got a miss/igniton problem....compression. SUGGESTIONS NEEDED, HELP

[KEMP]

So still on my conservative tune, i decide to put a little race gas in, it ran fine, then acted like it flooded and started a miss.

i checked plugs and a few were fouled looking, so i replaced them.

didnt fix, its missing completly in cyl 4, if i unplug the injector, nothing changes, if i unplug the coil, nothing changes.

i do the same on cylinder 3, and it barely makes a difference

i have no ided what could be wrong, maybe killed a couple injectors? timing is fine, it didnt jump.

at first i could drive it with a miss at idle and cruising, if i pushed it into boost, it would stop missing and roll out like normal. then it got worse after more driving, and i had a maf wiring prblem, but then fixed that, and the worstening miss continued.

i compression tested it, 1&2 were even compression(i dont trust my gauge cuz i dropped it, so i jut look for consistnce in the readings.)

3 &4 were even, but significantly lower than 1 and 2.

any help? what could have happened.

i didnt raise boost, even when i put 110 CAM2 in it, i just wanted to try racegas in it.

but help me out here please

[KEMP]

also, no overheating, no smoke(besides black) no fluids are being lost, burn, or mixed.

[Ca_Silvia]

What were the compression test numbers?

[KEMP]

i honestly didnt even look, i looked at consistancy, because i proved my gauge to be wrong after i dropped it.

i tested it against my uncles comp tester.

somewhere in the neighborhood of 100 1&2 and 50 3&4

but those numbers are not correct, again, my guages reads lowww

[sjbsuperman1425]

i'd get a new gauge and do it again.

[KEMP]

it doesnt matter, either way, 3&4 are low, what happened? lifted back of head?

[Ca_Silvia]

Doubtful, if you lifted the head at all you would have coolant/oil coming out.

Just sounds like you need a rebuild man.

[bentvalves]

who do you have building your engines for you??

Send me your longblock and have me build it already.

[KEMP]

ha, its not the bottom end, it was built by a very reputable shop, performance motorsports, noone has had any problems with them at all.

the car does not smoke, leak, or lose any fluids.

and i dont need a rebuild, the bottom end is solid and has shown no signs of problems, the leak down test was just fine.

is it possible for it to lift between cylinders 3&4? that would cause it to do this.

it has low compression in 3&4, no signs of the bottom end being problematic and i know the bottom was built by a very good shop, that noone has any complaints with.

what else could have happened?

[KEMP]

and something else is kinda weird.

i know its not missing do to spark because i have tested that, and usually my AFR's at idle are 10.8 and now they are 14-15. leaving me to belive, cylinders 3&4 are just pushing out heir compression adn those injectors or one, is fried from the race gas, causing a lean reading do to the unburnt/mixed air being shot out the exhaust valves on 3&4

any thoughts?

[bentvalves]

Your thinking to deeply into this. Why would race gas kill a fuel injector? Do a wet compression test (tblspn of oil in cylinder) on cylinders 3 and 4 and see if it changes. If numbers shoot up, you need to re-ring it. If the numbers stay low, suspect bent/burnt valves. No its not possible that its lifting the head between 3 and 4 on boost. Are your headstuds torqued down? Double check.

[KEMP]

i did a wet test, numbers were consistant, i also lossened all studs then retorqued, and it was the same.

any other suggestions?

im thinking burnt valves.

[bentvalves]

if you poured oil into cylinders 3 and 4 and did compression test and they stayed low then yea look at valves.

[ca18detgabby]

so I will say it before Dee does..... Good GOD what are you thinking?

running untuned is stupid, experiementing on an untuned motor is rediculous.........

ever consider a leak down test?

PS how does one burn up valves running heavier octane than needed?

[bentvalves]

how much boost did the engine see on this "conservative" tune.

[MeanGreenS13]

iirc you said you were running at 10.0 or 10.5 AFR at Wide Open Throttle... That my friend is what happened, you wiped out your rings. I can almost promise you that.

Running that rich, you probably washed down the cyl walls. Fuel is not a very good lubricant, and you probably just flat out wore your rings down to almost nothing.

[boost_boy]

i did a wet test, numbers were consistant, i also lossened all studs then retorqued, and it was the same.

any other suggestions?

im thinking burnt valves.

Sorry bro, burnt valves don't happen with the CA. What you probably done is what MeanGreenS13 said and thats cooked some rings or something. I know you want answers, but you are learning about this engine the hard way. You've raced some pretty fast cars and you pushed your car pretty hard to win some races, so you was bound to get a failure. Because your engine is not fully/completely tuned, you are running on semi-guessing and that's bad; especially with W.O.T applications. My 240 has 750cc injectors, big/dumb turbonetics hairdryer, cams, standalone, MSD DIS-2 ignition system, and 13years of experience and I still cringe at W.O.T runs. Even though I am my own tuner and I would like to think I kow what I'm doing, you don't know what events is taking place with your motor until it tells you. So in all, time to tear it down and see what you've busted-up again.

Dee

[KEMP]

ok, not to be a d!ck, but if it were rings, the oil in the cylinders on a comp test would show rings, which it didnt.

not a drop of smoke, not a drop of oil in the cylinders.

10.5 afrs ?? yes, but once i got a little tuning we got them to 11, rich will not kill a motor in 2 cylinders and have perfect comp in the other 2.

you cant answer rings to every engine problem.

we'll see today when i pull the head.

[KEMP]

soo, just pulled the head, got it down to an hour job

hg between 3&4 was blown, not just blown, but missing, had a gap about 1/4"

and a nice groove in the head between those cylinders about 1/8-1/4" deep and looked like someone took a grinder to it, the groove was completly smooth.

not sure how this happens, but please help if you know, the bottom was perfect, no scoring or any flaws.

i need a new hg and head, but other than that i wanna know why this happened so it doesnt happen again.

im thinking bad injector in one/both of those cylinders, and leaned out and combustion temps went way high and melted the head, but the pistons had NO det marks...

[davidricardo86]

Got pictures?

[bentvalves]

^

[ca18detgabby]

in for carnage pics