Hi -- In the process or dropping my SIII XK cylinder head on this weekend after a gasket redo. Had it skimmed just to clean it up, but putting a straight edge on it after I put the manifolds on this morning I checked it with feeler gauges and found I have 10 to 12 thou clearance between cylinder 3 and 4 and about 6 thou between 5 and 6 , and 1 and 2 .

Is it too warped or will it pull down when I torque it up. Planning to spray Hylomar or both sides of the gasket.

Should I strip it down and send it back and get it faced ----- or will it be OK

I used my Father's engineers straight edge --- a good 70 years old and has checked more heads and blocks than I have had hot dinners, so I think its OK

I did not check before hand but torquing down the manifolds put load on the head ???

What do you think ---??

Getting older and motivation is harder to find so I don't want to go through the whole process in a few weeks.

Cheers Mike

 

mike, did you check the surface of the block as well? were the compressions good before? i'm making an educated guess that you won't have a problem refitting & correct tensioning on this job, i usually use the squeeze tube hylomar but if the spray has worked for you before that's good, providing the block isn't out of shape, should be ok...tom/Sydney

 

Lossen the manifold bolts and try agin. Spec for most 6cyl straight engines is .006. You're double that. Technically speaking a skim cut should flatten the head perfectly. If its still out after loosening the manifolds bolts bring it back to the machine shop and have them check it with their straight edge too for a 2nd opinion. If its not flat ask them to do another skim.

 

I've thought about that variance. First, whether Dad's rule was still true? If the head were off, I'd suggest a double check. A couple of ideas as to how.

It isn't, so now what.

This six in a row head is a tad longish, only a straight eight head would be longer.
And alloys are less stable than cast iron. So, a bit of a bow isn't unusual. Center high, ends low here.

However, most if not all torqnuing sequences start center out, so this one probably does as well.

Conclusion, if you did that torque pattern, all will be just fine.

Angst not necessary!!!

Carl

 

also bare in mind, that on OHC engines, if the head is warped the cam bores are also, so if you surface deck flat the cam bores are gonna be out of alignment permently, and somtimes cams seize and crack.

the process of doing a proper head recondition on OHC is quite intricate, most times try to get the head straightened 1st, then resurface it, and somtimes you may have to align-bore the cam bores ,install replacable bearing inserts.

 

My 86 head has been straightened with welds to heat it and untwist, when i took it into the shop the first test was a straight edge on the cam cover faces not the head face, its amazing what you can learn from an enthusiast

 

you can see the welds

 

you do realise that water flows counterclockwise in the southern hemisphere, so blood flow(thru the brain) being 80%water flows opposite from the northern hemi.

so you guys come up with some very interesting ways of doing things, many are very good.

or did your grand relatives leave old Britain just to do things there way? LOL..

called thinking out of the BOX. HEY, long as it works.

 

So, since the head is torqued down it seems a reasonable test would be:

1. Lay a straight edge on the cam bores and note any deflection. If the head flattened out on torqueing, so would the cam bores.

2. lay in the cams w/o connections at the ends to the chain. Apply the caps. if the cams turn freely w/o a bind, the head is probably seated well.

Caveat; I'm not sure you can do that one. valve collision issue. So, on further reflection, scratch 2.

Carl

 

Jcad, if the block is flat and the head is NOT,explain how the gasket is gonna seal?

just cause you torque it down dont mean its gonna be flat.

 

Nope.


I had concluded that the head was on. So, the suggestion was couched in hopes that torqueing would bring the bow down and allow the head/block to seal via the gasket. That is why I suggested the rule along the cam saddles to see if indeed the saddles were now on the same plane. A fair sign that the head had flattened. A bare hope with a long alloy head. None with a short iron head!!!

Now, I see that stripping means removing the valves and followers and cams and get it straightened.

Yup, in that scenario, absolutely. Too much at stake not to in terms of work and materials.

Way back when, I couldn't get my T to run on more than 2 cylinders with an occasional 3!! Would not hold a gasket. Oddly, at that time a new one was rare!!!

At last, I pulled the head one more time. Not a big deal on that simple motor.
I laid it on the cement. Oh,oh, that thing rocked like a cradle!!!! No wonder it would not seal!!!

I got my best used copper/asbestos gasket and laid it in. Tightened the head bolts down. Sorta by pattern and torque by arm strength.

Yahoo, no leaks, and all four banged to life!!!

Carl

 

In the world of Mk III Supra Turbos which are prone to blowing head gaskets
due to inadequate head bolt torque at the factory, the recommended practice
after blowing the gasket is:

1) check or line bore the cam saddles for straightness

2) skim the head

3) skim the block

4) lap the head and block surfaces with a piece of plate glass or marble large
enough to completely span the surfaces

5) install with a metal shim gasket and increase torque from 55 ft/lb to 75 ft/lb

That treatment is good for 18+ psi boost.

 

how do you know where to apply the welds?

 

THAT my friend, is the art of metal working, and an uncanny sense of expansion and contraction!

 

Jcad, you didnt mention cylinder pressures, maybe a T is not as high as a Turbo Supra!
ron

 

Why not just buy another head ?

 

if its used ,it may not be what you need!

 

I forgot one detail on my T tale. I selected another head from my spares. did the rocking test on the cement. it passed. so, on it went!

No question about it, cylinder pressures not even close to any modern car's engine.

I just read a neat article in Auto Restorer. A lady restored a beautiful 24 T roadster. She has a different idea as to how to hand crank it. but, seldom does as the starter fires hers. My early T's rarely had functional starter/battery combinations!!

Somewhat later, I and a friend visited a machine shop down town. He agreed to chop not skim the head if we brought it down. We pulled it right in the street. He did his magic and we popped it back on. Same copper/asbestos sandwich gasket. Wow, a lot harder to pull it over. Fired and ran sharp. Hard on connecting rods after that, but, fun.

Some decades ago, my neighbor gave his turbo Supra to his son. Blown head gasket. Fixed it in his side yard. Nice looking engine, ran fine, but had some odd engineering. Another little turbo in his side yard now, awaiting a fix for it's blown gasket.

My son has that sense of metal and how it can be manipulated. Fixed my hyperextended Jaguar door by judicious use of a wedges and a slide hammer with a "special" tip he made for it.

Slight scarring along the lead edge, but functions perfectly.

Yeah, he knows the issues in the warped head. A replacement might be warped as well and not have healthy guides and seats. and other stuff, corrosion, misligned cam saddles, etc.

Carl