Cylinder head flatness

[hayesbd]

I read the manual and there is no actual spec for flatness, just a vague note that the surface should show uniformity with the "lamp black" test. I have a cylinder head iwth .003" bow in the middle. Do I need to have it shaved or is this flat enough?

Thanks,
Brian

[focodave]

I'd leave it alone, but make absolutely sure you torque the head bolts in the proper order.
The fact that it's aluminum makes it acceptable to have .003" bow, in my opinion.
I assume it is bowed along the longest axis (front to back) as opposed to being bowed across the width (side to side)?
That should not be noticeable when torqued properly and in the correct order.
According to the shop manual, though, if you are more than .002" warped, you should re-surface the head.
I'd measure several times to make absolutely sure it is warped no more than .003" and if you think it is really warped, say, .004" ----- you may want to consider having it shaved.

[hayesbd]

Yes, .003" in the longitudinal direction. The head was not leaking in the middle, but was indeed leaking oil from the rear passenger side (some oil in the coolant). Based on the condition of the head, I don't really understand why, unless it was a poor installation from long ago.

On another note, does everyone still do the re-torque at 500 miles like the original recommendations stated, or are modern head gaskets good enough to forego that operation.

Thanks,
Brian

[garion]

Even if the gaskets are good enough, whats the harm in re-torquing? I would just do it. (and have done it).

[So Cal Mark]

If I had that head off, I'd resurface it

[majicwrench]

Metal shaved off a head cannot be replaced. Cam timing now off a tiny bit, compression goes up. Head may have been shaved previously, do you want to take off more?? And at least in my neck of the woods, machine shops tend to find problems or create more problems. If you do send it out, take some measurement before hand so you know just how much they shaved off.
I would not shave a head with a 3 thou warp. In my humble experience that is not going to cause an issue. Aluminum head and iron block expand/contract diff rates, so gasket is constantly getting some shear forces, doomed to fail sooner or later on most engines even with everything dang near perfect.

I can't remember the last time I re-torqued a head, but like was said, is not going to hurt anything. When replaciong gasket, get bolt holes clean (they will fill with antifreeze and oil). Avoid orbital sanding discs, they get things all nice and shiny but not flat.
Good luck,
Keith

[BEEK]

And at least in my neck of the woods, machine shops tend to find problems or create more problems. If you do send it out, take some measurement before hand so you know just how much they shaved off.

being an owner of a machine shop, and a fiat mechanic. if a machine shop finds a problem, then it is a good thing as you didnt find the problem, they dont create the problem, they just find what you may be overlooking. as far as creating problems, then that machine shop is not one i would use. i would find a competent shop. just as mechanics, a poor mechanic will cause you more problems than they solve, the same should be said for machine shops.

but .003 i wouldnt cut it either. but if i had a head off, i would do a valve job,(reface valves and seats) why wouldnt you?

[hayesbd]

Thanks for all the replies. The head is off for three reasons: 1) noisier-than-I-like intake valves that were not explained by clearances, 2)leaky valve guide seals, and 3) passenger side rear oil leak.

Sure enough, I found that all of the intake valves are slightly bent and there is evidence showing the right rear oil leak. Of course the valve guide seals were all hard as a rock.

The valve seats are nice, and all other parts are not worn out, so I probably would not send it to a machine shop unless the flatness was an issue. I did notice that the PO did not have a three-angle valve job done the last time the head was off, but I am not inclined to send it out for just that issue, either.

Brian

[majicwrench]

Beek,
Would love to have a competent machine shop available, and I am sure there are many out there, just hard to find (just like good mechanics). I live in a tiny town and have to send a head a hundred + mile away to get work done. Many shops are quick to call back "that head is cracked, we will sell you a new one.." etc. This is really an issue with domestic stuff. Last head I sent out for a valve grind, the shop SURFACED THE HEAD without asking me. When I called (irate) because I had told them "Don't surface" they claimed the head was warped. Must have somehow got warped in shipping , because it was not warped when it left my shop. Many other times over the last 35 years I have had shops butcher items I have sent them. I now measure and mark heads before I send em out, so I know I get the same one back, and know what they did to it.
Whew!!!!!!!!!! Now I fell better, sorry for the rant.
Hayesbd, are you replacing the valves and not grinding?? If they were bent car would have ran like crap.
Keith

[hayesbd]

The car was running just fine, with compression test showing around 110 in all cylinders. The bends were very slight and were noticed only when you rotate the valve in the guide and find only partial contact on the valve, but full contact on the seat. You can do this with Prussian Blue or with valve grinding paste. I will be replacing valves and lapping them to match.

I once had a broken belt on my 74 TC at idle. I put a new belt on, hoping that the idle condition meant no bent valves. Alas, they were severely bent and I promptly dropped a valve head through a piston.

I just want to avoid that possibility, and that is why I don't really want to risk keeping the current valves.

Brian

[131]

I've always re-torqued the head bolts on new gaskets. The car I recently bought had a new motor in it, reco head, bored, new pistons, rings, bearings etc. It had no miles on the engine when I got it, after about 500 it started blowing smoke when getting back on the throttle after gear changes or running down a hill, I was thinking valve guide seals, but the smoking got worse until it happened continuously. I've got another engine in the shed I've been building for a couple of years, I figured I'd better hurry up and finish it. In the mean time, I decided to re-torque the head, the smoking stopped completely, the engine now has about 2000 miles on it and is running nicely, although it's still leaking oil, so I'll swap it anyway when I get the other one finished.

[fiatfactory]

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