Caterham 7 Circuit Racer

[A30Racer]

The other thing Wiscombe has highlighted is the gearing is not too clever for competition driving. I was using 2nd off the start as 1st only seemed good for about 10yds, & still having the option of lots of wheelspin!! Anyone fancy swapping a 3.89 for my spare 3.63 diff? 

[Hamish]

The wet is a great leveller power wise.

you only need to change the gearing if you really have to change gear whilst in the 1st 64ft in the dry. 
 

surprising how many of those 1/10’s can be gained in those 64ft. 

[Nick Jones]

1 hour ago, A30Racer said:

Anyone fancy swapping a 3.89 for my spare 3.63 diff?

Probably got some 3.89 gears...... whether they are any good.......  Why not just try the 3.63 if first is that short?  Not very much between 4.11 and 3.89?

Slippery.... oh yeah.  Remember marshalling there years (decades) ago in the esses and going down on my arse when I hopped off the bank to sweep the track between cars.  How the cars were (mostly) staying on, I have no idea.  Gave the spectators something to cheer   I know the track has been resurfaced since then, but there's between plenty of time for the tree-slime layers to build back up and polish!

[A30Racer]

We're going back to Wiscombe next weekend, so will conduct some more experiments on the start. No time to change the diff  this week, as the tow-car is feeling unwell and needs attention (steering fluid leaking away). Hopefully the weather may be a little less moist! 
The basic problem is the Sierra box has ratios suitable for a low-powered saloon, not a low-powered sports car. First could do with being quite a bit taller, but I think the 3.63 may blunt the acceleration in the intermediate gears a bit. Not a massive issue, but something to ponder.

[Escadrille Ecosse]

12 hours ago, Hamish said:

The wet is a great leveller power wise.

you only need to change the gearing if you really have to change gear whilst in the 1st 64ft in the dry. 
 

surprising how many of those 1/10’s can be gained in those 64ft. 

Rarely a truer word said

[A30Racer]

It certainly sorts the heroes from the wimps!

[A30Racer]

We did Gurston Down hillclimb on saturday. A nice day, but it revealed that the engine is not the most virulent. Gurston has two speed traps & the fastest we went was 71mph. To put this in perspective, the Caterham that won the class was doing 105mph at the same point! Some engineering may be needed over the winter.....

[Nick Jones]

More powaaaah 

New engine?  Or just a cam where the lobes haven't gone round?

[Hamish]

Just make sure those cars were like for like. 
 

those 7’s and westfields can have some wicked engines 

talking to a guy at 3 sisters

1400cc hayabusa 230bhp

that’s about 500/tonne !!!

[A30Racer]

The existing engine is not exactly a fire-cracker as standard (100bhp from 1600 on twin 40 dcoe) but the cam has been losing the lobes of the cam which doesn't help (I think caused by oil starvation while circuit racing before our ownership). Our competitor at the weekend (nice blokes who know how to drive!) had a Caterham with a Vauxhall 2 litre XE engine & Sadev sequential box. So about 240bhp and an LSD. My co-driver isn't ready for that level of performance yet, so we are looking for an intermediate stage without wasting too much money......

Anyway, the equation has come into sharper focus, as yesterday we had difficulty getting 5th gear. On closer inspection, the right hand engine mount has lost one bolt and sheared the other two. I think the engine will need to come out to get the broken stubs out, so was planning to see if we can swap the alloy sump onto the 2litre 8v engine in the shed & pop that in instead. The 2 litre has a longer stroke, so the sump may not fit. Will report in as the job progresses

[A30Racer]

The conversion to 2 litre is now well under way. Sump has been swapped (needed some 6mm to 8mm adapters) and the inlet manifold needed to be changed as the 2 litre inlet ports are about 1" higher on the head. All else went pretty smoothly & the engine will be back in the chassis tomorrow (hopefully).

[Nick Jones]

Looking good.  Here's hoping the laws of unintended consequences have been kinder to you than they usually are to me 

[Escadrille Ecosse]

12 hours ago, Nick Jones said:

Looking good.  Here's hoping the laws of unintended consequences have been kinder to you than they usually are to me 

[A30Racer]

After a bit of messing about (due to the new inlet manifold placing the carbs further back and lower) with a new throttle linkage and the water pump letting all the water out, we have a running car again. Took it out for a tentative drive yesterday and it seems totally different. The old engine was very lethargic by comparison. I had an 8v Cavalier as a company car years ago and it was a flyer. This same type of engine, although relatively standard is very torquey and happy to rev. A couple of minor fettles to do - clutch adjustment and carb balancing mainly. May need to space up the engine on the drivers side to get clearance round the air filter / bonnet clearance.

Feeling quite pleased with it.

[Hamish]

Always great to get progress on a project, especially when it’s something a bit different from the workshop book !! well done.

[Nick Jones]

A torquey 130bhp in a car that weighs about the same as an empty fag packet ought to give fairly brisk performance.

Suspect the old engine had already given its best well before you got it and you may have near doubled the horses in reality. Enjoy!

May make the LSD quest a little more urgent…..

[Escadrille Ecosse]

Should definitely add a bit more pep!

Nice installation too 

[A30Racer]

The quest for the LSD is underway. I have bought a Ford English axle that will be sent to Arch Motors to be modified to fit the Caterham suspension mounts. Then a plate-type LSD will be added to the wanted list. The straight cut box should be with us very soon. A busy winter on the cards!

On other news, we have entered the Wiscombe hillclimb at the end of september, which we hope the weather will be kind.

Regarding the power-to-weight ratio, the Caterham is in a good position to use all of the available power. Current weight is approx 530Kg, so 140ish bhp goes a long way.

[Hamish]

1 hour ago, A30Racer said:

The quest for the LSD is underway. I have bought a Ford English axle that will be sent to Arch Motors to be modified to fit the Caterham suspension mounts. Then a plate-type LSD will be added to the wanted list. The straight cut box should be with us very soon. A busy winter on the cards!

On other news, we have entered the Wiscombe hillclimb at the end of september, which we hope the weather will be kind.

Regarding the power-to-weight ratio, the Caterham is in a good position to use all of the available power. Current weight is approx 530Kg, so 140ish bhp goes a long way.

I have a plate LSD from these guys via Pete cox 

https://www.3jdriveline.com/webshop/limited-slip-differentials/

https://petecoxsportscars.co.uk

 

[Nick Jones]

You could try speaking to Paul Hughes at 2Spec transmissions.  He's a CT man and has been known to enjoy the occasional 10CR.  I bought my Blackline ATB from there but I believe they also do plate type ones.

http://www.2specgroup.co.uk/contact/

Or this lot, which are part of Dave Mac propshafts

https://gripperlsd.com/

[A30Racer]

A bit of a guilty update (was busy in the summer & autumn with my lovely co-driver & I getting married). We entered Wiscombe Park hillclimb in late september & had a fun weekend. 1st in class both days! The 2litre 8v Vauxhall engine has transformed the car. Although it 'only' showed 105bhp at the wheels, there is some big urge low down and the torque is much improved. It pulls away in 2nd on the start & easily gets to the limiter in 5th which is a bit mad! We then entered a sprint at Clay Pigeon kart track two weekends after............Fastest Caterham there and another class win. Admittedly, the weather was a bit moist, but was pleased to finish the season on a high note. Looking forward to next season.

[Escadrille Ecosse]

Well congratulations due all round I would say. A very successful year indeed

On 8/22/2021 at 10:35 PM, Nick Jones said:

Or this lot, which are part of Dave Mac propshafts

https://gripperlsd.com/

Following up on the LSD I have an Gripper for the Spitfire when I was using it in competition. Even set very light I found it excellent and an improvement over the Quaife ATB I had been using.

Having said that the Quaife is back in the car as it is a little more civilised for road use.

[Nick Jones]

Healthy 2L performs better that broken 1.6L then…… as one would rather hope 

Torquey 105bhp clearly “adequate” in the right hands - great results!

Just need to anticipate what all this extra power is going chew up (Triumph related axle most probably) and get that dealt with before next season…… IIRC you already have a plan in motion?

[A30Racer]

The drive-train enhancements are in-hand.........

Bought a Ford English axle with 3.89 diff (a little higher geared). Just about to send the axle case to Arch Motors (who built the chassis) to be modified so it will fit the current suspension mounts. Diff gone off to AC in Taunton to be fitted in an alloy casing with plate type lsd. Will need new prop & rear wheels too.

The plan then is to keep it like that until the co-driver / management / wife starts to request more power. No point having too much at this stage, as one needs not to be scared of it to extract the best out of the car!

[Nick Jones]

1 hour ago, A30Racer said:

The plan then is to keep it like that until the co-driver / management / wife starts to request more power. No point having too much at this stage, as one needs not to be scared of it to extract the best out of the car!

Wise.  Too much power too soon can result in (expensive) mishap!!