Head gasket replacement

[stevend34]

Looks like my head gasket has gone on my Sierra. I’ve got a kit on order. Any tips for doing the job on these G13s before I jump straight into it?
Are new head bolts optional?

[Cohengoo]

the g13a is probably one of the easiest motors to change a head gasket on, you can do it fairly quickly, new head bolts can't hurt in any way, I have always had success with reusing the old ones.
The only advice I have is to take your time with the torquing sequence and don't overdo it.

[greyghost]

and to add,

get the head skimmed, if the gasket is blown, the head is no longer flat and no amount of torque will get it to seal properly.

[Jonno]

There is a guy near me called "headworks" in carnegie, he does a good job on machining heads. Basil is his name

[stevend34]

and to add,

get the head skimmed, if the gasket is blown, the head is no longer flat and no amount of torque will get it to seal properly.

I'm aware of a place near me that could do it. what would you expect them to charge?

[gwagensteve]

and to add,

get the head skimmed, if the gasket is blown, the head is no longer flat and no amount of torque will get it to seal properly.

I don't know how much faith to put in this, but I've heard from a well informed source that the stock heads are surface hardened heat treated and skimming them tends to cut through this layer, resulting in issues with sealing.

I'll stress I don't have a source to confirm this and it doesn't entirely gel with my understanding of heat treatment of aluminium. Some quick googling indicates surface hardening of aluminium is a pretty experimental/advanced field so I suspect it was out of the realm of what Suzuki were doing on cheap engines in the 1980's and 90's.


However, I've observed that that once the head gasket has failed, G engines rarely seem to go on to live long and happy lives. I suspect that it's not just the head that isn't flat, it's the block as well.

Lots of people talk about lots of things relating to G series longevity, like heads going "soft" etc that metallurgy and facts disagree with. The annealing temperature for aluminium is above 300˚C. I think we can agree that if the head has reached 300˚C, there are bigger problems than it going soft.

[greyghost]

Steve raises a good point here.
check that your block is flat at the head surface too.
there are lots of tutorials as how to do this, but all you need is a straight-edge and a set of feeler gauges
and while you are doing this you can check your head as well.

greyghost wrote: ↑Thu Nov 11, 2021 11:15 am
and to add,

get the head skimmed, if the gasket is blown, the head is no longer flat and no amount of torque will get it to seal properly.

and what I'm getting at here is that you cant exert enough torque on head studs to get the head flat, you'll pull the studs out of the block

[luigi]

Hi Fellas.
I successfully replaced my head gasket 6 years ago. The problem was water leaking into number 4 cylinder.
I did not get the head skimmed or the block machined.
My brother in law (qualified mechanic) suggested to use copper coat head gasket sealer on the new gasket, which I did.
I also used the old head bolts and retightened them after the engine cooled.
There was no obvious damage to the head or block.

I agree with all that has been said......I was lucky it all went well and the engine is still good.
But it is an easy job and if it fails not much is lost and experience gained.
Regards. Wayne.

[stevesierra]

i just used a straight edge on my block and head to check if it was warped
also used a quality head gasket , i thinks it was a permaseal ...still running 2 years later

also recheck the valve clearances after i finished the job

[gwagensteve]

I can't seem to see any consensus about the use of copper coat, especially with MLS gaskets. Some people seem to imply it's a good idea with dissimilar head and block materials

I have seen copper coat used on high HP Cummins, but "only at high power levels". (? no idea why - if it works why not use it whenever the head gasket is replaced?) - noting they're a steel block and head.

I've heard about an aviation product that, I think, Nelson racing use on their high HP builds - apparently it sticks the head to the block so hard they basically need to be porta-powered apart on disassembly.