Engine swap in a 1970's merc
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Discussion

ssray

Original Poster:

1,344 posts

254 months

Just asking, not going to be a thing unless I get really rich.

I've always liked w108 era mercs, 3.5 or 4m5 petrol engine is a little thirsty if this was going to be a daily driver.
Looking at the specs a b5 Passat is about 100kg less than the w108.
So why couldn't you put a pd130 into the Merc?
I understand the gearbox etc would have to be sourced.
Ta Ray

Super Sonic

14,146 posts

83 months

Why would you?

ssray

Original Poster:

1,344 posts

254 months

Super Sonic said:
Why would you?
3.0 straight six has been done and would still be a bit thirsty for daily.
I'm asking if it would work the Passat and w108 are only 100kg different in weight

Super Sonic

14,146 posts

83 months

Are you asking if it is possible to put an engine from one car into another car? Yes it is. The question I'm asking is, for the amount of work it would entail, what would be the benefit.

OutInTheShed

14,341 posts

55 months

One reason is that the car would lose its zero VED status and probably acquire a Q plate?

How many miles a year is anyone going to do in a 70s Merc?
I'd expect packback in fuel savings to take a long time indeed.

I did know someone who had done a DIY EFI conversion on a couple of big old gas guzzlers, resulting in a significant fuel saving.

Crafty_

14,048 posts

229 months

Would it work ?

Probably, assuming that it physically fitted and you could fabricate mounts
you'd have to figure out CAN wiring or standalone system, (probably) junk the original dash and use a passat one or aftermarket.
Fuel system transplant too.
Gearbox would also need some attention to ensure ratios worked well and probably make or have made an adapter / bellhousing.

But a VAG engine its an odd choice frankly.
If you were determined to do it, why not look at the V6 diesels from an older C class (and others). The newer GLE etc have a straight 6 diesel, at least you'd be keeping it in the family and could be seen as resto mod. A quick look around shows AMG V8 engines being used so thats an known path and thus simpler as all the headaches have been tackled.




BuyaDuster

1,066 posts

210 months

I am in the middle of fitting an 5.0l SEC V8 into the 1966 W111, similar chassis architecture as a 108.
This is the M117 engine.
The M104 is a good choice too as both are relatively easy to make work with the original ECUs and good power and efficiency.
No wheel speed sensors or aftermarket ECUs.
Anything manufactured post mid 90's will be difficult.

But a clattery VW diesel? no thanks!

The difficult bit is not fitting the engine and making it work.

It is finding a reasonably affordable car that isn't rotten. They are all rotten.