Alternative Engine Tuning

After covering over 12.000 miles on my engine with the 970 'S" rods and five speed gearbox, I suffered my first ever engine failure. Not a big bang with parts going in every direction, but a subtle and teasing - not to mention testing - component retirement.

It had been one of those weeks when everything was proving to be more than an easily solveable problem. Downright peeving and definitely more hassle than your average saint could cope with. In short. my road tax had run out, followed by the discovery that so had my MOT. Hells teeth! So I made relevant arrangements to get the MOT sorted while on one of my "driveabouts··. That day I arranged to stay overnight with someone close to where I was due to have the MOT done - also being in close proximity to the other folk I was due to see. I leave Mini Spares, and on trolling up the AI, the engine develops a misfire. Poopl Stop Remove plugs to find number 4 has no electrode. Had this been caused by the pinking I'd experienced the day before? (caused by bad fue!?) Ah welL 1"11 finish the journey slowly on 3 plugs. Next morning I have to be at the Doctors for a full medical at 8.30am. Slowly limped to the Doctors then to nearest car spares shop. Buy plug, fit in hole, wonderful. 4 cylinders again. Drive to first point of call, carry out necessary meeting. Now to MOT place, replace two blown bulbs, twiddle CO to get tickover right. and it passes with no problems.

Next stop is Peter Baldwin at the Marshalls of Cambridge rolling road facility. Engine starts pinking again! Strange, just filled up with BP super unleaded. Then the 3 cylinder thing happens again, a very slow journey to Peter's, apply compression tester to number 4 cylinder - Oh dear. Only 35 PSI. All others OK. Peter smiles wryly and suggests it is probably a burnt exhaust valve. I know it can't be that simple - it has been one of those weeks. So I finish up business with Peter, and start a long slow drive home. That night I take the head off and guess what? Collapsed piston. After expelling a few expletives, I retire.

The next day I had to get a new piston, fit it, and put the engine back in. Easy eh? Well like I said, ifs been one of those exhaustive weeks. The piston crowns have been machined to allow use of the longer 970 rods. I"ve just moved to St Albans, where I know nobody in the engineering trade. I always had my stuff done at Titan Motorsport or Anglian Engine Services - both in St Neots, Cambs - when I lived in St Ives, Huntingdon. I also had to get to Mini Spares to get a new piston. then find somewhere to machine it while

I waited - all this without any transport. Now this was going to be a challenge. I wanted the engine back in that night. Fortunately a friend of mine proved what mates are for. I originally asked to borrow his motorbike, instead he offered to chauffeur, not only to Mini Spares, but up to Titan's and back too! God bless his cotton socks. I was back home by 11.30am. I wanted to strip the 5 speed box to check on how it was wearing, so I had to fit a different gearbox. I had the original one out of the car, so I stripped this, cleaned it alL and reassembled it - it wasn't AI , but it would be OK. While I had the engine apart, I thought it a good time to strip the head. as I have run this engine purely on super-unleaded fuel, to see how it was fairing. I was pleasantly surprised to find that the valve seals were not at all recessed and were only slightly more "spotty" than usual. However, I would say that anybody wanting to run un leaded fuel in a head without exhaust valve seat inserts would need to lap the valves in every 15 to 16 ,000 miles to prevent poor valve seat sealing. After cleaning, the head was rebuilt.

After VERY carefully honing of number 4 bore to take the new piston and rings, I cleaned it out with copious quantities of cellulose thinners and paper towels, keeping at it until no dirt showed on the towels. Popped the piston in, and put the whole engine back together. The whole time I was doing all this, it was running through my mind why this should have happened. After all. the other pistons appeared OK. It may have been because I am using the cheapest low compression pistons in an engine running high compression. with a bit skimmed off the top and constant high speed. On the other hand, what caused the intermittent pinking? - I"d checked the timing several times with a strobe light.

I popped the dizzy out. removed the cap, checked the vac. advance unit , and then removed the base plate. And there it was, a broken secondary advance spring. I couldn't believe it. Still there's a first time for everything I suppose. I replaced the whole dizzy for the one I had in my spares bin that I new to be a "safe" curve and that worked OK. Back in went the engine. and all this before 7 .30"

Then the phone calls started. Everybody had decided this was a good night to 'phone "KC. I"d put the 'phone down from one call, get as far as the car, pick up a tool, and the damn thing rang again. I couldn't believe this eitherl I finally got the car fired up at 10.15pm. It ran, no problems, but I"d better not annoy the neighbours. I"d retorque and reset relevant bits in the morning. Good night!

All this has had a stalling effect on my development programme on alternative engine tuning. However, I can give you some mileage stuff using the five speed gearbox.

Driving like a respectable and responsible. planet-loving human being the gains in miles pergallon were very gratifying. The worst I saw was 38 mpg. the average 52 mpg, and the best a very creditable 56 mpg. As you may have deduced, mpg figures in excess of 50 were the norm. This proves that the five speed gearbox is a must for those doing high mileage.

The engine will stay as is until I find time to put the five speed gearbox back in. when the next step is to put an MD266 cam in. followed by modifying the head. I had thought about going back to standard length connecting rods. but I have become addicted to the definite improvements the longer rods bring about at higher speeds! Keep reading!

Keith Calver

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