[Starbase89]

So I have this 420SEL that I am constantly bouncing around regarding what I want to do with it. The engine is likely shot based on some information I obtained about the car. Of the slew of commonly available American V8s, what can be put (without too much modification) into a 420? I was thinking in terms of a Ford 4.6 or 5.0, or a Chevy 5.0 or 5.7. If possible, I'd like to retain the MB transmission. What is available?

 

[joeSEC]

Ls1s bolt straight in and match up to the trans no worries
All you need for the wiring is a kit on the internet which costs $7
and the exhausts just bolt straight to the engine


Nah that was just lies
There is no easy option
If you wana go bigger chuck in a 560 m117engine.
I wouldnd waste my time and $$ trying to fit a chev/ford v8 to the factory trans there are plenty of options that live behind those engines

 

[glideslope]

There ought to be a divine law against the installation of non-Merc engines into a W126.

Anyone found guilty of such sacrilege should be required to fit monstrous spoilers and fins on every surface of their vehicle, upholster the interior with shiny leopard-skin patterned plastic, and install non-functional twin chrome exhaust pipes that weigh as much as a living room couch.

There, I feel so much better with that off my chest.

 

[bondavi]

Someone did a Toyota Supra turbo engine in one.

 

[Benznoob26]

So I have this 420SEL that I am constantly bouncing around regarding what I want to do with it. The engine is likely shot based on some information I obtained about the car. Of the slew of commonly available American V8s, what can be put (without too much modification) into a 420? I was thinking in terms of a Ford 4.6 or 5.0, or a Chevy 5.0 or 5.7. If possible, I'd like to retain the MB transmission. What is available?

probably the 4th or 5th time ive posted a ford engine...no way in hell of retaining a MB trans and a real hot engine would kill one anyways, the transmission is a 5speed.

rough total cost $19k(complete engine,trans,diff,ecu,wiring harmess,shocks,brakes) for a 412HP/390lb if you DIY. btw that's the 2011 ford gt engine, and close ratio transmission and differential would make it feel sportier. your gas mileage would be terrible but it'd be BA.


these engines are badass
Ford Racing Performance Parts
transFord Racing Performance Parts

 

[Darth V8r]

A Ford Coyote engine would not give bad gas mileage. Well, not if you could keep your foot out of it anyway. I'd expect it'll do better than the original engine as far as MPG is concerned (substantially?).

I'm researching doing a Chevrolet L76/6L80 out of a Pontiac G8. From what I've seen so far it'll just be a bunch of work (like all my projects ). The L76 is basically a detuned LS2 with active displacement. 360 hp with another 40-50 hp available through cheapish bolt ons - 400 hp ought to be enough to terrorize Vettes and 911s at lapping days.

You guys that are down on non-OEM engine swaps need to get with the times. The U.S. manufacturers have finally got their collective sh!t together and are making excellent engines right now. To say some 1970s-1980s M-B lump is better than current Ford/Chevrolet engines is myopic. Now, the guys that want to retain an M-B engine to keep a pristine example of the car pure, I'm all for that. But $3000 project cars that get beat on, who really cares where the power is coming from?

Don't bother trying to retain the Mercedes transmission. It won't live behind a modern V8 and would be more expense than it is worth to retain. If you are worried about retaining the MB shifter you can always adapt the original shifter to the new transmission or put in a new shifter that came with the donor vehicle. In my case I want the tiptronic style shifter out of the G8. I may try to adapt TCI paddle shifters later.

My biggest concern about starting this project? What to do about the brakes?

 

[joeSEC]

What to do about the brakes?

Ah nothing ...MB brakes are fine, 4 wheel disks and reasonable pad surfice area
Ive had a couple of emergency stops in mine and the brakes have performed admirably..
I would have thought the main thing to worry about woud be how to get the engine and exhausts to fit around the steering box which apears to me to pose swap space issues
The guy on here doing the LS1 swap had to covert his car to rack and pinion IIRC..

 

[strife2]

You guys that are down on non-OEM engine swaps need to get with the times. The U.S. manufacturers have finally got their collective sh!t together and are making excellent engines right now. To say some 1970s-1980s M-B lump is better than current Ford/Chevrolet engines is myopic. Now, the guys that want to retain an M-B engine to keep a pristine example of the car pure, I'm all for that. But $3000 project cars that get beat on, who really cares where the power is coming from?

I agree - there is a place for pure original cars, but those are generally not driven. I have the luxury of an SL that I leave alone (or can restore to original very easily), and a cheap and imperfect one that I drive every day including in winter. I would have no problem at all spending some money on it installing a non-original engine if I could get 20+ MPG and 280 horsepower out of it. I'm capable of doing the work, but not capable of some of the engineering and fabrication.

I'm often surprised that no one has made a kit of parts like the ones available for 70/80's Jaguars, that included almost everything you needed to drop in a GM engine/tranny and have the A/C and gauges just magically "work". The 107 poses slightly tougher problems than the 126, putting in a wider, 4 valve/cyl engine is tough, no matter who made it, and that's how most V8's are made now.

OTOH, it did my heart good this weekend to see a 380SEL at the pull-a-part (sorry, nothing good worth mentioning) that had 350K miles, and mechanical engine problems did NOT kill it...certainly, it must have had at least a valve job in its life, but we shall see if these new sophisticated engines have that kind of durability.

 

[vdubpower]

i wish we could p[ut in a nelson racing engine, imagine 1500 hp mercs w126

 

[jdc1244]

There ought to be a divine law against the installation of non-Merc engines into a W126.

Given that soon next year the youngest non-SA 126 will be 20 years old, it’s not becoming financially feasible or practical to keep the original engines or find original replacement engines. For these and other reasons it may be necessary for some to install non-MB engines. Besides, whatever is done can be undone should an acceptable original engine later become available.

 

[Darth V8r]

I'm often surprised that no one has made a kit of parts like the ones available for 70/80's Jaguars, that included almost everything you needed to drop in a GM engine/tranny and have the A/C and gauges just magically "work". The 107 poses slightly tougher problems than the 126, putting in a wider, 4 valve/cyl engine is tough, no matter who made it, and that's how most V8's are made now.

I think a lot of this stems from the fact that the Jag engines were percieved to be problematic even when new. People found/made solutions to get by at the time.

On the other hand, the Mercedes stuff of this vintage was pretty bullet proof. There was no need to find solutions as by the time the engines were worn out enough to merit a refit the cars were considered old enough or cheap enough to consider not being worth the effort. Hence, no market for refit kits. I guess it didn't help that M-Bs aren't considered "sporty" either.

I'm not saying its right, just seems to be what happened.

The draw of the Chevrolet engine versus say the Ford engines is that they are a cam in block engine instead of [D,S]OHC. They are quite compact due to not having cams in the heads making the engine wide and tall.

Pushrod engines sound like old tech but the current Chevrolet small blocks are far from the crap that was designed in the 1950s and run into the mid 1990s. You can find lots of specifics here:

GM LS engine - Wikipedia, the free encyclopedia

Truth be told I'm more of a Ford fan in general but as far as engine swaps are concerned you can't beat the size, weight and power of a modern Chevrolet V8. All the electronics to run them are relatively self contained also - makes it easy to retrofit into another chassis.

2¢

 

[Darth V8r]

Ah nothing ...MB brakes are fine, 4 wheel disks and reasonable pad surfice area
Ive had a couple of emergency stops in mine and the brakes have performed admirably..
I would have thought the main thing to worry about woud be how to get the engine and exhausts to fit around the steering box which apears to me to pose swap space issues
The guy on here doing the LS1 swap had to covert his car to rack and pinion IIRC..

Regarding the brakes, I guess it will depend on expectation levels. If I go forward with a conversion the car will have to be able to put up with 30 minute sessions on a race track. At our local track that probably equates to three full G, emergency style stops a minute.

Steering I don't see as a big deal. I haven't scoped it out yet but changing the steering rack/box is not a big deal provided I don't have to getting into modifying the knuckles. It's just cutting/welding steel I'd suppose.

 

[tusabes]

Non mb engine swaps cost more than any 126 is worth

It's simpler just to buy another 126 or find an eBay/ junkyard engine. They aren't hard to find

 

[pegscraper]

Pretty much any swap into any car costs more than the original car is worth. I once bought a chevy Vega for $300 the SBC swap for everything was at least $3000 (we tubbed it too) but the car was a blast and I traded it for a nice 916 ducati worth about $6,500 at the time.

I would be willing to bet a 126 with a 2jz and a 6speed from a supra would be worth a couple bucks to someone. I know most people here are happy with 240hp in a 3900lb car, but I think these cars deserve more.

I hope someone gets a kit together before I get to the swap. 500hp on a single turbo
2jz is nothing. If I could get that out of a 117 I am all ears!

 

[Darth V8r]

Non mb engine swaps cost more than any 126 is worth

It's simpler just to buy another 126 or find an eBay/ junkyard engine. They aren't hard to find

There's the rub - exactly.

Engine swaps are always more trouble and money than a car is worth - most of the time.

It's a function of what your end game is. Doing an engine swap to keep a daily driver on the road is stupid. I've done it a few times and regretted it afterwards each time. It's just not worth the time and money to keep an appliance working in the end.

Doing an engine swap to end up with a "special" car at the end is another matter. That is where I'm coming from. I've got a little collection of special cars on the go and I need a big, black sedan to round it out. LOL

 

[mramay]

An LS series engine (e.g., LS1, LS2, LS3, LS6, LS7, LS9) will fit just fine. The tunnel needs to be widened for a custom 4L60E 4-speed overdrive automatic and the "x"L60E series of tranny's are just too big unless you want to use a torch to open up the tunnel. The LS engine hit the steering gear box so I went to rack-n-pinion steering, which turned out to be a MAJOR pain to eliminate bump steer. The rack was installed on the custom engine cross member that holds the custom engine mounts. Did I mention the custom tranny mount as well as a custom shift linkage?

This is the FrankenBenz, the car I've been working on *forever* with an LS6/4L60E bolted in place. The rack-n-pinion is installed, the custom drive shaft is there attached to the custom 3.07 LSD differential. The custom fuel pump (Walbro) is installed. Yet to do is the custom drive-by-wire throttle pedal, custom wiring harness, SEC radiator with Z06 Vette dual electric fans. A custom dual-exhaust will have to be fabricated.

Please note the numerous uses of the word "custom" - this isn't easy, there is no "kit", you will have to do it all yourself. When this is done, I'll have an SEC with around 480hp that should have better gas mileage than stock. The engine isn't stock either, which upped the HP from stock 405 to a dyno reading of about 480.

No modifications are expected to the hood and I'm planning on using an MB skid plate underneath. Other than a Lorinser chin piece and rocker panel add-ons, the SEC will look stock.

 

[Darth V8r]

Look at all the room in the engine bay with the engine in place! It's practically swimming in there. Looks impressive.

Good comment on the custom bit. Do the math on the cost to do an engine swap, double it and then you might be within 80% of what it'll cost.

Some technical questions for you mramay...

Did you put your engine on the vehicle centre line or offset to one side?

Regarding the transmission, I've seen images of the 4L65 compared to the 6L80. I'm not seeing where the 6L80 is much wider than the 4L6x - might be an inch or so across the widest part? Housing is bulked up longer to the tail cone?

Oh well, have plasma cutter... will cut...

I've read the rear differential is roughly equivalent in size to a Ford 9". Is this true?

Have you adapted the VSS to the W126 speedometer? Is the W126 speedometer electric or mechanical? (too lazy to look in the FSM)

 

[Oake]

Apart from 2JZ, another choice for Japanese Engine that fits into your W126 is 1UZ-FE from Lexus LS400 / Toyota Crown. In my country, it's so popular and it's quite easy to find nice one from Japan.

One thing you will loose after replacing MB engine to Japanese engine is "Mercedes Feeling"

 

[mramay]

The 4L65E is the same size (uses the same housing) as the 4L60E and should be the one to use here. It can be built strong enough for this level of HP. The 4L60E is "only" rated to 380 hp so I had a custom one built to handle around 500. Here's the neat part: $1500 finished, with torque converter, put in my trunk and drove away. I can't get an MB unit rebuilt for that price!! I've recently heard several negatives on the 4L80 and 6L80, that they are NOT reliable. The drag racing guys can build a automatic tranny that can hold pretty much any power level.

My engine is on the centerline.

This is a "kinda-stock" differential. It's brand new inside but uses all MB parts. I read where Satish, with his V12 SEC, planned on leaving the stock differential, drive shaft, and flex disks in the car until he blew them up with the V12, then go to bigger stuff. Last I heard, the stock "stuff" is still in there. I'm planning on keeping the rear tires 265 or smaller in order to not put too much of a load on that expensive differential. I'd rather spin the tires that blow the diff.

My '87 SEC has an electronic speedo and I already have a Dakota Digital SGI-5 Speedometer Adapter in the car due to the new diff. I'll just take the GM Computer output and push it into that SGI-5.

 

[Darth V8r]

Considered the 1UZ in a Jeep build once. The Jeep XJ auto transmission is the same unit used in older Supras (AW4/A340) and it takes a bell housing change to get the 1UZ to bolt up. Took a pass in the end.

The complaints about GM transmissions being "weak" tends to be cyclical I find. Camaros are the hot new things so flat billed punk assed kids are beating the sh!t out of them doing pretend racing currently. They break, so it has to be a problem with the car's transmission, right?

Like you said, aftermarket rebuild will make it bulletproof.

Thanks for the data points.