Head Gasket Costs - 71 +2 s 130

[richardhallett99]

My pride and joy has let me down..............again

Plooms of white smoke on start up, followed by more smoke than is expected throughout driving. Also she is drinking water like a drug crazed teenager at a Rave. Soooooooooooooooo I assume that the head Gasket has gone (lucky me, the third time I have owned a car where the HG has needed replacing - is it my driving?)? I do not have the time, inclination or expertise to do this myself so need to put her into a classic garage repair shop.

How much should I expect to be paying for this job assuming the head does not need skimming (should it?).

[tdafforn]

just got charged 400 quid inc VAT for replacing the head gasket on my renault scenic.
Would have thought that there was a similar number of hours doing same for twink.
Tim

[Alex]

Interesting comparing modern versus classic garage costs. Renault charge ?80 per hour for labour and I'm sure classic garages are maybe ?40-50 per hour.

Form experience of doing both Lotus and Renault heads, there's much more to dismantle on a Renault. Most garages also include skimming the head in the cost. If they dont do it, and it blows again, they get an unhappy customer back complaining!

If just the gasket needs replacing, I'd expect a bill of ?200-300, but if it needs a skim etc expect to double it.

Regards,

Alex

[tdafforn]

it is interesting..
my renault was done at the local independent garage (?40 ph) and included a skim..
Interestingly had the same job done at renaults 5 years ago and they didn't skim it... lasted 60K miles,
(Sorry off thread!)
Tim

[richardhallett99]

Guys

Many thanks - interestingly enough I too had a Renault that failed in the same way...

So the costs are comparable. Fair enough - I will summon the courage to speak with the wife....

[reb53]

Make sure they don't skim it as a matter of routine.
Garages seem to do this to cover themselves without any thought of preserving servicability for future owners.

My Sprint head had a huge amount taken off for no particular reason other than " we always do that to be sure".

This was a while ago so hopefully garages are a bit more clued up now but I wouldn't hold my breathe.

Ralph.

[tdafforn]

How should you make the decision about whether to skim or not..
I have just rebuilt (although not run) my twink with a 711m block and just cleaned the face of the head. It looked in fairly good nick..
Tim

[rgh0]

Tim

Both flatness and surface finish are critical to good gasket sealing.

I geernally work on the basis that the head should have less than about 10 thou of an inch out of flat along its length or across its width at any point. Easy to measure with a straight edge and feeler gauges If more than this it probably should be skimmed the minimum amount to get it within this flatness. Some machine shops will recommend milling the head with less out of flat (say anything more than .005 inch) but modern composite gaskets are pretty forgiving if you use them and taking material off a twink head is always a last resort.

The surface should have not marks or corrossion in the gasket fire ring seating area and the general surface should have a very slight roughness due to the tool marks from the milling to aid in seating the gasket, it should not be polished smooth. A good quality engine machine shop will know what surface finish is required with the type of gasket you use but dont necessarily trust your local garage.

cheers
Rohan

[Alex]

The best way I find to check the flatness of a head is with a straight edge diagonally across the head. Check the clearance at the mid point. If it is warped, it will be greater across one diagonal than the other.

[denicholls2]

If you actually want higher compression, skimming is a way to get there. Lotus did exactly this with new engines.

BUT, skimming has consequences beyond the ability to preserve meat for future skims. Because it raises the compression ratio, it also raises the minimum octane on which your engine will run happily. To adjust for this, you need better fuel or less advance (which in turn means less power.)

For a road engine, I think the 10 thousandths guideline should make you happiest, again unless you value a bit more compression.

Another consideration, for a head that has already seen prior skimming (even from the factory), is valve-to-piston interference. Over-skimming can be accomodated with increased thickness head gaskets or reduced-height pistons, but there are limits to the amount of meat that a head can tolerate losing.

Finally, skimming will change the relationship between your cam and crank given the same or a replacement of the same timing chain. This will need to be factored in proper valve timing.