New Head or Machine Old Head?

[TG924]

I have a 99 GSX that I tested for compression and leak. Turns out the leak down showed a head gasket issue. I took the head off and sent it to a machine shop. They called today stating the head is warped. It's warped to the maximum tolerance allowed so they asked if I still wanted them to machine it or whether I wanted to look for a new head. Their cost to machine it is $185 and that includes putting the cams back in etc. I'm more concerned about doing the right thing to keep from having issues rather than the cost. I'm looking to ask what the recommendation would be from those out there with some experience. If it's going to take the head to the max tolerance is it worth it or do I get a new/used head in better shape? Thanks!

 

[gieri002]

Just have the head resurfaced. New head thickness is 5.200 min thickness, you can mill up to .015. If you need to shave more than that you can simply get a thicker head gasket. Take the cams off yourself to save a few bucks, it is an extremely simple task.

 

[TG924]

Just have the head resurfaced. New head thickness is 5.200 min thickness, you can mill up to .015. If you need to shave more than that you can simply get a thicker head gasket. Take the cams off yourself to save a few bucks, it is an extremely simple task.

He said it was warped by .015 and machining would most likely take it past by a fraction. I'll take the cams off and tell them to machine it. What would you recommend for the right head gasket to do the job and get the right thickness?

 

[2gtalonfwd]

I'd recommend a cometic Mls head gasket it worked wonders for my car when I bent valves due to bad timing.

Forget to mention adding some ARP head bolts would definitely help as well if you don't already have them!

 

[toybreaker]

He said it was warped by .015 and machining would most likely take it past by a fraction. I'll take the cams off and tell them to machine it. What would you recommend for the right head gasket to do the job and get the right thickness?

fifteen thou is a BUNCH!

A lot more information will be required to make an informed decision.





Got any pics?

Where was the headgasket compromised?






One thing to consider is that many machine shops do a piss poor job of thinking thru the ramifications to machining/running a head at the edge of the spec.

... and a lot of them don't take into account that she may not be a virgin.

Many time just a skim cut will put a head out of spec if it had been cut a few times before.

... so, make sure they have measured the total amount they have to work with. (and if they don't know that spec ... run )



Was the engine overheated?

A pic from the top of the head will tell many tales.

If the area where the cams ride is discolored, that's a bad sign.
Take a small screwdriver down in the big allen plugs in the center of the head and dredge them a little. Crunchy bits there indicate things got seriously hot, and that's never good.

At the very least, a head that has gotten this hot will require much more inspection/attention to return it service.






One other thing to consider is that machining the bottom of a severely warped head only addresses the gasket surface.

... Everything else will still be out of alignment, especially the cam bores.

This can create some serious issues, especially with bumpy cams/stiff springs

Be sure to check the cam caps before beginiing any machine work!

If the cam caps show any significant wear, this head is d o n e.



How are the valves/guides?

If they are going to need work to be returned to service, be sure to add that cost to your consideration!




Now if the man shows you where it's warped, explains that it can be straightened before it's decked, and has checked all the other factors that help determine that it's a viable core, it might still be worth saving.


One of the biggest issues I find on these heads in irregularities in combustion chamber size/position. Call it core shift shrinkage or whatever you like, just a lay a new headgasket on it and eyeball where the fire ring hits the head.

... you may just be unpleasantly suprised


Decking a head fifteen thou that already has a significant variance in combustion chamber position will result in a multiple compression ratios and that can make dialing in an optimal tune quite a chore.



Five years ago, I probably woulda pitched it without a second thought, but virgin/good/clean cores are getting harder and harder to find

... making "calls" like this a little more involved ...


Posting some pics/more information will help the folks here help you make a more informed decision.

 

[TG924]

Thanks Toybreaker.... here is a bit more info and I'll add what pictures I have right now.

The head gasket was compromised between cylinders 1 & 2. The head has not been machined before so this would be the first time but like you said, it's a bunch!

The head did get very hot....I did not notice any discoloration on the cams. I don't have a picture of it before I took them off but it looked to be okay. I will take the head gasket and check the fire ring to see how it lines up...never thought of that part of it.

At this point, I assumed I would be working on the valves. I figured while I had it apart that I would do that as well.

 

[jasonj92]

Cant find a local guy with a cylinder head or maybe in the classifieds?
185 seems a bit steep to machine it.

 

[BogusSVO]

ToyBreaker makes some very good points.

Measuring cylinder head thickness will be important.

http://www.dsmtuners.com/forums/cyl...how-measure-4g63-cylinder-head-thickness.html

You can go a tad past spec and be ok.

At .015 warp, I would be checking for cam tower distortion. Simple enough to check, pull the cams and the followers. Then install the cams and torque the caps to spec.If you can turn them with your fingers on the cam snout, no cam gear installed, and they spin smoothly, not sticky, you should be ok.

I would prefer to straighten the head, but alot of small shops do not have the equipment nor the knowledge on how to do this procedure.

Also one thing not brought up is valve seating. In the relaxed state the head is in now, off the block, the valves may be sealed to the valve seat. once installed the valves could crack off the seat causing low compression, and a skip/miss to the engine.

So unless the shop you are dealing with is on the ball, you may be better off buying a known good used head, or a reman from a supporting vendor or freelancer. But if you do go reman, check into the core fees and what they call a usable core.


EDIT

TG294... you are wrong, the head has been off before and thu a machine shop.

You have non oe valves in the head, The factory installed valves have 6T cast into the valve heads. You have some sort of replacement valves. Most are a 2 piece design that the valve head is welded to the valve stem. Personally I do not trust them for turbo use.

I would bet in some point in time the head suffered from a snapped timing belt, and bent all the valves. The guides may or may not have been replaced. If not replaced, I would look for cracks and chunks missing.

 

[toybreaker]

Thanks for the pics!

... gotta admit I don't see so well anymore, but it "looks" like at least a few of the valves have been replaced at some point during it's service life. (look at the valve faces, they tell a tale when they don't match)

... at any rate, she don't appear to be a virgin, that's for sure!


please be sure to measure the deck to rail height at several different points around the head ( there's a write up on how to measure this by Dale on here somewhere)


What do the cam caps look like?

The force on the cams is an upward force, so just looking at the cam saddles in the head only tells a part of the tale, the real wear happens on the caps.



... I'm not so good with words, (wrenching is what I do), but do you get why I'm concerned with just facing the head without addressing the warpage by straightening things as flat as possible before decking the head?


fifteen thou is a game changer!

... whacking fifteen thou off the deck will get it flat, but it'll leave the cams journal bores mis-aligned enough to cause some accelerated wear/problems. This happens because the cam will have to bend as you torque the cam caps down.

the result is cams that are hard to turn/binding.

Since they are riding on bare alluminum that is much softer then they are, this leads to accelerated wear in the best case scenerio,

... and significantly increases the *potential* for skipping time/t-belt issues in the worst case when they get all hot, bindy and bothered.



If your machinist is worth his salt, he'll discuss these things with you/know what you're asking.

Explain what your goals (and budget!) are, and listen respectfully to what the man has to say.

... just be respectfull, and do it in person >not over the phone<

... nothing irritates a man in the trade as much as intrweb "readers" that are "experts" at everything!!!


One of the best ways to get the best advice/a working relationship going is to offer to buy lunch/a pizza for the shop (works wonders when you show a little appreciation. They are taking time away from the job to speak with you!

... and the guys in the back doing the work will remember you in a good way.


Have him go over the whole thing, soup~to~nuts style, whilst showing you these things on your head. "show and tell" always works better than just "tell"


Dialing in a head is a major undertaking, but done once, done right only hurt$ once

... when you pay the bill


... for the rest of the service life of the vehicle, it'll put a smile on your face

... and a look of anguish on all that are left behind at the light



If you do roll the dice on this head, please be sure to check that the cams both turn well when the head is installed and torqued down.

It's best to do this without rockers/lifters installed, so what you're feeling is only journal drag.

Make sure everything is CLEAN clean and the journals are well lubricated with some lubriplate 105/redline/assembly grease of your choice.

They won't spin as easy as a happy crank, but they should turn without undue effort.


Good luck, and please update the thread with your choice, and the end results.


[edit] Dale makes a few good points, and types faster 'n me [/edit]

 

[TG924]

BogusSVO....You are correct, the head has been off before. I had it to a mechanic to just get it running when I bought it. He said the block was fine but now I know it's not. I didn't even get 100 miles out of it before it heated up and here I am. You're probably right also that it may have been a snapped belt at one point. The mechanic said he had replaced some bent valves which are probably the ones you noted from the picture. If I end up keeping the head and replace the valves is there a recommended brand that is a solid one piece valve?

I appreciate the help in finding out the right question to ask. This is the first time I've torn an engine apart and know what to ask is important. I'll be talking to them tomorrow and get some info on the cams...I have them at the shop also.

Toybreaker....I'll find out from them about straightening things before they deck it. It makes sense to me but the first conversation I had with them they didn't say anything about straightening or checking it before decking. They had only mentioned decking then pressure testing it.

I told them this is my first rodeo tearing an engine apart and needed their expert opinion/eyes to look at it. I like the idea of lunch for the shop. It could be the best money spent!

 

[BogusSVO]

The budget valves would be the factory 6T valves, they would have to come out of another head if you can find them. The next step would be a set of stainless steel valves. I use and Install alot of BC and Engnbldr stainless with out issue.

The procedure for straitening a head would mean a full tear down and valve job, along with the pressure test and surface, and a chance of changing some guides, due to the mechanic just slipping some valves in.

By this point, you are at the price of a decent reman head to bolt to the block and go in with.

Also remember, not all shops mill heads the same way, ask the shop you deal with how they are going to mill the head.

If they say anything about a belt surfacer, get your head and go.

 

[TG924]

Here's the latest:

I had taken a picture of the cams before I took them off, gave it to the machinist today and took them with me. He said the cams looked fairly new without any severe wear on the caps. But, based on the picture I took, he said the cams were installed incorrectly by the previous mechanic. Some of the caps for the intake were on the exhaust.

Total deck height would be right at the .015 tolerance but he said his experience tells him if they need to take .015 off, it will most likely be .016 based on several measurements around the head.

They don't use a belt surfacer which is good news.

He stated after they deck it he would pressure test and check valves. If valves need done he would give me the option of doing it or have them do it.

Cost to deck the head is $145. If it needs new valves and guides, another $185 using solid valves and not the type that are two piece welded.

It may be hard to see, I had it on my computer and blown up but here is the pic with the valve cover off....

 

[BogusSVO]

Did he tell you the brand they plan to install for the valves?

Will you post up the pics you have of the head?

 

[TG924]

Did he tell you the brand they plan to install for the valves?

Will you post up the pics you have of the head?

No, he didn't say the brand they used but if it came to that I would ask for a brand you suggested.

I'm still up in the air and gathering as much info as possible. I definitely want to put the car back the right way and don't want to pull the head again in another few thousand miles.

Added a pic up above...

 

[BogusSVO]

From the looks and sound of it, I would suggest you look into a reman

$145 to mill the head + $185 for valves and guides, then the cost of a set of seals

Like I said before I would not trust the valves you have now, they may last at stock levels, but I am leery of them.

It also looks like stock springs from what little I can see. If they have 120k or more, I would bet they are weak, Most I have tested are.

The more you say, and the more I see. The more I would suggest that you talk to a few of the supporting vendors/freelancers and see what they can do for you. (Check feed back on anyone you want to deal with)

With a shop that builds more than the one 4g head a year, they are more familiar with them and know the weak points and what needs to be corrected.

Most vendor websites I have looked at have heads in the $400-500 range for stock/stage 1 heads, plus core charge.

Find out what the core return policy is and how much the core charge is, and what they will accept as an acceptable core.

Also since you are a proven member, you can check the classifieds and find a head to fit your needs, for about the same money you are looking to spend local.

 

[TG924]

Shop got back to me today and they say everything is straight, looks good and should only need to be machined. They did say they would replace four valves that probably don't need it but would do it as a precaution. I'm going to roll the dice, machine it for the $145, replace the valves myself and throw it in. I'll run it and if I have to take it out again I will at least know I'm shopping for a new head.

 

[BogusSVO]

Why replace 4 valves?

None of them are stock....

 

[TG924]

Why replace 4 valves?

None of them are stock....

Yes, you're right. I'm going to replace all of them. When I put it back together I'll see how it runs and tests with compression etc. If it isn't up to what it should be I'm going to shop for a new head and chalk this one up to experience!

 

[BogusSVO]

Ok I can understand you want to learn.

How about you get the head, and take it apart, see what is needed.

Then make a good informed decision?

If the guides are cracked, that can be a deal killer for a DIY.

Read through the links and you will see what you are looking to do.

http://www.dsmtuners.com/forums/newbie-forum/341218-how-change-valve-guides-4g63t-head.html

http://www.dsmtuners.com/forums/cylinder-head-short-block/420045-how-have-4g63-head-rebuilt.html

http://www.dsmtuners.com/forums/new...face-4g63t-cylinder-head-mls-head-gasket.html

http://www.dsmtuners.com/forums/newbie-forum/341287-how-test-valve-springs.html

http://www.dsmtuners.com/forums/articles-engine-fuel/341636-how-lap-valve.html

http://www.dsmtuners.com/forums/newbie-forum/420313-how-fluid-test-4g63-cylinder-head.html

 

[TG924]

Ok I can understand you want to learn.

How about you get the head, and take it apart, see what is needed.

Then make a good informed decision?

If the guides are cracked, that can be a deal killer for a DIY.

Read through the links and you will see what you are looking to do.

http://www.dsmtuners.com/forums/newbie-forum/341218-how-change-valve-guides-4g63t-head.html

http://www.dsmtuners.com/forums/cylinder-head-short-block/420045-how-have-4g63-head-rebuilt.html

http://www.dsmtuners.com/forums/new...face-4g63t-cylinder-head-mls-head-gasket.html

http://www.dsmtuners.com/forums/newbie-forum/341287-how-test-valve-springs.html

http://www.dsmtuners.com/forums/articles-engine-fuel/341636-how-lap-valve.html

http://www.dsmtuners.com/forums/newbie-forum/420313-how-fluid-test-4g63-cylinder-head.html

Absolutely want to learn so I appreciate the links and advice. I'm betting I end up back here for a remanufactured head but at least I will be a little smarter than I was a couple weeks ago and know how or what to do in the future.

 

[Isabelledc5]

Get a new head. If your head is warped 15/1000 or more, you will have to deck it to a 20/1000. For a turbo car, that is way too much. On a naturally aspirated vehicle, it would work because you would just need to run a thicker head gasket. I would get a new head that has never been decked before.

 

[TG924]

After all the advice and more time to think about it, I'm going to look for a new head......dumb question...what if anything can I do with the old one?