Is this repairable?

[morbias]

Took the head off today and things are worse than I was expecting

All the exhaust valves need replacing at a minimum as they are burnt and pitted to b*ggery. The bigger problem is the valve area on number 6 cylinder; there is a fair bit of pitting but the section between the seats is really bad, is this even fixable? The weird thing is both seats look to be in near perfect condition.

.

Number 6 intake looks to have been replaced at some point, there is a valve shaped imprint on the top of the piston -- maybe a PO was a bit ambitious with a downshift and threw a rocker arm. But yeah, the exhaust valves are toast

.

 

[camerashy]

What the hell happened to that! It's almost like aluminium corrosion?!

 

[pmac]

IMO..................IMO................IMO

Beyond economic(or sensible) repair.

PM/call to discuss.

There will be pleny of others along soon with helpful suggestions Im sure.Most of whom wont agree with me.
Afterall this is the Z club
Cue..............................................................................................................

 

[pmac]

What the hell happened to that! It's almost like aluminium corrosion?!

It is aluminium corrosion................................
Caused by water.

 

[Rob Gaskin]

I would not reuse that head - now that's telling you something!

 

[morbias]

I figured that was going to be the general consensus, cheers guys.

The car was sitting for 19 years so I'm guessing it had a valve open on number 6 all that time. I will be getting in touch sometime Pete but first I want to get the pistons out and see what condition the bores are in. I can't see cylinder 6 as it's at TDC and I have a feeling bad things may be hiding there, though the piston top looks mint.

Also I have a question about the cam -- it has E30 stamped on it, is that the original cam for this engine? L26, P30 block, E88 head

[EDIT] nevermind, I just found this thread

http://zclub.net/forum/240z-260z/1863-how-do-you-measure-cams.html

 

[SKiddell]

Detonation
The cause of which will need sorting prior to any rebuild

 

[morbias]

Previous owner = cause of detonation.

The distributor mechanical advance was frozen in place so there was no advance at all, PO had just advanced it where it was running at a constant ~18 degrees BTDC.

But it gets better... The car had dual 2" SU carbs on it fitted with RI needles which were way too rich. But it looks like someone decided they weren't rich enough and attempted to re-profile the needles. I'm fairly sure this is how not to do it :

Seriously, this car was owned by a total numpty at some point in its hard life, the brake lights were even wired into the door switch

 

[morbias]

How do these bore measurements look?

Top of bore / bottom of bore
1: 83.04 / 83.04
2: 83.00 / 83.02
3: 83.00 / 83.01
4: 83.01 / 83.01
5: 83.01 / 83.01
6: 83.02 / 83.00

Measurements are rounded to the nearest decimal point as my gauge only does two decimal points. I don't know why cylinders 2 and 3 seem to have worn at the bottom of the bore, how would that even happen? I double checked and the readings are correct.

The Haynes says to measure at the wear ring at the top of the cylinder bore, but there aren't any wear rings so I measured about 20mm down. Also, all the pistons have '2' stamped on the top, except for number 6 which has a '1' that has an 'X' stamped over it and a '2' stamped next to it, does that have any significance?


[EDIT] My mechanic mate brought a more accurate gauge round, he wasn't happy, it's peeing down outside

Top of bore / bottom of bore
1: 83.040 / 83.042
2: 83.012 / 83.017
3: 83.011 / 83.003
4: 83.008 / 83.013
5: 83.018 / 83.018
6: 83.015 / 83.003

 

[Mr.G]

FSM says that the inner diameter of the bore should be between 83.000 to 83.050.

You've done a Taper reading from Top A to Botton B, and the FSM says (if I've read it correctly!) it shouldn't be less than 0.02.

You also need to do an out of round test on the bore, take two measurement around the bore, do one side (x) and then measure the opposite side (y) of the same bore. The difference shouldn't be less than 0.02.

Before you chuck the head make sure you take off all the salvageable bits off, like rocker arms, lash pads, rocker pivots etc... They may come in handy.

 

[morbias]

Cheers, I didn't bother with the FSM, I only have the one from the xenon site but the EM section is practically unreadable.

Are you sure the difference shouldn't be less than 0.02? Less would mean tighter tolerance to spec, surely it should be more than 0.02 is out of spec?

Looks like I'll have to phone my mate up again and get some more measurements, he did mention about out of round wear but we didn't get that far.

I'll keep the old head knocking about for spares, or might just sell it as it is - someone will probably want the salvageable bits. The cam looks to be in decent nick at least.

 

[Mr.G]

The spec page says less than, but I guess it may be saying that the difference shouldn't be more that 0.02. I'm not sure why it's written like that?

Hopefully the engine builders amongst us will chime in with their take.

 

[SKiddell]

3 and 6 look like they need futher investigation
I would do an out of round test as George suggests, top of stroke, middle and bottom plus at 90 degrees so 6 measurements on each cylinder
Beware of trying to hone out issues as they can make any taper or oval irregularities worse

 

[pmac]

Hopefully the engine builders amongst us will chime in with their take.

Hopefully not, cos all that will happen is an extended round the houses debate that will establish precisely nothing and will take days to get there.

If Morbias wants a 100% reliable engine of a quality suitable to go in a fully restored car of considerable rarity and value then no further debate or measurements are required.
There is only one simple answer.

if on the other hand he wants to carry on in the traditional Z car/club mode of bodgit, scratchit and " that will do boy" then i will leave you all to debate for a few more weeks.

 

[STEVE BURNS]

Hopefully not, cos all that will happen is an extended round the houses debate that will establish precisely nothing and will take days to get there.

If Morbias wants a 100% reliable engine of a quality suitable to go in a fully restored car of considerable rarity and value then no further debate or measurements are required.
There is only one simple answer.

if on the other hand he wants to carry on in the traditional Z car/club mode of bodgit, scratchit and " that will do boy" then i will leave you all to debate for a few more weeks.

From the above reading between the lines you think its a no goer then Pete.

 

[bigblock]

I actually thought that head wasn't that bad i've repaired worse lol, but as mentioned not economically viable especially if you farm the work out.Nowt wrong with filing needles down with the appropriate knowledge(mind you they could have been done with a bastard cut file)Trying not to be blunt or cause offence as i have no idea of your abilities, but is there a reason why you are holding on to this engine(ie,trying to save money) and not moving on to better ones available,or do you have the abilities,time,facilities and patience to rebuild/repair a reliable,long lived engine.If not get rid and save youself the ball ache.Apologies for any offence in advance

 

[Rob Gaskin]

Hopefully not, cos all that will happen is an extended round the houses debate that will establish precisely nothing and will take days to get there.

If Morbias wants a 100% reliable engine of a quality suitable to go in a fully restored car of considerable rarity and value then no further debate or measurements are required.
There is only one simple answer.

if on the other hand he wants to carry on in the traditional Z car/club mode of bodgit, scratchit and " that will do boy" then i will leave you all to debate for a few more weeks.

Pete, don't put the guy off posting - this is an interesting thread.

 

[pmac]

Pete, don't put the guy off posting - this is an interesting thread.

Morbias/Ian and myself have spoken at length in the past and Im sure he will be in touch on this one too. So Im not putting him off at all.

From the above reading between the lines you think its a no goer then Pete.

Thats not what I was inferring really.
There are two routes that could be followed.

 

[STEVE BURNS]

From the above reading between the lines you think its a no goer then Pete.

Thats not what I was inferring really.
There are two routes that could be followed.

But one would be the far more sensible route though

 

[pmac]

But one would be the far more sensible route though

Yep as it would follow my usual mantra.....................................
Do it once and do it right.