how to inspect a head for potential rebuild ?

[achtung-e30]

so i bought a 325i fully assembled head - was in storage for 15 years -

visually looks to be in good condition -clean - its on my bench

but dont want to install this head and find out it needs to be rebuilt-

happy to post specific close up pictures if helpful, but of what ?

what should be done to this head as a matter of standard operating procedure prior to install ?

what should be checked ?

hot tanked as fully assembled unit ? (po painted it chevy red)

what if this head was stored vlave face down ?

u get the idea, thanks in advance, as i have quite a bit of experience working on cars ect but none with respect to internal engine work -

[jeffnhiscars]

If you are comfortable disassembling it yourself then do it. Either way bring it to a reputable machine shop and have it cleaned, pressure tested, decked, have the guides and cam checked and have the valves, stem seals and seats done.

Skip any part and you are wasting your money.

[TobyB]

Hmmm, there's a lot you can do on your own, IF you are willing to take it apart.

Otherwise, a machine shop's worth the money.

A straight length of drill rod and feeler gauges will tell you if it's warped, and how much.
Pulling the cam is a good way to be sure it's not twisted, or warped and milled later.
The dot will tell you how much it's cut, as can a caliper. Yes, the $10 Harbor Freight
one is good enough IF you don't freak about the last .001"
The valves, cam, rockers, pivot rods and cam journals can all be visually inspected with
the aid of your fingernail.
The $10 Harbor Freight dial indicator will tell you if the guides are 'good enough'
A $7 tube of lapping compound and a $3.49 lapping stick can tell you the rest about
the valves and seats.

And common sense gets you the rest of the way.

I'm about 5 for 5 with 'good used' heads this way- as in, if they pass, they work.

The machinist missed one with a corrosion problem once, and that taught me to
poke at it myself even IF I paid him afterwards.

t

[achtung-e30]

I thought these pictures might help, thanks again.

[achtung-e30]

thanks for reply yea i do feel confident stripping down the head and checking measurments against spec - couple of follow up questions

pior to any work based on pics how does it look ? comments welcome

whats the best way of at home cleaning of head, valves, chambers ?

i can install new valve seals but whats best method of checking valve guides ?

thanks

[jeffnhiscars]

Hard to tell what's been done but the dimples on the face have to be visible or it's been decked too far and the edge of the valves should not be too thin. To check guides stick a valve half way in and wiggle. There's a spec for this but by feel,there should not be a whole lot of side to side. Typically exhaust guides where more.

For backyard cleaning, I use generic engine degreaser and a stiff parts brush (something that won't scratch machined surfaces) then follow up with some simple green. Smaller bits I put in a can of chemclean or the like. From what I see the head looks fairly clean so it may have need worked on. Just keep in mind that virtually all of them are not flat once they've been installed so while you may be able to wing it and get lucky, if it's your first time, I'd get pro to check it.

[achtung-e30]

ok will do

yes I would say that these heads have seen some work - that's kinda why I'm reluctant to have it sent out if not necessary

let me ask this, where exactly are these dots located ? I guess there are 3 on an untouched head so where exactly would I find them ? thanks

[AndrewBird]

The dimples are on the sealing surface of the head (where the gasket is). They are little dimples.

Definitely at bare minimum have the head skimmed to be sure it is flat. They almost always warp a tiny bit when removed from the block.

[Som]

Not a "materials" person, but I'd wonder if the valve seals could be kept dry for 15 years without hardening/cracking. Not sure what they're made of though, and someone else could correct me if there's no cause for concern there. Otherwise, it's something I'd definitely swap.

Som

[achtung-e30]

yea seals will get changed out 4 sure

but im having trouble finding those 3 "dimples" or "dots" where exactly on the mating surface of the head would they typically be located ?

[achtung-e30]

ok so search really is my friend ) turned up the following.....

By dimples that means 3 recessed circles, one on the intake side between cyl 2 and 3 and then two more under exhaust ports for cyl. 1 and 6.

the head has been re surfaced at as i found an issue
so houston ? we have a problem..only see 2 on the intake side none on the exhaust side

what if anything should i do about this ?

[achtung-e30]

ok thanks for your help - im moving in right direction - im going to strip the head down take some measurments and go from there - hoping i can get away with just a skim and seals prior to install -

[jeffnhiscars]

If you decide not to get the valves done at least hand lap them as best you can.

To check guides push the valve up til the head is flush with the guide. From there the lip of the valave should have .8mm or less side play.

[achtung-e30]

10-4 got it ty - top of valve flush - wiggle -measure - also have ball hole gauge on order

[AndrewBird]

Some good reading here:

http://www.r3vlimited.com/board/showthread.php?t=275515