The Rebuild Begins

[MK1_Oz]

[MK1_Oz]

Took the head off today after buying a 12mm triple square (exy!!) and welding up a suitable mounting bracket for the engine stand.

The head gasket measured 1.3mm at the fire ring (correct term?) which I believe is correct for a Felpro? All looked intact. I have never looked closely at a head gasket before so is it normal for the majority of the water passages to be covered over with only a few small round holes left for coolant flow??

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The head looks to be in great condition. I have included a few pics for those that like heads.....

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Several of the chambers have a hard crusty deposit in them. Expect this is normal?

More to follow.............

[MK1_Oz]

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All looks fine to me.....


The pistons are very discoloured (again I assume this is normal) but the nasty news for me in within cylinder 4. There is significant scoring to the bore. I cannot measure it but it catches my finger nail easily :( These bores are currently 92mm. Obviously the bore will need to be redone but what is that likely to mean in terms of pistons? Can the bore be made larger but retain the current pistons or does a re-bore always mean fitting larger pistons? (Go easy I am learning here.......)

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I ran out of time to pull the sump off but I think it is clear that I will find the bearing on No4 rod knackered. I am just praying and hoping that the crank is re-useable............

[mickas]

Rebore new pistons...

[Warren Heath]

No 4 piston looks like it's been pinging it's head off, maybe that's why yout bearing failed?

Cheers
Warren

[gen mk 1rs2000]

I have never looked closely at a head gasket before so is it normal for the majority of the water passages to be covered over with only a few small round holes left for coolant flow??

Gasket_101212.jpg



Head4_101212.jpg

I Have often thought about opening up the water jacket holes in the head gasket
,but i have never tried it , has anybody else ever done this ???

[MK1_Oz]

[Warren Heath]

[MK1_Oz]

I did notice that there was a 4mm chunk of the spark plug ceramic electrode missing that would have bounced around the cylinder. Might be something to do with it. The only mixture checks were overall so I get your point re 1 cylinder pinging.

Would a damaged bearing not potentially allow the pistons to slap around and vertically score the bore as has happened? I was surprised to read that you did not expect bore damage due to a bearing failure but then as said before, I'm learning here.

As for the block issue, I just ran what I brang and nobody complained. Scrutineering was not very thorough to say the least. If I need to re-bore the block then I agree it may be worth sourcing another standard block. Currently it sits at 2046cc which puts it in the 2000-2500 category (just). I need to decide whether to stay under 2000cc or maybe go a little bigger as in the handicap classifications I am being penalised for an engine up to 2500cc so may as well get the additional oomph from the max permissible size (around 2330cc). Comes down to cost - guess I am up for new pistons either way so depends how much to prepare a new block vs reboring the current one.

Will look more tomorrow re your comments on the alloy deposits....

[Warren Heath]

[MK1_Oz]

Cheers mate. The head is legal as "heads are free" but agree re the bottom end.

Is the only thing that could be causing that detonation the fuel mixture? The horrible filter sock that I put on the trumpet (last minute thing no time to put something better on before the event) is pushed up against the bulkhead so maybe airflow into no4 is not as good as the others.

More investigation and more research needed by me.......

[MK1_Oz]

Sump off and as expected no4 rod is very loose on the crank. No surprises there. I will leave the rods as they are for the engine builder to pull apart - I am in denial that the crank may be shagged too

Looked very carefully at the gasket not that I really know what to look for. You can see from the pics below that the metal on the firing ring appears to have 'pealed' on both sides. This has happened on all cylinders to a degree but no4 is probably worse. I would have thought this is just from being clamped between 2 lumps of metal at high pressure. The thin inside edge (the bit that effectively forms part of the combustion chamber) has some loose sooty deposits on it but once wiped off it leaves a nice smooth edge all the way around. If it was detonating would I expect to see damage to this area?

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The deposits that can be seen in the chambers in the previous photos will scrape off easily and then grinds to a powder. Just carbon deposits I assume and nothing to worry about.???

As for the "...alloy deposits stuck to the bore at the top..." that Warren thought he could see I have taken a close look at there is nothing stuck on the bores. However, the other 3 bores have a carbon deposit around the top 6mm of each bore (ie combustion deposits above the compression ring) but no4 is just shiney bore with no deposit. Not sure what that would mean?

Lastly, I noted that none of the pistons appear to have any significant damage to their tops. There are several small impressions on a couple but only slight. No4 however had some slightly deeper (again nothing I would have thought might be an issue) dents in the area highlighted with matching dents in the head face. Maybe this was the ceramic spark plug piece bouncing around? Could those pieces also be responsible for the bore damage? Note, these pistons were not brand new this event so for all I know these dents may have been caused along time ago.

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I am unsure where to go from here mainly due to my lack of experience. I am reluctant to rebuild the motor if there is the chance that it will detonate again but I cannot nail down what may have caused it in order to prevent it!!! Might just have to take it to the engine builder and let his knowledge diagnose.

Just so that I can get my head around whether I have to sell one or both kidneys to pay for this, a new set of forged pistons is likely to be around $800? How much is it likely to cost to get a new block prepared?

Great learning experience.............

[stuart]

How much did you pay for a 12mm triple square ??? i only paid $14

http://www.toolmart.com.au/ss12m.html

[MK1_Oz]

$35 for a sidchrome one from SA All Tools. I didnt ask the price....only noticed after I paid!!!!

[PaulMK1]

Finding blocks with a good standard bore is almost impossible now, so really you need to consider sleeving the block back to a standard bore to stay legal.

The last quote I got was scarey - $400 to bore and fit sleeves, $25 each for the sleeves, $120 to face the block, then $100 acid clean, $80 crack test, etc. (all plus GST).

But then again if you get another block you'll probably need a bore and hone anyway...

Paul.

[MK1_Oz]

Add a set of standard size forged pistons.......add add add..... depressing stuff.

Might end up being cheaper to re-bore to whatever is the next up from 92mm and just pay for new pistons. Several options to investigate.

[Matt1975]

Not sure on the history of your block but if you go the next size up in pistons (93mm) you will probably need your block tested to make sure it'll take it as I have been told this will be too much for some blocks.

Good thread though.

Cheers

Matt

[MK1_Oz]

What's a standard Pinto block bore? 90.7mm or 90.82mm are the 2 figures I have in my head.......

[Warren Heath]

90.82 is the std bore size. To keep the engine under capacity in the car I built we started with a virgin block, and bored to the minimal size (which from memory was 91.1mm) then offest ground the crank to bring is back under 2000cc.

Virgin blocks are getting herd to get, but not impossible. I think I have 3 left if you need one, 2 of them will be sold complete.

Cheers
Warren

[Warren Heath]

P.S. if you're planning on doing it cheap, forget about it, it will bite you if you do.