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  #1  
Old 12-07-2010, 02:00 PM
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3.5 to 5.6 engine swap

i found a very old thread regarding such a swap and was hoping that someone could help to get the dialogue going again. i have a 71 280se 3.5 that i will be putting a 89 560sel motor and trans in. my main concerns are can i keep the battery and the brake booster in current positions, how should i motify the arms for the motor mounts, and any other input or advice from someone in the know would be greatly appreciated. thanks

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  #2  
Old 12-07-2010, 09:02 PM
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I m looking for some of the same collective experience from this crowd .
Someone has done it .
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  #3  
Old 12-08-2010, 05:54 AM
GGR GGR is offline
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You should post a link to the discussion you are refering to. Where are you located? Is your car a LHD or RHD? Is it a W108 or a W111 Coupe? Is your 3.5 a manual or auto trans?

The engine mount brackets of the 3.5 will fit the 5.6 engine (with longer bolts) and it will bolt right up on the front axle. Same with the transmission, it will bolt right up on the rear valance and if your car is an auto trans the shifter rod will also fit straight.

You should transfer the trans flange from your 3.5 trans onto the 5.6 trans so that you don't have to modify the trans shaft.

The engine will clear the engine bay, though it's a bit wider and higher. The brake booster on the 3.5 should clear, if not you could use a W114 Diesel booster which are smaller and are a direct fit.

The biggest challenge will be the exhaust manifolds. The r107 560 SL ones will clear the chassis and you will have a bit of fabrication to connect the downpipes. I recommend you use a 6.3 exhaust as it will fit your car and has bigger diameter pipes.

If your 560 engine ws originally equipped with tri-Ys then the r107 500SL will fit but will require a slight modification of the right chassis rail.

You also could use the center part of a 6.3 rear axle with A 2.88:1 ratio.

You will also need to get that device that converts the electric signal from the transmission into a rotating cable for your speedo.

If you find a W112 radiator you're in good shape as it has one more row and the inlet is on the right side.

The steering center link may touch the back of the oil pan when you steer lock to lock. Some like mercmad6.3 lower the relay arm bracket on the chassis. I guess the relay arm itself could also be modified. I personally lifted engine and Trans up half an inch with thick washers between the engine brackets and engine mounts and fitted longer bolts. This also requires machining of the brackets to shorten them engine side as they go up at an angle.

Oh, and the battery tray should clear, but if not it's not hard to relocate.

Keep us posted!
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  #4  
Old 12-08-2010, 08:46 AM
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great info and much appreciated!!! thanks for the details!!

my car is a LHD, 111.026 coupe with automatic trans and floor shifter. here is the thread i saw on this website regarding a 300SEL 3.5 swap:

http://www.peachparts.com/shopforum/sitemap/t-119814.html

and here is a link i found regarding a '72 350SL swap

http://www.carcentric.com/MB2MBswap.htm

the '72 swap mentions modifiying the engine mount arms and changing the SEL oil pan for an SL pan. will the SL pan benefit my swap?

GGR, are you saying that the front engine mounts and the trans mount just mount and bolt directly to the chassis with no mods??
that sounds too sweet. and the shifter linkage will work as well?

have you done such a swap?
can i use the entire rear end from a 6.3 or does that pose a problem? the 3.69 from the coupe will have to go, but i was thinking of a 108 4.5 rear end to solve that problem. thanks again!
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  #5  
Old 12-08-2010, 09:32 AM
GGR GGR is offline
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Quote:
Originally Posted by merchauser View Post
great info and much appreciated!!! thanks for the details!!

my car is a LHD, 111.026 coupe with automatic trans and floor shifter. here is the thread i saw on this website regarding a 300SEL 3.5 swap:

http://www.peachparts.com/shopforum/archive/index.php/t-119814.html

and here is a link i found regarding a '72 350SL swap

http://www.carcentric.com/MB2MBswap.htm

the '72 swap mentions modifiying the engine mount arms and changing the SEL oil pan for an SL pan. will the SL pan benefit my swap?

GGR, are you saying that the front engine mounts and the trans mount just mount and bolt directly to the chassis with no mods??
that sounds too sweet. and the shifter linkage will work as well?

have you done such a swap?
can i use the entire rear end from a 6.3 or does that pose a problem? the 3.69 from the coupe will have to go, but i was thinking of a 108 4.5 rear end to solve that problem. thanks again!
Yep, straight fit. I did two swaps: One 300hp 5.6 in a 111026 and I'm currently doing one with a 5.0 fitted with manual transmission in a 111021. Mercmad6.3 has also done a number of them on RHDs.

You may have to machine the 3.5 engine mount barckets if like me you choose to lift the engine a bit. But that's easy.

Both SEL and SL oil pans will fit. The SL oil filter housing (in case you source youe engine from an SL) won't fit, so it will need to be replaced by a W126 one.

You can use a complete 6.3 rear end if you modify your rear chassis rails to accomodate the braking torque absorption system anchoring points (this has been done by Pagodino, search his threads). Alternatively you could have the brake flanges welded to the wheel tubes (which is the case on my 300 hp conversion.

You could certainly start with the 3.69 rear diff. Not much difference with the 3.27 of the 4.5, so I wonder if it would be worth the expense and work.

Where are you located? the US and European Markets offer different options. The ideal would be a 300hp euro version, but they are not that easy to source in the US. Otherwise a US 560SL donor car will make your life easier.
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  #6  
Old 12-08-2010, 10:02 AM
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6.3 exhaust manifolds and downpipes will just bolt right up to the 560?

Regards,

David
__________________
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2000 Honda Accord V6 137k miles

1972 300SEL 4.5 98k miles

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  #7  
Old 12-08-2010, 10:06 AM
GGR GGR is offline
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Quote:
Originally Posted by WANT '71 280SEL View Post
6.3 exhaust manifolds and downpipes will just bolt right up to the 560?

Regards,

David
No. 6.3 Downpipes may have to be reworked to fit the r107 560SL manifolds.
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  #8  
Old 12-08-2010, 10:50 AM
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i am located in Florida

my donor engine is from a 1989 560SEL. i was under the assumption that i would need both the 560SL oil pan and oil filter housing. The oil filter housing MUST be from the SEL??? and if either oil pan works, is one BETTER than the other?? will the SL pan eliminate the need for lock to lock steering issue?

i am thinking that a 112 radiator would be hard to find?? since i live in florida, i am concerned about cooling. the 3.5 has the side oil cooler which the 560SEL does not. does the 112 radiator have a cooler? if not does it have a larger core for greater cooling? i am sure i can have a radiator shop relocate the inlet tube on the top tank without much effort? i think i should be more concerned with water cooling rather than oil cooling??

i am assuming on your 5.6 111.026 swap you did not need to change the booster? and the SEL exhaust manifolds will not work??

have you heard of a 111.026 to 5.6 radical conversion done by someone in Germany?

looking forward to and enjoying the replies.
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  #9  
Old 12-08-2010, 11:32 AM
GGR GGR is offline
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The SL and SEL oil pans differ in the front, while the problem with the intermediate link is in the back. I would keep the W126 oil pan that will give you a better ground clearance and will enable you to lower the car a bit. Yes, oil filter housing MUST be a W126 one.

You could start with the 3.5 radiator. If in good shape it will do the job fine. The W112 radiator is the same width as the the 3.5 one so you will be able to keep your 3.5 oil cooler. That radiator is a 4 rows instead of three on the 3.5. It will need the 3.5 radiator side plates to be grafted to it because the fixation points are different. If ou want to keep the oil cooler you will need to source a euro M117 oil filter housing to get the fittings for the hoses.

Oil coolers are needed for long distances at high speed, like on the German autobahns. Not really needed in the US. This is why US W126s don't have it. Frankly, I would do without an oil cooler and fit a Wider radiator out of a W116 for example. Les parts, less weight and less chances or something to go wrong.

My 111026 had a 6.9 stuffed in there when I got it. So I don't know if the booster had been relocated for that earlier transplant or not. Basically, the M117 engine will be half an inch higher and half an inch wider. Look at the clearance you have at the back of your left cam cover, allow for 2/3 of an inch for engine movement and you will know if you need to relocate the booster or not.

You have Autoschmiede that grafts a W111 body on a W126 platform. Mercmad6.3 is currently doing it. But the amount of work involved not comparable.
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  #10  
Old 12-08-2010, 12:27 PM
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so the 126 pan is more shallow and the 107 pan is deeper??

i agree with dropping the oil cooler.

can i just add a 4 row core to my 3.5 radiator? will the W116 radiator drop in the the 111 chassis or will i need to modify it.

do i have to use 107 exhaust manifolds? will the 126 manifolds work?

where do i find a conversion for the speedo drive?

my car ran at 4000 rpms with the 3;69 rear end at 80 mph. i am assuming i am going to have the same problem with the new set up? will the 2;88 solve the problem? how easy is it to find one? can i just swap the ring and pinion?
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  #11  
Old 12-08-2010, 01:03 PM
GGR GGR is offline
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Quote:
Originally Posted by merchauser View Post
so the 126 pan is more shallow and the 107 pan is deeper??

i agree with dropping the oil cooler.

can i just add a 4 row core to my 3.5 radiator? will the W116 radiator drop in the the 111 chassis or will i need to modify it.

do i have to use 107 exhaust manifolds? will the 126 manifolds work?

where do i find a conversion for the speedo drive?

my car ran at 4000 rpms with the 3;69 rear end at 80 mph. i am assuming i am going to have the same problem with the new set up? will the 2;88 solve the problem? how easy is it to find one? can i just swap the ring and pinion?
I put a 560SEL oil pan next to a 5.0SLC one and the W126 is shallower and wider. Don' know what the 560SL looks like.

If you drop the oil cooler you will have room for a wider radiator, no need to mess with the 3.5 one. You have to see which one fits best. I believe the W116 without oil cooler will be a good fit but you should confirm that.

W126 manifolds will hit the firewall. 560SL are the easiest (450SL or W108 4.5 will also fit but inner diameter is smaller that the 5.6 exhaust port and centered differently. You will loose power which would be a shame on the already rather low powered 560US version.

There is a company making these speedo conversion devices, I would need to look on the net as my archives were lost in a crashed computer.

A 3.27 will give you 3500 rpm at 80mph and a 2.85 3000 rpm. The 6.3 ones are not that easy to find, nor the 3.27 ones as all the Pagoda crowd is after them. But you can be lucky looking in junkyards.

You can't transfer a 2.88 ring and pinion in the 3.69 rear axle because the center casing is different. But you can fit a 6.3 center casing with internals on a 3.5 rear axle. You have to make sure it has the bracket for the center spring as not all of them have it. You also have to make sure you know what you're doing because clearances are quite delicate and must be respected to avoid a noisy rear end. You would have to buy a used 6.3 rear end to get a ring and pinion set anyway.

Another option is to fit a W124 rear end. Mercmad 6.3 will tell you more on what is involved, but apparently it's not that complicated.

Fitting 15'wheels with 205/70-15 tires can also help.

Last edited by GGR; 12-08-2010 at 01:13 PM.
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  #12  
Old 12-08-2010, 01:39 PM
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ok. i am clear on the pan, manifolds and radiator.

you mentioned low power on the 560 US version. what is the HP spec and what can be done to juice it up a bit. i thought this motor has gobs of power and torque, especially compared to the original 3.5. also have been told that the SL motors have lower performance specs compared to the SEL??

can i assume that removing all the pumps not needed like smog and suspension stuff, will help with power??
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  #13  
Old 12-08-2010, 02:30 PM
GGR GGR is offline
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The 3.5 has 200hp at 6000 rpm and 29kg of torque at 4000 rpm. The US 560 has something like 242 hp at 4800 rpm and 38kg at 3500 rpm. the 560 SL is 230 hp at 4750 rpm and 38 kg at 3250.

some Euro 560 are 300 hp at 5000 rpm and 46 kg at 3750 rpm. You can get all the details here: http://carfolio.com/search/results/?terms=mercedes+560&x=18&y=9

You can improve things by replacing the camshafts. A good option would be a reproduction of the 300 hp ones that could give up to 275 hp on your engine with a well sorted ignition and injection and without all the depollution rig. Add 15hp if you source some r107 500SL tri-Y exhaust manifolds. You will have more info on these camshafts here:
http://www.benzworld.org/forums/w126-s-se-sec-sel-sd/1542676-trek-up-north-holy-euro-motor.html

You could also go for AMG reproduction ones, like here:
http://www.benzworld.org/forums/w126-s-se-sec-sel-sd/1538122-m117-performance-camshafts-500-560-a.html

More generally, you will find some performance upgrades for your engine here:
http://www.benzworld.org/forums/w126-s-se-sec-sel-sd/1433087-w126-performance.html
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  #14  
Old 12-08-2010, 02:56 PM
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a lot of the specs i find are different and confusing. are all US 560SEL engines of the same cloth or are different years with differing performance?

i am thinking and hoping that this swap will provide me with the power that i have been looking for: not a hot rod or tire burner, but just more that what i have had for the past 20 years with the 3.5.

what is the tri Y setup??? sounds like taking all the clutter off the motor and installing this set up will even give a bit more?
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  #15  
Old 12-08-2010, 03:20 PM
GGR GGR is offline
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They may be some variations, but all the US spec engines have more or less the same power. You may get more powerful engines but they will be out of the grey market.

The 3.5 is a very nice engine, but the auto transmission doesn't do it justice. peak torque is at 4000 rpm and there i not much below that. With a manual trans it's another beast as you can exploit it's characteristics much better.

If what you want is a nice cruiser and if what you have is a US spec engine then go with it. You won't be disappointed. It has 30% more torque better spread all over the rpm range and it comes earlier. It is torque that makes a drive pleasant, not peak power. In addition, the US spec 560 has some room for easy and reasonably cheap improvements, up to the 280 hp range and over 40 kg of torque. Finally, you will relieve 70kg from the front of your car due to the alloy block, making the car lighter and better balanced.

A tri-Y system is a different type of exhaust manifolds. There are four exhaust manifolds that join exhaust gases from two cylinders into one pipe. Then you have four down pipes that each join into the two exhaust lines. The 560 tri-Y system won't fit your car, but the r107 500SL/C will, with a slight modification of the right chassis rail. They are not that easy to find, but are definitely worth the search. You could start with a stock 560 engine and 560SL manifolds. You could leave the camshafts and the tri-Y system for later, as an evolution of your project.

If after all that you still want more, you can go for a blower. The 9:1 compresiion ratio of the US engine will accomodate it well and you can get up to 30% increase in power and torque.

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