Roadster Rebuild Diary from Cornwall

[meverett]

Re: Roadster Rebuild Diary from Cornwall

Thanks Hugh and Dave,
Hugh you are more than welcome to pop around, I will also try to pop out to see you.
I spent another hour or so flattening back the bonnet and out with the polisher. I was recommended Menzerna cutting compound so bought the 3 stage pack. Not used the ultra fine though. I am learning as I go and results below, happy with that.

6E18A211-721D-4832-B7B8-0813BE2EDF64.jpeg

6CB3D060-C075-4224-B468-45DB569B32AF.jpeg

[milliemarlin]

Re: Roadster Rebuild Diary from Cornwall

I’m not a big fan of two fans. The engine is designed to run at an optimum temperature. Most wear occurs during the warm up. In general use the forward movement of the car should be more than enough to cool the radiator. Marlins have well vented engine compartments. Essentially even very slow speeds should be enough to ensure the air touching the radiator is at ambient temperature. Even a 10-20mph breeze will keep things cool. The fan should only be needed to draw air through the radiator in stationary air. If you are having problems with cooling it is almost certainly fuel mixture or timing issues. The most common being a lean mixture.

IMHO the thermostatically operated electric fan would be best, ideally fitted to the rear of the radiator to shield from ill-fated insects. It also makes routine cleaning of the radiator easier. I originally fitted Millie’s fan in front of the radiator. So I have done the experiment and can confirm the result. The electric fan will not operate during the warm up period. The engine mounted fan will slow engine warm up and waste energy in normal operation.

Sorry to mention the fan again but to me it looks like a glaring slip-up on an otherwise outstanding rebuild.
Paul

PS: I expect to gain no fans from my first sentence.

[meverett]

Re: Roadster Rebuild Diary from Cornwall

Thanks for your input Paul,
It turns out that I am just using the thermostic fan. I purchased the inline thermostatic switch that Hugh recommended and when plumbing in the classic Mini rad it became obvious that the engine fan would spin too close to the pipes so I have removed it.
Cheers, Martin.

[boustrophedon]

Re: Roadster Rebuild Diary from Cornwall

Whilst I would agree with the comments about using an electric fan, I think the statement that the engine bay is "well ventilated" to be wrong.

Air can potentially get into the engine bay OK, but is stalled on the way out by the high pressure air trapped by the wings and forced under the car as it moves. The wings force air up into the engine bay creating high pressure behind the radiator. The only way out for the cooling air is through the tiny area of the bonnet louvres and back under the car against the air trapped by the wings. A blast of hot air comes up through the handbrake slot in mine. This I believe is the real reason for the poor cooling found in many Roadsters.

The engine driven fan does very little as it is unducted and too far from the radiator to do any good at all.

[milliemarlin]

Re: Roadster Rebuild Diary from Cornwall

Whilst I would agree with the comments about using an electric fan, I think the statement that the engine bay is "well ventilated" to be wrong.

Air can potentially get into the engine bay OK, but is stalled on the way out by the high pressure air trapped by the wings and forced under the car as it moves. The wings force air up into the engine bay creating high pressure behind the radiator. The only way out for the cooling air is through the tiny area of the bonnet louvres and back under the car against the air trapped by the wings. A blast of hot air comes up through the handbrake slot in mine. This I believe is the real reason for the poor cooling found in many Roadsters.

The engine driven fan does very little as it is unducted and too far from the radiator to do any good at all.

I agree the aerodynamics of the Marlin leave a lot to be desired. Quite few members add vents to the top of the bonnet to improve flow through the engine compartment. When on the motorway home from one car show I discovered that the engine compartment is indeed at a higher pressure than the surrounding air when the bonnet popped up. Some clown must have inspected my engine compartment and not replaced the bonnet catches.

I have read that engineers spend more time getting airflow through the engine compartment than around the bodywork of production cars. Anyone interested in F1 will also recognise the importance of cooling airflow. I don’t suppose anyone has access to a wind tunnel it would be interesting to see the actual airflow over a marlin.

The fact remains that most Marlins, even those with V8s, are able to tow trailers and caravans uphill without overheating.

Perhaps “adequately ventilated” would have been more appropriate.
Paul

[stevejgreen]

Re: Roadster Rebuild Diary from Cornwall

The fact remains that most Marlins, even those with V8s, are able to tow trailers and caravans uphill without overheating.
Paul

Except that numerous forum entries and Pitstop articles tell a long history of overheating. Recognised by Paul Moorehouse as well!

[milliemarlin]

Re: Roadster Rebuild Diary from Cornwall

Except that numerous forum entries and Pitstop articles tell a long history of overheating. Recognised by Paul Moorehouse as well!

Perhaps “mostly adequately ventilated” would have been more appropriate.
Paul

[meverett]

Re: Roadster Rebuild Diary from Cornwall

I wonder how all the 7’s cope with cooling.
On another note my seats turned up today, yay.

31CB7DF3-E7FB-4D56-997B-1798B2D94B36.jpeg

[listerjp2]

Re: Roadster Rebuild Diary from Cornwall

Pretty, pretty

Adrian

[meverett]

Re: Roadster Rebuild Diary from Cornwall

Fairly old and will need trimming sometime in the future but they are comfy.

[h_m_cumming]

Re: Roadster Rebuild Diary from Cornwall

Are you going to put them on the Marina runners like mine?

[meverett]

Re: Roadster Rebuild Diary from Cornwall

Hi Hugh, I don’t have any Marina runners just a set of universal adjustable runners that were on the old seats. These were mounted on some alloy box section to raise them up a bit.
Do the Marina runners raise them up so I can do away with the box section?

[listerjp2]

Re: Roadster Rebuild Diary from Cornwall

I have to admit I have bolted mine directly to the floor.

It does mean that I sit lower and the standard Marlin buffeting isn't so apparent.

Adrian

Hi Hugh, I don’t have any Marina runners just a set of universal adjustable runners that were on the old seats. These were mounted on some alloy box section to raise them up a bit.
Do the Marina runners raise them up so I can do away with the box section?

[acbluemarlin]

Re: Roadster Rebuild Diary from Cornwall

Regarding "how do all the 7's cope" my last daft car was a least loved Caterham (not least loved by me, but least loved by marque officionados. Least loved meant cheapest for sale in the UK when I bought it), the 1600VX Classic which used the 1600 Vauxhall 8 valve OHC engine (big block, so Cavalier/Vectra and not Astra). This always seemed to run cold, so I assumed the thermostat had stuck open and started looking for part numbers on the owners forum. This lead to discover that when Caterham had switched to this engine, they tried every thermostat rating they could find in an effort to stop the lump from overheating. Eventually they hit on the genius idea of leaving the thermostat out altogether. Apparently if anyone realised their Caterham didn't have a stat and rang up to ask for one they were supplied one free of charge from the large box kept under a desk where they put all the stats they originally removed when building the cars. I live in cold Lancashire, not balmy Surrey where they presumably did all their testing, so I did buy a very cheap low temperature opening stat off Ebay for a couple of quid, but i could never bring myself to fit it before I sold the car... I did give it to the new owner, but related the tale and decided to leave it to him to make up his own mind.

And there was also the time I took a Blackjack Avion to Harewood Hillclimb school on a warm June day and was told in the paddock after a run that I'd left coolant on the circuit. When I lifted the bonnet and they'd gazed at the aircooled twin pot for a few seconds they went to have a closer look at the crossflow engined 7-alike Sylva Striker that had preceded me up the hill and had previously insisted "it wasn't me mate, must have been that weird 3 wheeler".

For reference, my original Cabrio never seemed to overheat either with a 2 litre Pinto or the eventual 2.8l litre Cologne - but i can't remember if we fitted an electric fan or just kept the engine driven item. But I think the radiator and cowl opening is substantially larger than a Roadster, and the design meant it was easy to make sure pretty much all the air passed through the rad. If I did fit an electric fan it was definitely on the engine bay side.

My current Roadster did have an electric fan fitted that I've just replaced. Both original and replacement are on the entrance side, mainly becasue there is so little room between steering rack and radiator.

[milliemarlin]

Re: Roadster Rebuild Diary from Cornwall

Hi Hugh, I don’t have any Marina runners just a set of universal adjustable runners that were on the old seats. These were mounted on some alloy box section to raise them up a bit.
Do the Marina runners raise them up so I can do away with the box section?

The box section may be there to strengthen the floor. The flat steel floor can act like the button on a jam jar lid giving the car an insubstantial feel as you step in. With my Cabrio raising the front of the seat also made it more comfortable. I am on the limit on height for a short wheelbase and raising the front of the seat causes your leg to be naturally a little bent.

I spent a long time with blocks of wood getting the angle of the seats right. Given the hours you may spend sitting in them it’s worth the effort.
Paul