Author Topic: A few 6.9 questions as I reassemble my engine  (Read 219 times)

3l33ter

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A few 6.9 questions as I reassemble my engine
« on: 28 May 2019, 07:18 PM »
I just mounted the cylinder heads and now I have a few questions / issues that need resolving.

Before I reinstall the fuel injection / CIS stuff, is there anything I should do to it? I.e. is now a good time to do anything like take it apart and clean it? Or submerge the injectors in solvent or something? My experience is all with EFI, so my 6.9 and my 280S are both alien to me, haha!

What is the best spark plug to use on the 6.9?

What is the best oil viscosity for this engine? I am a believer in zinc (zddp) so I'll look for one with it.

Is the dealer the only place to get oil filters?

Any tips on things to do while I have it all apart? Like a super hard-to-reach sensor or a trick to gain HP with a simple intake mod??  ;D
'75 280S
'77 6.9
'82 300TD

daantjie

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Re: A few 6.9 questions as I reassemble my engine
« Reply #1 on: 28 May 2019, 10:11 PM »
Personally I would replace all 8 injectors with new ones.  KJet injectors are cheap as chips, about $30 a pop, cheap insurance IMHO, especially after all the hard work already done.

Oil filter is Mahle OX65D. Part number 0001800409.

Oil, I run Castrol GTX 20W-50.  Many folks do so.  You can also go with a HDMO 15W-40 Diesel oil like Chevron Delo or Shell Rotella, both excellent choices.

I would check the screens in the Warm Up Regulator are clear.  Perhaps run the fuel pump and make sure you are getting clear flow out of the fuel distributor before you fire it up.  Any crud in the line will make your K Jet very grumpy.

Plugs, I run NGK BP5ES.  Nice and hot ;)

Good luck!
Daniel
1977 450 SEL 6.9 - Astralsilber

3l33ter

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Re: A few 6.9 questions as I reassemble my engine
« Reply #2 on: 30 May 2019, 01:41 PM »
Thanks for all the info!

With those plugs, do you use the factory gap? I found a few mentions of NGK BP6ES in the archives - have you ever tried those?
'75 280S
'77 6.9
'82 300TD

daantjie

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Re: A few 6.9 questions as I reassemble my engine
« Reply #3 on: 30 May 2019, 05:30 PM »
Thanks for all the info!

With those plugs, do you use the factory gap? I found a few mentions of NGK BP6ES in the archives - have you ever tried those?

Yup I just take them out of the packet and drop them in, I don't even check the gap to be honest, I know this probably fills most with horror, and in the past I buggered around with the feeler gauge, and I found them super close to spec right out of the packet, so I don't worry about it anymore.  BP6ES is fine too, the 5 just runs hotter and as I do mostly city driving I think it's best to run hotter to burn off most of the richness, but that's maybe just an old wive's tale ::)
Daniel
1977 450 SEL 6.9 - Astralsilber

3l33ter

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Re: A few 6.9 questions as I reassemble my engine
« Reply #4 on: 31 May 2019, 01:14 AM »
I don't have a PhD in sparkplugistry, but I think you're right about hotter plugs burning more residual fuel. Also copper plugs are better at this than platinum, so I was thinking of trying the NGK copper in heat range 6 (BP6ES) or platinum in heat range 5, but a quick web search got me no hits on a "BP5EGP" which should be a platinum plug with heat range 5. Maybe NGK doesn't make it.

I would definitely check gaps though. It's easy, and there are always 1 or 2 per set that are off by a bit.
'75 280S
'77 6.9
'82 300TD