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M117 Intake Refurbishment

Started by TJ 450, 07 December 2008, 10:12 AM

TJ 450

This morning, I decided to continue removal of the intake manifold from the 450. The reason for this was a significant vacuum leak, which turned out to be a loose fitting, the connection for the brake booster's line at the plenum chamber. It has been removed and cleaned, although not to my satisfaction just yet.

Unfortunately, I only had my phone with me during the removal phase. I have lost the USB cable and can't access the photos. So there are not photos of the "vee" at this stage. Although it is nice and clean now.

I also prepared the 6.9 for next weekend's adventures.











...Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

Big_Richard

#1
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TJ 450

I drilled the head off, now I'm left with a 1" protruding stud siezed in the cylinder head. It is soaking in INOX at present. I'll get my stud remover onto it this next weekend. If it snaps off, I'll just have to get the heads refurbished.  8)

Yep, I had to use IE as you suggested. I posted the message with Firefox and uploaded the images with IE. ;)

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

WGB

I assume you have been keeping it coated in WD 40 or whatever.

Try some gentle heating of the stud end to see if it will loosen the corroded threads.

Usually if it won't come and snaps off the hole drilled for an "ezy-out" with relieve pressure/ease out the threads.

I guess the worst scenario should be to drill out the piece and use a helicoil.

Just don't get too vigorous and break off the aluminium from the head.

Bill

Big_Richard

#4
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koan

Quote from: TJ 450 on 07 December 2008, 10:12 AM

This morning, I decided to continue removal of the intake manifold from the 450.


Is a 450 plenum chamber same as a 6.9?

koan
Boogity, Boogity, Boogity, Amen!

TJ 450

Both the manifold and plenum chamber are quite different. The bore diameter is smaller among other things. Throttle body is the same. The manifold on the 6.9 is specific to that engine only, unfortunately.

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

TJ 450

I haven't touched the remainder of that bolt yet, although I'm sure it won't be too hard to remove (touch wood). I'll play it by ear.

BTW, there is a channel that runs across both cylinder heads beneath the ports that's completely clogged with carbon. There is also a port in the manifold connected to this. The 6.9 has a similar arrangement, only there are just two ports in the centre of the cylinder heads, equally as "carboned" up. I'm wondering what purpose these serve? Is it part of the air injection system?

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

koan

Quote from: TJ 450 on 08 December 2008, 04:38 AM

Both the manifold and plenum chamber are quite different. The bore diameter is smaller among other things. Throttle body is the same. The manifold on the 6.9 is specific to that engine only, unfortunately.


I know the manifold is different but given the throttle body is the same I thought the plenum might be as well.

I reckon the throttle body strangles a 6.9, one of the HP calculators (megasquirt) gives a maximum of 243 HP from a 65 mm throttle body. If I could get a spare plenum I'd attempt to fit a larger throttle body and see if there was any HP increase.

koan
Boogity, Boogity, Boogity, Amen!

TJ 450

Yes, it's strange how it necks right down at the throttle body. I reckon the throttle body should flare out in a logarithmic fashion where it mounts to the plenum chamber too. PB suggested having a polished surface inside the ports, too. I wonder how that would affect performance?

Tim

1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

koan

Quote from: TJ 450 on 08 December 2008, 10:45 PM

Yes, it's strange how it necks right down at the throttle body. I reckon the throttle body should flare out in a logarithmic fashion where it mounts to the plenum chamber too. PB suggested having a polished surface inside the ports, too. I wonder how that would affect performance?


Why the throttle body necks down to the plate and then out again I don't know, it doesn't need to be a venturi, it needs to be bigger!

Polishing ports was big years ago then suddenly it wasn't the thing to do any more.  The logic was that the rough cast surface helped mix fuel and air whereas the smooth polished surface allowed fuel to stick and separate out.

That's on carburetor engines though, that doesn't  apply to injection where the fuel added with an atomising nozzle 20 mm from the valve.

I'm convinced a larger throttle body would add lots of top end HP. My approach would be to machine off the existing mounting from the plenum and mount a larger throttle body to it.

koan
Boogity, Boogity, Boogity, Amen!

Big_Richard

#11
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TJ 450

Quote from: Patrick Bateman on 09 December 2008, 03:36 AM
More air voliume - but then what?

Isn't tje K-jet system pretty crap in this regard, you'd probably need to run modern engine managment also. I'm pretty sure the 65mm throttle gets the air flow meter flap close to bottoming out anyway at wide open throttle, all a larger throttle would do if its bottomed out already would make it run too lean at wide open throttle. Certainly would make part throttle driving Much more responsive and make the accelerator pedal rediculously sensitive, like that of a VN commondore - WOT at 5mm then nothing more the rest of the way to the floor.
I would think the system could be adjusted to compensate so as to add more fuel relative to meter position. Could it be as simple as adjusting the control pressure? The K-Jet system was used on quite high performance vehicles, the fuel pump is able to supply a very large volume of fuel as well.

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

Big_Richard

#13
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TJ 450

Hmm, I see what your saying, although increased control pressure would counteract the force of the air on the plate wouldn't it? I suspect that it (the metering device) also works in a linear fashion, which should be fine, as there is a larger volume of air across the board with a larger throttle body.

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500