tompollock

And it's a 1991 car with the Ford Crossflow 1700 Supersprint motor, not that should affect matters.

Just digesting the replies received so far.  Thanks so much.  Very, very helpful.  I should just add that the engine is dry-sumpted, but it is the after market Neil Brown Engineering one, and I expect the car still has the standard Sierra CRB setup fitted.

Eight months in to Caterham ownership and I'm still chasing this illusive clangy rattle coming from somewhere in the middle of the car. It's on a 1700 Supersprint / 5 speed Sierra box / De Dion rear, with 20k miles on the clock.  Apologies for the long thread but I'm running out of ideas.

The clutch (original AFAIK) works perfectly, no slip, good bite point, and the pedal lines up with the brake pedal. Took the rubber boot off the bellhousing and was puzzled (and horrified) to find a good 50mm of rattly slack in the clutch release mechanism before the CRB touched the clutch diaphragm. How long it has been like this I've no idea. Perhaps it had a new clutch some time before I had the car and was never adjusted correctly afterwards.

Shouldn't the CRB be pre-loaded against the diaphragm spring so that it is always spinning at engine revs, or is this particular design/application different from the usual?  Either way do you think the rattly slack in the mechanism, amplified by the acoustics of the bellhousing, is likely to be the source of my clangy rattle, ? Proof of the pudding would be to find a bit of broken tarmac that sets off the rattle, preferably downhill, and drive across it both with the clutch engaged and disengaged.

If I'm right what is the correct amount of pre-load to apply to the CRB when adjusting the clutch cable? i.e. Adjust until the CRB touches the diaphragm, then 1/8th more of a turn on the cable adjustment to pre-load?  Too little pressure and the CRB could get hot spinning against the diaphragm, too much and you could end up overloading the bearing.

Thanks in advance,

Tom.

Thanks for the swift replies.  Googled and found 2 more forum members happy with the way the TR1's performed on their 7's so that's good enough for me!

I need to replace the very old Toyo T1-S and T1-R tyres on my C7 1700 Supersprint which runs on 15 inch rims. Road use only and with cost in mind.  Not worried about longevity as I don't do enough miles, just driveability, in all conditions.

Are any members using Toyo TR-1 tyres and how have they found them? Other lower priced recommendations welcome!

Thanks in advance.

Thanks Paul.  I saw your original answer but didn't realise the petty strut went that far forward.

Hi Everyone,

Thanks for all the suggestions .  My C7 is a 1990 1700 Supersprint (no honeycomb in those days!) with competition manifold. There is no centre exhaust support bracket on this model but that's just down to poor engineering in the first place.The system really needs extra support.

As I said I've just had the silencer front pipe re-welded to the main box after the weld failed. I'm amazed the manifold itself hasn't failed somewhere considering all the loads placed upon it.  A little job for me to rectify in the future.  I think I'll revisit the underside next and look around the gearbox mounting area for the source of the rattle.

Meanwhile here's the MYSTERY BOLT.  Lhs door card. Not one on the other side. Still no ideas anyone? 

Thanks for all the suggestions. I'll rule out the silencer for now because I've just had it off to get the front tube re-welded where it had parted company with the box itself - absolutely sound as a pound inside there with nothing loose, surprising after so many years. 

It's also just been through the MOT and I know what a stickler the tester is, he lets nothing through. I'll check the screen wash bottle though and anything else fastened with rivets. It's not going to get the better of me!

Lots of happy Protech customers out there. And they do look very shiny!!!!!  I'll give them a call tomorrow and see what they come up with. 

I've only had the car since October so I'm still getting to know the handling. I'm sure the shocks are the main cause of the bad manners on bumpy roads, after all they're 32 years and 20k miles old. I'll get the shocks sorted first then get the geometry sorted afterwards.  Looking forward to the warmer weather

Thanks Geoff.  I'll try the seat fixings anyway but its a definite rattle, not a buzz or a sizzle, and is dependent on the depressions in the road surface and not on engine revs/hf vibrations.

Ditto the re-valving.  Surely they come off the shelf from Protech already suitably valved as they are Caterham 7 specific?  Did you use them oem spec. before having them re-valved, and if so what difference did it make?

Thanks.

My Seven sits on its original Spax Gas shocks (adjustable spring platforms).  The piston rods are corroded and the car gets quite lively accelerating at speed on narrow bumpy tar. I chicken out at around 75 mph unless the road is quite wide!  I suspect the dampers aren't doing much.

Can members recommend the best bang for buck adjustable dampers. I would like to use the original springs to save costs. Replacement Spax are reasonable but are there better out there for not too much money?

Mine doesn't have a heat shield.

Yes, its bright cadmium plated and shiny.  Haven't taken it out to measure diameter but similar to the bolts that used to retain an old fashioned seat belt swivel bracket, the one mounted on a saloon B post.  The rattle occurs with a passenger strapped in so don't expect it to come from the seat belt or fittings.

I've been trying to find the cause of a rattle coming from the passenger side on lumpy blacktop.  Its not coming from the front or rear suspension and sounds like its coming more from the middle of the chassis, but where?

The exhaust mounting is sound with a new bobbin fitted, and the windscreen frame screws are all tight, as is the heater box assembly and the dry sump tank.  Not much else to rattle.

Then came across the Mystery Bolt (11/16 AF with a short head) on the inside of the "door" card adjacent to the lower edge of the dash.  Could this be the culprit?  This was a little loose and took nearly a full turn to tighten up. What does this retain?  There isn't a corresponding bolt on the driver's side.

Thanks in advance,

Tom.

Thanks for the replies, especially about the mounting bolts.

>Are you sure it has the bolts fitted from below, above the rear shock absorbers?<

The rollcage came fitted but I will definitely check on the bolts before attempting to hoick the car up by the cage and get underneath!

Tom.

I plan to do some rectification/renovation to the chassis powder coating at the back of my Caterham as soon as it warms up a bit. My ramps don't get the car high enough for this and I don't have either a pit or a lift.  

Can anyone see any problems lifting the back end up using a block and tackle attached to the competition rollover cage? (Adding supporting stands afterwards of course.)  Anyone tried this?

Thanks,

Tom.

So much information on Dave Andrews pages.  Very good.

I will check that out.  Fitting the 50F9 idle jets have more or less cured the problem, even before checking that the timing is as it should be. 

I am hoping to extract more power from the engine in the spring.  Probably need to get it on a rolling road to optimise everything. We get so spoiled by modern engines with their perfect engine management systems. 

My daily is a bog standard 80000 mile 2007 Cooper S and it goes like the clappers.  Though I haven't compared them back to back, I'm sure the Mini is quicker off the line, and especially at higher speeds when brick wall aerodynamics defeat the Caterham.

In the end I filled up with 1 litre, slightly over the Haynes manual recommended amount but well under the 1.2 litres that came out and recommended by some. 

There was already a slight misting of diff oil visible on the de dion tube and I can't see any benefit in making matters worse by submerging the seals in the stuff. There are enough gears splashing around through the oil in the diff anyway to guarantee adequate lubrication everywhere.

The web says 0.9 litres is the correct amount to put in, as does the build manual, (though it doesn't specify which diff this applies to). However, I've put a full litre in and the oil isn't yet up to the filler plug level.  About 1.2 litres came out!  Was it previously overfilled?

Tom.

Thanks for all the replies.  Just about to order from Neil Brown Eng when I saw Shaun_E's comment.  Brilliant, the very dodge I was looking for.  Saves the hassle of taking the tank apart and buying the O ring!  This forum is brilliant.

Thanks Roger.  Yes it is a distributor you modified. Still have the original instruction sheet that came with it. I'll do a timing check first, then balance the carbs again and reset the mixture.  If no better I'll change the slow run jets to 50F9's

Thanks Stu.  Now to get a new O ring.

Tom.

Hello Gurus,

My recent 320 mile round trip to Arch Motors was my first long journey in the 7, giving me plenty of time to appreciate the car's idiosyncrasies.  My only real complaint is the engine's part throttle histrionics.  "They all do that Sir" seems to be the general opinion on the forum but I can't help but think things can be improved somewhat.

Refurbishing the 40 DCOE's is next on the to do list, but before I do I'd love to get advice from forum members on getting the engine to run more smoothly on part throttle.  I suspect a lot of the problem is due in part to having a distributor optimised to give an ignition advance curve that produces maximum engine power output on full throttle rather than smooth running on part throttle.

My 1700 Supersprint engine is standard, specified with the optional 4 into 1 competition exhaust and Lucas High Performance ignition system, and it is in good health with all compressions around 160psi.  It has subsequently been dry-sumped and at some stage the distributor was modified by Roger King - bob weights and springs changed to alter the advance curve perhaps?  Instructions are to set the timing to 35degrees BTDC at 5000rpm). 

I have quickly set the idle mixture and balance with a manometer, with the only observation being that the two outside chokes are drawing a tiny bit more than the inner ones which I'm sure would be sorted with the rebuild.

I came across a detailed post from one member saying replacing the main jets to 130 (originally 120), air correctors to 180 (165) and idle jets to 50F9 (45F9) really helps matters.  Have any other members tried this or can offer other suggestions that have worked?

Thanks in advance,

Tom.