I have a good, spare 18 cast in my attic. I have been considering buying a 22 to install on my SDL as it's the latest and best. Yet it raises a few questions for me...



Any modifications for this head to fit the early blocks?

Doesn't the late head require different prechambers? Any issues reusing old 'chambers?

If it necessitates those, will it need different injectors? Is it the body or nozzle?

Last thought, is the 22 that much better than the 18?

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

After 1989, angled prechambers were used. The prechambers, collars and injectors are different.

More efficient, somewhere around 5% better economy and less smoke.

Hm, so my 18 head should have all that crap already then I assume?

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

What year(s) were the #18 and #22 heads initially installed in the 603 engines?

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daw_two
Germantown, TN

Links:
Sold last car --- 05/2012 1984 300D Light Ivory, Red interior
Cluster Needles Paint
New Old Stock (NOS) parts

Past:
3/2008 1986 300SDL "Coda"
04/2010 1965 190D(c) "Ben"
& many more

If you have a good #18, I don't think you can justify the cost of a new #22. Of course, if one turned up at a salvage yard...............

You need longer bolts from the head into the front cover. #14 takes 50mm bolts, #17-up take 80mm bolts.

You can turn down #14 prechambers [edit] to work in #17-up heads. Dave's website has pictures that were good enough for my machine shop. I don't recall paying for different lock rings going this route

If you look at straight and angled injectors side-by-side you'll see the difference - one has threads near the tip, the other has threads near the hex. Dave would know if the innards can be swapped.

You can probably persuade #14 injector lines to attach to angled injectors.

Angled prechambers take a different thread pattern injector so note that you need a different compresstion tester adapter if it comes to that.

US 3.5 cars came with #17 heads. #18-up are replacements but might be original on crate engines.

If you're pulling the head, consider swapping in a Euro or 140 exhaust manifold that doesn't have that goofy reverse layup feed pipe arrangement. You might need to rework the downpipe.

uhh... use a 3.0 head gasket on a 3.0 block

Sixto
87 300D

The #17 head (started 07/89) has the reinforced areas to prevent cracks, should be fine. The #16 head was a short-production run with some improvements, but not all of the reinforcements. I'm not sure whether the #17s take the angled injectors or not.

The 602 turbo head changed at the same time to the 08 casting, for the same reasons.

Not to argue with Sixto, as he's one of the most accurate posters here, but both of the '91 3.5L cars I've been into had #22 heads. They didn't look replaced. I'd be interested if anyone here with a 3.5L has a head casting lower than #22 on their car, mostly because it would tell me whether my 22 head is a replacement or original on this car.

__________________

Gone to the dark side

- Jeff

Please argue. I'm notorious for making official statements with little basis In this case, the dozen or so 140s I've seen with original engines, and one I had with a replaced engine had #17 heads.

I *think* the EPC lists the #17 head (by part number rather than casting number) as the earliest available for 3.5 126. I don't know if the EPC is a reliable indicator since the 3.5 126 might be been originally spec'd for the #17 then actually sold in the US with a later head casting.

Is there a date code cast into the head?

Sixto
87 300D

I've seen a '91 350SDL with a 22 head, car was hit in rear real hard... and I've seen a 17 on a '92 300SD. What does that mean? Not sure. Perhaps the 22 headed cars have replacement motors?



What's the preferred gasket? Elring? OEM? Reinz?

My No 18 is still complete, injectors in the chambers and all. So I will assume it was fine as it came off a good running 3L. It will be going to the machine shop to be rebuilt. I will be doing springs, seals, and guides... any reason to replace valves or should they just be refaced and lapped?

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

I've heard of valve seat regression, but the valves are usually fine. Have the valve height in the head checked.

__________________

Gone to the dark side

- Jeff

Oh, anyone have a pic of what the headgasket failure looks like on the No 1 exhaust port?

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

Surf gsxr's website. In the extreme case of his 2.5, chunks of gasket lodged in the oil passages to the lifters!

Sixto
87 300D