C1j piston damage?

[robx1r]

New poster! (less than 10 posts)

Here is an odd one, recently the liner cracked on cylinder 1 (water pump. i know it should be the other way around but hey)

so i've taken the piston and liner out and thought while i'm at it i'll replace the seals on the others and inspect them just to be sure!

pistons 1 and 4 are fine

piston 2 and 3 have marks on them where a valve must of hitting it but this was hidden under carbon build up there is about .1mm of a lip on it. on piston 2 the mark is on the right hand side and on the left on piston 3

now my head is fine and there is no signs of damage on said valves

what could of causing this? all the pistons have the same stampings on them, so i assume the are a matching set.

[SCHWARTZ]

Pistons have most prob hit valves in a previous head and just been left in. As for the liner have you got anything to monitor fueling? How much boost you running?

[5 turbo]

As long as it aint penatrated the crown i wouldnt worry,,if its been running well then sod it..

As above, valve contact or debris from previous mechanical failures...

[robx1r]

New poster! (less than 10 posts)

nope it would be best descibed as a heavy scratch.
nothing to monitor afr at the moment, and its boosting 1.2 on the avcr
running a Gt28r
I brought the liner down to one of the best tuners who does a lot of classic rally cars etc and he said it wasn't boost that split the liner as its cracked at the bottom too!

[Brigsy]

The liner will have cracked due to lean fuelling/det. Ive seen similar marks on pistons in these engines before, it will run fine if you put it back together as is..

[robx1r]

New poster! (less than 10 posts)

here is piston 1 liner



and the bottom( the bit with no preasure on it)

[J$£5GTT]

i noticed when i took an old engine apart,totally standard lump to,that one of the liners was cracked a good 25mm up from the bottom to,what would cause that anyone?

[markey b]

my dead liners (i have a few) look exactly the same...

mine were due to det, high compression, high boost and lots of advance, went like stink before it popped though

[robx1r]

my dead liners (i have a few) look exactly the same...

mine were due to det, high compression, high boost and lots of advance, went like stink before it popped though

oh it went like stink off boost let alone on boost.

possible culprit is my head is a grand 71mm thick. so i can only imagine what compression i was running

[5 turbo]

my dead liners (i have a few) look exactly the same...

mine were due to det, high compression, high boost and lots of advance, went like stink before it popped though

Didnt want to say it first..

Op you said the heads 71mm...Thats erm low.

If not already get it pro measured to be sure, as that sounds like you gonna need a new head mate

Need an engine builders op as to options..

[robx1r]

yeah i reckon i will need to replace the head, but it was running fine before, i popped at 19 odd psi well 1.4 on the avcr i have another head there but needs a little bit of work so i might just run that head untill i sort out the other one, ie port and polish it, uprated valves etc

[Markey Mark (BD)]

Your high compression would have been the cause of your liner going, thats very thing that head and at 19psi if you got the timing sensor set to standard position then that would of caused issues. What turbo you running at 19psi and is your carb jetted correctly?

To be honest don't fit that head back on, clean the other one up and fit that. Personally theres no need for porting and larger valves unless going silly power

[Sparkie]

you could fit

2 x

that'd lower the compression.

[robx1r]

Your high compression would have been the cause of your liner going, thats very thing that head and at 19psi if you got the timing sensor set to standard position then that would of caused issues. What turbo you running at 19psi and is your carb jetted correctly?

To be honest don't fit that head back on, clean the other one up and fit that. Personally theres no need for porting and larger valves unless going silly power

i've a gt28r and aparently its got a group a carb, i personally havent messed with it i have it since july and have clocked up 2000 miles trouble free ( aside from a window reg giving way)

@ sparkie

[robx1r]

and power wise i'd really like 220-240

[TNT ANDY]

you could fit

2 x

that'd lower the compression.

Can you actually do that?

[Sparkie]

yes, i've helped someone do it. worked well at 20+ psi daily. - they weren't even lined up properly.

what choice have you got? get another head of shady origin, or use your proven head that has unfortunately been over skimmed???

[Tony Walker]

You can buy shims for alot of heads from an engine shop, not sure if theres one available for the c1j as ive never had to use one. basically like multiple gaskets.

[Sparkie]

similar to what courtnay did to the novas when they started turboing them.....?

[Tony Walker]

possibly not sure, i know there around for standard heads, corsa z10xe engines are about £60 pretty common for warping alot when overheating.

[J$£5GTT]

You can buy shims for alot of heads from an engine shop, not sure if theres one available for the c1j as ive never had to use one. basically like multiple gaskets.

what are these shims made of?

[Markey Mark (BD)]

i've a gt28r and aparently its got a group a carb, i personally havent messed with it i have it since july and have clocked up 2000 miles trouble free ( aside from a window reg giving way)

@ sparkie

Ok so the grp A carb, bet thats not fuel correctly for the boost you running.

Your best bet is to either source another head or if you want to keep that head skim the tops of the pistons of machine the combustion chamber out alittle to bring the comp down to a reasonable level. Thats only my personal opinion though, i see other mentioned other ways of doing it which is all possible too

[Karlos]

take a mm off the squish :-)

[robx1r]

Ok so the grp A carb, bet thats not fuel correctly for the boost you running.

Your best bet is to either source another head or if you want to keep that head skim the tops of the pistons of machine the combustion chamber out alittle to bring the comp down to a reasonable level. Thats only my personal opinion though, i see other mentioned other ways of doing it which is all possible too

well it ran for 6 nearly 7 months fine, in fairness it did spike at 1.4 its set to 1.2

you can skim a piston? by how much,

i dont know if i would tust two head gaskets.

[Markey Mark (BD)]

It prob would run ok for while but only takes the right amount of boost and charge temp to get it detting then it'll crack liner.

Yes you can skim the pistons, will mean taking them all out and off the rods to do them though. Be easier to either get a set of low comp pistons of machine the combustion chambers outy alittle to bring comp down.
After that have it set up correctly and check that its not detting again

[Tony Walker]

I wouldnt worry about headgaskets failing, think of it as a fuse, better to pop a gasket than crack a liner could get expensive popping 2 if it did it often tho lol.

[robx1r]

well worked out my Cr at 9.4:1