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Blown Head Gasket

Started by _Inj gtr202_ , Oct 28 2014 07:14 AM

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16 replies to this topic

#1 _Inj gtr202_

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Posted 28 October 2014 - 07:14 AM

Hi all,

I thought I'd throw some pictures up of my blown head gasket from the 202, and ask for peoples opinions on the cause. I have a few theories but it's always good to hear opinions from other people (especially people who know this stuff backwards)

I The motor is a 250hp 202 running a solid cam and fuel injection if you want the whole story on the motor it can be found here http://www.gmh-toran...ion-manifold/.

The car was not regisered or driven the best part of 12 months, it had a full tank of fuel. Being a tight arse I thought I would be able to just drive it sedately until I used a half a tank then top it up with some fresh stuff. This seemed to work but once that tank was empty and I filled it with 100% new fuel it felt like I had an extra cylinder so I gave it the flogging you would expect and it loved it!!! (or so I thought).

The next time I drove it I heard what I thought was an exhaust leak, long story short... no it wasn't, the air was escaping between the head and block.

Thinking back, I thought I heard slight pinging when I was doing 110 with the stale fuel but I figured because I was only cruising with not much load I wouldn't be doing any damage. It cruises easily with an AFR of around 15.5 at that speed, I'm thinking I'll bring that back now to 15. I'll most likely take .5 degrees off the total timing as well just to be sure. Also I will NEVER use stale fuel again...

Looking at the pic's can anyone else see anything that I should be worried about? I'm hoping it was just a bit of detonation under light load, then I when I gave it some stick I blew it out properly.

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#2 _judgelj_

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Posted 28 October 2014 - 10:27 AM

That's why i chuck in $10 at a time unless on a big drive. You always end up with stale fuel in these things.

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#3 N/A-PWR

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Posted 28 October 2014 - 11:14 AM

Hi Adam,

I have a few Blue 202 Head Gaskets here blown out the side at #1 and #6, and between #5 and #6 etc.

Finally this does not happen anymore, as the Head bolt Torque tension is not keeping the head gasket tight.

At each Head Gasket change:-

- First thought was to change the spark plugs and coil.

- Second thought was the straight unleaded causing too much heat.

- Third was bad Head Bolts ( measured thread and length, OK )

- Forth was a warped head. ( checked Flatness diagonals, OK )

- Fifth thought was bad head gaskets.

The final test, used the #GTR head gasket ( $64 ) with the gasket sealer, lead fuel additive,

and a new spark set, blue thread sealer, which that great gasket blew out too. :furious:

The last time the Head was torqued down, three of the block threads gave up the Final Settings.

Got another Lucky Engine block, and haven't had any problems since. :clap: :spoton:

So the moral of the story, was the head bolts were loosing torque. :banghead:

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#4 N/A-PWR

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Posted 28 October 2014 - 02:00 PM

First Gasket blew out of #1:-

1st to go joe.JPG 108K 1 downloads 1st to go.JPG 51.62K 1 downloads

#2 and #3 blew between cylinders, with the #GTR one, blew #1 and #3 water Jackets:-

Attempt 2,3 and 4.jpg 85.51K 2 downloads

First time, ever seen this happen.

Engine blocks are getting old now.

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#5 _LS1 Taxi_

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Posted 28 October 2014 - 02:03 PM

Very interesting thread and great photos guys.

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#6 _datpsi_

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Posted 28 October 2014 - 02:03 PM

I had similar to this happen not long ago. . The head was slightly warped and far too much timing..

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#7 N/A-PWR

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Posted 28 October 2014 - 03:57 PM

Glad I never bought a $300 Copper Gasket to try on that donk.

Just a thought, from those in the know,

What would be the Torque Settings for Higher Horse Power 202ci's etc, 10% extra?

I had no problems with the normal Head Bolt Torque Settings,

with the spark plug compression gauge having 250psi cylinder compression.

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#8 N/A-PWR

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Posted 28 October 2014 - 04:38 PM

What would be the Torque Settings for Higher Horse Power 202ci's etc, 10% extra?

Better state,

that the above question was for a Naturally Aspirated Engine,

where as a Turbo Engine would be from Experience.

All good, if this is 'TOP SECRET'.

as cast block's can have their Head Threads damaged easily.

Edit:-

is there any need for Helicoil inserts for this case? other than damaged threads.

Edited by NA-PWR, 28 October 2014 - 04:43 PM.

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#9 caterham2

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Posted 28 October 2014 - 04:48 PM

Not bottoming on the dowels due to machining of head and /or block.?

Edited by caterham2, 28 October 2014 - 04:49 PM.

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#10 N/A-PWR

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Posted 28 October 2014 - 05:01 PM

Not bottoming on the dowels due to machining of head and /or block.?

Had 100 thou shaved, did't bottom out here.

Great Point but.

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#11 _datpsi_

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Posted 28 October 2014 - 07:22 PM

Don't add any extra torque. Remember these are old cast blocks. ..

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#12 N/A-PWR

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Posted 28 October 2014 - 07:29 PM

Great Comment thank's.

Don't add any extra torque. Remember these are old cast blocks. ..

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#13 _Lazarus_

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Posted 28 October 2014 - 07:52 PM

I'm surprised you were able to drive it with fuel that old.

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#14 SA EH

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Posted 28 October 2014 - 08:13 PM

Good post Adam, bad bloody luck though mate.
Hope you get that thing back together for some summertime fun.

On a side note, I'll now be draining out my stale fuel before driving it next weekend...

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#15 rodomo

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Posted 28 October 2014 - 09:04 PM

Did it ever "ping"

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#16 _Inj gtr202_

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Posted 29 October 2014 - 06:33 AM

Thanks for all the input, great photos Dave.

The block and head have both very recently been machined and are very flat.

The bolts definitely don't bottom out.

I have re-torqued the head bolts up to 80 ft lb (instead of 75). Hopefully this hasn't done any harm.

Jonesy, the gasket goo is setting as we speak and I'll be test driving tonight.

Rodomo, I'm pretty sure it was slightly pinging with the stale fuel when I was sitting on 110k, I have the tune set pretty lean in it the areas of the fuel map where their is high vacuum and little load. I was under the assumption a slight rattle with very little load on the engine would not be a problem. It never rattled or pinged with good juice...

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#17 EunUCh

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Posted 29 October 2014 - 05:24 PM

No expert here..just looking ,could just be a trick of the light but looking at #1 pot it looks like it has a bevel on the bore where the gasket blew out ?
#1-4 look a bit bit different compared to 5 & 6 in terms of carbon deposits,but then again it could be the light ?
Looks a bit too clean around the edges of piston.
Pinging at 110 light load does not sound good and over tensioning a head bolt is what all car makers do these days (torque to yield).
Which basically means they are frokt and a use once item.They are a "spring" and that's why they recommend the torque setting.