Mercedes V8 Inlet Manifolds

[c107]

Not too worried about the value of the car (my fantastic condition 280S would be lucky to get $8-9k - anything else V8 in comparable condtion would be $25k+), I'm not too keen on playing with EFI, may be the only option though.

I've never heard of anyone get a mercedes V8 to run well on carbies, and a few have tried.
Not saying its impossible, but have never seen it. Since they never made a carby version, there are no factory parts.

If you want to V8 swap your car, I would personally buy a K-jet motor. K-jet is quite simple and requires a lot less electrics than D-jet, and most troubleshooting can be done with basic fuel pressure gauges. Go with regular K, not KE. A 380 may be a go, as being an alloy motor will probably weigh similar to the M110 and it has a four speed transmission. The iron block 350/450 are quite heavy. Rusty 380SE/SELs are often being wrecked and parts cars are quite cheap.

even better get a whole 380SE/SEL parts car.

 

[Nab]

I have picked up a complete but rusty 350SEL hence the question. The conversion has been on my mind and now this car has basically fallen into my lap so I thought I would look further into it. Been sitting for almost 10 years, fairly sure the D-jet system will need a decent overhaul. Motor runs well when fuel is put into the inlet manifold, compression test show 160psi+ on all cylinders so a seemingly good candidate. I'm not super keen on rewiring/installing an EFI system. Just thought if a carby manifold was relatively straightforward I would give it a go.

 

[c107]

I have picked up a complete but rusty 350SEL hence the question. The conversion has been on my mind and now this car has basically fallen into my lap so I thought I would look further into it. Been sitting for almost 10 years, fairly sure the D-jet system will need a decent overhaul. Motor runs well when fuel is put into the inlet manifold, compression test show 160psi+ on all cylinders so a seemingly good candidate. I'm not super keen on rewiring/installing an EFI system. Just thought if a carby manifold was relatively straightforward I would give it a go.

Ah, ok. Well the main thing they all need is new flexible fuel hoses. If you can get it to run well in the 350SEL body, then it may just transfer over as it is. These cars often got parked due to terminal rust rather than engine issues.

The D-jet system is more complex than the k-jet system but there are a lot of cars happily running it today.

350SEL is quite a rare car. I've only seen a couple come up for sale over the years. Mostly rusty imports.

 

[Nab]

Yes its an Australia delivered model, still pretty rusty though!
I'll start a new thread to keep this one about manifolds...

 

[Oversize]

Current status is the redesign is complete & has been sent to the fabricator. With complexity being the main concern, the updated design may even perform better than the first concept. Now due to a lack of suitable material, the prototype will be constructed using alloy base and intermediate plates with reinforced fibreglass runners incorporated.

 

[Oversize]

Well I’m close to returning all outsourced fabrication to my original choice, since the current mob have been sitting in their hands for the last 18 months! Not helped by me having to move everything once again, but now that job has been completed I can get back to my intended projects.

Talking to a highly experienced mate has convinced me that patents are largely a waste of time & money so the kits will need to be ready for distribution before a temporary patent is secured & the design is released (ie unfortunately kept secret till then).

Meanwhile others try to improve the original manifolds & fail to address fundamental flaws in their redesign:

 

[Oversize]

 

[ProfessorExperimental]

If they're going to ITBs, why would they stick with the original injector location in the head when surely plugging those holes with a match to the port profile and siting the injectors immediately downstream of the throttle bodies would improve mixing, not to mention allow a more compact (possibly even single) fuel rail on top of the runners with less injector-injector pressure variation (already a known problem e.g. on the m113 fuel rails) and scope to allow broader injector choice with less space constraints?

Also to my mind they should ovalise all the runners and move the front 4 throttle bodies back, the rear 4 forward so that each runner has the same bends (just #4 and #5 are mirrors of their "bank mates") for uniform curl.

But what would I know

 

[Oversize]

I sometimes wonder if they positioned the injectors close to the ports to cool the valves?? It looks like they spray directly onto the back of the valves

 

[ProfessorExperimental]

Theyll cool the valves better if the droplet size is smaller. Sure you may dump more fuel per cycle with a poorly atomised spray to get the same effective AFR but it's about heat transfer capacity (which favours surface area to volume ratio) more than it is about heat capacity of the liquid fuel (which favours dumping excess unburnable liquid on the valves)...

Injectors close to ports on a plenum intake manifold system makes sense because then you get each cylinder's fuel going into that cylinder only and avoid reversion problems at rpms where standing waves may blow some of the fuel out into the plenum, especially since the m116/7 runners aren't very long. Totally irrelevant with ITBs and a single pipe from throttle plate to cylinder.

Look at e.g. the Honda RC211V motor, it has secondaries down near the port, sure, for when the air is moving at high speed, the airbox is pressurised and intake scavenging is working hardest... But the primaries are on a gantry like an inch, maybe 2 *above* the throttle plate, and they're the only injectors firing up to around 8 or 9k rpm...

 

[Oversize]

The manifold is at another fabricator now but I needed to check some measurements. I finally downloaded a CAD program & found it’s pretty accurate when compared to my measure by eye n ruler method! I haven’t got time to create it all on CAD since I’d have to teach myself, so this is just for a bit of fun until the real thing is made & duplication becomes a reality. I now have a mate who's keen to work on the prototype & a contact for a new scan when it’s complete.

 

[ProfessorExperimental]

Shut down Edge and Chrome when running Fusion, and close any parts you don't need open. That'll help alleviate the load on your GPU.

 

[Oversize]

Yes it did crash a few times & I wondered why lol! Thx

 

[Patrick_R]

Nice work Mark.

 

[Oversize]

Just to add some better pix…

 

[Oversize]

And if you want to make your own gaskets…

 

[Oversize]

AMG definitely favoured twin throttles, separate plenums & cross rams back in the day. It worked well on the Mampe SLC but not on the Interserie AMG McLaren probably due to the very long runners.

 

[Oversize]

Slow progress is better than no progress I guess lol!!! It’s a piece from here & a piece from there, but it’s actually coming together now! I did another significant redesign of the manifold, so it’s back to another scale drawing before fabrication. It’ll even work on the Ford small block Windsor 302 & 351 with a little tweaking! Others yet to be checked…

I found a place that can do alloy castings from CAD scans, so that’s the direction I’ll take assuming the fabricated prototype works well…

 

[Oversize]

Nearly got all the parts I need….

 

[Oversize]

I’ve discovered the system will work on any engine (not just Benzes) and of course includes M100, M119, M113, M110, M103/4. The M120 is harder but not impossible