Transforming a 380SL

[ajsimpson]

Hello everyone, I'm new to this group and, in the process of trying to get better performance from my 1985 380SL 4 speed automatic (us version). I'm usually tuned into the Jag-Lovers site. I've had my 380 (great shape) for 3 years and, I can get in it and drive across country tomorrow (runs good). The major problem is that the 3.8L engine is just too slow. I recently acquired a rusty 350SLC (1976 euro) 4 speed manual. I have plans to convert the 380 automatic to a manual 4 or, 5 speed. I believe that this, sole upgrade, will transform the soul of the car.
I'm also thinking of, just, transplanting the whole setup into the 380. Can anyone provide any insight as to what I should gain from my troubles.
Also, because, the 350's engine is unknown to me I'm toying with the idea of rebuilding it prior to the transplant. Any idea what type of expense would be involved with the rebuild or, is it, even worth it? Keeping in mind that I will look to perform all of the work myself.
Any and all, opinions are welcomed.

P.S. I'm sure I'll have at least a few more questions

Thanks, A.J.

 

[Michel]

Hello everyone, I'm new to this group and, in the process of trying to get better performance from my 1985 380SL 4 speed automatic (us version). I'm usually tuned into the Jag-Lovers site. I've had my 380 (great shape) for 3 years and, I can get in it and drive across country tomorrow (runs good). The major problem is that the 3.8L engine is just too slow. I recently acquired a rusty 350SLC (1976 euro) 4 speed manual. I have plans to convert the 380 automatic to a manual 4 or, 5 speed. I believe that this, sole upgrade, will transform the soul of the car.
I'm also thinking of, just, transplanting the whole setup into the 380. Can anyone provide any insight as to what I should gain from my troubles.
Also, because, the 350's engine is unknown to me I'm toying with the idea of rebuilding it prior to the transplant. Any idea what type of expense would be involved with the rebuild or, is it, even worth it? Keeping in mind that I will look to perform all of the work myself.
Any and all, opinions are welcomed.

P.S. I'm sure I'll have at least a few more questions
Thanks, A.J.

AJ,

Welcome to the Forum all the way from Indiana...

First and foremost, you might need to check with your local authorities on the legality of the transplant (in view of smog and pollution laws).

IMO, the 350 engine would be just as weak as the 380, but will obviously be more preppy due to the 4 speed manual gearbox... and so would the 380.
I'm not familiar enough with those physical characteristics of the two engines to be able to tell you if the 4spd box would fit on the 380.

In anycase... you have a far more reliable piece of equipment than a Jag...

Good luck with the conversion...

 

[Styria]

Hi A.J. Simpson, the way I see, you are faced with a somewhat unsatisfactory situation all round. I guess it depends what is acceptable to most, but not to some.

The 380 engine lacks torque down low, so is not a sparkling performer until you tramp on the loud pedal and/or get up to 4000rpm (max. torque) but, by that time, you're well over the legal speed limit in top gear. It is not an engine that allows you a relaxed and restful foot position on the highway - one always seems to have to hold down the accelerator pedal at, say, 3000 rpm.

I have my doubts if the 350 would be any better - perhaps a bit more powerful, but you then have to cope with the older style electronic, and expensive, fuel injection system and not everyone, including myself, understands and is able to work on that system.

The manual 4- speed box is an enigma. Its origins probably go back to the fifties, when 190's and 220's had to tackle some of those mountain passes in Europe in first and second gear, but with a huge gap to third and fourth gear.I have, at length, driven a 350 manual Coupe with the 4-speed box, and it is satisfactory on most counts, including long shift throws, ease of operation, and that gap between 2nd and 3rd. Also, keep in mind, that parts for the manual box will be, or can be, very expensive and relatively difficult to come by. Other than that, I don't have too many useful suggestions. I also would extend a warm welcome to you from all of us on Topklasse. Regards Styria

 

[116Benz]

Another idea, and I dont know how effective it could be is to swap over to the M117 5.6 engine & box. The bigger V8 has a bit more sparkle, and the auto box has a 1st gear lockout (can use the gears similiar to a manual) also might help getting past the smog laws too. As i say, dont know wether that might help or not.

 

[ajsimpson]

AJ,

Welcome to the Forum all the way from Indiana...

Thank you and, I'm glad to have stumbled upon this forum.

First and foremost, you might need to check with your local authorities on the legality of the transplant (in view of smog and pollution laws).

Indiana happens to be a state that has no smog & vehicle inspections so, any modifications that may be made are not a concern. Having said that, I'm confident that the car can be made to run as clean if not cleaner then the original design, even with mods.

IMO, the 350 engine would be just as weak as the 380, but will obviously be more preppy due to the 4 speed manual gearbox... and so would the 380.

Wow, I'm really surprised to hear that. I've always be under the impression (maybe a false impression) that the cars that came from Europe were more powerful than the ones made for the U.S.

I'm not familiar enough with those physical characteristics of the two engines to be able to tell you if the 4spd box would fit on the 380.

I'm not familiar with the shape of the bellhousing either. I won't know that until I actually remove it from the car. I do know that as far as the automatics are concerned, they aren't mix and match items. The 350 auto's bellhousing will seperate and, the 380's bellhousing will not.

In anycase... you have a far more reliable piece of equipment than a Jag...

Well, it's been my experiance once a Jag is sorted out their quite reliable.

Good luck with the conversion...

One can always use a bit of luck, thanks.

 

[ajsimpson]

Hi A.J. Simpson, the way I see, you are faced with a somewhat unsatisfactory situation all round.

I'll drink to that. It's almost like being damned if you do and, damned if you don't. On the one hand, I've driven this car across country several times since I've owned it. It's a quite comfortable and, enjoyable car to drive but, a performer, it's not. It's become very frustrating.

The 380 engine lacks torque down low, so is not a sparkling performer until you tramp on the loud pedal and/or get up to 4000rpm (max. torque) but, by that time, you're well over the legal speed limit in top gear.

There is allot of truth in your words. Mid range torque is dismal and, there isn't any top end performance to speak of.

I have my doubts if the 350 would be any better - perhaps a bit more powerful,

Only a bit more powerful? Not allot more?

but you then have to cope with the older style electronic, and expensive, fuel injection system and not everyone, including myself, understands and is able to work on that system.

The ignition & fuel injection systems on either of these cars are of little concern because, although adequate and, possibly cutting edge for their day. They are no match for the stand alone modern day systems such as Megasquirt and, others.

The manual 4- speed box is an enigma. Its origins probably go back to the fifties, when 190's and 220's had to tackle some of those mountain passes in Europe in first and second gear, but with a huge gap to third and fourth gear. I have, at length, driven a 350 manual Coupe with the 4-speed box, and it is satisfactory on most counts, including long shift throws, ease of operation, and that gap between 2nd and 3rd. Also, keep in mind, that parts for the manual box will be, or can be, very expensive and relatively difficult to come by. Other than that, I don't have too many useful suggestions.

I guess I've been ignorant about the euro cars. I thought they were Autobahn capable and, able to cruise 130, 140 mph/210, 220/kmh. In my car I've only been able to lumber up to 110/mph, 180/kmh and, believe me it was miserable getting there.

I also would extend a warm welcome to you from all of us on Topklasse. Regards Styria

Thank you, A.J.

 

[ajsimpson]

Another idea, and I dont know how effective it could be is to swap over to the M117 5.6 engine & box. The bigger V8 has a bit more sparkle, and the auto box has a 1st gear lockout (can use the gears similiar to a manual) also might help getting past the smog laws too. As i say, dont know wether that might help or not.

I've explored that idea early on and, pretty much decided against it, for a few reasons. It seems that the cost of acquiring a healthy M117 5.6 can be quite grand. Although, from the information that I've already been able to gather. The implementation of the 560 is a pretty straight forward process (I'd use a Megasquirt engine management system).

My initial hope & dream was to install a 6.9 engine but, that just seems like too large of a task. Even if accomplished there just, seems to be to much weight placed on the front end of this car.

I've toyed, for a long while about trying to install one of my V12 Jag engines into the car (I don't know).

I guess part of my issue is the current condition of the car. My car is rust free and, in pretty pristine condition. I don't want to chop it up, if you know what I mean.

Luckily, I do have a rusty 350SLC that I can use to experiment with before making a final move to the 380SL.

A.J.

 

[Michel]

AJ,

Perhaps a 500 engine would be less pricey?
But that also would be less powerful... (forget that option)

However, if you are hell bent on doing an engine upgrade, you'd be better finding a 560 engine in a rusty body as you'll save in labour and modifications as well as you will keep, if not increase, the value of your car.
Putting a 350 engine or a Jag or anything else would be detrimental to keeping your car's value.

 

[ajsimpson]

Good points Mike. At a minimum I'll be transferring and, installing the manual setup from the SLC. I'll then need to decided what transmission to use. I have a couple of Toyota Supra Turbo 5 speed R154's, sitting on the shelf.
It seems that whatever I do the value of the car is going to change. This car, as with any other car that I've doctored up, I do it for my own sake. I'm not doing it with a view towards selling it. No matter what happens it's probably going to turn into some one-off thing anyway. What's important to me is the quality of workmanship that goes into the upgrade. It's got to look good.

A.J.

 

[BenzBoy]

And perhaps it would be more economically efficient to leave the car alone since it is in good condition and go and buy a 6.9 for restoration. Michel (Mike? ) can attest how good a well-sorted 6.9 can be.
On the other hand, what is the condition of the 380 motor? Could it be time that it was given an overhaul? I have a neighbour with a 380SL that has only 50,000 miles on it and it is quite sprightly.
Regards,
BenzBoy

 

[s class]

On the other hand, what is the condition of the 380 motor? Could it be time that it was given an overhaul? I have a neighbour with a 380SL that has only 50,000 miles on it and it is quite sprightly.
Regards,
BenzBoy

PErhaps, but I assume that A.J. has a U.S. spec engine which could be 10 to 15% less gutsy than euro.

 

[BenzBoy]

PErhaps, but I assume that A.J. has a U.S. spec engine which could be 10 to 15% less gutsy than euro.

True. However, the 380SL I refer to is an Australian complianced vehicle with functioning anti-pollution gear - it may fall somewhere closer to the US model than the European one.
Regards,
BenzBoy

 

[ajsimpson]

Well, I've had the car about 3 years now and, the 380 motor is what creates the dilemma.

The car had 34,000 miles on the clock when I got it and, for a weekend driver, I put about 20,000 miles on it the first year. No issues to report until last summer, when a hot start problem presented itself. I've only driven the car about 3 or, 4 times since last year. Partly because, it needed a new rag top which is on order as we speak.

I get allot of pleasure from driving, as I'm sure most of you do, too. When driving around town and, short distances (100 miles) the car is perfectly fine but, when I'm driving across the country devouring 3, 4, 5, 6 states at a clip and, piling on the miles, (500, 1,000, 2,000, 3,000) in a single outing, that's very different from driving. These are the times when the reality of what you thought you had and, what you really have, distinguishes itself. I find it to be very comfortable for long journeys. I'd just like it to perform better.

After hearing the different points of views that this group has been, nice enough to furnish. When I get some time, I think (subject to change) my plan of attack (not nessasaraly in this order) will be.

Take some compression readings of the 350 engine and, try to determine how healthy the engine really is.

Look into the cost effectiveness of obtaining parts and, rebuilding the 4 speed manual transmission (if I'm going to use it then it needs to have a good bill of health).

Try and determine if any other transmission can be bolted to the back of either of these engines (potential bellhousing issues). I can use the 350SLC for any mock up fitting trials.

I'll keep you posted as to the progress of this project and, report back what information that I find along the way. Hopefully the finding of this project will help someone else with similar projects in the future or, at a minimum add to information to everyones knowledge base.

A.J.

 

[ajsimpson]

Just to clarify. My 380SL is a U.S. spec car & loaded with all of the pollution devices that Mercedes had to offer at the time

I just spoke to a lady that's trying to sell a 1974 450SLC 4 speed manual (euro spec). If I remember correctly, I believe she said that there is about 80,000 miles on the car. She is asking $2,000 for the car. I haven't seen any pics yet but, I do believe that it has rust in all the usual places but, supposedly the car runs.

What do you guys feel about that car, power wise? Did that model perform adequately as an autobahn cruiser? Do you think it's worth going after?

Thanks, A.J.

 

[Michel]

Just to clarify. My 380SL is a U.S. spec car & loaded with all of the pollution devices that Mercedes had to offer at the time

I just spoke to a lady that's trying to sell a 1974 450SLC 4 speed manual (euro spec). If I remember correctly, I believe she said that there is about 80,000 miles on the car. She is asking $2,000 for the car. I haven't seen any pics yet but, I do believe that it has rust in all the usual places but, supposedly the car runs.

What do you guys feel about that car, power wise? Did that model perform adequately as an autobahn cruiser? Do you think it's worth going after?

Thanks, A.J.

A 450 is a far better performing unit than a 350 and a 380.
Personnaly, I would still hold out for a 560....

 

[John S]

As your car is a US spec model (way down on power compared to the European model) the easiest upgrade is probably to obtain and install the cams and distributor from a European 380 engine. I don't know if the emissions would be a problem for registration where you live, but in Australia it would not be a problem.

 

[ajsimpson]

As your car is a US spec model (way down on power compared to the European model) the easiest upgrade is probably to obtain and install the cams and distributor from a European 380 engine. I don't know if the emissions would be a problem for registration where you live, but in Australia it would not be a problem.

John, now this is good stuff to know. I was completely unaware of any differnces in cam profiles.

To delve a little further into this subject. In general, (this is in the form of a question) the U.S. & Euro blocks across the board are the same? Would you know if there are piston differences between the two countries? Also, are there any differences in the structure of the heads?

I apologize for asking so many questions but, technical specs for Euro models have been hard to come by. I have several publications across different models but, none of them talk about the Euro stuff. Perhaps someone can point me in the right direction for obtaining Euro publication manuals.

Thanks, A.J.

 

[B13]

I just spoke to a lady that's trying to sell a 1974 450SLC 4 speed manual (euro spec).

I don't think there is such a beast... M116 with a manual box = yes, M117 with a manual box = no.

Better make sure the engine number on this 450SLC starts with 117.

Might be another one of those trunk-badge engine upgrades you see from time to time.

I.

 

[ajsimpson]

I don't think there is such a beast... M116 with a manual box = yes, M117 with a manual box = no.

Better make sure the engine number on this 450SLC starts with 117.

Might be another one of those trunk-badge engine upgrades you see from time to time.

I.

This is an EXCELLENT POINT!

Out of curiosity I checked the back of my 1976 350SLC and, SURE ENOUGH, "450" is the badge on the trunk.

 

[ajsimpson]

Well Folks, after a time of looking around & waiting. I finally located and, secured a 1986 560 engine with 80,000 miles on it. The engine came out of a SEL model. The next step is to transplant the manual pedal assembly from the 1976 SLC into the 380SL.
Any suggestions on the choice of manual transmissions and, bellhousing?

Thanks, A.J.