Bringing my 1700 Super Sprint up to par

About a week ago I bought a 1987 Caterham 1700 Super Sprint from a friend of mine. I first saw at a summer party at his home a couple of years ago and thought that would be a fantastic car to own. We had just bought two Porsche Boxsters, so the time wasn't right, but I kept lusting for it. A year ago my friend brought it to our local autocross venue, a closed military airport, and saw it in action. More lust. I did notice that it emitted a cloud of smoke whenever he lifted the throttle, so I knew something was worn.

The car has pretty much sat for the last decade and needs work. My first priority is the engine. Make sure that it gets a good tuneup, and then evaluate whether any kind of rebuild is needed.

Finally all the pieces fell into place. I was able to get spousal approval and my friend realized that the car needed to go to someone who would use it. Pricing was a little tricky. We finally left it as he would decide how much he was willing to sell it to be for and I would pay him that amount if I could afford it. No dickering. He worked out a price and I accepted it, so the deal was done.

A week ago I drove it home. The temperature was right around 40 degrees F and it was a bit hard to start and needed both starting fluid and choke, a two person job since the car didn't have a choke cable. First time I drove it in traffic. Pretty rough in the 1000 to 3000 RPM range. Lots of farting out the exhaust and popping out the carburetors. As soon as it hits 3000 RPM it smooths out and pulls like a champ.

My plan is to give it a thorough tune-up ASAP and then decide whether there is a need to rebuild any component. This weekend proved ideal to get the project going. Yesterday was in the 40s, today and tomorrow in the mid 60s. Terrific for Massachusetts in January.

Yesterday I started out having the car inspected. I registered it earlier in the week and got the license plates Friday. The state inspection is similar to the UK MOT. It was a hoot. Everybody was really interested in what it was and took a lot of pictures. The inspector insisted on driving it in and needed instruction on how to get in. Once in, I had to show him how to test all of the controls. Everything worked as it should and the car passed and got its sticker.

After I got home I started by installing a choke cable. Once I get it tuned right I suspect it won't be needed, but right now it is. My plan was to tune the Webers, but as soon as I started I noticed that any push on the carbs make the idle speed change and the manifold mounting nuts seemed really loose. Tightened them a bit and then decided it was prudent to get some expert advice. Glad I did.  Didn't realize that the manifold mounting is flexible to reduce frothing in the carbs. End result was that I ordered the parts to replace all of the mounting hardware.

Today started with a carburetor tune after replacing the spark plugs. The carbs turned out to be balanced perfectly. The idle mixture was not right with the air filters off. I did set them as described and it ran fairly well, but after putting the air filers on it was clearly off. That prompted me to get a K&N filter cleaning kit. Used it, and now have the filters drying inside the house, so no more carb work. Next was a compression test. I did it dry and found that the cylinders all are very close to 150 PSI. Cylinder 4 is a tiny bit lower. I need to find out whether this is good. I was relieved, however, to find them so close. 

Tomorrow I'll put some oil in the cylinders and do a wet compression test. That should tell me if there is any piston blow-by. I will also do a road test and see how it feels.

At this stage I suspect that both carbs would benefit from service at a specialist and also that the head also should be given a rebuild. The valves seem to seat well by the compression test, but the smoke at lifting indicate that the valve guides and/or the valve seals may be worn.

Comments

Progress!

I finished, to the 99% level, the engine tuneup today. Yesterday I cleaned the air filters and let them dry overnight, and today I oiled them. After mounting them I started the engine. The carbs were out of sync, so one of the filters must have been a lot dirtier than the other. I also went over the carb mounting nuts and made them evenly tightened. When that was done the revs didn't change when pushing and pulling, gently, on the left carb. They changed, of course, when I did the same on the right carb because it is slaved to the left carb throttle. The idle mixture also needed to be richened because the dirty filers had a choking effect.

Yesterday I also found the timing notches in the front crank pulley. They were almost impossible to see, but I used a screw driver to expose the metal in the notches. I broke out the timing light and checked the timing. It was set at 10 degrees at idle. The Weale book is a bit confusing on what the advance should be on the 1700 Supersprint. I interpret it as depending on the distributer, whether it is Bosh or Caterham. Correct? Decided to set it to 12 degrees at idle and then give it a test run.

A marked improvement. Smoother running at medium revs, a bit of gentle popping out of the exhaust on throttle lift and next to no spitting out of the carburetors. Made the run a longer one. This could be the last warm (60's) day before late March/early April, so time to just enjoy the car. On the test run I took the side curtains off. Big mistake. From 60 MPH and up I get so much wind buffeting that I worry about losing my hearing aids and glasses. On my next run I'll see how well the plastic wind deflectors work, have heard not too well. I'll wear a beanie so I don't lose hearing aids and glasses.

It is amazing how many admiring looks the Caterham gets. Our Porsches get some, but not nearly as many.

After the drive today it is time to put the car up on axle stands and attach the suspension and body work.

Anker Berg-Sonne
Stow, Massachusetts

1987 Caterham 1700 Super Sprint
2004 Porsche Boxster S
2009 Mercedes CLK 350 Cabriolet

Old fart pretending that age is just a number

I should have mentioned that I made the mistake to check the compression with a cold engine. Will do a dry and wet compression test later on a hot engine. The fact that all cylinders show the same compression tells me that I don't have any broken rings, which would be my biggest worry.

Anker Berg-Sonne
Stow, Massachusetts

1987 Caterham 1700 Super Sprint
2004 Porsche Boxster S
2009 Mercedes CLK 350 Cabriolet

Old fart pretending that age is just a number

So much for the wind deflectors. Since yesterday was the last warm day in this spell I took a longer trip and drove up to Chelmsford to show the car off to my friend Bill. On the way up I took the smaller roads and all was fine. On the way back I thought it would be a good idea to take it out on the highway (motorway) and let it stretch out. After my earlier run without any wind deflection I knew to wear a beanie that would cover ears and glasses, but at 80 MPH the buffeting was so high that I had to hold on to the beanie with one hand to prevent it from blowing off and steer with the other.

So, so much for the fun. This week the car will go on jack stands and I'll finish working on the engine and move on to the suspension.

It is interesting to write posts on a UK board. My upbringing was to a great extent Brithish english. I was born in Johannesburg, lived there until I was seven, then seven years in Denmark, followed by four years in Tanzania, followed by a return to Denmark. My high school certificate is an Oxford/Cambridge A level. At the age of 30 my wife, two young girls and I moved to the US where we gained permanent residency. After 5 years there we spent 3 years in Sydney, Australia and then returned to the US where we have been ever since. I am now 71, so it has been over 40 years since we moved to the US, and all the British english has been replaced by American english, with the exception of a trace of accent. So I know how to write bonnet instead of hood and hood instead of top, but it doesn't feel natural any more.

Anker Berg-Sonne
Stow, Massachusetts

1987 Caterham 1700 Super Sprint
2004 Porsche Boxster S
2009 Mercedes CLK 350 Cabriolet

Old fart pretending that age is just a number

Based on advice on BlatChat I have ordered an Aldon distributor with an Ignitor. By the time I return from soaking up some sun in Florida I should have the distributor and the new mounting kit for the carbs. Tackling the two jobs at the same time makes sense since access to the distributor is so much easier with the carbs removed. I have the Lucas electronic ignition system, but have read horror stories here about the beam breaker going lose, so the Aldon will give me peace of mind. I considered going full ECU, but I have a lot of projects ahead and need to be somewhat conservative with spending.

The aldon reps were really helpful selecting the right product for my specific engine and the fact that the highest octane fuel I can purchase in a regular gas station is 93, and 91 in some states.

Anker Berg-Sonne
Stow, Massachusetts

1987 Caterham 1700 Super Sprint
2004 Porsche Boxster S
2009 Mercedes CLK 350 Cabriolet

Old fart pretending that age is just a number