1973 Hillman Imp 1.6 De Luxe...........wait, what??!

1973 Hillman Imp 1.6 De Luxe...........wait, what??!

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rev-erend

20,572 posts

242 months

Tuesday 21st March 2017
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Another idea is a motorbike engine like a Huyabuasa or similar..

A mate has one in the back of his Mini cooper .. space framed the lot.

DocJock

6,642 posts

198 months

Tuesday 21st March 2017
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There's a fella on RetroRides who does conversions with the BMW K1200 engine as it has the correct rotation to work in a rear-engined installation.

Up to 185bhp (or 250 with turbo kit).

NiceCupOfTea

25,000 posts

209 months

Tuesday 21st March 2017
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Practical Performance Car did a feature on a brace of modified Imps 5 or 6 years back, at least one was turbo'd.

Kitchski

Original Poster:

6,342 posts

189 months

Wednesday 22nd March 2017
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AyBee said:
davepoth said:
What about putting a "bump stop" inside the bellhousing so that when the arm is in the disengaged position it prods the housing from the back and forces it to be vertical?
I like this idea - was also going to suggest adding weight to the bottom to change its centre of gravity.
A bit of time has passed, and some ideas have been raised and then dropped. One of them was the bump stop idea. The problem with that is that as the clutch wears, the finger springs begin to protrude outward. If there is a bump stop there restricting how far back the release bearing can travel, it'll start disengaging the clutch, causing slippage and much annoyance!
So then the idea of using a spring instead of a fixed bump stop was used, but we couldn't find a way to get the spring to sit squarely. Also, the spring would push the bearing into the clutch and cause the release bearing to be permanently engaged - something it's not designed to do.

So we went back to just having the bearing hanging there. Worst case scenario is that the release bearing chatters a bit on idle, but in fairness I don't think you'd hear it hehe

Funnily enough, adding weight and changing the COG would have been the best way to go about things, but it's difficult to achieve it, especially given the engine has to go back in and be running to know how successful you are or not!

TimmyJK7 said:
Great write up Rich! It is still very upsetting to not owning this but I know it is in the best of hands. I cannot wait for this car to be finally finished and being enjoyed on the roads! Good luck Rich!
Cheers Tim. Fair to say the car wouldn't be here today if it weren't for you.

NiceCupOfTea said:
I love this. My dad had 2 Imps in the early 80s, a bog standard one and an Imp Sport (Stiletto engine), lovely things. I can still feel the hot vinyl seats on my legs in the summer and remember the clang of the doors cloud9





Can't tell from the pics, but one of them is pretty much the same colour as yours!
Top one looks pretty similar. It's probably what this one looked like, originally! No vinyl under the thighs now - these seats have corduroy!

rallycross said:
I have seen this car and I love it but I cant help think that heavy lump from the Saxo should not be in there!

The original car had the lightest of engines, alloy, compact, light, just like an AX GT engine - if anyone can do it you can Rich, a lightly tuned Tu3-S on twin 40's would be ideal!
At the time the car was built, the VTR lump was the easiest to obtain (just buy a car!) and it would run 100bhp all day long. Also, the research I'd carried out suggested it wasn't much heavier than the alloy lumps, but having weighed everything it turns out it's 40kg more, or half of a me. Obviously lots of weight has been lost over the back end too, what with the carbon lid, radiator/battery etc. moving up front. Won't know the full extent until it goes on a weighbridge (which it will, one day).

My plan here is to get some decent miles on it, get a feel for it, throw it around and see what I think. I haven't driven it much, but on all the times I did before, I actually thought it handled nicely.
If, further down the road I decide that there is too much weight over the rear end, I have an AX GT engine sat here that I can rebuild, tune up a bit and fit. The clutch, exhaust, carbs, cooling pipes etc will all fit, but the gearbox adapter plate won't, as the PCD is different on an early alloy TU. So I'd either have to get another adapter plate made, or modify this one. But it wouldn't be too difficult, and the alloy TU is almost identical in weight to the original Climax-based Imp engine (about 3kg heavier).

rev-erend said:
Another idea is a motorbike engine like a Huyabuasa or similar..

A mate has one in the back of his Mini cooper .. space framed the lot.
Motorbike engine was thrown out at the beginning (superbike ones, anyway). They're horrible to drive in cars, as the lack of torque means you have to rev the arse off them so you don't stall them. Amazing on a track, but a PITA on the road. The BMW K-Series idea wasn't around too much back when we did this, but that's one I'd give more serious thought to now.

Spaceframe-wise, again we didn't want to do it. Firstly you get problems with IVA etc (as a professional outfit it has to be legit, and to be honest I see it as part of the challenge to act within the rules) and secondly it wouldn't be an Imp anymore. We could have cut the front off a Focus ST and stuck that in the back of the Imp, but wouldn't be an Imp anymore. This still is (for better or worse), it just has a different engine.

DocJock said:
There's a fella on RetroRides who does conversions with the BMW K1200 engine as it has the correct rotation to work in a rear-engined installation.

Up to 185bhp (or 250 with turbo kit).
Most engines have the correct rotation to work at the back, it just depends how you feed the power to the wheels. The gearbox on an Imp lump isn't up to 130bhp, let alone 250. I think most Imp guys running the BMW lump are at about 90-110bhp. I would have given it serious consideration as a suggestion to Tim if I'd know about it back then.


DocJock

6,642 posts

198 months

Wednesday 22nd March 2017
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That's the engine used in the Formula BMW race series. They used a Hewland gearbox, 6-speed sequential, but I doubt I'd want to live with that on the road wink

Kitchski

Original Poster:

6,342 posts

189 months

Wednesday 22nd March 2017
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A straight-cut 5-speed box is available for the Imps too, but on the road it's apparently.....awful!

TimmyJK7

13 posts

53 months

Thursday 23rd March 2017
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I think if I was to go back 8 years I would probably have still gone for the VTR lump. The BMW engines have been done numerous times (yes successfully), but a) I liked being different and b) it is in some way keeping with the Rootes heritage.

As Rich has said we played around with so many ideas as originally I was on the mind set I was going to run an R1 engine until Rich showed me the error of my ways.

Keep up the good work Rich!

onomatopoeia

3,466 posts

175 months

Thursday 8th June 2017
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Kitchski said:
A straight-cut 5-speed box is available for the Imps too, but on the road it's apparently.....awful!
Not sure where from these days, since Jack Knight vanished in a puff of smoke wink . I own one (Jack Knight) with substantial reinforcement welded around parts of the casing and a limited slip diff which certainly copes with 120bhp from a naturally aspirated Imp engine through very sticky slicks. I'd not like to use it on the road though. The dog engagement is great for clutchless changes up and down the box, but it's not really a pootling around town sort of thing. First, which is in the normal position for reverse, to second is a difficult change, and reverse being on a bonnet pull cable arrangement rather than selectable with the gear stick is also unhelpful!

Does mean you can theoretically engage both a forward gear and reverse at the same time, if you want an big repair bill.

Evangelion

5,844 posts

136 months

Thursday 8th June 2017
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I once had an Imp which was fitted with an 1100 engine from an Escort. I wanted a 1300 and bought it unseen from a scrapyard; on finding it was an 1100 I decided to fit it anyway. (I say 'I', this is a sort of royal we because i didn't touch the thing, someone else was doing it for me.

The adapter plate came, I believe from Jack Knight. The engine was mounted using a Corsair crossmember thus reducing the rear panel to mere decoration. The Ford clutch was cable-actuated, so the linkage had to be modified. The back seat and part of the underlying metalwork had to be removed to make room for the engine as the Ford lump was vertical, whereas the original was canted over at 45 degrees. The front-mounted radiator was from, I believe, a Fiat 124, and finally larger 13-inch wheels were fitted at the rear to raise the gearing.



The clutch would frequently slip out of adjustment and become unusable, the treatment being to stop, jump out, open the bonnet (boot?) and give the adjusting nut a turn or two before being able to move off again. In the end, adding a locknut cured that. The long pipework to the radiator meant bleeding the system was fun too, you had to face the car uphill to bring the radiator to the highest point.

Unfortunately the car ate gearboxes at a terrible rate. They tend to flex if too much torque is put through them, which lets the oil out the gaps. It also kept popping driveshaft doughnuts but eventually we found some special racing ones which lasted longer than most. And if you looked at the driveshafts themselves (which were the thicker ones from the Commer Imp van, 1 inch thick instead of 7/8ths) you could see they were twisting because the seams were no longer straight.

It was a little overgeared for an 1100 so performance was less sprightly than it could have been, a 1300 would have been ideal.

The previous owner, who had done the conversion, had used it for grass track racing, with a Lotus Twin-Cam fitted. He claimed to have beaten Win Percy's Datsun 240Z with it.

This was in 1975; I'd had two other Imps before this, the first was a standard 875.



The second had a 998 but the photo was taken before it was fitted which is why its tail is in the air.


Kitchski

Original Poster:

6,342 posts

189 months

Tuesday 11th July 2017
quotequote all
onomatopoeia said:
Does mean you can theoretically engage both a forward gear and reverse at the same time, if you want an big repair bill.
laugh

And who doesn't!?

Kitchski

Original Poster:

6,342 posts

189 months

Tuesday 11th July 2017
quotequote all
Evangelion said:
I once had an Imp which was fitted with an 1100 engine from an Escort. I wanted a 1300 and bought it unseen from a scrapyard; on finding it was an 1100 I decided to fit it anyway. (I say 'I', this is a sort of royal we because i didn't touch the thing, someone else was doing it for me.

The adapter plate came, I believe from Jack Knight. The engine was mounted using a Corsair crossmember thus reducing the rear panel to mere decoration. The Ford clutch was cable-actuated, so the linkage had to be modified. The back seat and part of the underlying metalwork had to be removed to make room for the engine as the Ford lump was vertical, whereas the original was canted over at 45 degrees. The front-mounted radiator was from, I believe, a Fiat 124, and finally larger 13-inch wheels were fitted at the rear to raise the gearing.



The clutch would frequently slip out of adjustment and become unusable, the treatment being to stop, jump out, open the bonnet (boot?) and give the adjusting nut a turn or two before being able to move off again. In the end, adding a locknut cured that. The long pipework to the radiator meant bleeding the system was fun too, you had to face the car uphill to bring the radiator to the highest point.

Unfortunately the car ate gearboxes at a terrible rate. They tend to flex if too much torque is put through them, which lets the oil out the gaps. It also kept popping driveshaft doughnuts but eventually we found some special racing ones which lasted longer than most. And if you looked at the driveshafts themselves (which were the thicker ones from the Commer Imp van, 1 inch thick instead of 7/8ths) you could see they were twisting because the seams were no longer straight.

It was a little overgeared for an 1100 so performance was less sprightly than it could have been, a 1300 would have been ideal.

The previous owner, who had done the conversion, had used it for grass track racing, with a Lotus Twin-Cam fitted. He claimed to have beaten Win Percy's Datsun 240Z with it.

This was in 1975; I'd had two other Imps before this, the first was a standard 875.



The second had a 998 but the photo was taken before it was fitted which is why its tail is in the air.

That's really interesting, thanks! And there's me thinking a Saxo engine might be too heavy....... hehe

The Saxo lump needs no crossmember, as the mounting points are still 'outside' the engine, though we did brace the rear crossmember a fair bit as I had a feeling the Saxo lump might wriggle around a bit more than the Imp one! Same vertical issues with the TU engine though...no parcel shelf anymore, and, realistically speaking, no back seat. That one's a bit of a bummer, I would have liked to have retained some kind of seating arrangement there, but it's not a big deal.
Bleeding the cooling system in on this one's a bit fun too, though it does self-bleed to an extent at the back end. It's only the front end that needs the bleed point, but it takes a lot of coolant! I think it's about 9 litres!

I'm nervy about the gearbox myself. I've gone from 45lbft or so, to 110lb ft, and unlike the tuned Imp engines (or bike engines) the torque is delivered in the midrange. It's very much undergeared, but then it'll pull like a train in 2nd, 3rd or 4th. The speeds are low, and the smiles are big! And it gets there pretty swiftly! I know if there are any full-bore starts the gearbox will pop. It's not a car to just get in and rag around, but then I would never really drive it like that anyway.
It's got the Elan rubber couplings (though I'm keen to upgrade to proper UJs) and it's already running the Imp Sport/Van driveshafts.

Made a bit of progress now, so update coming shortly....




Kitchski

Original Poster:

6,342 posts

189 months

Tuesday 11th July 2017
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Many nights have passed since I last updated the thread, and that's because many nights have passed since I last did anything to the Imp!

However, progress has, at last, been made! So to pick up where we left off, I had decided to use an original Imp release arm (modified) and mount a slave cylinder externally, as per the original Imp design. I had space issues as the original Imp cylinder lay over the original Imp engine, and because I don't have an original Imp engine, I don't have anywhere for the original Imp slave cylinder to lay. There's a lump of iron where that would go, so a slimline clutch slave cylinder was obtained and fitted.

Initially, we'd been running with a solid spigot bearing (an oilite bush, if we're being pedantic). The first one that went in was awful - too small, and it broke out. The second one that went in last year ended up being too tight on the end of the shaft. Different ideas were floated, before we actually found a supplier of needle-roller bearings in various sizes. The TU engine doesn't use a spigot bearing, as the MA gearbox a Saxo is normally fitted with has the support bearing on the input shaft, but happily there was still a bore hole in the end of the crank, and into that I managed to fit two very lightly greased needle roller bearings:



Another modification made through the process was shaving 0.5kg off the flywheel, by using an AX GT item, rather than the 106 Quiksilver item that was already fitted (the original Saxo VTR setup didn't fit in the bell-housing as it used a bigger clutch). I think the half a kilo saving is purely down to the fact the 106 unit had an enlarged timing ring on the outside of it, presumably for the TDC sensor on an injected engine. This change also necessitated the use of an AX GT clutch cover, rather than the 106 one, but that was fine as I had beaten ten bells of st out of the 106 one trying to remove the gearbox a week or so before!
The AX GT flywheel was refaced, checked for balance and fitted to the VTR engine:



The issue with all this was that I was going to have to space out the release bearing from the housing, which itself just pivoted on the end of the release arm. In a normal Imp, the issue of balance wasn't....well, an issue at all, seeing as the COG of the housing was spot on, and the bearing was actually a carbon bush.
Different ideas were floated around on ways to extend the reach of the bearing (because of the thickness of the adapter, and it causing the gearbox to sit further away from the engine), but without having the issue of the whole assembly tipping over and getting too up close and personal with the clutch cover fingers. That would be a fairly annoying noise!

Eventually, through researching bits on eBay and playing on Google, I arrived at something I thought might work. First step was to obtain an MG Midget (1.3.......I think) release bearing, as seen further above. I then had my business partner turn up a delryn insert, that would fit inside the bearing housing (having removed the carbon bush). I have no decent pics of this, but in this image I'm drilling a tapping it, so that I can fit some small retaining bolts from behind (all they'll do is keep it up against the housing, and stop it trying to rotate in the housing, should the bearing seize up or something:



Here it is with the bolts fitted. I'd love to tell you they're not fitted in an even PCD for a particular reason, but the truth is it was late in the evening, it won't affect how effective it is, and (perhaps crucially) nobody's going to see it...



In the interim period, I'd been speaking to a guy who used to race Imps. He said a trick back in the day was to bend a nail and weld it into the inside of the release bearing fork. I didn't fancy that, so I found some M8 studding and used that instead. I've been pretty crap with getting pictures, so this is how it looked to start with. You'll have to take my word that I fitted it!



Next step was to modify the top of the arm. Risky business, as I'm now altering the swing ratio, but as I measured before, I need 8mm of movement. The release bearing gives a maximum of 15mm (I think), and through the measurements I worked out I needed 12mm of movement at the slave. I made a new end for the arm, beefed it up pretty much everywhere and finalised the design:



Then it was time to paint and fit, along with the pushrod I made from an old TVR Chimaera clutch master cylinder rod, connected to a rosejoint. I made it adjustable, so as the clutch wears down I can shorten the pushrod to compensate. I don't want to be changing it again for a long time!



In order to keep the bearing vertical, I managed to come up with a really simple but effective solution right at the end (at the point I was contemplating life with a release bearing that chattered its tits off everytime I pulled up at the lights). All it took, was a spring!




Here it is all fitted and with the retaining springs lockwired in place to stop them dropping out.

So what I ended up with, was a bit of a mis-mash of bits.

Citroen Saxo VTR engine
Hillman Imp mk3 transaxle with a custom input shaft (with Ford splines)
Citroen AX GT flywheel
Citroen AX GT clutch cover
Ford Sierra 1.6 clutch plate (turned down to 180mm)
Fairly heavily modified Hillman Imp release arm
Saab 900 release bearing
MG Midget release bearing housing (with custom delryn boss)
CBS shallow clutch slave cylinder with modified TVR Chimaera actuation rod and HEL braided line

Before I even through about putting it back in, I had to check it all added up. I knew the slave cylinder was the same capacity as the original Imp one, and it was running a standard Imp master cylinder, so the piston ratio should be the same. Only one way to check whether it all works or not.....rig it up!



Luckily, thanks to the HEL braided line, I had just about enough spare hose to sit the engine on the floor and bleed it in! It seemed to bleed in OK, and it was operating the arm, so I made the decision to actually fit the engine and see if it worked or not.

I did! I have no picture of the engine back in place yet, but the driveshafts were fitted up and the clutch bled in once more. I put it in gear, tried to rock it backwards and came up against the engine resisting it. I depressed the clutch.....and still it wouldn't move. I sighed, loudly. I pushed harder and realised I could move it, but that it was dragging heavily. I had a feeling there was some air trapped in the system, and suspected the slave as the bleed nipple is mounted at a less than ideal angle. I removed the cylinder, bled it in my hand with the bleed nipple pointing the right way, refitted, tried again.....YES! The clutch was working!



I rigged the engine back up and got it running. I tried to select gears...no problem at all! The pedal is a perfect weight, and the clutch is silent both disengaged and engaged. It actually couldn't have gone better! I took a quick video, which I'll upload to the tube, but early signs are great!

Last time it was on the road, I remember there were some issues which I'll need to resolve, but I've booked an MoT for Thursday, so I'll see if I can get it through and begin testing it. It needs a new battery, and I'm going to fit a proper 063 rather than that stupid cyclic gel thing that goes flat every 5 mins.

In the meantime, I completely forgot I'd applied for a spot at the Goodwood Breakfast Club classic car meet. The Imp's been accepted, so fingers crossed it'll be there on the 6th August biggrin

lufbramatt

4,111 posts

92 months

Wednesday 12th July 2017
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Really enjoyed reading through all this, ingenious fix for the clutch, looking forward to more!

Thanks for sharing smile

Mark Benson

5,774 posts

227 months

Wednesday 12th July 2017
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I do enjoy your updates (and the determination to make everything you do Gallic in some way).

Kitchski

Original Poster:

6,342 posts

189 months

Thursday 13th July 2017
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lufbramatt said:
Really enjoyed reading through all this, ingenious fix for the clutch, looking forward to more!

Thanks for sharing smile
Cheers smile The clutch spring idea came to me just as I was about to put it all back together. Seemed so simple, and so daft that I hadn't thought of it already!

Mark Benson said:
I do enjoy your updates (and the determination to make everything you do Gallic in some way).
Ha! There was genuinely no intention to inject any Gallic-ness into the Imp. Originally when the idea behind the car was conceived, it was a candidate on a list of potential engines that actually began to make sense the more we thought about it. And then there was the tenuous Rootes > PSA link (which goes around the houses a bit).

MoT is later today at 4pm. Actually more nervous than I normally am!

PixelpeepS3

6,046 posts

100 months

Thursday 13th July 2017
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epic. great car..

when's the turbo going on? laugh

Kitchski

Original Poster:

6,342 posts

189 months

Thursday 13th July 2017
quotequote all
PixelpeepS3 said:
epic. great car..

when's the turbo going on? laugh
About the time I fancy finding out how many pieces it's possible to smash an Imp transaxle casing into..... hehe

PixelpeepS3

6,046 posts

100 months

Thursday 13th July 2017
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Kitchski said:
PixelpeepS3 said:
epic. great car..

when's the turbo going on? laugh
About the time I fancy finding out how many pieces it's possible to smash an Imp transaxle casing into..... hehe
That's the trouble with you youngsters.... no sense of adventure!

laugh

fine workmanship OP, you are a true craftsman!

Kitchski

Original Poster:

6,342 posts

189 months

Thursday 13th July 2017
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You know you're nervous about an MoT when you wash the car first....


gert biggens

45 posts

52 months

Thursday 13th July 2017
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You know there have been many, many, many fine cars brought to my attention of this forum, spanning the sublime to the absolute Barry. But this project I think, aside from being incredible, represents the absolute encapsulation of the PH spirit. So much love, ingenuity, craftsmanship, creativity and man-hours has gone into a project that makes no logical or financial sense whatever, and yet it just lifts the spirits to see it. To take an Imp, which, let’s be honest, looks great, but never quite had the engineering underneath that it should have had… and then just roll up your sleeves and GIVE it all that, with lathes and hammers and bits of dead other cars…

…Kitchski, I salute you, and all who sail in you!