Flat six powered Hillman Imp - now with added cake!

[911hillclimber]

I've competed at Prescott and Shelsley (and others) for 32 years now, special places and special cars turn up regularly.
The Imps are remarkably fast esp at Prescott that has a lot of bends..

Small world.

[Ian Donkin]

I've just finished reading this thread (thus far) cover to cover and watched the YouTube videos - it's absolutely awesome and the sort of thread that DDK is famed for! Bravo and here's to many more entries

[yoeddynz]

Over a month has passed since the last update. That went quick!

I've been busy on other jobs so the Imp had to get time where I could. The cooling system was what I wanted to sort out. I had emailed Davies Craig about their electric water pump controller. I explained the issue in detail and the friendly tech fella there ended up calling me a few days later. We chatted for 45mins and ran through the system. He'd actually taken the time to read the full build thread which he said he'd really enjoyed. This also meant he was well informed about my setup.

From the conversation I learned that I could have a more effective bleed system setup which will help not only filling the system up from dry but also possibly help the warm up. If it didn't warm up effectively enough after changing that then I could add a traditional wax type thermostat in.

I had already gone down the path of starting to make a remote thermostat housing before the phone call anyway so I continued with that first. We had popped to the wreckers and got a thermostat and its cover from a Nissan k11 (of course..).

I machined up a flange to take that and welded it onto a tube. Then stepped the tube down in size, added extra alloy I could drill and tap to suit the 3 temp sensors. In the end the whole thing was made from about 7 bits of alloy. Its not pretty but it fits in the same location as my original sensor pipe.







You can see the added bleed stub sticking out. This bleeds off air to the new expansion tank I was going to make. I have added the same size take off onto my original sensor pipe which I'll be using first - just in case I might not end up needing a thermostat.

Originally the sensor pipe had a larger feed pipe taking fluid from the expansion tank - which I was informed was the wrong location because the sensor pipe is on the pressure side of the pump, coming off the engine. Not the suction side that it should be feeding into.

Silly me.

So I now had to add a feed point somewhere into the system before the pump. Luckily there was just enough room to do so on the pipe just before the pump. I removed the pipe from the car and added this feed here...



I also removed the main front to back pipes that run under the floor. I was happy/relieved that they come out ok without having to take out the fuel tank. I wanted to drain the complete system of the old water/dirty coolant mix but these two pipes can't be drained properly and they hold quite a lot of fluid.

So I fixed this issue. Machined up some drain points and welded them at the lowest point..







Super easy to drain the lot out now without having to even touch a hose clip.

Now onto building a new expansion tank. I have been planning to do this for some time. The old one that came with the race car is steel, heavy, ugly and rusty. It also sits in the wrong spot and upsets my engine bay Feng Shui. It just had to go. This is also where some time got lost....

I started by machining up a filler neck to accept the smaller type of radiator cap.





Then some simple cad work...



Welded bits..



Cut, bent, folded, welded, machined and out popped this...





Wire brushed it...



Painted it in epoxy paint (and the thermostat housing too)



Bolted it in place...



Then chopped it up because I didn't like it...



Yep. Bit of time down the drain that. But I just wasn't happy with it. It was still too obvious, too sticky outy and upsetting the generally symmetrical engine bay. It was also going to make my planned bulkhead cover more awkward to make and fit neatly. So back to the drawing board. I cut out the filler neck, machined it clean and started over. No pictures of it being built because I just cracked on and got it done. Finished result though..





You'll see how it fits soon.

Next job was to see if I could quieten down the exhaust boom. Those exhaust valves didn't seem to make much difference in sound and it was more than loud enough anyway. So they could get lost. I took the muffler off, such an easy quick job. Took it apart...



Removed the exhaust valves and made some extra baffles to hopefully knock a bit of sound off. V shaped 'ceilings' in the first expansion chambers...



and extra baffles on the outlet chambers...



I also removed the crossover hole between the two halves. Simply not needed on a flat six and I suspect it was stopping the distinctive flat six sound at idle.

Bolted it all back together and got stuck into the next fun job.

Not an essential job at all. But one I wanted to do. I have never liked the ugly, non symmetrical covered up hole where the Datsun cylinder head used to pop up through the parcel shelf. I've wanted to hide it behind something nice. So I got a sheet of alloy from our rack and cut out a cover. Gave it a curve in the folder...



Had to recess it in the very centre right where the Plenum/spaceship resides. Not much luckily.

Cut some strips of 4mm alloy...



Gave them a 'brushed' look with my poor mans linisher...



I had been ringing around all the various upholsterers about my district and no one had any black leather in stock plus the prices they quoted were absurd. I had bought some black vinyl instead but wasn't really happy with the idea of something so flammable being above the engine. Popping into Tasman canvas on our way home from town was just an idea at the very end of the day because I thought maybe a canvas could work. But they had some leather left over from a job and were happy to help out with some offcuts.

Leather carefully glued in place...



Then the alloy strips were carefully bolted in place. Before fitting the leather Hannah and I had deliberated over the positioning and spacing of these for some time. The idea is that I can remove them at a later date, cut them short so the middle has a gap in which I can fit a badge/logo of some sort. This will then mean there's six strips, 3 each side, much like a flat six.

Deciding on what to put in the centre is now the hard part.

So some pics of it all in place, along with the new expansion tank tucked away to the side...(the little bolts will be changed to dome heads when I next get some from the city)







I'm pretty happy with that. I might well change it out later on but for now its hiding the ugliness behind. The new tank is a huge improvement in looks and its tucked away neatly. The new bleed system is a massive improvement too. I filled the whole system up so quickly (9 litres in total ) and the air bled out really quickly this time.

We started the car up today. New exhaust is quieter but still a bit boomy at certain revs. Not a concern right now as its not a daily. Just a fun toy.

The cooling system heated up much quicker (A very cold clear 10 degree mid morning at the time of testing today)

(EFI tuning talk time. Carb folk look away) I'm now going to spend some time really trying to fine tune the idle. Its idling happily at a touch over 700 rpm but I think that's a little low. The hesitancy just off idle when for example you squeeze the throttle to pull away needs to be tuned out. I think I'll get it sorted on the VE table alone. Its not an acceleration enrichment issue. I want to get this area sorted so anyone can jump in and drive it about town slowly without any stumbling or hunting. Its still on open loop warm up idle control which I want to have dialled perfectly before I look at maybe going to closed loop.

[misteralz]

Brilliant. I dunno if teaboy's still around here, but that's how you sort a tank...

[yoeddynz]

I never realised @teaboy was on this forum but it makes sense.
He's seen it over on retro rides forum though. Hopefully he's inspired, he'll sell that BMW thing and crack on with his porker

[Nine One One]

Even the engine lid stay is nicely engineered!

[yoeddynz]

Even the engine lid stay is nicely engineered!

Thanks man. Its actually a stainless shaft and plastic knob from an old coffee plunger that I bent to suit

[911hillclimber]

What a great thread this has been, or possibly still is!
Bit of snagging to do maybe, but what a satisfying result for you, let alone the audience.

Will you leave the engine bay open or seal it like a 911 is?

[yoeddynz]

Cheers. I'm happy its still entertaining you all.

Engine bay sealing? Not sure what you mean?

[Nine One One]

Think he means like a VW Beetle, and the 911 which is air cooled and keeps the fan air over the top of the engine, so only sucking in cold air from the vents, the sealing tinware all around the top, inside the engine bay, stopping hot air being sucked in by the fan, especially since the exhaust is also right under it.
Not a necessity on yours as it is water cooled, and any additional cooling for the bike engine, will come by air flow under the car as well. You would not enclose a bike engine with tinware so why this project???

[911hillclimber]

Keeps it clean top side!

[yoeddynz]

Ahhhh ok. I see what he means.

I'll keep it all open because it allows heat to radiate off when staionary plus, more importantly...... it allows folk to be able to see my pretty engine complete

Only issue with the vents on the engine cover (its a fiberglass replica of the hillman Imp sport engine cover) is that the low pressure zone created when moving draws all the road dust into the engine bay. But I tend to stay off gravel roads and I'm happy to clean it when needed (before a car show etc etc)

[yoeddynz]

I've been chipping away at bits on this. First off was to sort out the idle tune (warning - more efi jargon coming up).

Since that day I started the engine for the very first time on the bench there have been a few settings changed that are not ideal. I'm not even sure why I changed them but I think it was when I was mucking about trying to sort out the hot start issue very early on. I think also when I changed the idle control valve I might have played with some settings.

So in order to start afresh so to speak I looked back through the restore points. These are saved every time the tuning program is used. I can go back through the files, look up a date and 'backdate' the whole tune or part of the tune. I went back to the default warm up curves that are loaded with the firmware, altered a few bits, turned the EGO correction back on (not sure why I had disabled that) and generally gave the settings a once over. I enabled 'incorporate AFR' and set up a suitable ignition based idle rpm timing curve - previously disabled.

I then rolled the imp out into the evening light...



Removed the engine access hatch from inside...



Then I wound out the idle air screw a half turn until the revs came up to around 800ish..



Later on after dinner I went back out and sat inside what was a very cosy, warm, slightly noisy tuning room and tweaked the hot idle until I was satisfied with the idle.



The following day we went for a good drive into town. Did a bit more road tuning but the temp was still not really getting high enough and would drop on downhills. I was going to have to fit a mechanical thermostat. Took the car to our local Repco branch and showed the crew in there. Lots of revving up of the engine took place

The fuel tank pump access lid was weeping through the 'fuel resistant' gasket card and apart from the fumes its not really the safest situation to have.



The clutch master cylinder was still leaking so that needed attention too.



Plus I wasn't happy with my fuel lines under the tank - a mix of copper pipe, different offcuts of hose and many hoseclips because it was all I had left the weekend of the first drive when all I wanted to do was drive the car.

So out with the fuel tank. I ordered a brand new master cylinder and a high flow 82 degree thermostat which arrived in the mail the following day.



Here's some pics of the 'frunk' with the fuel tank removed. Radiator shroud in place. It works really well at directing the hot air out and keeping the tank cool.



Removed..



Fiat/lada tandem master cylinder and brand new clutch master cylinder. Note my unsatisfactory fuel line routing..



I got a deal on a 5m roll of injection hose and re-did the lines, ending up with a handful of spare hoseclips in the process. Pic of work in progress..



As for the leaky fuel tank lid. I ordered some 70% nitrile rubber sheet. I'd rung up lots engineering supply places and various workshops locally hoping to find what I needed but no-one had anything to suit. So I bought some from a supplier in Christchurch and the postage cost the same as the bloody rubber! Our local barefoot postman was pissing himself when the square foot of rolled up rubber sheet that could have been posted in a small post bag turned up in a huge box. FFS.

Cut the rubber to suit including a new gasket to suit the sender unit..



The thermostat I'd bought was up next. I fitted it into the housing I had fabricated a few weeks ago. Hannah asked if I was going to check it for leaks before fitting but I was confident my welds were fine and it would be ok.

Nup. It leaked. I counted 4 pin holes..



So I welded them up and to be sure of sealing I painted the inside with epoxy paint before fitting it back into the car.

This morning I woke up and was now a half century old. Wow. Cool. I felt the same tbh but I'm always a bit happier on this day because Hannah usually makes me one of her amazing carrot cakes..



So after a very relaxed morning of cake and coffee I refitted the tank. Since the tank was bone dry we measured in the petrol because I have been wondering for some time about the accuracy of the fuel gauge. Turns out that its bang on. The little tank holds 27 litres when full and with 6.75 litres poured in it measured exactly 1/4. It remained accurate at 1/2 and 3/4 full. Hannah duly jotted the findings down in the little imp book of notes ...



We then went for a birthday drive. The engine warmed up so much quicker and stayed warm. It was a very cold and wet day so I wasn't expecting it to get super hot. It sat around 85-90 degrees which I feel is fine in such weather. We did a good 50km route with a variety of hills, straights and twisty bits to extend the engine so allowing the autotune program to do its job more effectively. The tune was much improved with the idle now being very consistent. I still can't get over just how smooth this little engine is. It's amazing.

We noticed that at 6000 rpm when the engine hits the limiter the needle on my 2" rev counter ($7 second hand from a swap meet many moons ago) does a big kick-swing. It must be affected by the limiter? I am looking forward to building the new instruments though. An accurate speedo that doesn't swing and a rev counter in line of sight will be a nice thing to have.

The gear shift seems to be lightening up in action and getting smoother. I think this is due to the shifter base and shaft guide bush bedding in. There's always been a metal on metal hard knock under full power shifts which I had discovered was one gearbox mount knocking the cross member. I'll insulate it with some rubber and down the line I want to look at stiffer mounts all round.

The handling seems fine. Definitely a bit more weight out back, how much I'll only know when I next weigh the car. I'd like to borrow some corner weight scales so I'll ask about my local race car mates. In such wet conditions like today I just drove it as one should drive any rear engined car. Get my entry speed sorted before the corner, don't lift off mid corner and then just power on out. It sounds fantastic and is very fun.

Speaking of noise. We are both already used to the drone which comes in at around 2200rpm. Its gone by say 2600-2800 and is worse when under load. So I select the right gear and most of the time its easily avoidable. Its more fun holding onto a lower gear anyway.

When the rain had eased I took some pics ..





Hannah is in charge of the laptop..



Got home, car still in one piece, oil and coolant still in their respective places. Tyres definitely in need of replacement though (but not until I sort the front camber out). Overall a good result and a nice way to spend a birthday afternoon.

To top it all off a friend of ours dropped around a home made sponge cake because I'd looked over her van for her earlier in the week. She told me the cake is very naughty... so this next half century is starting off with a few extra calories

[911hillclimber]

2 cakes!
Bloody hell, you won't make 100!

Hanna looks a happy cell-mate, the very best birthday pressie.

Car looks so standard parked up, excellent job.

[hot66]

Love that pic overlooking the beach