Petrol In The Catch Can?

[GunMetalR33]

I have been having a problem with flat spotting.

I run NGK plugs with a heat range of 7 and on cold canberra winter mornings they flat spot until I get some boost over them, then they are fine.

I have tried using a heat range of 6 and they dont flat spot in the morning but they do flat spot with higher boost levels and they also knock a little higher (I am guessing pre-ignition)...So I am sticking with the 7's gapped at .6

Anyway could this flat spotting be the reason why my catch can has fuel in it? The catch can does not feedback into the inlet and I have blocked the PCV valve.

Also does a smaller gap rob you of any power?

Any ideas on the matter would be great

thanks in advance.

Edited September 25, 2006 by GunMetalR33

[r33_racer]

too much knocking or something else has caused your rings to lose their tension and petrol is bypassing them and its going round with the oil.

[GunMetalR33]

too much knocking or something else has caused your rings to lose their tension and petrol is bypassing them and its going round with the oil.

That's what I figured but there is no oil in the catch can and the compression in all 6 cylinders is within 10% of each other. If the rings were worn it would show on the compression test and I would think there would be oil in the catch can???

[GunMetalR33]

Anyone, I cant be the first one this has happened too

[Beer Baron]

yes, smaller gap will rob you of power. why are you gapping the plugs so tight? 0.6mm gap is tiny. you should be somewhere between 0.8mm and 1.0mm.

edit: I have NFI how you are getting fuel in your catch can, but it's not good. 2. are you sure it's fuel?

[r33_racer]

well the petrol thing isnt...we had a similar problem in our race rb25det except the rings were shagged and the compression was down, regardless if they were all down the same or within a certain amount it was still happening, petrol in the catch can, not just oil.

I cant see another way of it bypassing and getting into the catch can.

[blind_elk]

With such a smal gap, you are probably not burning the fuel properly. Unburnt fuel is then being dissolved in the oil on the cylinder walls and taken down into the sump.

Open the gap. (usinga really small gap is only masking the real problem)

[dead32]

compresion test with fuel washing away oil on the bore is not a acurate test, remoove the plugs + the fuel pump relay, crank the motor over and let all excess fuel out, then re oil the bore and potentialy change the engine all oil together, lightly lube the bores with small amounts of oil then allow the car to sit for a lil while then perform another compression test..

[Scooby]

do you mean there is raw fuel in the catch can, or oil that smells of fuel?

[T04GTR]

hmm. interesting.

fuel in it ? it will smell like fuel. but its just oil from blowby.

most of the time if an engine is worn all will be whithin 10% of each other. unless theres a busted ringlad or something

[GunMetalR33]

Thanks for all the replies.

To answer a few questions:

1)Yes I am sure its fuel, very little oil, only enough to slightly discolour the fuel.

2)I run .6 of gap to stop flat spotting. Anymore gap and it flat spots. However I have removed a big restriction in my zuast since gapping the plugs down so I might gap them out and see what happens.

3)The max compression in was 150 psi in one cyclinder with the rest being within 10%. Most above 140 psi.

Could it be a head gasket problem? I am running 19 psi (yea forgot to mention that)

[GunMetalR33]

PS => if the rings are worn which I am sure they are (at least a little) how long will they last. Will they continue to wear or will they just sh*t them selves one day :{

Also how much for a re-build with forgies if I take the engine out and deliver it??? Just after a ball park figure. I am tring to save for a house :{

[leech_]

having spoken with Timmy and hearing the power you are putting out with standard internals it would not surprise that it is starting to die. Standard internals + the power you are making = upcoming rebuild... sorry to say it

oh also forgot to mention alot of the SAU Canberra and even Sydney guys who have had rebuilds have gone and seen Greg @ proengines. Maybe give him a call he may be able to offer some advice. http://www.proengines.com.au/

[GunMetalR33]

having spoken with Timmy and hearing the power you are putting out with standard internals it would not surprise that it is starting to die. Standard internals + the power you are making = upcoming rebuild... sorry to say it

oh also forgot to mention alot of the SAU Canberra and even Sydney guys who have had rebuilds have gone and seen Greg @ proengines. Maybe give him a call he may be able to offer some advice. http://www.proengines.com.au/

Yea, a lot of power to timmy is 140rwkw or what ever his old beamer used to make I have about 260 now and plenty of guys run that sort of power for a while. But I think you are right, engine is starting to get a little tired now

[race_snooze]

if hes only running the 246rwkw then stock internals are fine. As for 20psi and fuel in catch can also its missing.... What do all the plugs look like? If for some reason there is fuel in the oil look at the bigger picture your oil is f**ked now its thined out which will damage your bores.

I cant see how fuel gets into the oil, ie its sprayed into a chamber compressed then detenated and push out the exhaust valves.

You must have some bad underling problem eg craked head, head gasket to oil, valve guides, oil rings.

[blind_elk]

... I am running 19 psi (yea forgot to mention that)

There's the reason for your flatspot - the engine probably can't ingest air at 19 psi. Back the boost off a bit - I reckon 1 bar is more than enough.

[GunMetalR33]

if hes only running the 246rwkw then stock internals are fine. As for 20psi and fuel in catch can also its missing.... What do all the plugs look like? If for some reason there is fuel in the oil look at the bigger picture your oil is f**ked now its thined out which will damage your bores.

I cant see how fuel gets into the oil, ie its sprayed into a chamber compressed then detenated and push out the exhaust valves.

You must have some bad underling problem eg craked head, head gasket to oil, valve guides, oil rings.

I only just replaced the oil 1 month ago, I had 245rwkw before I shaved down a restricting turbo spacer to the correct diameter. Car is a lot faster now... I estimate about 260rwkw...

Plugs look good, a nice bronzy like colour but not too light...

So you reakon I should change the oil again? This motul stuff aint cheap

[GunMetalR33]

There's the reason for your flatspot - the engine probably can't ingest air at 19 psi. Back the boost off a bit - I reckon 1 bar is more than enough.

Yea, I will re-grap the plugs to .75 then wind down the boost till she stops flat spotting. Does anyone know the coversion between psi and bar, as in what is 17psi in bar?

[Lazy-Bastard]

If this is the case...maybe see if you can borrow a set of splitfires for a day and gap your plugs to .8. I still had major issues with those bosch coil packs (if you're still running them?) and haven't had a hint of a miss since I got the Splitfires

With such a smal gap, you are probably not burning the fuel properly. Unburnt fuel is then being dissolved in the oil on the cylinder walls and taken down into the sump.

Open the gap. (usinga really small gap is only masking the real problem)

[leech_]

hehe yea thats is true i however thought he mentioned you were up around the 280rwkw which is pushing the limits of standard internals... and shauno just you wait till you put out that power lets see how long yours lasts