This is what the Pagoda might have had if there had been a 1974 model

[Tom Colitt]

It’s been more than 2 years since I last wrote about my 280SL 3.0l engine conversion and I wanted to report to the group about the results after two years of daily driver use. Although I also had upgraded the rear axle ratio in this 280SL (my own personal Pagoda) to a 3.27, in order to get the most out of the standard automatic transmission, I will focus on the engine modification here. My goal was to get the most horsepower gains out of a stock 280SL or 280SE engine, at a minimal cost, without any visual differences externally, while I was already rebuilding my 280SL’s engine. It is known that the Mercedes engineers had concluded that the bore size was already very close to the limit on the M130E engines, so I only increased the bore to 87.5mm, within the range of available factory repair sizes. I increased the stroke by 5mm (+/- 2.5mm), for a total displacement of 3 liters. As anticipated, this allowed me to stay with the original connecting rods and a modified, stock crankshaft to provide the extra crank throw and custom forged pistons that I had designed (finally my old engineering books from the Technical University in Berlin came in handy again). I used a lower compression 280SE cylinder head with a custom camshaft derived from the European specification cam and built by famed camshaft manufacturers Iskandarian (Isky Cams). With the 280SE head I was able to keep the sometimes detonation-prone engines below a 10:5 to 1 compression ratio. That way I was able to use premium gas of 91 Octane (RON + MON /2) which is the lowest premium grade available in California. This is roughly equivalent to the German/ Worldwide 96 RON rating (http://en.wikipedia.org/wiki/Octane_rating ). This way I was able to keep the cost of rebuilding the engine (I used a 280SE engine, so as not to “ruin” a genuine 280SL engine) to barely more than what it would have cost to do a standard rebuild.

The result: I could not be happier :-) This engine pulls so strongly from the lower rpm range, that the car actually now feels like a quite powerful sports (almost muscle) car, even with the normal 2nd gear start on the automatic transmission. The best thing is, that despite the strong low-end torque, the power still keeps on building smoothly and steadily all the way to the same high rpm of the stock engine, but with a sense of urgency and thrust that you don’t have with the stock engine. I have not found any 280SL that has come close to having the same acceleration, even with a manual transmission. The exhaust sound seems about the same. The fuel consumption is lower than it was before although the comparison might not be very accurate since the 280SL/ 3.0l engine is new, compared to a previously, slightly tired stock 280SL engine. The sound and feel are still distinctly that of the peppy 280SL, but with more power all around. There hasn’t been a single issue that has come up. The stock fuel injection pump easily adapted to the requirements of the new engine and the coolant temperature is the same as it’s always been (which is just over the 180 degree F mark).

I 'll be happy to have some discussion and answer any questions. Also, how would I re-badge my 280SL (although I do like the standard wolf-in-sheep’s-clothing 280SL badge): 280SL-3.0 ; 3.0SL ; 300SL CALA (ClassicAutosLA)

Regards, Tom Colitt
ClassicAutosLA

[TR]

Hello Tom.

Have you had it dyno tested?  It would be interesting to know how it compares against a standard US-version 280SL.

[gugel]

Tom,

The car sounds pretty great!  For the badge, I like your suggestion of 3.0SL, except that it really should be 3,0SL.

Now just make sure the car doesn't get stolen!

Chris Earnest

[webmig]

Tom, wow sounds great!

Who makes or can make this modification to increase the stroke?   I suppose any shop that grinds crankshafts but who did it well for you?

Mig

[Tom Colitt]

Thanks for the 3,0 Sl Chris. It's a little out of the Mercedes-Benz Konzernkultur, but maybe we can make it work :-)....

Mig, it's been a while, but it was a well known crankshaft grinder in Orange County, CA. These guys are all very familiar with doing this kind of work and I probably drove them a little nuts with all my engineering question related to durability, which they had already answered for themselves through many years of experience, but couldn't quite express in theoretical terms. There was even a second alternative, also nearby, but the wait was longer, so I used these guys.... Let me know if you get serious about sending out your crank shaft and I can help you locate them.
Please understand that having the crankshaft throw increased is only a small part of the project, the geometry, so to speak. Most of my engineering work went into figuring out how the dimensioning of cylinder head and my forged pistons went together, in order to get a usable and efficient engine, in other words how compression ratio, breathing, fuel, valves, valve timing and ignition timing would all go together to translate that geometry into good power....

TR, the reason I haven't done a dynometer test, is that I didn't think it would tell me that much to get some rear wheel horsepower figure, let's say between 170 to 180hp and then not know how to compare it, since I hadn't done any benchmark test on the previous engine (also, rear wheel horsepower ratings are said to be about 15% lower than the DIN ratings, but who can really say for sure how that would compare on a car equipped with a 40 year old drive train design, with an automatic transmission, radial tires....) My sense is, that the two numbers would just be like apples to oranges and not worth the effort. I DID take some benchmark horsepower measurements with an on board G-tech accelerometer and I just need to take the corresponding measurements, now that the car and engine are all dialed in. Hopefully that won't be too far off, but I always find I'm more busy working on Pagodas (currently even a 1970 Opel GT) than these fun extra-curricular activities ;-)

Regards, Tom Colitt
ClassicAutosLA

[webmig]

Tom, yes I'm serious about it, I live in the mountains surrounding Mexico City at 2,800 mts above sea level, at this altitude engine's power decreases a lot and it can be boring when in a road and everybody is passing you.   I did consider exchanging the engine, lightly turbocharging it with a small T3, etc.

This is where I am at this moment "undecided but reading as much as I can from everyones opinions in this and other forums"...    My thought as for today would be the stroke increase so the engine, exhausts, etc. would still look the same.   While awayting for the name of the shop who did a correct job for you, I searched and talked to a few shops; there's one particular shop in California which is really into stroking engines for racing purposes, they respond quickly and seem very interested (basically bike or inline engines no V's) http://www.aperaceparts.com/   This shop would apply a special alloy, grind with the required offset, finish grind and nitride for surface hardness.

After talking to them and going arround and arround the idea I ended up with the following "How to compensate for the stroke increase? Shorter rods, or pistons with the pin location raised? where to get this new pistons..."

Before contacting you, I had many crazy ideas but before I would do anywith my original engine, I had thought of doing it with a spare engine that I had bought to experiment with, it is a good running M110.990 2.8lts 6 cil inline (I know injection and everything else is different but it fits).

Engine is allready out since I am going to repaint the engine compartment.

Let me know your comments/suggestions.

MiG

[webmig]

Some other pics on the process (everything in the suspension is also being dismantled because the bad old black paint)   What I have done with other Pagoda on the suspension is to Cold Cadmium Plate each part and forget about future rust.   After plating we can repaint in black.  Yes I know it does not look original.

[webmig]

Engine compartment with Cadmium Plated items

[Tom Colitt]

Hi Mig

It looks like you are doing a nice and thorough job. The name of the crankshaft grinder is Marine Crankshaft in Santa Ana, CA. Here is their link: http://www.marinecrankshaftinc.com/

If you are interested in using my engine design, you could either ship your engine to me and I can do the complete job, or I would be open to supplying the vital components like the crankshaft, ground to my specifications as well as the custom pistons and camshaft to you. Keep in mind that this is not the whole scope of the job, since these parts all need to work together, but it would be a good start. Please email me off-line at tcolt@netzero.com, so we don't have to use this thread.

Enclosed is a picture of the 3.0, the way it currently looks. Please keep in mind that this is literally a daily driver, so not everything is quite as tidy as I would like to have it.

Regards, Tom

[webmig]

Perfect job, thanks for the pic.

I have the same oil cap that you have, I used to have the other one, I don't know the name in english but it's the alum one that looks like gear...   One day when I opened the hood I saw that a thief had replaced my original with his...

[Shvegel]

migmig,
If I am not mistaken the oil filler cap that looks like a gear requires a different valve cover entirely. The thief would have had to swap the entire valve cover. You Might want to have a talk with your mechanic.

[webmig]

I have done all the mechanical myselve but sometimes I have taken it for engine and undercarriage pressure wash and grease-point refill, this job has been done on different shops where I have dropped the car in the morning and picked up in the afternoon, that's the only place someone could have the time to exchange the valve cover...

Do yo know the part number for the correct valve housing?

[Tom Colitt]

Miguel

I don't have the part number off hand, but the valve with the screw-on aluminum cap was only used through the 1969 model year on Pagodas. After that the bayonet style steel cap was used.