Author Topic: Issues building M100 FrankenMotor  (Read 141 times)

raueda1

  • Classic
  • **
  • Posts: 359
  • W116 Enthusiast
  • Location: Salt Lake City, Utah
Issues building M100 FrankenMotor
« on: 05 October 2019, 11:16 AM »
The question at hand relates to my other thread on the scored valve rotator seat.  By good fortune I've got another set of heads from a "low mileage 6.9," except in this case I know the history and it's real (~72k miles and maintained by local MB dealer).   From the top the heads look beautiful.  This suggests just using those heads instead of going to all the trouble of redoing the original ones.  It would also save the headache of drilling and retapping a couple snapped intake manifold bolts.

Nothing is ever easy though.  One of the new cams is a little scored on a couple lobes along with corresponding rockers.  Not terrible, but noticeable.  The old cams/rockers are perfect.  The obvious solution is to move the old cams and rockers with corresponding lifters and thrust pieces over to the new head.  I'll check the guides and replace valve stem seals.  So why not?

I'm making a few assumptions here.  First is that Euro and USA cams are the same.  I'm pretty sure they are but will confirm.  Second is USA heads going on a euro block. The only obvious differences between heads is some smog piping.  It doesn't seem like a big deal to just plug it. 

Any caveats or reasons not to do this?  I'm pretty far down the rabbit hole on this whole thing, so this is far preferable to getting the old head(s?) redone.  Thanks and cheers,
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

s class

  • W116 Addict
  • ****
  • Posts: 4,151
  • I'll keep the 116's, the rest can go
  • Location: Squeezing 3 W116's into a double garage
Re: Issues building M100 FrankenMotor
« Reply #1 on: 05 October 2019, 10:50 PM »
You are going to first need to measure both sets of heads for thickness.  I think that will be the deciding factor.  For whichever set you select, issues like valve guides, broken studs etc will be solvable.

'76 6.9 Euro, '78 6.9 AMG, '80 280SE, '74 350SE, '82 500SEL euro full hydro, '83 500SEL euro full hydro , '81 500SL

Randys01

  • Classic
  • **
  • Posts: 127
  • W116 Enthusiast
  • Location: adelaide australia
Re: Issues building M100 FrankenMotor
« Reply #2 on: 06 October 2019, 01:32 AM »
Dave...time to take a deep breath matey. ;)
Swapping all that clobber over may turn into  Ben Hur.
Get a professional opinion on the original heads and what is required to remedy them.
If cams and rockers are all good, it bodes well things aren't too bad.
Getting a few snapped studs fixed is neither here nor there.
I would be endeavouring to fixup the originals unless pro diagnosis reveals deal breaker repairs.

Whilst I'd be confident the USA heads [compare mfg date and p/nos ] and cams etc would bolt onto the Euro without to much kafuffle I don't see it's a risk that needs to be taken. You will end up reconning those Euro heads later  in any case[unless you need some paperweights]  so do it now..keep the motor all Euro and you still have a decent set of US heads in hand.

btw: Re the swap over..........transferring the existing ex euro cam towers..cams..sprockets lifters/rockers to the US will require a full clearance check on all 16 rockers. Unless you are the luckiest b...t..d on earth, there is no way the Euro shim set up will match exactly the valve seating in the US heads. .You might fluke a few...again ask yourself    "am I feeling lucky"??   Oh, I've done this  too many times and it's a pain.

Get the existing heads assessed and report in!
 

raueda1

  • Classic
  • **
  • Posts: 359
  • W116 Enthusiast
  • Location: Salt Lake City, Utah
Re: Issues building M100 FrankenMotor
« Reply #3 on: 06 October 2019, 08:18 AM »
Dave...time to take a deep breath matey. ;)
Swapping all that clobber over may turn into  Ben Hur.
Get a professional opinion on the original heads and what is required to remedy them.
If cams and rockers are all good, it bodes well things aren't too bad.
Getting a few snapped studs fixed is neither here nor there.
I would be endeavouring to fixup the originals unless pro diagnosis reveals deal breaker repairs.

Whilst I'd be confident the USA heads [compare mfg date and p/nos ] and cams etc would bolt onto the Euro without to much kafuffle I don't see it's a risk that needs to be taken. You will end up reconning those Euro heads later  in any case[unless you need some paperweights]  so do it now..keep the motor all Euro and you still have a decent set of US heads in hand.

btw: Re the swap over..........transferring the existing ex euro cam towers..cams..sprockets lifters/rockers to the US will require a full clearance check on all 16 rockers. Unless you are the luckiest b...t..d on earth, there is no way the Euro shim set up will match exactly the valve seating in the US heads. .You might fluke a few...again ask yourself    "am I feeling lucky"??   Oh, I've done this  too many times and it's a pain.

Get the existing heads assessed and report in!
OK, OK.  In my heart I know you're right, just need a whack over the head to quit looking for shortcuts.  In the meantime, guess what?  Yesterday I got the other head apart.  Lo and behold, it had exactly the same circular scoring on the corresponding valve.   What an odd coincidence.  They are the exhaust valves on cylinders 8 and 4.  It was piston 8 that jammed up.  Another odd coincidence?  I doubt it, yet valves aren't bent and no evidence whatever of valves hitting the piston.  Hmmmm.  More grist for the mill.

Anyway, looks like the heads will be making a trip to the shop in the morning.  This feels like that old vaudeville act where you pull on a thread on your cheap suit and the whole thing unravels and falls off on the floor.  More to follow!  Cheers,

-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

daantjie

  • W116 Addict
  • ****
  • Posts: 1,696
  • W116 Enthusiast
  • Location: Vancouver, BC, Canada
Re: Issues building M100 FrankenMotor
« Reply #4 on: 06 October 2019, 11:59 AM »
Good luck Dave!  Makes me think of a clown car at this point, who knows what else will come tumbling out ::)
Daniel
1977 450 SEL 6.9 - Astralsilber

Randys01

  • Classic
  • **
  • Posts: 127
  • W116 Enthusiast
  • Location: adelaide australia
Re: Issues building M100 FrankenMotor
« Reply #5 on: 06 October 2019, 04:01 PM »
Without seeing them, I'd wager she has run hot at some time and exhaust valve 4 and 8 are the hottest.....just starting to nip up a bit.
Examine the head gaskets fairly carefully on no 4 and no 8 and see if there is any tracking/decay of the gasket on either side.

oversize

  • W116 Addict
  • ****
  • Posts: 1,325
  • W116 Nut
  • Location: Melbourne, Australia
Re: Issues building M100 FrankenMotor
« Reply #6 on: 10 October 2019, 09:56 PM »
Interesting that the heater connects to the LHS cylinder head (#8) but not the RHS (#4).  The RHS connects to a pipe which goes under the inlet manifold and I presume goes back to the water pump.  I wonder if this contributes to #4 running too hot?
1979 6.9 #5541 (Red Bull)
1978 6.9 #4248 (Skye)
1979 6.9 #3686 (Moby Dick)
1978 6.9 #1776 (Dora)
1977 450SEL #7010 white -P
1975 450SEL #8414 gold -P