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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

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