head gasket troubles

[CP]

Been looking into the prob causes and it seems possible from reading some stuff on the SBD site that it could be caused by detonation as result of using fuel with too low a RON value. Although I use mainly optimax it sits around in my tank for quite a long time mostly and apparently the modern additives to raise the RON deteriorate quite quickly.

:(

[jatinder]

so what does that mean that optimax is bad?

[ollster]

Petrol does loose its octane rating quite quikly when sat, thats shy with my nova (only used on sunny days, so sat in a garage a lot lol) i use super unleaded, as at worst the ron is going to deteriate to normal 95. Ive never been convinced with optimax, heard too many bad stories about it, the sbd has had some quite nasty encounters with it.

Also when filling up try and make sure that you get the petrol from a garage with a quick turnover, as if you pick a garage thats not very busy then it can sit in their tanks for months.

Also are you sure that the head gasket has gone cp, is there water oil mixing, because there is always a possibility that the low compression is due to burnt out valves etc.

[Stuart]

either way the heads got to come off


i think optimax is a fad that shell devleped to go with their F1 use.

[Dicko]

ye the heads easy enough on those engines, took mine off on sat (see album for pics of my fooked piston :(

[Dave_Hay]

do you really need optimax cp???

and from what you said in your other post about compression - surely the fuel wouldnt cause such a loss in compression, you had two bores down to 50psi didnt u? could also be some trouble with the tbs if car sits around a lot?

fuels maybe too rich and engines internals dont like it much??

[Stuart]

fuelling is fine, its been checked. yes its running rich (12.7:1 ish) for max torque. but not stupidly rich.

[CP]

I'm almost positive its head gasket:
1. Its 2 adjacent cylinders, 3 & 4 which have the same low compression.
2. When i put the compression tester in 1 it chuffed loudly in the other and vice versa.

I would bet 500 notes that its blown thru the gasket at its narrowest between the 2 cylinders - i've seen it before. Cos it was sudden and got so badly worse relatively quickly ( it wouldnt run at all within a mile) it must be a big blow thru between the pots. If it was into an oil gallery etc I would have seen the other symtoms which i didnt and also it would have probably continued to run well enough to get me home.
I would expect if it was a valve problem for it to be only a problem in 1 cylinder - this usually happens with some sort of incident such as overrevving on a gear change etc. This happened at low revs.

I'm pretty convinced its a det problem - I also occasionally use LRP cos it has a highish RON value. I now realise that this a stupid move cos if ever there is a fuel that kicks around not being used much this is it and it can be of dubious quality anyway.

And dave - you cant damage an engine like this thru being too rich - its being too lean thats the big danger and thats also been what its been running at for quite sometime as we discovered when we finished the mapping :(

[mikeoxford]

think im gonna keep of the optimax for a while then

keep us informed cp as we want your car on the track at trax!!!!!!!! :twisted:

keep the faith - ull get there

[CP]

Got the head off tonite - it was as i suspected a big bit burnt out of the gas sealing ring in the gasket between No.3 and No.4. It had very nearly burnt thru between No.1 and 2 as well. Otherwise no other significant damage. If detonation has been occuring its not damaged the head, pistons or valves in anyway that can be seen with the naked eye. One of the exhaust valve seals has been leaking a bit of oil.
The most interesting thing was tho - 3 pistons looked the same -ie coked up a bit and generally blackish brown incolour. No.4 tho was completely clean and unmarked with no coking and only just a slight tinge of colour to it - it looked pretty much brand new still! The zorst port tho was just as sooty and coked as all the others and so were the valves...-?? WTF?

[Snowface]

maybe its only been running on 3 cylinders all its life? lol, joke.
Weird that.

[mikeoxford]

im un aware of how the engine is setup or whatever but could it have a dodgy or faulty injector? if it has these?

[ollster]

if one of the pistons is dead clean then its lightly that water has been seeping into this cylinder, as it basically steem cleans the piston. I ahve seen this on a few blown gaskets.

[CP]

nah - tisnt water getting in - gasket fine around water galleries. have been wondering about fuel injector tho' - I think I may get them tested to make sure

[Stuart]

its possible that the inkector leaks, causing a nice cleaning solution into the chamber, OR its not doing anything, but then the exhaust port would be clean too.


i'd say send em down to me to test and clean but that would take a fair while. best off going somewhere local for that :)

[Dicko]

is it possible this cylinder is gettin more air, and therefore runing lean, with the other running rich this might explain, but you would usualy get a sandy coloured sh1t on the piston/plugs

[Dave_Hay]

wouldnt your mucho ????????????? engine mapping have seen a injector not working right???

thought you had a quality management system ?

if u were running lrp as well.... couldnt that have coated the inlet valve on cylinder 4 and when running optimax the combustion didnt take place correctly due to a "knock" effect? or fuel sticking to valve/guides and not getting proper swirling effect in bore - hence "underfuelling" but excess fuel in valve/bore near valve would be making the temp very high - hence damage to gasket?? if thats even at all fucking possible lol

kinda sounds like ignition not happening correctly/engine not getting rid of heat quick enough (but aint that through excess fuel in cylinder as opposed to running lean??)

but hey i know fuck all im just trying to chuck some ideas into this :)

[Stuart]

if the lambda sensor is in the correct place then technically yes the ecu could tell if an injector was faulty, but only in the sense of too much or too little fuel. apaprt from that it can only tell if the coil is passing current.

even very expensive ECU's cant tell you if a soleniod that you activate moves etc. thats a viewing test :)

[ollster]

nah - tisnt water getting in - gasket fine around water galleries. have been wondering about fuel injector tho' - I think I may get them tested to make sure

The gasket does not ahve to be broken near the water galleries to allow a small amount of water in, if the head has warped slightly during hard track use, or when the gasket blew, it could allow a small amount of water (enough to steam clean your piston) under the gasket. Its only a sugestion, it could clear up the mistery of why that piston crown is so clean :?:

[mikeoxford]

have been wondering about fuel injector tho' - I think I may get them tested to make sure

8)

:oops: was only having a stab in the dark.

hope you get it sorted cp :cry: one of my favourite motors!

[nova---chris]

What compression you running CP? Just wodnering?

Im thinking maybe a slight warped head seeping water through.
Maybe only underload(track or thrash) worth checking the head

Guess a game of trial and error first. Just try another gasket for the time being.