Difference between M117 and M116

[oscar]

Apart from 4.5 L compared with 3.5 L. 

On more than a few occasions I've read that the M117 is derived from the M116 by simply giving it a larger stroke or is it bore. 

My question is, is the 4.5L motor bigger externally than the 3.5L?  It looks bigger.  How was the increase in size achieved if the same block is used?

There's so many parts that are the same like valves but others like timing chains are different.

So what was enlarged to make the difference?

[gregdeklerk]

Ze Jermin engineers are playing tricks on ze eyes, her Oscar!!

[oscar]

Nein, zer not.

I remember seeing comparitive pics.  I know that the hydro suspension pump is easier to remove off a 450 than a 350, I know the timing chain is larger, I know the engine looks taller or wider.  So what's the go if it's presumably the same block.  How does a 4.5L reach 4.5L from 3.5L?

Hmmm, anyone, anyone?  Bueller?

[13B]

I'm pretty sure the bore/stoke details are in the Haynes 350/450 W116 manual.

Hint for keen observers: The M116 3.5L V8 was englarged into the 380SE/SEL engine and 420SE/SEL engine and the M117 4.5L V8 was enlarged to the 500SE/SEL and 560SE/SEL engine in the W126 era.

Hi W116ers, btw.

[oscar]

Hi 13B and welcome,

I found my Haynes manual under the computer desk at home the other day, so i'll have to look at it and look for clues to find the differences.

You're right about the W126 engines.  I had misconceptions about what became what, believing the 350 became the 380 (which it does) and the 450 reduced to become the 420 (which is wrong).

So how about this then, can my 350 block be bored out to fit 420 pistons? EDIT: basically can a 350 be bored out to 4.2L?

[WGB]

I would check block thicknesses as obviously the later engines were completely different castings made from aluminium with nicasil bores and it is possible that the casting thicknesses were different from the original cast iron 350 motor.

You don't need a porous block.

Why not put in a 450 motor and not tell anyone - after all that's what M-B did in the USA in the last of the 108's.

Bill

[oscar]

Yeah Bill, you're right.  It's interesting looking at US parts sites and seeing what models got a 4.5L engine.  A 4.5 L swap would be the cheapest way to go.  I'd hate to think what I will do if I ever break the 350, btu that would be the cheapest option (bar a mercules style Ford implant).

I'll have to load PB's EPC and check what part numbers are the same between the 4.5 and 3.5.

[13B]

EDIT: basically can a 350 be bored out to 4.2L?

Ask on the net or ring around - someone is bound to have tried it.  I would, if I had a tired 350 block, get someone to bore it to the size of the 420 pistons and check the surface or porosity.  On the plus side if it works you can have 4.2L performence from an engine with matching engine numbers with the chassis.

Thanks for the welcome, my background and interest is in club motorsports so most of my posts and thoughts will be best towards speed / output, and less to do with originality.

[gregdeklerk]

Hi 13B and welcome to the forum!

[Mforcer]

Thanks for the welcome, my background and interest is in club motorsports so most of my posts and thoughts will be best towards speed / output, and less to do with originality.

Welcome to the forum! It will be great to read about your thoughts on speed and output improvements.

[oscar]

Club motorsports eh?  "so most of my posts and thoughts will be best towards speed / output,"  Ditto what Mforcer said.

You can see what I'm getting at.  I don't have a tired block as yet.  The thing's too bloody well made.  However, parts cars are so cheap.  When talking about w126's and problems with aluminium blocks, I would assume the pistons are ok.  But given a worn out engine, I'd go by PatB's philosophy  -"fix it or completely stuff it".  But I'm way off from that point.  450 bits into a 350 is where my curiosity  lies.   

BUT!! I very much like the idea of a bored out 350 with 420 pistons and the engine number to remain the same.  A torquey short stroke 420.  I'm guessing a 350's crankshaft and conrods could be used.  Hmmm   Food for thought!

[116.025]

Club motorsports eh?  "so most of my posts and thoughts will be best towards speed / output,"  Ditto what Mforcer said.

You can see what I'm getting at.  I don't have a tired block as yet.  The thing's too bloody well made.  However, parts cars are so cheap.  When talking about w126's and problems with aluminium blocks, I would assume the pistons are ok.  But given a worn out engine, I'd go by PatB's philosophy  -"fix it or completely stuff it".  But I'm way off from that point.  450 bits into a 350 is where my curiosity  lies.   

BUT!! I very much like the idea of a bored out 350 with 420 pistons and the engine number to remain the same.  A torquey short stroke 420.  I'm guessing a 350's crankshaft and conrods could be used.  Hmmm   Food for thought!

The 420 also got a somewhat longer stroke than the 350, so even if you bored it out and put 420 pistons in, you wouldn't get 4.2L...if memory serves, the M117 was mostly bore increases, whereas the M116 was some bore increase and some stroke increase.

[oscar]

Yeah, we'll forget the 420 pistons, and the 450 pistons for that matter.

I went thru my Haynes manual like 13B suggested and there is a wealth of info for comparison.  There really seems bugger all room to move for wider pistons and what's more, the bore for a 350 and 450 is exactly the same.  Bore - 92.0mm.

Looking at photos of the top of the blocks, I believe it would be possible to widen the bore but to what extent I don't know.  I haven't found a figure for max allowable width.  So take a few mm off, I don't know what stock piston could be used and doubt if oversize rings could make up the difference with the current one.  Who knows.

Anyway.  Again, I'm amazed what is the same between the two.  Checking out more parts between a m117 and m116, they use the same rings, crankshaft bearings, timing chain sprockets, valves, camshaft and so on.

The only differences I found so far to do with capacity are basically-

Stroke - M116 65.8mm - M117 85.0mm
combustion chamber - M116 15.85 to 16.15mm - M117 17.85 to 18.15mm

What puzzles me is how the extra stroke for the M117 is achieved.  The crankshaft, conrods and pistons seem to be the same.  Anyone know how the extra piston travel is achieved

[torana68]

Hi,
if the bore is the same then the stroke isn't , it would be longer, can't change maths! whilst the cranks may interchange (giving you a 350 instead of a 450, maybe a 450 instead of a 350??) the conrods might not. The rods in the 450 are either shorter or the piston pin is higher in the piston to make up for the extra stroke. The camshafts whilst possably being interchangeable would be different in their timing (well SHOULD be). The other bits should be interchangeable to reduce manufacturing costs and still have 2 different capacities without going to the expense of making 2 completely different engines. Perhaps have a look at the 560 and see if it even longer stroke? you may be able to use rods crank and pistons from one of them.
Roger
Ooooooooo! its also possable that the block has a higher deck height (distance between the crank centre and top of the block) meaning a 19mm higher engine? to make up for the extra stroke.

[13B]

combustion chamber - M116 15.85 to 16.15mm - M117 17.85 to 18.15mm

I was wondering what this means exactly?  Is this the different compression ratios? If so and there are low compression pistons available for the 350 then a whole new world of modification opens up which would be interesting to explore, turbo charging.  High compression is the scourge of reliable turbo charging, but the fuel system seems to be up to it, and you could get the M117 power or more from an 350 M116 with forced induction.