Playing with carbs

by Alex

After two hillclimb events in the car with the new engine set-up, we have some work to do to fine tune things.

At a very wet Wiscombe at the end of April, the front engine carb jet dropped out after running really well. It happened quite quickly with little or no poor running beforehand, suggesting that the jet had been adjusted out too far when on the rolling road, and that the needle may be too lean thus requiring artificial enrichment by screwing out the jet.

We rebalanced the carbs and lock-wired everything in place as a temporary measure.

The following weekend at a sunny Werrington the car ran reasonably well but without the sizzle it had before. We then experienced misfire at the start line usually coinciding at the first gear change then clearing. The car revs out to 9k and the misfiring only happened on Jenny’s run after mine as the ‘A’ driver. This suggested that the plugs were fouling up with all the tickover waiting time, so perhaps the needle could be too rich low down. The plugs certainly looked fouled up but it was difficult to tell after a run up and then back down the hill. Changing them certainly helped, as did getting Jenny to rev it like a boy-racer before the start! On further inspection of the old set some of the porcelain had broken down.

Our conclusions are that the needles are too lean at the top and too rich at the bottom, as the plugs seem to be getting too hot and fouling up at the same time. Also, starting requires the choke but the engine will not run at all with it left on and a very light foot is required on the throttle.

We also wondered about dirty fuel, the facet silvertop pump has a poor filter which is easily blocked.

We are using SU needles in Strombergs, so using www.mintylamb.co.uk found a couple of alternatives using their comparison graph. BG which is much leaner low down and richer top looked perfect, but the curve proved too steep at the crucial 3 to 5k rev range, so we have tried CS2 which has the same curve as the CS1’s previously fitted, but richer at the top with a smoother curve.

After road testing and installing a glass filter before the fuel pump we await Wiscombe on the 17th/18th May with baited breath!

The Howells Championship 2014

Our first event this year was on March 30th at Clay Pigeon Kart track for a sprint, our first one. The track is very twisty as would be expected, and we are still not sure whether or not we like it!  Still it was good weather and a warm up for us and the new engine/gearbox and we had some fun sliding round the corners.. it would be interesting in the wet!

April 26/27 saw a very wet weekend at Wiscombe Park hill climb and the first proper test of the engine. All was going really well and the track wasn't too bad, Alex got very close to last year's personal best on Saturday afternoon.  On his last run the jet fell out of one of the Stromberg carbs, luckily falling on to the custom belly pan and not onto the track until he got to the top finish paddock.  Having found the jet he refitted it and Jenny got her final run.

Having made steps to prevent it coming out again, we started on Sunday but soon realised that the carbs were out of balance and we couldn't better 63 seconds.    The final run was cancelled because of the muddy/slippery state of the paddock, it was only a matter of time before a car slid into another, or worse into a pedestrian. Getting out and loaded up and away from the site was organised in batches so we were pretty much first away being in the first batch.  The quickest we've ever loaded the Imp on to the trailer and packed away the stuff in the van!

The carbs are being checked out, and hopefully the car will be running better for Werrington hill climb this weekend.

You can find a couple of videos from Wiscombe on YouTube:
Jenny final run Sunday:  http://youtu.be/GomQBB05lxc
Alex fastest run Saturday: http://youtu.be/B1dNTTFTHTM

The score in the Howells Championship to date is Alex 2 - Jenny 1.

If you haven't already found it, we now have a Facebook page at www.facebook.com/imphillclimb - come and find us!

South West adventures at Werrington

Last weekend was the wonderful Werrington Park hillclimb organised by the Plymouth Motor Club, and held near Launceston which according to Googlemaps is about a 3 hour drive from us.  We were planning to have our new trailer ready, in fact this was the first event that we really wanted it for, but irritatingly it still hadn't materialised.  We couldn't borrow the one from Alex's work because they were using it (most inconsiderate) and we refused to pay to hire one for a weekend.  So there was nothing for it, we were going to drive the Imp and the van down to Devon/Cornwall on Friday afternoon.

We both got home from work early and after some final preparations (which included buying some get-you-out-of-the-mud grippy things for the van) we set off at 1.45pm with Alex in the Imp and me driving the Transporter with camping gear and dog.  All went well and we swapped over roughly halfway in the middle of Dorset somewhere.  I had the dull half which was mostly dual carriageway and a bit of motorway, so amused myself by singing loudly while bowling along at what I thought was 65 mph ish and we arrived without mishap at the venue.   At which point Alex said 'Why were you driving so slowly?' - it turns out that the speedo is reading about 7mph fast and hence it took us about 4 hours to get there.

We found ourselves a good camping spot at the top of the paddock in lush green grass, pitched the tent and fell into bed pretty early. Unfortunately our neighbours decided to party... but we managed to fall asleep about 11.30.

Saturday dawned wet, oh great.  The paddock announcement was 'there is a lot of mud on the road, please take care!' Werrington Park is an estate with a big house and cottages, and it turned out that somebody had driven a tractor through the estate on Friday morning, after it had been meticulously cleaned!

We both therefore took it easy on the first practices especially as it was our first time there, so put in un-amazing times but that was fine. It had stopped actually raining and rapidly dried out so all our runs from then on were on dry tarmac and got steadily faster with Alex ending the day on around 59 seconds and me on 60.   After a social barbeque on Saturday evening, we went to bed and slept very soundly, awaking raring to go on Sunday which was warm and dry. 

Somehow, after lunch on Sunday, we both managed to knock 1.5 seconds off each of our times. In my case it was because I had trouble selecting 2nd gear going into the 90 degree left so changed down later. A-ha! Now to try that intentionally.  In the final timed runs we ended up even faster with final best times of 57.83 for Alex and 57.66 for me, we were enjoying having our own private Hillman Imp championship!  With 1380 Minis etc in our class there was no way we were troubling the prize-winners, but we had a blast.

Alex drove the Imp all the way home since I said we'd get home quicker than if I drove it!  There had been a bit of rattling and knocking over the weekend and when Alex investigated on Monday, he found that the bolt holding the alternator on had sheared off and the alternator was working loose. Thank goodness it didn't come off completely or things could have got nasty.  We still need to take a look at the track rod ends and the suspension in general to check things over before the next event.

All in all it was a great weekend and we'll be back for more next year (it's a shame there is only one hillclimb a year at Werrington, it's a good, challenging course).  In the meantime we're off to Wiscombe again in a couple of weeks so looking forward to that.