoit.....)



Welded the ends onto the main box, curved in bit to help with flow and also hide the external bobbin mounts from view a little.



Now I had a collection of parts that would come together and form a london underground of tubeways for the exhaust gases to follow.



I was pretty happy with the layout for its potential silencing effect. However I now wondered if it might just end up being a touch too quiet and restrictive.

Luckily I had come up with an idea early on where I could add some valves. Quite a little bit of extra work involved but the more I'd thought about it the more I was convinced it could work well. With this in mind I had built the middle chamber width to allow for some valves and made sure they could be removed to fit said valves in place.

I cut some 44mm holes in the middle chamber lids and made some to valves to suit...



Whipped up a little press form to create brackets..





Valves mounted.



Underside of lids have the heart halves which help direct flow from one tube back too the next, or up and out through the open valves..





Valve shafts stick out through back of box. Sealing will be by a combination of spring loaded fibre and silicone washers.



Now for an exciting point in life that every shed 'Barry' looks forward to. Emptying out those boxes of little random fittings that have been stashed away 'just in case you might need them'...



Such fun! I selected my (stainless!!!) treats and scribbled on some alloy.



Made lots of alloy swarf..



Ended up with these levers. Pinch bolted to the shafts along with added grub screws. The short length of threaded rod will be changed for a long length of stainless rod, actuation method from within the car yet undecided. Possibly a 12volt door lock motor etc or maybe mechanically with a bicycle cable.



Recessed the backs to allow for seals..



So yeah. Lots of parts! Compulsory photo of thing exploded into many bits...



All together now with some arrows. Remember each side is just a mirror of the other side (there is a small cross over hole in the centre plate that separates the sides)

Valve closed...



Valve open...



I think it'll be quite a difference in sound and look forward to hearing it.

The valves can be seen in action in this very exciting video....




So It's pretty much complete except for the mount points which I'll do once I've got some bobbins from engineering shop along with seals. The lid will be sealed by running a bead of silicone which I'll let set before clamping the lid down.

Oh I weighed it too. I was worried it might end up quite hefty but it will be only about 6.4 kg once all the bolts are in/packed with fibreglass..



The box will be painted satin/matt black leaving the tailpipes shiny. Silencer mounted in place...







View from above showing plenty of room for the valve linkages in place.



I ended up cutting a tiny bit more of the valance away so there's room for a stainless heatshield.



I then covered the valance with some masking tape to help prevent it getting too scratched while I put back in some internal strengthening and capping it all off. I'll also be adding mount areas for the bobbins.



I'll remove the engine next and add in the big multi-pin connector to the engine loom.

Then I'll be seriously very close to removing the Datsun engine and cutting out the under seat area just as I have on this rusty shell. Wow!!

[Darkspeed]

No less than what we have come to expect - Although I am just a little disappointed you did not emboss "Rootes Motorsport" into the casing....

[yoeddynz]

haha - missed opportunity !

[blackpopracing]

Awesome work as always.

[legend]

love it

[jjeffries]

Amazing, fascinating, inspiring and more. Or, really kind of a giant mind-fook.

Impressive how you envision it, engineer the way it will need to work, then make it happen with such exquisite craftsmanship.

Best, John

[yoeddynz]

Wow- crikey. Cheers for the very kind words.

[horrido]

Brilliant. Love these updates!

[giuliettaevo]

Not only am i amazed at the amount of thought, design and work you put in to it, but also that you're able to leave it at that.

I would have to hook it up to the engine to hear it immediately.😅

[biturbo228]

Well no wonder it was an exhausting job, you've created the space shuttle of silencers! Very impressive work 6.3kg really isn't too bad either. The profusion one I've got on the Rover (3" bore, 4x9x14", staggered exit) was 4.6kg and that's got none of the wizardry going on with yours.

[yoeddynz]

Well that's good to know. So its not too bad at all.

I was worried it was going to end up alot heavier. I am glad I've gone for thicker stainless now. Hopefully it'll stop any tinny sounds.

[Tamber]

I do like the idea with the little valve flaps in the exhaust; looking forward to seeing/hearing how well they work out, because I've been noodling over doing something similar with the Bedford.

(Rowdy mode!)

Impressive how light that box is, for what it is, too! Very well done!

[PhilA]

Nice. You may find you need some stiffening ribs beat into the flatter sections if it gets some bad resonance (there's plenty reasons most silencers are round or oval). Good luck, it looks real smart!

Phil

[yoeddynz]

Getting closer!!!

Next job was to strengthen and close up the rear valance.

Pics..

Added internal bracing. I probably didn't need to. Its not really under much stress now without an engine hanging on it as per on an original imp setup. Just closes off the back end, gives something to hang an exhaust on and something for the fiberglass engine cover to latch onto. But hey, I'm only adding a little bit of extra weight...





Gave the inside an extra layer of zinc rich paint ..

Closed it up..



Flap disc on the welds and trial fitted it. I won't yet fit any exhaust mounts. i want to weld those on when the engine is sat in the blue Imp so its all done to suit its home as no two imps are exactly the same. It looks neat in place though.



Speaking of exhausts. I needed a bit of rod for a customers job and went searching through the steel rack...



..and I found this bit of stainless rod with an eye pressed in at one end. Its perfect for the valve actuation rod that'll run along the exhaust box..



I've been having a little browse at various actuators on Ali express and I think one of these could do the job well...

vi.aliexpress.com/item/1005003796596080.html?spm=a2g0o.cart.0.0.148738damrmWCz&mp=1&gatewayAdapt=glo2vnm

With the valance sorted and covered in some epoxy paint ready for a skim of filler I could now remove the engine from rusty green imp. That's the last time it'll be sat in there.

Not sure what will become of that shell. Maybe garden art? Maybe just chop it up and keep any useful repair panels in case I have a whoopsie with Blue imp? Its not too rusty and could be saved but it would take another fella like me to do such a silly thing to a car where you can buy better shells, rego on hold, for not much money. British imp fans would probably save it though as its a good solid base compared to what I have seen on offer in the UK.

Green imp was then pushed outside into the cold and I sat in front of the wood burner, warm and cosy. I cut the main engine loom in half and let in a big multi plug. I'd been contemplating whether I'd be bothered to do this for some time now and I'm really glad I did for it didn't actually take very long to do. It'll make removing the engine even easier with no need to disturb the ecu wiring under the rear seat.



I then removed the gearbox and made a cover plate for the gap located below the flywheel. The bellhousing opening it covers faces forwards and I don't want to fill it with stones, dirt, dead possums etc.



Removed the flywheel and carefully ground a lead onto each tooth on the Subaru ring gear. Its designed for a different rotation on the starter and in use the starter would sometimes not mesh properly and make a horrible loud 'gnashing of metallic teeth' sound. Not keen on that. I'd also given the pinion a similar grind so hopefully they'll slide in nicer. Time will tell.





I then machined up a basic clutch disc alignment tool..



I refitted the valance and exhaust to the blue imp, drove it into the workshop and then removed the lovely comfy, but not exactly period correct (like as if that's an issue with me....) Tomei steering wheel which will now be fitted into our Nissan Micra.

I then cleaned up the lovely Moto-lita steering wheel that has been hanging on the wall for years since I sold my Viva HB. My Uncle in the UK worked for a short time at Moto-lita many moons ago and got this wheel then. He'd fitted it in several cars including a few Morris Minors. When he died my cousins gave it to me after his funeral.

I'm very happy to be fitting it in the Imp. It's more in keeping and looks great. I was also happy to discover that Imps and Vivas share the same spline pattern so I was able to use the original nicely made boss.



I also removed the stereo, speakers and parcel shelves. The speakers were always in the way and getting knocked by my feet when I entered the car so they won't be going back.

Then all the blankets and other stuff that's accumulated in the imp. Lol at the several British airways blankets that had found their way into the imp...



Next up were the Recaro seats. Out they came. Definitely going back in though. Might not be period correct but they are lovely. In the future, once I've won lotto I'll get them recovered in a more suitable style. Looking quite bare inside now..



I do love the two tone red/black colour scheme on the door cards and the red rear seat.



But I don't love the super sticky flashing tape I'd used to hold down the loom under the rear seat. This stuff is great if you don't want things to move or you desire tired hands trying to remove it.



Now it was finally time to remove the Datsun engine.

Actually now it was time to make a 'Datsun 1200 wheely stand 2000'. I want to have an easier system to remove/refit the Datsun lump without having to use a top mounted engine cradle and sling - a setup that was due to the centre mounted engine cross member. So I made this..



Yes, a bit over built, but it'll find other handy workshop carting uses in the future if the flat six proves itself and the Datsun setup gets sold on.

Fitted sturdy wheels, painted it workshop grey and whipped up a plywood engine cradle with room in the centre to drop the cross member down into.



Now in action. Much easier and way faster!!!



Engine out...



Still a neat little engine. If I was to keep it in the Imp (like said above, the flat six has to prove itself) I'd rebuild it, balanced properly, fit my oval port head, sporty cam, itbs and full engine management. Then promptly destroy the Imp transmission...



Arty shot...



I stripped out the remaining bits from the engine bay, the rear suspension and cross member. Drained the fuel tank, luckily only 5 litres to bother with, removed it and stashed it away in the garage which is now filling up with imp parts.



Brought the green imp back in from the chill so I use it to take measurements from.



Measured and marked out the cut lines where I need to chop out under the rear seat base for the taller Subaru transmission.



Covered the inside glass surfaces with paper. I'll get Hannah to block grinding sparks when I'm doing any cutting from under the car.



So that's where I'm at now. Next job is cutty cutty time.

[mrbounce]

Ooooh it's getting closer! Such a cool car!

[vitesseefi]

Ah…. The anticipation……. High excitement 🙂

[yoeddynz]

Totally that. I'm itching to get it finished but also don't want to rush these last bits.

It'll always be work in progress though as I've many plans for future interior updates etc