What happens to a head in a machine shop
 

What Happens to a head in a machine shop

First Not all shops have the same equipment and the procedures from one shop to the next can and will differ.
Some shops cater to domestics and others imports or even diesels.
Some shops will view everything as a “stock” rebuilds.
So….
The most important thing to know is the shop you use and the equipment they will use.

The subject head is a Mitsubishi 4G63 7 Bolt

The first thing that should happen is the machinist looks at the head. Checking for the obvious damage, broken bolts, stripped bolt holes, bent valves, ect.
Attachment 4655

At this point it is up to you as the customer, inform the shop what you want done, such as…
1) Pressure test for cracks
2) Valve job
3) Surface
4) Guide work
5) Any performance work wanted
Also now is the time to speak about who will provide what parts, valves, seals, guides, springs, ect.

Now the shop should be able to give you, the customer, an approximate estimate of what the parts and labor will cost.

You as the customer have the choice to agree, or go somewhere else.
Now that your head is at the machine shop, and you have agreed to have the work done.

The first thing to happen is the head will be disassembled.

The tools needed are
Attachment 4656

Wire basket for small parts springs, valves, ect
Small container for valve locks
Valve lock release tool (socket method)
Hammer
10mm socket
12mm socket
12mm socket
Ratchet
5.5mm allen bit socket or wrench
Pocket magnet
Long reach needle nose pliers w/45* bend
Impact gun (not pictured)

Cam gears come off first, use impact with the 17mm socket
Attachment 4657

Next remove the cam tower caps, use impact or ratchet w/12mm socket.
Start at the ends working towards the center
Attachment 4658


Attachment 4659

Once the cam caps are removed, lift the cams out.

Attachment 4660

Next lift the roller followers out
Attachment 4661

Now you can remove the HLA’s
Attachment 4662
Attachment 4663
Now remove the oil spliter
Attachment 4664


Now remove any other small bolts
Attachment 4665

This is a “heat tab” Most machine shops use them.
The center will slide down at 240-250* and totally dissolve at 260*
Attachment 4666

Next is to remove the valve train.
Yes the same method that a lot of DIY people use are used in a machine shop.
Use a basket and a paint cap, have a pocket magnet handy too.
Attachment 4667
Have your “tool” and hammer ready to go
Place the tool on the spring retainer and give it a firm whack.
The locks will stay in the tool and release the retainer and spring.
Place the retainers and spring in the basket
Attachment 4668
Fish the valve locks out of the head casting with the pocket magnet.
Attachment 4669
Place the valve locks in the paint can cap.
Attachment 4670
Now remove the spring seats with the pocket magnet and place in the spring basket to be cleaned.
Attachment 4671

Next roll the head over and remove the valves and place in the basket.
Attachment 4637
This head was rebuilt once before, it must have had bent valves.So I will change the valve guides.
Now roll the head back over and remove the valve stem seals, throw these in the trash.
Attachment 4638

Next grab the 5mm allen bit and remove all the oil galley plugs. Keep these to be installed later, place in the paint cap with the valve locks.
Attachment 4639
The last thing done is to remove the cracked valve guides.
Attachment 4640

Now that the head is fully stripped, it can be tech’ed
First thing is to do a quick clean on the head gasket surface.
Attachment 4641
Next is to measure head thickness.
Attachment 4642
Now to check to see how bad the head is warped.
Attachment 4643
Notes are taken to reference back too.
Attachment 4644
If it all checks out, it goes to cleaning.
It gets thermal cleaning, then glass beaded.
Attachment 4645
Next oil port mod #1 is done
Attachment 4646
Next all the oil galleys get gun brushed
Attachment 4647
Now the entire head will be blown off with compressed air, including every bolt hole to make sure there is no glass bead media is left in or on the casting.
Attachment 4648
next is a coat of spray paint to seal the casting.
Attachment 4649
Now new guides can be installed.
Attachment 4650
They are set to height.
Attachment 4651
Now the valve seats can be cut.
Fist is to set the head in the machine and secure it properly.
Attachment 4652
The proper sized pilot is selected.
Attachment 4653
The head is now leveled in the machine.
Attachment 4654

Now to set up the seat cutter.
First is to find where the seat is to make contact on the valve.
Attachment 4621
Now the cutter bit can be set.
Attachment 4622
The seats are cut.
Attachment 4623
Now the valves are lapped.
Attachment 4624
The small parts of he head have been cleaned, retainers, springs ect.
Attachment 4625
Valve springs are tested.
Attachment 4626
Most valve springs have been found weak, so New BC1100 springs will be installed
(stock spring on left, BC spring on right)
Attachment 4627

A broken exhaust stud was found and removed.
Attachment 4628

The valves are ground.
Attachment 4629
Ground and ready to be installed.
Attachment 4630

Now the head can be surfaced.
The head is set up and secured to the milling machine.
Attachment 4631
The proper surface finish is milled for the head gasket to be used.
(a composite for this one)
Attachment 4632
The head is now blown out to remove metal flake from milling and seat cutting.
Now that the machining is done, it is time to assemble the head.

Valve tip height is checked to make sure it is in spec.
Attachment 4633
The valves are removed, lubed up and slid back into the same hole they came from.
Attachment 4634
A package of valve seals found in a head gasket set.
Attachment 4635
Now the seals are pushed on by hand
Attachment 4625
Now seals can be installed, this is my “hi-Tech” seal installer.

Attachment 4606
Now the seals are tapped into place securely.
Attachment 4607
Now spring shims are installed if needed.
Attachment 4608
The spring shim goes on before the spring seat.
Attachment 4609
Now the cleaned spring seats are installed.
Attachment 4610
On top of the spring shims.
Attachment 4611
The new valve springs, BC1100
Attachment 4612
Now the new BC1100 springs are placed in the head, on the spring seat.
Attachment 4613
I will set the head back in the TnS 2000 Seat and guide machine, Using this adapter I will compress the valve springs.
Attachment 4614
Now before I compress the spring, I will take the valve spring retainer.
Attachment 4615
Install the valve locks,
Attachment 4616
Then place it on top of the spring.
Attachment 4617
Now with the spring and retainer compressed,
Attachment 4618
I can push the valve locks into place.
Attachment 4619
Repeat the process till all the springs and locks are seated properly.
Attachment 4620

Now this customer is going to install new 3g HLA’s. So no need for me to install the last of the valve train.
I check the valve to seat seal one last time.
Attachment 4599
I did install the cam tower caps on their proper side and position.
Each cam tower bolt received a quick dip in oil, since all the bolt threads are dry.
Attachment 4600
Now the oil galley plugs received a dab of sealant.
Attachment 4601
Then started by hand to prevent cross threading.
Attachment 4602
Then tighten to seal.
Attachment 4603

I measure the head for thickness and make a not of how much was removed.
Attachment 4604

The final step is to CC the combustion chamber so proper compression ratio can be calculated.
Attachment 4605

This head is now done, and ready for the customer to pick up and install.

Just another day at the office, eh!
How many hours for the process?
Did you get my P.M.'s yesterday?

Yep! Just another day! :D

From tear down to being bolt on ready, a stock head will have 4-6 hours into it. Depending on the head some can have as much as 12-14 hours like a 2JZ, but that includes setting the cam lash.

SBC stock heads can be done in about 2-3 hours, they are simple and sloppy, A set for dirt track about 4

Now a 4 cyl 16 valve DOHC, with bronze guides, and full port work, fitting over sized valves I can have 25-30 hours.
More if I had to developed a custom spring set up, or work up specs for custom ground cams.

Yes I did get your PMs, just did not have time to get into them yesterday.