Lola SL142/20 Restoration

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Re: Lola SL142/20 Restoration

Postby Reto Kuprecht » Mon Apr 08, 2013 9:25 am

Jack, see also earlier posts around Dec 17, 2011 on the body panel topic. R.
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Re: Lola SL142/20 Restoration

Postby Reto Kuprecht » Sun Jun 23, 2013 7:23 pm

What's going on with the Lola? I took it to Hockenheim in April. Chassis setup astonishingly good, but I had some difficulties with the gearbox, and something was not right with the engine. Despite the apparently good dyno runs, I suspected that there was still a fuel/mixture issue and decided to tackle this myself. I really wanted to understand what is going on in these Weber IDAs. The first step was to be sure whether I was on the lean or rich side. I purchased a air/fuel ratio sensor with an analog indicator. Installation went very easily. I made my own dial for the gauge to make it look older and match better with the other instruments:

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Next, I compiled all the documentation on Weber 48 IDA I could find. Starting of course with the original Weber Tuning Manual, Pat Bradens "Weber Carburettors", Haynes Weber Owners Workshop Manual, and David Vizards "How to build Horsepower, Carburetors and Intake Manifolds. The latter provided me with the best information, explaining the workings of Emulsion Tubes, various jets, fuel pumps, all in theory and practical tips.
My first idea was to completely rejet my Webers, based on my own findings. But when I put all the knowledge I found together, calculated the ideal choke size and appropriate jets to start with, I realized that I was already close with what I had installed. So, I had to step back and I started to look at the fuel pump. I thought this was just the right setup, as it came with the engine, recommended by the engine builder. It was a big Magna Fuel pump with a by-pass feeding to a regulator. I calculated what I needed for my engine with the help of the Vizard book and realized that this pump was much to big, capable of feeding over 750 HP at 18psi. Slowly I got the Picture... This pump was building up lots of pressure against the regulator set to about 3.5 psi which is what 48 IDAs Need. Pressure built up and the spring/plunger type by-pass opened back to the tank. As we know, pump volume and pressure are different things, and I assume this big pump could not deliver the needed volume because pressures between pump and regulator rose much too high and the action of the by-pass valve brought the whole thing out of sync and created a lean situation. So I decided to replace the whole fuel delivery system. I decided on a Mallory 110 pump, together with a return style regulator. I also put together a choice of jets and planned for a test session:

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And bingo, after some changing of jets, I got pretty close to an AFR of 12 thhrough the whole range. A bit rich still at lower RPMs, but much better than before. The main advantage of the whole exercise was that I learned a lot about how these carburetors function, and how to play with choke size, idle, main and air correction jets and emulsion tubes.

The gearbox issue had mostly to do with the selector fork rod's indexers set too strongly - which makes it hard to move the shift forks forth and back, i.e. is a pain to shift.

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Never a dull moment obviously, but I think the car gets closer and closer to what I had imagined and I am still somewhat surprised how few quirks it has considering a build-up from nearly nothing.

Besides this, I used the time to clean up my workshop and build up my machinery arsenal. Most importantly a mill and a lathe - something I had in mind for a long time but always thought doesn't make sense because master machinist Martin always helped me. But I also like nice machinery just for what it is, and couldn't resist to an opportunity for a used Emco mill and lathe in perfect condition:

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Another long-time dream of mine was a sandblaster - a temptation to which I finally succumbed too :lol: .

There's a reason behind this of course :roll: i.e., I am preparing for the next project, which has been in the works for nearly a year now since the first discussion with the seller. It's a Lola again, this time SL150/1, one of the two cars Lola brought to Indianapolis in 1968 for Al Unser/Bignotti. The chassis had to be built back to it's original form after it had been mutilated by Jim Hurtubise for the 1973 races and it should be done soon. But I have the engine (aspirated 255 Quad Cam Ford) and the gearbox. The question is, should I start a new blog on this restoration, or just build away in my own four walls :?:
Last edited by Reto Kuprecht on Mon Jun 24, 2013 8:29 am, edited 1 time in total.
Reto Kuprecht
 
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Re: Lola SL142/20 Restoration

Postby 911hillclimber » Mon Jun 24, 2013 6:27 am

In answer to your last question:

Personally, start a new thread exactly along the lines of this one!
Same level of activity, quality photos and comprehensive detail.

Gets my vote!
Graham.
Avid hillclimber, just bought a Lola T 492 to hillclimb.
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Re: Lola SL142/20 Restoration

Postby Reto Kuprecht » Wed Jul 03, 2013 2:39 pm

Your one and only vote is enough for me to do as you suggest :wink:
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