31/8/04 Five years of the Rat

My, how the years have flown. It was September 1999 when I first got it onto the road. At that stage it had the old 1300cc engine that came with the donor vehicle. The 1300cc was a bit of a disappointment actually, as the donor, a 1965 VW Type 3 (variant) fastback, had TL1600 emblazed on it’s rump. While visiting ARCO motors to buy some other VW part, Brent showed me a “1600cc” engine that he had for sale on behalf of someone who had found it under his hedge, or something. So I chucked this one into the ‘Rat just before we headed off on the 2001 club summer trip which took in the Wairarapa, Hawkes bay, Taumaranui, Taranaki etc. The new engine went quite well, except for a persistent tapity sound, and a curious dropping-off in power that took me two days to realize was that the heavier return spring on the carb of this engine was causing the accelerator pedal to bend. By the time we got to Harewa we were getting only half the throttle opening at full Welly. A cable tie fixed that.

I then tried a single-carb twin-choke 36mm Dellorto in place of the std VW carb. I had to modify the engine cover to make room for the aircleaner. This gave more power but, despite experiments with different jets and a plenum chamber, it was always prone to flat spots. Next I got a matched pair of Dellorto carbs off trade and exchange. These came from an Alfa Romeo I believe. This twin-carb set-up is what I have on the car now and together with heavy duty valve springs on an otherwise “standard” motor has proven to be a good torquey combination that can still rev up to 5,000 rpm without any trouble. Well, not too much trouble. Last year on the way up to Manfeild for the club track day the pesky tappet rattle suddenly turned into a much louder sound as an exhaust valve dropped it’s head. At this stage I had started to build a new engine so I just got the hole in the damaged piston welded up and new valve guides put in for some old exhaust valves I found in my garage. Good old VW technology.. this engine “blow-up” cost just $127.50 to repair. Having been driving this engine round for three years, you can imagine my surprise to discover in the course of this repair work that it was actually a 1835cc engine, not the 1600cc that it was supposed to be. At some time in its earlier life someone had machined the case and heads to fit a big-bore piston and cylinder kit. I never knew.

The great thing about a VW beetle is how easy it is to take the engine out and put it back. But make this mid-engine and it’s a different story. The way I built the car in the first place was just to make the minimum structure needed to locate the engine, transmission, suspension, battery and fuel tank. Everything else is just added onto this basic structure as bolt-on, plug-in bits and pieces. So, to get to the engine the whole rear of the car has to be taken apart sequentially piece by piece, in the reverse order to how I built the car in the first place. There are no short-cuts. This includes taking off the body panels and removing the spare wheel, fuel tank, battery, battery box, transmission, linkages, five bits of exhaust etc. I’ve just done a count-up on my fingers and it tallies up as: 21 Screws, 61 Bolts, 5 plugs, 8 electrical connections, 5 cable ties and a bungee. This takes about three hours and fills up about four cardboard boxes and a whole garden shed with bits. Then the engine just rolls out the back of the car on a trolley jack, with the car still sitting on its wheels. It takes a lot longer to put it back together, but mostly because there are inevitably some little improvements to be done at the same time.

Make it – Use it – Enjoy it

I have enjoyed doing a lot of stuff with the car. Club trips have been a highlight. I use it whenever I can for trips where two seats are enough. I take it to work some days. Bad weather can be a bit of a disincentive. My usual approach is that if I have a reasonable chance of getting there dry I’ll drive the ‘Rat and take my chances on getting wet on the return trip. I made a roll-up stow-away awning style roof that can be attached if the weather turns seriously nasty.

Along with other club members I took the car in the parade through town with the Rugby Sevens tournament teams one year. We were with the Tongan Team. For three years now we have gone in the Hutt City Christmas Parade with various themes including Wonder Woman, Pokemon and something involving angels. For these events, I leave off the rear deck lid, take out the spare and bolt a plywood floor over the petrol tank making the ‘Rat into a sort of mini-ute. Then, with a high-level grab rail fastened onto the roll frame, “Characters” can stand on the back and wave to the crowds.

Gymkhana’s have been fun. These events quite suit the ‘Rat and it is easy to do quite well, especially on grass. Also, I cheat by fitting separate handbrakes for each rear wheel. This makes it possible on grass to execute a U-turn from a standing start without going further forward than about one meter. Bearing down on a cone at speed the trick is the pull on one wheel brake, which slows the car and turns it into the corner, steer a bit as required, then add some power with the brake still hard on, modulate everything until pointing in the desired new direction, then release the brake. It pays not to attempt a gear change during this maneuver, as one doesn’t seem to have a free hand for it.

Manfeild

I do enjoy track days. I really recommend them to everyone. We are lucky to have folk like Ron Robertson in the club who can make these happen for us in a constructive, fun, cheap and safe fashion. As an aside, marshalling on track days is also very enjoyable (even if you are doing it because you just blew up the engine on your car). I had earlier thought that since the Road Rat has only the power/weight ratio of a very average modern family saloon, it would be a bit of a damp squib on the track. But I had forgotten that all the great sports-car traditions are hardly based on big horse-power. The original MGs and Morgans etc were popular because they were fun to drive and “sporty”. Not because they were particularly powerful. I don’t have much experience to be able to compare the Road Rat with any real performance cars, but I just like getting out there on the track and being able to try different lines and speeds into the corners until the limit starts to become a bit obvious, and to try later and later braking points. The track is so wide at the corners that I find the car can pretty much stop in a straight line within the width of the road if you find you have overcooked it a bit. Despite having two thirds of the weight on the rear wheels, it doesn’t exhibit much in the way of over-steer. At speed (about 140k is the fastest it gets up to), the bulky rear body and minimal frontal area seem to keep it more stable than at normal road speeds. Turn-in is really good and by keeping plenty of brake balance to the front, there is never a problem with the rear sliding going into a corner. I find I can go pretty much full throttle all the way to the 50m mark before jumping on the anchors. Coming out of a slow corner it lifts the inside front wheel and suffers quite a lot of under-steer. This is probably due to low rear roll stiffness. I could do something about this, but actually I find it rather fun, so I doubt I will. It’s very easy to control, just not the fastest way out of the corner. There’s not enough power (yet!) to spin the inside rear wheel. The only time I have had an incident is midway round the hairpin where the G forces are the greatest, it seems that in the final analysis the rear tyres just have less grip than the front ones. This mainly became an issue when I put on new Yokohama tyres on the front. These are 175-60 profile replacing the old Bridgestone 165-60s. The Yokos are much better. The wider section seems to soften the effect of the walls and gives them a bit more compliance than the previous tyres. This makes the car react less to road imperfections, which is a bit more relaxing, and they grip much better under braking and achieve more weight transfer, which is a good thing. I should get some Yokohamas for the rear as well.. but at the rate the old Hankooks are wearing, this is scheduled for about the year 2020.

So, how fast is it? I think I do a good lap about 1:40 (wet or dry). To do better than this you have to be able to go much faster down the straights, and you need a bit more than 70hp for this. I enjoy it on track days trying to keep-up with other cars. “Wow.. I did well last session, I almost kept up with XXXX, and he must have at least 200 Hp.”

Two more things I would like to mention while on the subject of Manfeild. One is that I believe that for scratch-built cars, we should have as part of our scrute process a requirement that the builder (or some other brave soul) should take the car out on a track day and pound the living daylights out of it round the track for eight or ten laps non stop. If it can do this adequately, and still be on four wheels (or three as the case may be) and have brakes still working at the end, then this should take car of any doubts anyone might have about it’s general roadworthiness and safety, and take a bit of the risk off the shoulders of the certifier. The other thing is, I can’t work out what it is that the braking point signs actually indicate. The one that says “100”, for example. If this is 100m, where is it actually measured from? Where is the “0” point? It obviously isn’t either the start of the curve, or the apex of the curve. It seems to be somewhere in between. If anyone knows this.. maybe they could do an article for the mag or something. Also, while I was doing a spot of marshalling during the last club day, during a slack period, I went and paced out the distance between the 50 sign and the 100 sign at the end of the back straight. This came out to be about 37 meters by my reckoning. Maybe they are just handy numbered road-signs. I guess it doesn’t really matter.

Performance

I did a few very unscientific tests and I think it does 0 to 100 in about 11 secs. This isn’t all that great, but there is one other statistic that you might like to compare with your own ride. This is something of a family matter. My Father, when aged 16 in 1934, owned an AJS 500cc single. You know Bolton Street? That’s first on the right going up The Terrace and continues as a steep bridge over the motorway. Well Dad’s AJS would go up Bolton Street in top gear.. and so can the Road Rat.

Brakes

The standard VW disk – drum setup is quite large for the size of car, and with the smaller weight of the Road Rat the standard brakes are quite adequate. I have replaced every brake part with new items, including slightly larger than standard rear wheel cylinders, and fitted a proportioning valve to the front brake circuit. With only 200 kg on the front axle this is very necessary to avoid the front wheels locking if the surface is not very grippy. I have the version that has a leaver that clicks through about 7 positions. I don’t know how these valves work, and I don’t like the pedal feel they produce, but they do the job.

Cooling

The motor doesn’t really run too hot, even with 90% full throttle running on the track, but I was keen to try to get more cool air through the cooling system by ducting external air directly into the cooling fan intake. For this I made an air scoop and modified the body to accommodate it on the left side of the car and made up the necessary ducting. I then used some water-manometer “U” tubes to measure air pressure in the system and basically decided that it wasn’t really helping much. But it looks cool, so it can stay.

Gear Ratios

One thing has become pretty obvious, and I suspect this applies to most of our club cars, the gear ratios that come with the donor gearbox are rarely ideal in the new car. At Manfeild the Road Rat has only a two-speed gearbox. Once under way it doesn’t go slow enough to use second gear, and so that just leaves 3rd and 4th. Who needs a sequential gearbox when you only use two gears? I found an internet site that trades used aftermarket gearbox ratios for VW’s at about NZ$50 a gear set. This would make a close ration 3rd and 4th easy to achieve, but a long diff ratio to make it all work on the road is just not available. These ratios are designed for the off-road market with huge tyre sizes. So, too bad, have to flag that one. My next car will have a motorcycle engine. Not so much for the motor, but this is the easiest way to get a good close ratio 6-speed sequential gearbox.

The new BIG motor

Because I can. That’s why. I’ve just got a few small adjustments to do and I will have completed building a new motor for the ‘Rat. Now, the traditional VW engines through the 50’s and 60’s were commonly 1200cc. Then VW brought out 1300s and 1500s finally the 1600cc engine all based on basically the same 60’s engine case. By using a longer throw counterweighted crank and larger pistons my new motor will be about 2175cc, but the external engine dimensions are unchanged from the original 1200. I am using heads with bigger ports and valves, double valve springs, chrome-molly pushrods, a cam with a duration of 299 degrees, 5kg chrome-molly flywheel and 1700 lb clutch. So, lets see what happens when we light the touch paper. It would be more prudent of me to say nothing about this little project before actually test running it. I have acquired bits from so many different places that there is a fair risk one or more of them has some serious fault which will become evident very early in the new motors life with grenade-like results. So I’m keeping my fingers crossed.

Building the motor has not just been a case of buying the bits and screwing them together. Very little actually fitted without some modification. On the two new after-market heads, the rocker-shaft mounting studs were not the same distance apart, needing a modification to one of the new rocker-shafts. The insides of the engine case needed to be “clearanced” for the larger crank, this involved grinding off about 2mm of aluminium from all sorts of places by a trial and error method. This took at least 20 goes to get right.

One reason for building the new motor was to address oil surge. The lit-up oil warning light has been a common sight at sealed gymkhanas, track days and the usual top ranking Wellington roundabouts. It’s a tribute to VW solidness that the car has survived to this day. I have had to run the oil level about 15mm above normal level to avoid loss of oil pressure during hard deceleration and cornering. I suspect this high oil level also contributes to the engine running hotter than necessary. I have addressed this in the new engine by using special pushrod tubes that have longer skirts to discourage oil from flowing up the tubes to the head during cornering and by including a windage tray. I have also made a little tea cup sized sump (thanks Phil) that adds about 40mm to the depth of the engine and enables the oil pickup to be extended downwards about 50mm. This is equivalent to running the oil level about 30mm higher, so it should make a big difference. I will need to make a special protection skid plate, as this sump decreases ground clearance by an extra 10mm below the current adjacent low point.

Parts for the new engine have come from friends, from Trade & Exchange, from NZ suppliers and by mail-order from several different sources in USA. With the strong Kiwi Dollar, and the ready source of parts from Brazil, where up until last year they were still making new air-cooled VW’s, many parts for the new engine were quite cheap. For example, a set of four new pistons, rings, cylinders and gudgeon pins (pretty much the main wearing items in the engine) cost just NZ$400 including freight by parcel post. And by mail-ordering in small consignments, GST doesn’t seem to happen. However, other things, like machining work and courier charges from USA pushed the costs up a bit so I realize I could have bought two perfectly good used-import Lexus V8s for the sum I have now “invested” and still had change. These would give me something like 5 times the horsepower as well… but I would have had trouble fitting all 16 cylinders into the Road Rat engine bay.

And, what next?

Once the new engine is in, a priority will be to add an oil cooler. I have got a good one for the job. It came off an XJ6 Jag at pick-a-part, but I will need to modify the bodywork on the right hand side to accommodate it, and this may mean relocating the gearshift, which needs some improvements anyway. Having given up on changing the gearbox ratios, I would still quite like to make a sequential shift mechanism. I might give that a go. And I really must make some better and more laterally supportive seats. It really never ends.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . You are honoured visitor number: . .