Cylinder head questions

[Gransin]

I found another head closer to me today and went after it. Made/marked -81, but it has the newer style water jacket ports? Supposedly sat on a M30B28 before.
I can't find any cracks in this head so I'll be using this one if the shop can't find anything wrong with it when I bring it to be machined.

What is the minimum height of the head, and how do I properly measure it?

Cheers,

 

[Markos]

I found another head closer to me today and went after it. Made/marked -81, but it has the newer style water jacket ports? Supposedly sat on a M30B28 before.
I can't find any cracks in this head so I'll be using this one if the shop can't find anything wrong with it when I bring it to be machined.

What is the minimum height of the head, and how do I properly measure it?

Cheers,

Cool!

I'm selfishly interested to see what the mechanical fuel pump area looks like on the head. The one on my '81 looks like someone stuck a bolt in the mechanical pump hole, but I'm not sure why this would need to be the case in '81. I found a pic of another '81 head online and it dind't have the hole for the fuel pump driveshaft. DeQuincy just recently pionted it out. Ignore the orange square below, this is just a pic to show where the VIN is at.

My '81 Head - Casting 277358 (Notice the three bolts on the fuel pump area, plus the sunken casting area around the middle bolt.

Internet '81 Head - Casting 277358 - Notice it's flat, no pump hole and no sunken casting areas around where the fuel pump would go.

Internet - 277358 Head. Notice the 'sunken casting area'

 

[HB Chris]

Your second pic is a Motronic head, see the dizzy housing, so no need for fuel pump boss. CSi heads had the boss and no hole, and your head with three bolts were added by someone very crudely to block it off. At some point replacement heads probably came without the hole but had the boss so it could be drilled out I am thinking.

 

[Gransin]

Markos, I've been staring at different M30 heads for two days straight now, so I might mix things up, and I'm not close to the garage right now so I can't check, but I'd say my 81 head looks like your third picture.
I'll check closer tomorrow!

Cheers,

 

[deQuincey]

1. some info here
   
   
   1975 head: central 8mm hole, and two M8 studs
   
   
   
   
   1985 head: (not easy to make the 8mm hole as that M6 stud is already there, we will use a bushing)
   
   

and how to deal with this,
work done, inserting a bushing:

 

[Markos]

Your second pic is a Motronic head, see the dizzy housing, so no need for fuel pump boss. CSi heads had the boss and no hole, and your head with three bolts were added by someone very crudely to block it off. At some point replacement heads probably came without the hole but had the boss so it could be drilled out I am thinking.

Thanks Chris. I'll pull the bolt out to see what I find. Presumably a tapped hole. There are two things that I found confusing. First, the head in question is from 1981. Which M30 cars had carbs in '81? I was thinking maybe a 630CS, but it appears that they stopped in '79. Perhaps a low-end euro E28? Those were all M20's though. What am I missing?

Also, I know the casting numbers aren't terribly helpful, but the divot in the closeups that DeQuincy posted are clearly cast into the head. Knowing nothing about this stuff, I would assume that if you change the actual casting, you change the casting number. However, the motronic head that you mentioned has no hour glass shaped casting 'cavity' near the mechanical fuel pump flange, but the other 277358 heads do. I find this confusing, but I'm not particularly surprised. What did it take to change the casting number? Was it the head design? I know it changed several times, and there was that spanish AMC head.

There is a good faq on first fives...
http://www.firstfives.org/faq/cylinder_head/cylinder_head_faq.htm

 

[HB Chris]

I'm not an expert on these but an 81 casting can be for earlier cars not just 1981.

Just for fun I looked up a 1974 euro 525 in RealOEM and it shows the head with the off center hole and studs. But it also shows a mechanical fuel pump!

 

[Markos]

I'm not an expert on these but an 81 casting can be for earlier cars not just 1981.

Just for fun I looked up a 1974 euro 525 in RealOEM and it shows the head with the off center hole and studs. But it also shows a mechanical fuel pump!

Ahh sounds like I was on the right track with a lower end euro e28. Anyway I'll put this thread hijack in the parking lot, and end it with a predictable pic:

Honestly seems like a decent way to plug the hole, versus a plate.

 

[Sven]

What is the minimum height of the head, and how do I properly measure it?

I believe it is 129 mm. Some of the heads, at least b35's, have "wear" dimples on the bottom mating surface. If the dimple is gone then the head can no longer be shaved.

Measure from the bottom face to the top flange (where the valve cover mounts to).

 

[Gransin]

Ahh sounds like I was on the right track with a lower end euro e28. Anyway I'll put this thread hijack in the parking lot, and end it with a predictable pic:

No worry about hijacking, it's all interesting and educating. I remembered correct, my head looks like your third picture, here is a picture from mine:

I believe it is 129 mm. Some of the heads, at least b35's, have "wear" dimples on the bottom mating surface. If the dimple is gone then the head can no longer be shaved.

Measure from the bottom face to the top flange (where the valve cover mounts to).

Thanks!

 

[Stevehose]

Here is text from a post from SFDon that I kept handy:

A good skim is 5 thousands not twenty five thousands. Over 5 thousandths is warped or damaged

(let's keep this in inches - machine shops in the states stare at people who want things done in mm)

A new head is 5.079 inches Minimum size is 5.063 inches

Do the math- you can cut a head .016 inches. The extra thick head gasket is .011 extra

 

[sfdon]

Bottom line to me is any head cut 16 thousandths is a one use only head with a greatly diminished value.
Which means I wouldn't touch it.