Head off

[Robbie693]

Hi all,

I am taking the head off tomorrow and wondered if you all could give me some pointers on what to look for to find the cause of the blown gasket and also the best way too clean up the surfaces for the new gasket?

Thanks in advance

Robbie

[david.g.chapman]

I just use a small sharp kitchen knife with a slightly convex edge. This works well on the cast iron surfaces. Just make sure you keep all of the crap away from the cooling and oil holes in the block. You could tape up these holes, do most of the scraping, then remove the tape for the final bit around the holes.

For the aluminium surfaces, more care is needed. I have used a knife with some success, but the scraping angle has to be low to avoid the knife digging in and scratching. For more safety somthing softer could be used with paraffin/white spirit to get rid of the old sealant that the tool slips over.

For piston crowns smear some grease on the crowm and use the "soft" scaper to remove the carbon. The grease will trap the carbon and stop it getting everywhere.

Use a straight edge and check the head for flatness. I dont know what the limit is over the head - anyone know?

Finally, unless you have just done it, grind in the valves, especially on the exhaust side.

Dave Chapman.

[steveww]

I find cellulose thinners works well for dissolving carbon, wellseal and just about everything else actually.

Just some quick tips:

Set crank at TDC
Take cams off the head first
Lift head

Chances are you will not see where the blow is unless it is a big one. The gasket on my Elan went between cylinder and water but could not see any sign once the head was pulled. I replaced the gasket with a composite one from QED. This has so far stood up to the abuse. BTW it is a good idea to re-torque the head bolts as part of the service. One by one back off each bolt 1/4 of a turn then torque up to specification.

Expect profanity when removing and re-attaching the exhaust manifold

[peterako]

Expect profanity when removing and re-attaching the exhaust manifold

Been there........

[twincamman]

hold up there ----do a leak down test first -----then if it fails then remove the head ---ed

[types26/36]

Hi all,
if you all could give me some pointers on what to look for to find the cause of the blown gasket

As well as checking the head for warp check around the water jackets (particularly around the rear holes) as the head tends to corrode if used without a rust inhibitor (anti freeze)

[Robbie693]

Thanks for the help guys,

I have cleaned the block up and had to stop before I had chance to do the piston crowns. So I smeared oil on the bore walls to prevent corrosion while I left it.

I think my finger must have caught some carbon on the crowns because I have some very tiny specs of carbon between the piston and the bore, which worries me - is this really bad? Will it score the bores when I turn the engine over?

worried..

Robbie

[rgh0]

I would not be to worried.

Just clean out the gap as best you can using something thin and flexible and flush with a squirt bottle of some sort with oil. Moving the piston up and down while repeating this will help extract any carbon trapped there

cheers
Rohan

[Robbie693]

Thanks Rohan - I feel better now

[Robbie693]

I am in the process of cleaning up the head and have been trying to measure for warping - I can see a slight gap, the smallest feeler gauge I have is .002" and the gap is smaller than this.. (assuming my straight edge is straight)

Can anyone tell me the the tolerance allowable please?

Also I have some corrosion around the water way at the back of the head (see pics) and some pitting in the surface. Is this severe enough to cause a problem?

[twincamman]

the old way is to put the head on a piece of glass with valve grinding compound and make figure 8 motions rotating the head every 10 times ------but I think the gasket will accept that small a deviance ----ed

[rgh0]

Less than 2 thou distortion in head face is Ok. I normally only worry about it if more than 5 thou. I use modern composite head gaskets which are more tolerant of distortion than the orginal copper / steel laminate ones.

Corrossion on the head looks Ok also - I have seen a lot worse give many years good service. The composite gaskets also reduce the electrolitic corrosion you get between the copper / steel and aluminium mix in the orginal assembly.

cheers
Rohan

[Robbie693]

Thanks very much chaps,

This is all very encouraging!

I've just got to finish cleaning the head and chase out the head bolt threads, which are full of crud.

Now if only I could get it back together without work getting in the way...

Cheers

Robbie

[Robbie693]

Thinking about it rather than actually doing it ( ) and I have another question please:

I have read that I should leave a ring of carbon around the top ege of the piston crowns, thing is parts of my piston crowns are bare anyway - the car has done less than 10k since rebuilt.

Should I just scrape all the carbon away?

Pic of the block immediately after head removed:

[Bruce Crowthorne]

Personally, I would clean up all the carbon.
There is no such thing as a good carbon deposit!
Be careful not to leave any "ragged" bits as it may lead to pinking.

And I wouldn't worry about bits of loose carbon in the top land on the piston (eg above the top piston ring) the minute you start it up it will just get blown out the exhaust port.

By the way, how awkward was it to get the exhaust manifold off?
I built mine up with the cast type of manifold as I didn't get my tubular manifold in time.
So now I have to swap over from the cast to the tubular type and I can't say I am looking forward to the task
Bruce