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MartinClan 18th August 2020 14:30

Marlin Roadster (Re)Build
I have just acquired a previously built Marlin Roadster which I am planning to re-build/restore.
It has an interesting history in that the guy I purchased it from is the original builder. The car itself is correctly registered although never really finished having never been painted or trimmed. You could call it a blank canvas!
The kit is based on a Morris Marina (yes really!). This particular car used a 1.8 as the donor and so has a BMC B series engine. Not exactly a firecracker and pretty heavy but due to the love of the MGB there are plenty of tuning parts about.
It won't be a quick re-build so don't expect frequent updates!

The car currently looks like this: by Robin Martin, on Flickr

But I am not planning a standard build. So it may end up looking like this: by Robin Martin, on Flickr

Or this: by Robin Martin, on Flickr


PS - Must try to understand how the pictures on this forum work.

Mitchelkitman 18th August 2020 16:12

Well it looks like you've mastered how to do pictures!
For info (as far as my knowledge goes) there are only small differences between the Marina 1.8 and MG 1.8 engines (dependant on age the Marina one may be more powerful than an older MGB one for instance). IIRC the crank on MGB was forged, but not on Marina. There may be some cam differences...... Just in case anyone tries it DON'T fit a 'fast' or 'high lift' cam to one of these as you'll kill the torque and (as they aren't meant to be a high revving engine) never exploit the extra power at high revs. Someone was bitterly disappointed years ago when his kit car (with 'stage 3' or whatever tuning parts he'd paid a fortune for with expert fitment) was noticeably powerless compared to my bog standard MGB engine(same kit car). The crankshaft pulley is a bit bigger than the MGB, but fits either crank (ask me how I know!) but of course needs a slightly longer belt.

Lucky@LeMans 18th August 2020 19:49

Nothing wrong with those old "B" series engines. The 1800 TC ( Twin Carb ) Marina went really well and in the light Marlin will be quite quick. Simple upgrades such as an electronic ignition module to replace the points and the twin carb conversion if yours is a single will be all you need.

Mister Towed 19th August 2020 11:07

I was a huge fan of the Marina based Marlin back in the very early 80's - it was the kindest thing to do with BL's Finest (!!) saloon back then, far more subtle than dropping a caravan/grand piano/etc. on it like Jeremy C did regularly on Top Gear.

The old B series engine makes all the right noises and is simple and strong enough to be a very reliable lump with a bit of basic maintenance. Who cares if it's never going to worry a Fireblade rider in the insane 0-100-0mph dash between roundabouts on a sunny weekend?

As for the style to go for, it'd be option 1 above with Alfa badges for me all day long. A lot of people put Alfa/Fiat (and Toyota) twin cams in them back in the day, which justified the badges.

Hmm, I know I said there's nothing much wrong with a B series, but I wonder if the Twin-Spark motor from the cheap as chips 156 could be mated to an RX8 gearbox....

MartinClan 21st August 2020 15:32

I took a few pictures of the dirty bits yesterday before covering the car up till I am ready to start stripping it. by Robin Martin, on Flickr
Chassis is in good condition other than some surface rust. by Robin Martin, on Flickr
Front suspension. Tie bar bushes completely disintegrated![1] by Robin Martin, on Flickr
BMC B series engine with a mere 130k miles[1] by Robin Martin, on Flickr
Rear spring arrangement. Not the prettiest part of the car. I am considering shortening the spring by about 50mm and shortening the chassis accordingly thereby bringing the spring mounts closer to the rear tub. Sounds a bit drastic but I have seen it done on another car with no ill affects on the handling.

On the plus side I was ploughing through the history file that came with it and although it hasn't run for nearly 30 years it had an MOT just before it came off the road. So other than those items affected by time, mechanically it shouldn't be too bad. And I found an invoice for a new gearbox so that's one less thing to overhaul. The engine itself will need a complete rebuild I suspect. At least an unleaded head conversion. Currently thinking about the Peter Burgess EconoTune head which allegedly produces about 20% more power without much further modification.

Cheers, Robin

Mitchelkitman 21st August 2020 17:31

Instead of moving the spring mount, have you thought about creating a 'real valance' or similar to hide the rear of the chassis/springs?

Dpaz 22nd August 2020 18:02

Wow a dynamo! Remember if it is registered as a Marlin (some aren't) with the donor reg and pre-1980, it is probably tax-free. Have you joined the Marlin owners Club? Lots of help and advice there. B engined Roadsters do tend to overheat so if you have, keep the engine fan and put louvres in the engine side panels. No need to tune it, the B is no slouch. I have a B roadster. Good luck and remember it is supposed to be fun.P.S. I too love the look of the first pic. The Alfa look is great!

MartinClan 11th December 2020 19:22

Finally made some progress albeit on the dismantling. Front wings, bonnets sides, radiator cowl and radiator all removed. No real horrors but the car was built before the availability of cheap stainless fastenings so I have had to dremel at least 50% of the screws. by Robin Martin, on Flickr

A couple of surprises:
1. The engine still had water in it - but the original builder that I bought it from assures me it had been stored inside for the last 30 years so unlikley to have frozen up.
2. The offside torsion bar appears to have been making a bid for escape. It wouldn't have been much longer before that side of the suspension collapsed!

And some observations:
1. The bulkhead is beginning to crack arround the pedal box. Apparently a common problem.
2. The rad is quite compact but very chunky. I believe it originated from a Vauxhall Viva so I am suprised how deep it is. I have looked into alternatives but have come to the conclusion that getting it recored is the simpest solution.
3. The chassis itself has plenty of surface rust but nothing that a bit of cleaning up won't remove. I was a bit concerned when removing the rad is it had been fitted with just two primative brackets at the top and the bottom wedged between the chasis rails. but it seems no harm done.

I have also removed a few other odds and ends including the heater which wasn't salvageable. Anyone got a MK3 Spitfire heater going spare?

Cheers, Robin

Dpaz 11th December 2020 21:15

Apparently, if you replace the tie bar bushes with rose joints and remove the torsion bar coil-overs can be fitted on the front. They look nice too! BTW I am told by a reliable source that old plastic fans are liable to disintergrate.

redratbike 12th December 2020 09:49

Great to see these original kits being revamped I like the smaller wings/guards in your first post

Looks like a nice project to be doing

MartinClan 12th December 2020 15:46


Originally Posted by Dpaz (Post 105512)
Apparently, if you replace the tie bar bushes with rose joints and remove the torsion bar coil-overs can be fitted on the front. They look nice too! BTW I am told by a reliable source that old plastic fans are liable to disintergrate.

That's an interesting idea. I know some owners have replaced the tie rods but that alone isn't that useful. However replacing the torsion bars with coil overs means the suspension could be adjusted. Not possible with the torsion bars. I think a bit of investigation would be worth doing.
Cheers Robin

Mitchelkitman 13th December 2020 16:31

If they are the same torsion bars as Marina, then they can be adjusted by moving the nut/bolt where it meets the chassis.

AlanHogg 14th December 2020 16:16

That's ok for fine adjustment, coarse adjustment is by moving suspension arm on torsion bar splines

Mitchelkitman 14th December 2020 16:49

Ah -yes, I'd forgotten that. So lots of scope for adjustment!

MartinClan 15th December 2020 20:23

The problem with the torsion bar arrangement on the Marlin is the end of the torsion bar goes through a hole in the chassis. Meaning that the torsion bar angle and hence castor and camber angles are non adjustable. Changing to coilovers would eliminate that problem.
I found some info on the Marlin Owners Club forum about the coilover solution. The only issue I can see is that the original bracket for the damper mounting wasn't designed to take the weight of the car so may need beefing up or remaking.
Cheers Robin

Mitchelkitman 15th December 2020 22:16

Yes, but that's only important if there's a benefit of having the adjustment. I've known people fit vernier pulleys to camshafts, but leave them in the standard orientation - or worse still just change the setting without any knowledge of whether it's made the situation better or worse (for their desired outcome)

MartinClan 21st December 2020 11:40

Rust removal rust using electrolysis
I have been experimenting with rust removal using electrolysis. There is a lot of info about it on t'internet but I am always suspicious of magic solutions to rust removal so I thought I would try it. Amazingly it works!

I used a large food container with some re-bar as the anodes and a weak solution of Sodium Carbonate. I already hace a handy 12 volt supply in my "man shed" so that bit was easy. I adjusted the current flow to about 1 amp with a couple of resistors. Not sure if that is right or not but seems to work. I guess it depends on the size of the piece you are de-rusting. by Robin Martin, on Flickr

And the proof of the puddding (or before and after....) by Robin Martin, on Flickr

It seems to be a great process. Removes the rust without removing any underlying metal. And far lesss messy than a wire brush in an electric drill. If you try this though, the process generates hydrogen, so it must be done in an area with good ventilation or preferably outdoors.

Now all I have to do is the 100's of other parts...

Cheers, Robin

Lucky@LeMans 21st December 2020 21:09

I rigged up a similar tank when I restored my 49 Triumph Roadster. I could do a couple of parts at a time but it was an over night process. In the end I resorted to the blast cabinet with aluminium oxide grit. So much quicker and thorough in my opinion. What took 12 hours in the tank could be done in two minutes by blasting.

MartinClan 22nd December 2020 09:28


Originally Posted by Lucky@LeMans (Post 105553)
In the end I resorted to the blast cabinet with aluminium oxide grit. So much quicker and thorough in my opinion. What took 12 hours in the tank could be done in two minutes by blasting.

I don't have that luxury unfortunately. Electrolysis might be slow but certainly cleaner that the old wire brush in a drill. And I am not in any hurry.....

Cheers, Robin

MartinClan 1st January 2021 16:18

I have now removed most of the body and the floors. Lots of rusty M6 screws. Just the rear tub to remove now and that's the body stripped. by Robin Martin, on Flickr

The fuel tank mounting is - err - interesting. Just dangling from some metal straps. For some reason the builder had ignored the flanges on the chassis that it was supposed to be fixed to. It must have been reasonably secure as the car had done 30k miles like this. Does anyone recognise the tank? Rumour has it it was from a MK1 Escort estate. Now unobtanium of course so I will have to look for something else. by Robin Martin, on Flickr

And the boot floor was just a piece of hardboard resting on the top of the tank! Oooooo....
It was cut nicely to shape though.

Cheers, Robin

peterux 1st January 2021 16:33

Looks like it was held on by the filler pipe!!

These chaps do quite a few alternatives...
but I'm sure there are others
Cheers, Peter

AlanHogg 1st January 2021 16:53

Escort estate mk1/2 tank is what was used but not obtainable new anymore. Midget/Sprite is one i believe will fit or maybe better to go custom alloy/stainless.

Mitchelkitman 1st January 2021 17:31

Maybe hung on straps to gain a bit more boot space? :icon_lol:
If it's an escort estate tank, I bought a brand new one for my Rickman. (probably 3 years ago - time flies).

jonkoxe 4th January 2021 08:21

That's not an escort tank!
Hi Robin
What you have there is not an Escort van fuel tank. Looks quite different, which could explain the unorthodox fitting method. Keep an eye on eBay as the escort tanks do come up now and again. Looking forward to more rebuild pics.

Mitchelkitman 4th January 2021 08:29

An MG B or Midget tank will (I think) have a flat top, and will be easily available new.

MartinClan 17th January 2021 16:10

Removed the engine this weekend. I decided to drop it out underneath as that avoided having to use my hoist. Nothing wrong with using a hoist to remove the engine but it's not a job I like to do single handed. The old B series is a heavy old thing.
Getting the chassis up high enough was a bit tricky. The slightly dodgy looking supports (axle stands on wheels) were actually very stable. by Robin Martin, on Flickr

And the engine in all its oily glory. I had forgotton how old school british engines tended to leak. The gearbox is actually almost new in that it was replaced just before the car was taken off the road 30 years ago. Hence the green paint. by Robin Martin, on Flickr

Next job is to clean it all up before it is allowed to go into my fairly clean garage. Not looking forward to that....

Cheers, Robin

peterux 18th January 2021 15:58

Good progress, Robin!
That gearbox looks like it came off a tractor :-)

MartinClan 18th January 2021 17:56


Originally Posted by peterux (Post 105683)
That gearbox looks like it came off a tractor :-)

Must be the colour lol.

MartinClan 23rd January 2021 16:14

It's been too cold do do an awful lot on the mechanical side as the car is outside atm. But I have done a little work on the first of the fibreglass mouldings, all of which need some form of repair.
Here's a before by Robin Martin, on Flickr

And after by Robin Martin, on Flickr

My main question now is what primer to use? There doesn't seem to be one answer unfortunately. I have "discovered" Epifanes Multi Marine primer which allegedly is good for fibreglass, steel and aluminium of which I have all. As I will be coach (hand) painting the car it may fit the bill.

Cheers, Robin

Mitchelkitman 23rd January 2021 16:47

I'm also an advocate of brush painting. IMHO the most important aspect of making the primer 'stick' to GRP is the surface finish - 320 grit is my preferred preparation. Paint suppliers (who often know nothing about GRP anyway) state all sorts such as "you need plasticiser in the paint - that will be another £10 a litre please". Many years ago someone who'd painted his car said to me "just use red oxide primer". I was planning on painting the GRP 'bumpers' on my Dutton at the time. The Red oxide (follower by satin black) just using aerosols came out great, and gave no future issues. Ambient temp is also very important, much too cold at the moment!

Lucky@LeMans 23rd January 2021 16:55

I've used Davids 182 primer on GRP and had no issues. For ali you really need an etch primer, they are cheap enough and readily available in aerosol form.

MartinClan 1st February 2021 19:39

The front suspension is now entirely off revealing some fairly horrible construction in places. Odd bolts, holes in the wrong place etc. by Robin Martin, on Flickr
And aso plenty of evidence of the use of a large hammer when the suspension was removed from the donor, plus the torsion bars are well and truly rusted into the suspension arms at one end and the adjuster at the other. Amazing it ever passed an MOT but then things were rather different 30 years ago! Good job I bought a spare set of front suspension components off Ebay - between the two lots should be able to make one decent set. And the chassis itself hasn't been butchered at all.

Just the rear to dismantle now. The rear axle case is very rusty, particularly arround the spring saddles one of which has a hole rusted right through it. It looks like some serious repairs may be needed. I am also currently trying to get some prices for new rear springs. The plan is to:
A. Have then slightly shorter at the rear to avoid the spring sticking out look that the Marlin suffers from.
B. Have them made flatter than standard to avoid using the 'orrible lowering blocks that the car currently has. by Robin Martin, on Flickr

And I learnt something today. I was suprised to find that the springs are assymetric in that the axle is positioned further forward than centre of the spring by some 4 inches. Curious as to why that was I did some Googling and it seems it's to reduce axle wind up (tramping) under heavy acceleration. And I always thought leaf springs were simple!

Cheers, Robin

MartinClan 4th February 2021 16:31

The chassis is pretty now pretty much dismantled and ready to be moved up to the man shed for restoration and a couple of planned modifications. I'm surprised how heavy it is - I guess the box sections must be quite a heavy gauge. by Robin Martin, on Flickr

The rear axle, although being generally good, has rusted through spring plates and so I will have to do something about those. I think the only solution is to cut them off and fabricate some new ones and have them welded on. The position is fairly critical though. Apparently the diff flange needs to be 3 degrees off vertical otherwise the UJ's in the propshaft suffer. by Robin Martin, on Flickr

The rest of the spring mounting hardware seems to be OK other than the U-Bolts which I had to take the Dremel to. Even the rubber pads look servicable, although you can get new ones from SuperPro at a price that's not nice.
The large lump of rusty steel is a lowering block. It's 'orrible and doesn't feature in my rebuild plans! by Robin Martin, on Flickr

MartinClan 16th February 2021 18:52

In my drive for a slightly more modern and safe car, and after some searching, I managed to find a rare Marina pedal box with servo and dual master cylinder (wow). Both were options would you believe... by Robin Martin, on Flickr

The servo looks pretty grotty and new ones are non existant. It's possible to get them rebuilt but apparently with this type (crimped construction) they have to saw them in half and then weld the two halves back together! I suspect that may be outside of my budget. But a bit of Googling has revealed that the Landrover Seies 3 servo has the same mounting points and looks very similar, and importantly is freely available. So I may take a punt and buy a new one of those. Can always sell it again on Ebay if it doesn't work out.

I am hoping to be able to rebuild the master cylinder. next job is to strip it to see what the bores are like. Can anyone idenity the model number? It's (obviously) Girling but do the long string of numbers mean anything? Unfortunately the Marina, even with the rare servo and dual master combo, used 4 different models so I can't identify it that way. by Robin Martin, on Flickr

Cheers, Robin

AlanHogg 16th February 2021 19:50

I worked in the distant past for AP products {Lockheed, Borg and Beck] so not overly familiar with Girling . From what I remember the master cylinder number is only relevant for the first 8 digits ie 64678912. The Lockheed servo you could dismantle in that the two halfs locked together with a quarter turn, easy with the correct tools but possible with some ingenuity. I'm sure someone on the Owners club forum when looking for an alternative [similair problem] found a more modern set up that required little work to fit. Maybe off a Renault. Will see if I can find the details.

AlanHogg 16th February 2021 19:59

Seems Peugot 205 with an adaptor works well according to Marlin owners club post

Mitchelkitman 16th February 2021 20:13

When I wanted a servo to replace one on my Rickman Ranger (Escort mk2), a Land Rover one was ideal. £60 brand new (Britpart) compared with the £300 a specialist wanted to try (not definite) to fix the escort one. just needed a small mod to the pushrod and in under 3 hrs (taken at leisure) I'd removed and replaced. If it ever needs replacing I'm confident it will be available in the future.
ETA, the master cylinder (from Land Rover) looks like it would also have been suitable (with a union change on one brake pipe), but I was able to use the Escort one, as it fitted perfectly.

MartinClan 20th February 2021 18:35

Good and bad today.
First the bad news....
I attempted to dissasemble the master cylinder and it's just one mass of rust. I don't think it's worth saving. by Robin Martin, on Flickr
So the hunt is on for an alternative. After a lot of Googling I found the GMC234 which is used on the TR6. It is designed to be mounted at an angle, and the bore is 20.3. A bit larger than the cylinder used on the Marina but probably not disastrously so. by Robin Martin, on Flickr
It also has the advantage that the servo it is used with (still available new) looks pretty much identical to that used on the Marina.

And the good news is, after much fretting, I decided to go for drilling out the old studs on the exhaust manifold and re-tapping it to fit new ones. All my other efforts at removing the old ones had failed miserably. But in the end it proved to be much easier than I thought. by Robin Martin, on Flickr
The observant might notice one of them is a bit on the p!ss. Well 5 out of 6 isn't bad and I don't suppose anyone will notice!

And this arrived in the post. The Alfa 8C was what the Marlin was loosely based on. You can see the family resemblance. by Robin Martin, on Flickr

Cheers, Robin

MartinClan 25th February 2021 20:14

The TR6 servo and master cylinder arrived today. Pretty much a perfect fit other than the servo needed packing out about 6mm. Temporarily done with washers but I willl make a proper spacer. The angle of the reservoir on the master cylinder is identical to that of the standard Marina one so fluid levels should be good. I do like it when a plan comes together. by Robin Martin, on Flickr

I should mention that the Marina pedals are shortened for use in the Marlin and someone has drilled go-faster holes in them...

Cheers, Robin

peterux 25th February 2021 22:22

Looks like an excellent solution. It may be the camera angle but it looks like an unusually shallow reservoir, presumably to clear the tr6 bonnet?

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