99/00 1.8 BP Head inspection
 

I was shipped a head to inspect and go through.
Not a super fancy build, but just a solid rebuild.

The head was packaged well for shipping.
This is the inner box
Wrapped in plastic
https://www.miataturbo.net/attachmen...ine=1356139762
I did not need the cam gears, but they will be cleaned and returned.

Out of the plastic.
2 layers of cardboard.
https://www.miataturbo.net/attachmen...ine=1356138501

The head looks good to the eyeball, oily, but no sludge build up
https://www.miataturbo.net/attachmen...ine=1356138501

The HG surface looks ok, no pitting or heavy rot
https://www.miataturbo.net/attachmen...ine=1356138501

Removing the cams
https://www.miataturbo.net/attachmen...ine=1356138501

The cam towers look good, no scratches or scoring
https://www.miataturbo.net/attachmen...ine=1356138501

Stock springs
https://www.miataturbo.net/attachmen...ine=1356138501

Valve springs removed
https://www.miataturbo.net/attachmen...ine=1356138501

Pulling the valve stem seals
https://www.miataturbo.net/attachmen...ine=1356138501

The old seals
https://www.miataturbo.net/attachmen...ine=1356138501

Removing the spring shims
https://www.miataturbo.net/attachmen...ine=1356138501

Removing the oil galley plugs
https://www.miataturbo.net/attachmen...ine=1356138501

Cleaning the HG surface
https://www.miataturbo.net/attachmen...ine=1356138501

The long board barely scratches the surface
https://www.miataturbo.net/attachmen...ine=1356138501

The Machinist round edge and the feeler gauge
https://www.miataturbo.net/attachmen...ine=1356138501

You can see the gap, This head is warped a fair amount.
https://www.miataturbo.net/attachmen...ine=1356138501

A .012 is sticky under the round bar
When the head is thremal cleaned, I will straighten at the same time.
I would like to see less than .005 once done.
https://www.miataturbo.net/attachmen...ine=1356138501

Checking the cam towers for distortion
https://www.miataturbo.net/attachmen...ine=1356138501

No nocticable rock in the intake towers, minimal in the exhaust.
Ill check it again after it is straigten

More to come.....

Thanks. I'm about to have this done. :cry:

Why you cry?

Its not all that bad. It is rather simple.

I have a head sitting in the shop that's warped .012" that's labeled "Junk" and "Parts head". Hopefully the buyer knew it was that bad before he bought it.

How the the living hell do you "straighten" 0.012" out of a head, other than to deck it? Won't that significantly change the chamber CC?

Glad you're back Bogus :bigtu:

Yes if you mill a head .012 it will close up the combustion chambers.

The general rule of thumb is for every .007 milled the combustion chamber looses 1cc

So time this head is milled .012 -.014 it would be 2cc smaller.

When the head is set to be straightened, Ill post up.

I have salvaged heads that have had as much as .030-.035 warp across the bottom and had .005 or so cam tower warp.

Alot shops will not straighten a head, either they do not know how, or they just do not want to.
It takes some time, and sometimes you will not get all the warp out the first time.

Just a little more machine shop voodoo to show you all is why Ill straighten this one, instead of just grabbing a core to do.

Gotcha, makes more sense now. I could see why most shops would not want to touch a DOHC head with a twist in it. I know my guy took a hell of a cut on the FE D2TE heads in my truck, but that thing needs all the compression it can get so I wasn't really worried about it.

Out of curiosity, what's the factory max recommended cut on one of these heads, and how much does it take before you start screwing with timing?

+1
and decent quality pictures makes it even better :)

Alot of shops have older machinists that started off on the domestic v8 engines, and they have not moved into the import engine. They just do not get it. Also this is a fading trade, the avarage age of a machinist is in the 40-50.

The min thickness on a BP engine? Humm Ill have to check my AREA spec book.
But most the time it is about .015.

When will the timing be effected, That starts the first time the head is milled, but on a DOHC it is not as noticable as a SOHC

Anytime the C2C of cams to crank is changed the mechicanical timing is changed.



Thanks!

Thanks again Dale. I just finished torquing down the rods when you called.

https://www.miataturbo.net/attachmen...ine=1356195442

Going to try to get engine buttoned back up and in car by tonight.

Did you balance the rotating assembly? or at the at least the new rods and pistons?

I would like to know more about the head fix. I have a warped 94 1.8L head and figured it was junk.

I would like to see your method for removing the valves on a miata head. That's one of the few things I'm unable to do in my own garage.

Yes. I made a ghetto make shift fixture of the tool you have and got everything within a gram with my on sale $12 Harbor Freight scale. Highspeed grinder and belt sander took care of the rest.

https://www.miataturbo.net/attachmen...ine=1356240045

IIRC, the FSM says max cut on the head is .012 but people exceed that all the time. EP motors are cut .050", IIRC. You start screwing with the timing immediately, but you can correct for that with cam gears (or one cam gear and VVT tuning).

I think I have a man-crush on BogusSVO. This gives me more motivation to get enrolled at The Most Respected Name in Motorsports Education - School of Automotive Machinists.

Hmm, I'll be interested to see if you use a variation of the oven bake method or the torch method to straighten the head.

Good deal! how were they out the box?

Thanks on the info from the FSM!
Adjustable cam gears... what a great invention!


I looked into going to that school a few years back, I wanted to take just a few classes, to build on what I already knew. But I could not take just a class or 3 They wanted me to take the full 2 year corse. Then I flipped the book over and checked the credentials of the instructors, I giggled to myself when I read them, I had about the same, years of experiance, ASE certs. When I called to talk to them about the equipment they trained on, Serdi 100 head shop, not a bad machine, IMHO a bit sloppy, but simple to use. Surfacing was a segment stone grinder, Not a CBN/PCD milling machine.

I will oven bake, The torch method leaves ugly marks, and is an out of date method.

Head straighting set up
 

Well a few have shown intrest on how this will be done.

What is needed.

A steel plate, with properly placed holes.
A torque wrench, and socket
Pull bolts
Head bolt washers
Body washers
Anti-sieze
Shim stock

Attachment 62841

Place head bolt washers on the pull pins
Attachment 62842

Place the pull pins through the head bolt holes and through the steel plate.
Attachment 62845

Now coat the shim stock with anti-sieze and place under the head.
The anti-size will give the head some lube to slip on as the head straightens out.
Attachment 62843

Now place the washers on the pull pins, and snug the nuts down. Roll the head and fixture over and torque the pull pins.
Attachment 62844

The head and plate fixture will be placed in an oven for several hours, the temp will be watched closely, to bring it up to temp slowly, then stablized for a couple hours, then temp will be dropped slowly untill back to room temp.

Just curious and I'm assuming the answer is no. But would it make much of a difference to to have the cams torqued in when the head is cooked?

I never straightend one with the cams in.

I do not see any reason to do it like that.

Only reason I see is to try and keep the cam journals in line. If you've never had a problem with it I'm guessing you either line bore after or it doesn't affect the cam journals.

So a random question for you Bogus. Is it possible to set correct valve clearance with the head detached from the block? I know in the FSM it says to put the cams at specific spots when measuring, so I was wondering how you do that without the Timing belt on to hold them in the correct locations.

Not directed at me, but it's totally doable. You just need to set the lobe pointed away from the lifters you're checking, and that sets another set of lobes pointed straight down at a set of lifters. You can't do it with the head laying flat on a bench (at least not without being careful), but you can definitely get the cams to stay where they are without the TB. I do the valve lash on our new motors before the TB or cam gears go on.

The cams would still flex in the bores, they are not ridged enough to help with alignment.

With this head was warped .012 across the bottpm, but the intake cam bore was still perfect, and the exhaust side had about .002

I could see more issues having the cam in with the bolts for the caps , galluing and ripping the threads out.





Like Sav said, as long as the lash you are setting, the cam is on the heel you can set it.

nice to see your back! we bolted my head up and still waiting for the fabricator to finish up so we can get tuning! Is this Aarans head?

HW.. No, Not Aarons head....His is getting much more involved....

Just a customers sent in for some play time. :D

Dang.. I was wanting to hear some reports on how yours was doing!!

The straignting worked.

.005 is a tad "sticky" going under, and a .006 will not go.

Attachment 62937

Now to carry on with the head build

Damn! What kind of temps are we talking about?

Not as much as you would think.

Get the head too hot and all the machined areas will distort, like the cam bores and bucket bores.

No more than 350* and longer than it takes to bake a 20lbs turkey!

It spent 7 hours in the oven.

So do you have an oven at the shop, or do you take it home to do that part?

I would not put anything with anti-sieze in my home oven.

I have a gas fired one at the shop I clean heads and other parts in.


I do not think the anti-sieze would be what i worry about, but the burning smell of oil and carbon burning off.

This is relevant to my interests. Subscrib'd.

Bogus, do you always just bolt down the center of the head when you straighten them like that?

You bolt down where the worst of the warp is, and commonly that is the center.

very interesting.

I'm sure there is some mystical art in selecting the shim stock thickness and then torque spec to the plate as well. That looks like a big ass chunk of steel right thar.

This is what I was thinking when I asked about "straightening" earlier. I honestly didn't think you were going to deck 0.012" off this thing. Do you find that you have to line hone the cam bores after the the trip to the oven?

It is a big ol' cunk of steel. lol

The line bore of the cams is fine, no need to line hone. They were not far off to begin with.

No measurable distortion on the intake and less than .002 on the exhaust.

I wonder if I can find a local shop as good as you.

I couldn't. That's why you're looking at it.

Very cool. Curious as to the thickness of the shims and did you position them on the ends of the head?

Read through some of the links in my sig line, so you will have an idea what to look for when you go to the local shops.

;)

There is a couple diffrent views on how thick the shim stock to use, one is to use shim stock thickness equal to the amount of warp, the other is shim stock twice the anmount of warp.

The shim stock is placed at the each end of the head, about .500 under.

I looked around and asked some of my v8 guys and they pointed me in the right direction I hope I found one guy that does miata's and DSM's here local who is supposed to be the best this place has to offer I will find out this week if he can't fix my head I will be dropping Bogus a PM

yes I checked out the links. I also have a lot of friends in the business and was a machinist but I worked on medical and aerospace last. I have not done auto machine work high school.