Merc V8 420 to 560 question

[tigran]

The 420 is going into the workshop for some light spray work and to fix the airbags/lines whilst it's in there i'm planning to get the heads off and do a refurb on them - seals n' stems that sort of thing.

However i've heard some horror stories about them, stuff like there's a special tool to get the valve springs off - a normal big valve spring compressor won't work. Anyone back this up?

Also about the stem seals themselves - that they have to be pressed on with a press - again is this true? Just seeing whether I need to have them taken to a specialist/engineers/mechanics place or if I can do them at the workshop (it's a kustom kinda place so there's no specialist mechanics equipment apart from usual hand/windy tools).

Any help on this subject is muchly appreciated.

[Mr S]

If you've got the heads off, then a normal valve spring compressor is fine - there's a special tool to remove the valves whilst the heads are on the car, that's probably the one you've heard of..

I was planning on doing the same to mine, but I'm picking up a 100k mile 500 motor at the weekend for £50, so reckon I'll use that instead

Also, I don't think the stem seals have to be pressed in, the guides yes, the seals no.

Lemme go check my workshop manual CD...

[Mr S]

Yep 'remove valve stem seals with a screwdriver or pliers' - that's the official word on the matter!

PM me your address and I'll stick a copy of the workshop CDs in the post for you if you want?

Cheers, Martin

[BenzBoy]

I couldn't get a regular valve spring compressor to work on my 450 V8 heads. They're more or less the same as the later all-alloy V8 heads. For one, the shape of the heads made it hard to put the compressor on, and the valve springs are mega strong!
I suppose it depends on what type of spring compressor you have. I ended up making a bench-mounted tool to do the job in the end.

One thing I will advise is to get yourself a really good hex key socket (8mm I think) - Snap-On or something - for the head bolts. If the tool isn't an exact fit it can round out the head bolt (ask me how I know!). Even my Snap-On socket started to round by the second head.

[BenzBoy]

That reminds me, I've got a pair of rocker covers all cleaned up and painted gloss black, with brand new rocker cover gaskets if you're interested?

[tigran]

Hmm been pondering whether to spend any time money on this or opt for a 560 engine and box i have kicking about. MPG isn't a big deal as it don't get used that much - are the 560's really that good?

How compatible are they with where a 420 used to live. I know that the gearboxes are different and i'm presuming the ecu is different. But what about other gubbins. Thinking this would might be a better idea whilst the car's getting paintwork done and airbags sorted in the workshop i can get on with getting another engine in there.

[Mr S]

Exhaust manifolds are different, not sure about the rest though!

I'm going to be bunging a 500 motor in mine, so will let you know how that goes in a month or so - if you've not done yours first!!

[tigran]

Anyone know on the ecu issue?

[Mr S]

Also not sure on the ECU - I've got a 500SE ECU at my other garage, am going there tomorrow so will get the number on it and compare it to my 420SEL.

According to this site (www.theautomaticgearboxcompany.co.uk/pricelist/Mercedes.htm) they share the same transmission, so your existing 'box should be fine!

[tigran]

Hmmm i thought the ratios between the two were a bit different.