Setting carb up woes!

[GTphil]

jetted my carb today and it's fueling 11.5/12.2 afr at WOT at 24psi manifold

Got back after my second test run opened the bonnet and noticed my headgasket was leaking/weaping around cylinders 1/2

I have det cans installed and i didn't hear (or at least think i didn't) any det.

Just done a comp test and the results were strange

130psi 125psi 125psi 125psi in cylnder order from flywheel with a warm engine.

Squirted a bit of engine oil down the cylinders and the comp only went up by 5psi.

The car drives fine no knocks/bangs/smoke and no overheating, engine temp never went over the third line oil pressures fine 45psi when warm at WOT.

Could my head have lifted under boost?

As far as i can remember i tourqed the head bolts up to 70/75nm.

[GTphil]

Just done another comp test and I'm not getting any compression on any cylinder

When i put my finger in the spark plug hole there is a very slight bit of air movement but nothing like 130psi

[GTphil]

Scratch that the comp tester was sticking open.

[gtmatt]

you sorted it now mate ??

what afr meter are you using ???

[GTphil]

AEM, the ones that scoffsky sells. Top bit of kit, easy to install and use.

Not sorted mate, I'm hoping it's just the headgasket, getting one on monday.

Only problem now is time, I'm working and away at the lakes next week so don't think i will have time to change the headgasket finish off setting up. So pods not looking good for me

[Rob@Backyardracing]

So the car run fine yeah, how bad is the leak...?? could you not just leave it as it is for now?

[GTphil]

Yeah it runs fine, no smoke from the exhaust no apparant mixing of oil and water.

The headgasket only seems to be weaping but the gearbox side of the block is all damp and so is the front of the block at cylinders 1 and 2.

Don't think it would last long at that boost

[ranj]

Not good news mate .... them afrs look fine to me .... so maybe det is the problem .... what size is the head and are you running std ignition timing ????

Out of interest how are you getting 24psi ..... actuator or are you using a boost controller ??? Cos i gonna start a new thread as i cant get enough boost

[GTphil]

I have a fisher price my first actuator (GT tuning adjustable) set at a bar and bleed off for the rest.

Seems to hold it no problem no spiking at all

My ignition timing is slightly advanced by a few degrees.

I did split a vac pipe on my first run out and it was one that went to the aei could this cause the ignition timing to change? Even so unless my understanding of what det sounds like is way off then I didn't hear any.

My det monitor constists of a cheap stethoscope bolted to the front of the block piped up with 6mm nylon hard pipe. I do kind of get a vibrating noise high up in the revs but i wouldn't describe it as marbles in a jar ect.

Head is over 73mm can't remember the exact measurement, i also run low comp pistons.

[ranj]

I had to rebuild twice cos i couldnt hear any detonation .... so 3 rd time i went on some rollers with proper det cans to check everything and went there with ignition retarded to be safe ..... a split in the vac pipe can deffo cause detonation as the renix wont know what to do with the ignition timg as its getting fed flase vac readings ..... .... so with the advance you have already itmay have just pinked slighty .... enough to damage the head gasket tho .....

[GTphil]

I suppose now the only thing to do is have a look when it's all apart. check the gasket for signs of det ect.

I might have to cut short mine and the mrs few days at the lakes........... that will be me and the "car" in the dog house again.

Not exactly ideal changning the headgasket and trying to set up the day before pod

Ranj, Do you run a GT25 turbo? If so I seem to remember quite a few people getting to a certain amount of boost then struggling after that with those turbos.

[ranj]

I run a garret gt28r with a 0.49a/r back end on it .... if i start winding the actuator i can get more boost but i was trying to setup a gizzmo boost controller so that i could get 15psi manifold and then 20psi manifold on a differnt setting ... but i road tested today and all i got is 13psi manifold ( more wind needed) and 15psi manifold on 90% duty and 100% gain so only gaining 2psi ! ...... need a controller as i am not the only one who drives my car .......will start a new thread so it dont get mixed up with yours mate

[GTphil]

Just taken the head off my car gasket looks ok to me. fire rings are not ovalised and i can't see anything obviouse even when compared to a new gasket

What i have found is the last time i put my cylinder head back on i didn't put the washers in the correct place.

Two of the four washers that are suppost to go on the bolts that hold the rocker shaft down were just on the head.

There appears to be some marks on the cylinder head were the washer sits on the head were i used the thinner washers. I'm pressuming the head has either lifted or streched the bolts/washers??

I have checked the face of the cylinder head with a straight edge and it seems fine as it was skimmed around 2000 miles ago.

I'm now wondering if the head is scrap?

Or will i be ok fitting it with said washers in correct place and a new gasket and bolts?

[Mart]

No washers on the rocker-shaft pedestal bolts.

Always use the correct thickness (and grade of material) washers with the other head-bolts.

[TrixNFlix]

Get some pics up phil. The rocker shaft just gets bolted straight onto the head without washers, just need the big thick washers were your bolting straight into the head. So I think your head could of lifted with the cheap thin washers, especialy at that level of boost.

[GTphil]

No washers on the rocker!

I did get it wrong last time i put the head on!

Do you think i have furbar'ed the head in doing this?

[TrixNFlix]

Beat me too it Mart.

how bad are the indents phil, pics

[Mart]

No washers on the rocker!

I did get it wrong last time i put it back the head on!

Do you think i have furbar'ed the head in doing this?

Probably not, but I would get it flat-checked/skimmed (if needs be) to be on the safe side.

Defo use the correct thickness/grade washers when re-fitting that head again though

[GTphil]

Here is a pic of the washers, if you look closly you can see the two in the middle have mushroomed slightly The one on the right is a standard one, large differance in thinkness too.





This is both sides of the gasket, nothing appears to be wrong?



This is the bolts (circled) that the thin crappy washers were on

[Scoff]

phil, 24psi and timing advance is a recipe for disaster unless you are low compression ? I remember you had an "inconsistency" in compression ratio with one cylinder, that's been sorted now ? a close examination of the plugs is also a fair way of checking for detonation and to identify which cylinder is knocking if you look at them shortly after a pull.

[GTphil]

I have low comp pistons scoff, but the head has been skimmed it's still over 73mm.



I thought valves on this pic looked suspect, the dampness is coolant it had only bee off 5 mins.

The inconsistency was my "finger tight" with the comp tester

[Scoff]

no phil, I remember you had one standard compression and 3 low compression pistons at some point many moons ago the head looks fine to me.

[GTphil]

I have three dished pistons and one flat top, the cylinder with the flat top has a new valve guide also and it's around 5psi up on the others.

Still the ignition timing will be going back to standard it's only mildly advanced with the sensor knocked forward slightly. I'm sure it wasn't knocking as i couldn't hear anything through the stethoscope.

[TrixNFlix]

I have three dished pistons and one flat top, the cylinder with the flat top has a new valve guide also and it's around 5psi up on the others.

Still the ignition timing will be going back to standard it's only mildly advanced with the sensor knocked forward slightly. I'm sure it wasn't knocking as i couldn't hear anything through the stethoscope.

Is this a good idea? How did this setup come about phil?

[GTphil]

The pistons were in the car when i got it 7 years ago! simply couldn't be bothered with new ones as it has always ran/performed fine for 30k + miles anyway

I have a spare block that I'm currently building up (or trying!)

[Scoff]

"forward slightly" as in toward the front of the car ? that is ignition retard. advance would be toward the bulkhead.

[GTphil]

Thats what i meant, just checked and it towards the bulkhead by 5mm or so

[ranj]

5mm ..... can you see how many holes advanced that is on the metal bracket ??? May help give a indication of how much advance you were running .

[Scoff]

about 2 degress

[GTphil]

Just checked again and it's exposing one extra hole

[ranj]

about 2 degrees scoff says ....... that at 24psi on a std compression piston and a 73mm head would surely show det i would have thought ..... is there no markings on the head gasket fire ring of this cylinder ?????

[GTphil]

Not that i can see it looks identical to the new one, no dents in the fire ring or marks at all.

It was just weeping over cylinders 1/2 slightly it hadn't gone compleatly.

From the looks of it it's lifted under boost with the gash washers.

:edit: The pistons are low comp.

[TrixNFlix]

From pics the gasket looks good, are the liners stepped?

[GTphil]

They appear to be from the flywheel end upwards the liners still look good.

[TrixNFlix]

Cool, get your new gasket on with the correct sized washers and hope for the best

[ranj]

If you cant see any damage phil , just replace the gasket and see how things go ..... turn boost down a touch mate and maybe run a a bit of retard of ignition timing to be safe and then start playing wth things once you know all is good .... Best of luck

[GTphil]

If i want to make pod then thats my only option.

I have just put the timing sensor back to it's o.e position. Gonna clean the block surface, bolt it all back up (with said washers in correct place) give it a flush with some cheapo oil then change it for some good stuff. I might turn to boost down a little but i'm reluctant to maybe 22psi and take it up slightly bit by bit.

I suppose I could always do a bit of test and tune at pod! I'm sure it wasn't knocking, surly if i went right up to 6.8/7k rpm in fouth and fifth i would have had at least some signs of det if it was going to?

[Mart]

If you were running that level of boost upto the redline, without any fuel supply mod's to the carb, the float chamber will definitely have been empty(ing).

Note what I mentioned above about using the correct washers - They're only pennies each from Renault.

[GTphil]

Cheers for your help guy's it's appreciated

[newbstar*]

Think your being over diagnosive, Did you also get the head pressure tested when you had it skimmed. Plus, like we all think ,get the correct washers and make sure the heads not warped in the middle.

[GTphil]

Old thread aleart! Just thought I would finish it off.

The head must have lifted under boost, as it's all been put back with a standard head gasket instead of the thicker blue one. Ignition timing has been put back to standard. I was still putting it all back toghether at 3am the night before pod!

Drove it all the way there and all the way back and I have done another few hunderad miles inbetween.

It ran a 13.4 at 96mph @ 20psi but I had to come off the gas well before the line as the flote was emptying the afr's just dropped off to 16's instantly at the top of fourth. My best terminal of the day was 99.6mph.

I ran 23psi but it leaned off at the top of third at said boost

It will fuel for 24psi on the road but thats just giving it the beans in fourth, not all the way through the gears like at pod.

A few more fuel suppy mods to do and a bit of cam timing and I'm hoping to improve on that terminal speed as I was dissapointed with it. I may also play with the ignition timing.