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how to rebuild a 4g63 head? any suggestions?

thedsmguy

Well-known member
Joined
Mar 20, 2009
Messages
1,785
Location
Vancouver Washington
I'm wanting to rebuild my head. I have it torn down with the valves out. How do you go about replacing the valve guides or should a machine shop do that? How about the valve seals? Should the guides even be replaced if they are not cracked? Are there any tricks to getting the old valve seals out or just have at them with vice grips? Anything else I should do prior to having the machine shop pressure test, clean and surface the head? When I get it back, do I just lap the valves and its good to go or ?

I tried to do a search but didn't find much.

Thanks.
 

prove_it

Well-known member
Joined
Jul 3, 2008
Messages
4,201
Location
Sioux Falls, SD
I always have a machine shop do all that work for me. You need to measure out valve to guide clearance and installed valve height. You can do it at home but you'll precision tools to measure and the spare time for it.
 

iceman69510

Turn Right Racing
Staff member
Joined
Mar 5, 2001
Messages
10,971
Location
Michigan
Yeah, give them new seals and the head and parts. They can check if the guides need replacement, otherwise they will do a valve job (seats and valves) and reassemble it for you. they should lap the valves in during installation.
 

jepherz

Staff member
Joined
Aug 8, 2004
Messages
7,878
Location
KC, Missouri
Yeah, I don't ever mess with any of that stuff you mentioned. Too many measurements to screw up and the machine shop I use is super cheap anyways.
 

If you were to want to do it yourself, follow the following steps.
1)Disassemble keeping all valves, springs, shims etc indexed. If you mix them up you need a valve job.
2)Clean the head thoroughly, then check for flatness. Every service manual for every car tells you how to do this. The problem will be finding a straightedge flat enough. Machinists straight edges are about $100.
Spec: .0015 max warp.
If the head is far out from this, it will need substantial work. The spec for head grinding does not allow much material to be removed, so you will need to have the head baked in an oven under tension and brought flat. Most likely not worth it.

2)Check for valve guide wear by placing a bit of hose on the valve stem and inserting it into the guide. The valve should rest on the hose and be above the seat between 1/4-1/2 inch. Place a dial indicator with a magnetic base on the flat steel bench you are doing all your work on (right?!?!?!) with the indicator tip pressing against the side of the valve at right angles to the head. Preload it a bit and zero. Wiggle the valve gently back and forth, recording the total movement of the valve on either side of the zero, then add them together and divide by two. Spec:
Intake: .02-.05mm Exhaust:.05-.09mm
Limit Intake:.1mm Exhaust:.15mm
If the guides are out of spec, you are done. When the new guides are installed (by you or a machine shop) the seats will all need to be reground/replaced to make them square. If you do not replace the guides but merely install new seals, the seals will hog out due to valve stem movement, and your head will leak oil.

2)Check the margins on the valve with a dial caliper. When you grind the valves, this margin will shrink so if you are right at the limit already, buy new valves. The exhaust valve margin is especially important on our turbo charged cars. Do not skip this step! If your exhaust margin is the thin, the extreme temp/pressure in the cylinder will cause it to literally disintegrate, and then little bits of it will shred your turbo/pistons/cylinder walls.
Intake: 1mm Exhaust:1.5mm
Limit Intake:.5mm Exhaust:1mm

3)Clean the valves with the wire wheel on a bench grinder and inspect the valve face (where it contacts the seat)This area should be flat. If you have access to a grinding machine, follow the procedure for the machine to grind the faces flat, then remeasure the margin. Replace any valves with insufficient margin. If the faces are flat, skip to step 4.

4)Get out your tub of lapping compound and suction cup on a stick. Put the lapping compound on the face of the valve and insert the valve into the head (remember to take the hose off from the guide check) Put the suction cup on the head of the valve and spin it back and forth. The noise it makes should change after a few seconds. Pop the valve back out and clean up the face of the valve and the seat. Get out your dial caliper and measure the band the has appeared on the seat.
Spec: .9-1.3mm (.0354in - .0511)

After you have measured the mark on the seat, look at the face of the valve. The band on it should be right in the middle of the face. If you ground the valve, it won't be. Get out your angle cutters from Goodson ($800) and follow the instructions for seat grinding (too complicated to go over here) or send your head in to have the seat ground.

If people want I will go over valve stem installed height, spring installed height, spring squareness etc, but not right now. My opinion is that the best you can do at home is determine if a head needs work, not do the work yourself, unless you want to invest some serious bucks on equipment and do head work on the side. Basically, if your valve faces are flat and not hammered into an angle like \_ (should be like this \), your margins are good and your valve guides are within spec, double check your installed heights, spring strength and squareness, throw some seals on it and go.

 
Last edited by a moderator:

thedsmguy

Well-known member
Joined
Mar 20, 2009
Messages
1,785
Location
Vancouver Washington
You are incredible. I'm guessing that the machine shop doesn't even bother to check all these specs when you bring them a head to be resurfaced/pressure tested. What would you have to ask them to get them to really check everything out correctly? I have about 15 heads I wouldn't mind having looked at/fixed rebuilt or tossed if bad. Of course I have a need for a few of them myself but not that many!

Anyone know of a company willing to trade a bunch of head for maybe a few good rebuilt ones in return?
 

If you want a machine shop to check it over, tell them you want them to blueprint the head, they will understand that. It means check everything and write it down on a piece of paper, which they then give to you, so you can compare it to listed specs. With that in your hand you can know that everything is good. They will charge a premium for this though, maybe $100, unless you know them/have worked with them before in which case it may be free (with the understanding that you will have them rebuild at least some of these heads through them). Blueprinting is always cheaper when things are clean, organized and disassembled. Actually, any machine work is cheaper if those steps are followed.

My advice is to do most of the steps I talked about yourself, it will take some time but will save much money if you have that many heads (and why else did you buy the spring compressor, right?). The dial calipers and indicator with base can be had from Harbor Fright *shudder* for very reasonable prices. You get what you pay for in build quality, but I have verified their accuracy using high end standards (a piece of metal ground to a very exacting measurement you can use to verify/calibrate measurements). As far as the straightedge goes, I am thinking about having a machine shop cut me one, something that should be easy for them, and should be quite cheap, as opposed to purchasing one for the above mentioned price.

As for the pressure test, many shops will "leak test/pressure test" your head, and try to use this test to tell you that everything in the head is good. All this does is confirm that a closed valve does not leak/is correctly seating AT REST! It does not confirm that the springs are strong enough to make the valve snap closed at 7000RPM, nor does it confirm that your valves are not about to take a tremendous crap, or that your valve to seat contact is nice and wide or in the right place. Finally, it does not confirm that the valve guides are not bad, and if they are bad they will destroy your new seals in addition to making the valves hit the seat off center and then slide closed (making them float and causing seat/valve wear) etc.

All it means, at best, is that if you put the head on the motor, it will run okay for a while at low RPM.

As for where to get a good head, I just picked up a supposedly good head from a machine shop through ebay, price was 269 with shipping to and from them, with the understanding that when I get the head from them I will place my bad head in the box and send it in using the provided shipping label. When I get the head I am going to disassemble and check it over, as they claim to have worked it all to within factory spec. If it is good (or bad) I will let you know, if bad I will demand my money back and ship the head back to them with the conveniently provided label.

My guess is that each of the cores they get needs some work and some new parts, so they replace what they have to and do parts legos for the rest, thus cutting costs. It is possible that if you offered them 15 cores they might give you a couple rebuilds.
 
Last edited by a moderator:

EDIT: Found the spec for face to seat contact. Looks like I was a little under. Apologies.
 

Boostdtalon

Well-known member
Joined
Oct 15, 2009
Messages
913
Location
Buckley, Wa.
Quoting thedsmguy:
You are incredible. I'm guessing that the machine shop doesn't even bother to check all these specs when you bring them a head to be resurfaced/pressure tested. What would you have to ask them to get them to really check everything out correctly? I have about 15 heads I wouldn't mind having looked at/fixed rebuilt or tossed if bad. Of course I have a need for a few of them myself but not that many!

Anyone know of a company willing to trade a bunch of head for maybe a few good rebuilt ones in return?



you could try these guys. Graveyard Motorsports
 

As one last note, do not neglect to examine your springs (another thing not found with a pressure test) the springs on the head I am currently working on compress to the spec height of 1.5748in with only 55-75ftlbs of force, not the 177ftlbs which are spec! These springs would have hung the valves open under hardly any rpm!
 
Last edited by a moderator:

bigblock4g63

Well-known member
Joined
Feb 10, 2009
Messages
308
Location
new jersey
Quoting 687OF2000:
If you were to want to do it yourself, follow the following steps.
1)Disassemble keeping all valves, springs, shims etc indexed. If you mix them up you need a valve job.
2)Clean the head thoroughly, then check for flatness. Every service manual for every car tells you how to do this. The problem will be finding a straightedge flat enough. Machinists straight edges are about $100.
Spec: .0015 max warp.
If the head is far out from this, it will need substantial work. The spec for head grinding does not allow much material to be removed, so you will need to have the head baked in an oven under tension and brought flat. Most likely not worth it.

2)Check for valve guide wear by placing a bit of hose on the valve stem and inserting it into the guide. The valve should rest on the hose and be above the seat between 1/4-1/2 inch. Place a dial indicator with a magnetic base on the flat steel bench you are doing all your work on (right?!?!?!) with the indicator tip pressing against the side of the valve at right angles to the head. Preload it a bit and zero. Wiggle the valve gently back and forth, recording the total movement of the valve on either side of the zero, then add them together and divide by two. Spec:
Intake: .02-.05mm Exhaust:.05-.09mm
Limit Intake:.1mm Exhaust:.15mm
If the guides are out of spec, you are done. When the new guides are installed (by you or a machine shop) the seats will all need to be reground/replaced to make them square. If you do not replace the guides but merely install new seals, the seals will hog out due to valve stem movement, and your head will leak oil.

2)Check the margins on the valve with a dial caliper. When you grind the valves, this margin will shrink so if you are right at the limit already, buy new valves. The exhaust valve margin is especially important on our turbo charged cars. Do not skip this step! If your exhaust margin is the thin, the extreme temp/pressure in the cylinder will cause it to literally disintegrate, and then little bits of it will shred your turbo/pistons/cylinder walls.
Intake: 1mm Exhaust:1.5mm
Limit Intake:.5mm Exhaust:1mm

3)Clean the valves with the wire wheel on a bench grinder and inspect the valve face (where it contacts the seat)This area should be flat. If you have access to a grinding machine, follow the procedure for the machine to grind the faces flat, then remeasure the margin. Replace any valves with insufficient margin. If the faces are flat, skip to step 4.

4)Get out your tub of lapping compound and suction cup on a stick. Put the lapping compound on the face of the valve and insert the valve into the head (remember to take the hose off from the guide check) Put the suction cup on the head of the valve and spin it back and forth. The noise it makes should change after a few seconds. Pop the valve back out and clean up the face of the valve and the seat. Get out your dial caliper and measure the band the has appeared on the seat.
Spec: .9-1.3mm (.0354in - .0511)

After you have measured the mark on the seat, look at the face of the valve. The band on it should be right in the middle of the face. If you ground the valve, it won't be. Get out your angle cutters from Goodson ($800) and follow the instructions for seat grinding (too complicated to go over here) or send your head in to have the seat ground.

If people want I will go over valve stem installed height, spring installed height, spring squareness etc, but not right now. My opinion is that the best you can do at home is determine if a head needs work, not do the work yourself, unless you want to invest some serious bucks on equipment and do head work on the side. Basically, if your valve faces are flat and not hammered into an angle like \_ (should be like this \), your margins are good and your valve guides are within spec, double check your installed heights, spring strength and squareness, throw some seals on it and go.





great write up
 

bigblock4g63

Well-known member
Joined
Feb 10, 2009
Messages
308
Location
new jersey
Quoting 687OF2000:
As one last note, do not neglect to examine your springs (another thing not found with a pressure test) the springs on the head I am currently working on compress to the spec height of 1.5748in with only 55-75ftlbs of force, not the 177ftlbs which are spec! These springs would have hung the valves open under hardly any rpm!



you should
 
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