Warped cylinder head(RB30)?

[dom14]

Hi Guys,

I've got hold of a used RB30 cylinder head.
ATM, I'm trying to find out the degree of possible warpage on it.

With a straight steel ruler and feeler gauge, it shows around 0.03mm or so warpage in the
middle of the head.

Is that acceptable or bad enough for an oven heat straightening or machine surfacing?

I did the test by removing any previous head gasket residue off the cylinder head bottom.

BTW, I havent' checked cylinder head top warpage alone the cam shaft line.
Cam shaft, lifters, valves, cam pulley, etc are still on the head.

Thanx in advance for any advice.

[dom14]

I found below information from Haynes manual. If I'm reading it right, the cylinder head is good to go, as far as flatness concerns! Right?!

Did I interpret it correctly? Says 0.2mm is the "surface flatness limit".
What does it mean?

Does it mean any warping above 0.2mm means the head is scrap metal,
or does it mean warpage below 0.2mm does NOT have to be machined??!!!

Thanx.

[dom14]

Another thing I've been wondering about is that I haven't been able to find a feeler gauge with a thinner piece than 0.003mm(or 1/1000 inch).
Is that as thin as they get?

[mudnut]

Where did you score the head from?

[dom14]

Where did you score the head from?

I will upload few photos of it soon today.
I got it from a bloke I got to know online, practically for nothing.

Fleabay & guntree have few of them, but most of them are crap. It's hard to check for warpage when they
are covered in crap. Not easy to check for cracks either, but close inspection under the head to see any water leakage in between
oil and water lines can help.

[dom14]

Here are few photos of the above cylinder head.

[dom14]

One thing about this head is that it's pretty "colour damaged".
It's from an R31 Skyline on petrol. The bloke apparently blew up the head gasket first and
had this head redone at machine shop. Not soon after he blew either the top end bearings or bottom end ones.
He called it quits with the engine after tearing it apart to pieces to see whether he can rebuild it.
I'm guessing the crap "colour damage" was from driving it with the leaking head gasket?!

[mudnut]

Take it to a specialist, that you can trust. Get it crack tested and pressure tested. Also, If the head has been cooked, the alloy can go soft, apparently. I have been advised that an alloy head needs to be machined once removed anyway.

[dom14]

Take it to a specialist, that you can trust. Get it crack tested and pressure tested. Also, If the head has been cooked, the alloy can go soft, apparently. I have been advised that an alloy head needs to be machined once removed anyway.

Yeah, that's the real worry I have, even though I understand little about how alloy go soft after getting overheated and how it affects the head after that. I was told by an honest head rebuilder once that's happened, those gone "soft" cylinder heads aren't worth the trouble. I think he was saying they crack easily after that, even with a good rebuilding job.
I've seen Falcon heads that are not overheated badly or warped, being refitted with a new head gasket(without any machining) and going good after that.

I'm not sure how they test the heads for "softness" though.

I'm guessing there may be no such thing as cheap backup insurance, when it comes to cylinder heads?!

[mudnut]

An experienced head reco bloke would know what to look for. When I had the RB30 head done, the guy picked it up as he worked in Hamilton. He took one look at the exhaust manifold and told me the engine had been detonating for a while, due to the colour of the metal. He confirmed that by showing me the split fire rings on the gasket.

[dom14]

An experienced head reco bloke would know what to look for. When I had the RB30 head done, the guy picked it up as he worked in Hamilton. He took one look at the exhaust manifold and told me the engine had been detonating for a while, due to the colour of the metal. He confirmed that by showing me the split fire rings on the gasket.

Lucky your bottom end survived that if it's been happening for a while.
You didn't hear any pinging or funny noise?

BTW, apparently it's quite possible to tell whether the combustion chamber has detonation by having close look at the spark plugs as well.

[mudnut]

I wrote it up in the RB30 thread. It came back from the mechanics, pinging its head off. I backed the timing off so it stopped pinging, but it was still a bit advanced. The dyno guy set the timing back a bit further, but that was months later, so the damage had been done.

[dom14]

I wrote it up in the RB30 thread. It came back from the mechanics, pinging its head off. I backed the timing off so it stopped pinging, but it was still a bit advanced. The dyno guy set the timing back a bit further, but that was months later, so the damage had been done.

Probably the head was machined towards the last point.
This was the reason(or closer to it) that I decided NOT to machine my cylinder head for the second time when the
head job guy stuffed it up the first time. I resorted to "liquid glass" instead.
I didn't wanna put extra stress on already worn out bottom end.
I've seen few times, when a fully reconditioned head didn't help with the bottom end.
A falcon I used to drive only lasted few months following fitting a fully reconditioned head.
RB30's are far better than falcon crap engines, but still subject to the same rules.
Whenever I do my next cylinder head full recondition job, I will recondition the bottom end as well.