Whats a hardness test??? and how do they reharden the head???

Wow this is an interesting read. As a qualifided mech of 6 years i recomend you DO NOT use any sealant on head gasket or block the dowls will hold gasket in place. Not trying to be a c*ck head but if i was you i would not be taking advice from a 16yo.

Cjh your block looks very nice but why dont you have it set at tdc on no.1 not a good idea

And why dont mechanics go to the trouble of shining up and painting blocks and why dont they do the very best job they possibly can. The reason is we dont have the time and we dont get paid enough. When i do cash work for friends or family its another story

tickford 6 how can you charge $94/hr to replace head gasket on a ford 4.0, these motors would have to be easist motor for head gasket renewal you should try a gasket renewal on a holden astra did one the other day what a job. I stronly agree with most heads needing some work most need new exhaust valve guides at least but why would you re harden a head, these 4.0 heads are a dime a dozen, if the head is to soft you chuck em

ELboy

Why is it best to have no 1 cyclinder set at tdc???

Most of the mechanics i know charge $70-80 and these guys take care of a few taxi's and there a busy workshop so maybe they dont do the best job possible.

Makes u wonder how many times a mechanic has worked on ur car that they done the job right???

If i had a workshop id be taking pictures of everything to show my customers the wrok that has been done so there confident in what has been done, and why i charged them more than others.

If i get a quote for a headgasket for $1200 and another shop $1500 id be thinking im saving $300.00 so why is this guy more expensive??? but if the more expensive bloke had pictures of previous same/similair work to show what they do and why there more expensive id be comfortable to give them the job as i know whats happeneing.

Also when asking around u can ask how much labour they charge per hr and get an idea of price difference as parts are about the same money.

As a mechanic of going on 30 years experience I too have never seen the need for any sealants on the head gaskets of a standard engine. If everything is spotless and head and block surfaces have been cleaned using thinners etc and new head bolts if specified have been used. There should be no problems.
As for the I6 heads, Ive never seen too many that flunked the hardnedd test and the ones that did got binned. Just done the head on my own el and my engineer charged 440 for the full recon on it. K lined and all, 5 welds inc!
Would be nice tho to devote the time as I did on my own car to my customers cars, but like everything else these days. Cost comes into it. I do a proper job, but only what the car needs, and what customer wants.

On a OHC engine the cam is zeroed and the engine always set to tdc. Zeroing the engine. Makes life easier and when the engine is reassembled, if all the dots like up bent valves and engine that won't start can't happen

Heads would have a big chance of failing a hardness test if the engine has been cooked. Hardness test is usually done with a little hand held device while the head is on the workbench.

Cheers

ToranaGuy

if your talking about me then i suggest you get your facts straight i might be 16 but have been told this by a retired mechanic of over 30 years who owned his own workshop and fixxed cars of half the town and this person is also my dad if he believes its required for what ever reason then i believe it, he has enough knowledge about cars that id probly believe any thing he said.

I don't charge $94/h just to replace ford head gaskets. My hourly rate is $94/h because that's what it costs to keep the doors open and bills paid.. You don't adjust you labor rate just because the job is 'easy'. I don't find any of the work a mechanic has to do as being 'hard'.
some jobs take longer, some require a bit of thought, none are hard.

EDIT: I'm not interested in arguing about labor rates. If people don't like my rate there are two other workshops on my street It's a simple mater for them to move on to a different workshop. One of the others is over $100/h the other is cheaper then me. my self and the $100/h guy ALWAYS have more work then the cheap guy.

As for hardening a head or not, that is entirely up to the customer to decide. In the case of the 7MGTE engine in my other post, hardening was the only option. As both the customer and myself couldn't find a replacement that came with any kind of warranty.

Last edited by tickford_6 on Mon Mar 15, 2010 10:23 pm, edited 1 time in total.

from my point of view,
using sealent on head gaskets tells me the person doing the job has no faith in there own work..

Tickfords prices are pretty well on the money. If top job is wanted and a reliable car wanted after it can easily run to 1500 depending on the damage to the head or a good sechond head needs to be sourced, then that pressure tested and repaired as necessary. Even if the secondhand head looked new, it still goes in to be checked.

Been there, done, that, got the valves.
The first one I did years ago I learnt the hard way that..
1) The Ford manual was the best $300 I spent on the car
2) The notch doesn't line up parallel to the head
3) Ziptie the cam to the sprocket, and leave the engine at TDC.

Lucky it was only three valves.

A narrow-minded opinion. Not necessarily incorrect, but we don't have enough evidence to support this view as "fact".
Soapbox time..

My perspective is that there will always be movement of the head on the block, particularly engines that are driven in a way that is beyond design spec.
The theory is that two things are happening: electrochemistry, and gas/oil/coolant seepage under pressure and temperature.

The block/gasket/head interface is going to exhibit some corrosion over time, under the extreme conditions that exist there. Using a buffer layer (chrome plating would probably work too) in theory provides some protection.

Pressure and thermal cycling will allow at least a little gas/fluid into parts of the mating surface. In theory using a buffer sealant is like grease on boat trailer axle bearings - it will flex but should protect against breaking the seal. Head tension should squeeze out any excess, and the buffer will fill the inevitable tiny gaps/low tension areas between the surfaces. Unless all surfaces have been machined and measured to the finest tolerances possible, there will always be some irregularities in the mating surfaces. Not to mention the uneven internal shape of the head, block and gasket leading to dimensional distortion at high temperatures.
We're not sealing two rectangular blocks of metal here - they won't expand under heat evenly.
I'd love to see the out-of-flat variation on a hot block of head - I'm sure it would be significant.
In fact ideally the head would be machined at 75-100*C so the surface is flat at op temp - the conditions in which it will experience the most duress on the sealing faces.

When it comes to Ford heads, it seems everyone has their two bob to say.
Despite FMCA developing the old inline six to the point where it was a fairly impressive engine in 1995 (and now is up there with the best in the world of inline sixes except for the iron block).. it's still an inline six and its achilles heel is the long, thin head mating surfaces.
Since the alloy head, all I6's have a flaw. It took Ford years to work out a solution to the problem as seen in the AU - it's still there, but tighter tolerances and better gaskets patched the problem.
Whatever "we" can do to minimise this issue in our own engines is up to us to work out - which is why I'd like to learn what others are doing and to get some first-hand evidence of what using different approaches can bring.

If anyone has any "negative" anecdotal evidence regarding head gaskets it would help everyone to hear them. e.g., "The gasket failed in A or B way , and I did X and Y and the head gasket failed again in C or D way".

FWIW I'm pulling down an EF I did years ago with a Ford VRS kit and a copper-based spray, the engine was flogged extremely hard. I'll take some pics of the gasket surfaces and inspect for corrosion etc and report back.

I'd like to see the pics & a short write up on what was found. Will be rather interesting.

Last time my head gaskit went, it was between number 1 & 2 cylinders, it blew out from the cylinder ring to a water jacket. No corrosion in the area, so i would hazard a guess the failure was along the lines of the gaskit reached the end of it's life due to thermal cycling taking it's toll on the material, or the same with the head bolts, stretching enough to put more strain on the gaskit & that caused the gaskits failure. I had the cyl head crack & hardness tested, guides checked & new stem seals put in. Cost $150. Guides had a fair bit of life left in them, valves were just lapped. The head had been reco'd sometime in it's life. It will probably need a full reco next time it comes off.

I couldn't afford an AU gaskit set at the time, so i bought an ACL VRS set & AU head bolts. Had no issues yet, done 100,000 on it, so probably about 50,000 to go until it pops again lol.

Cheers

ToranaGuy

Alot of good info in this thread so keep it coming

Isent it always a good thing to have tight tolorences with engines???

Yeah, except between moving parts/bearings. Then, that's a tradeoff (bearing tolerances are a whole other story)..

The reality is, economics of manufacture and the law of diminishing returns means parts are manufactured to the worst tolerances that still meet targets of acceptable failure rates and designed service life.
Ideally everything would be made to tight tolerance, fit together perfectly under hot/cold conditions and probably not require any sealant at all - we can achieve this with modern manufacturing but it's not cost-effective to do so in a 'throw-away'/built-in-obselence market.
So it's up to the end-user to try and work-around the issue or improve on the OEM parts by better replacements or manual remanufacture..