2nd3rd4thgen

where the header gaskets blown when he got the car or did they just go out. but the coolant temp sensor is a good thing to check..

ATAY383

when i got the car like a month later they blew out.

pyronotic138

iTrader: (1)

well. changed the temp sensor. changed the fuel injectors with a new set that i had laying around and checked compression at 125psi on all cylinders. checked oil. there is no coolant leaks. we still have nothing. i am going to change the o2 sensors but want your opinion before spend money on them. also does anyone think that the torque convertor could possibly do anything like this. or the transmission. it has a 700r4 swap (dont know why) but could the torque convertor or the transmission be bogging down the engine. it seems like when it shifts from 1st to 2nd its BLAH. there is no *****. **** a stocker has more shifting ***** than that.

96capricemgr

iTrader: (1)

The throttle was blocked all the way open for the compression test right?

That reading is like 75psi lower than I would expect from a stock motor and more than 100psi down from my heads and cam on stock shortblock motor.

Alex94TAGT

Eesh.

1) Do you guys have any idea what compression ratio this engine was built for? It's good that all the cylinders tested consistently close to one another, but unfortunately they were consistently low.

Curious: what color is the 'smoke' you're seeing come out of the exhaust? You said black, which would mean rich, but is it possible that it's blue? Could the spark plugs be getting oil-fouled and not carbon-fouled?

-----------------------------
2) Anyway, another thought: You said the exhaust manifold/header gaskets are shot. If this engine is indeed running in closed loop, blown gaskets provide another source for oxygen to get into the exhaust, which could then get picked up by the oxygen sensors. In which case, the computer will "think" the engine is running lean (when it isn't), and react by dumping fuel into the engine. This is obviously a big 'no-no' when using oxygen sensors, so definitely fix the gaskets -- before replacing oxygen sensors -- and be sure to reset the PCM.

-Probably not the root cause of this, but something to fix.

pyronotic138

iTrader: (1)

well i have alldata and according to that it says stock should be at 98 psi. thats a 10.4:1 compression motor. this 383 is at 125 psi. and the guy that he bought it from said when he got it was supposedly a 11:1 car. soo. any other help greatly appriciated

96capricemgr

iTrader: (1)

At 180K miles my 10:1 bone stock Roadmaster wagon cranked 200psi, the Caprice cranked 230 on a 100K mile shortblock with this heads and cam.

Cam impacts cranking compression so these are not exact numbers to shoot for but they say 125 is a BIG problem if the test was good and gauge accurate.

onephatZ28

iTrader: (8)

did you get some bad gas or low octane that last night you ran it? Just a thought.

pyronotic138

iTrader: (1)

who is they. and like i said. on ALLDATA. a computer service manual. says stock compression psi is suppossed to be at 98 psi. and this motor is at 125. meaning higher compression motor. i used a snap-on compression checker and then verified with another one from mac. so i dont think the gauges are lieing. and the cam is a CC306. specs that we know of as of now.

stock block with .30 over. CC306 cam. stock mildly ported heads and intake. forged 383 eagle bottom end with about an 11:1 compression ratio. SVO 30#. stock fuel lines. numerous new sensors. a tune on it still that ran the motor good back in the day. and the plugs have white on the tips. looks like a rich burn which i bleieve is right. anything else lemme know

FASTFATBOY

iTrader: (23)

This engine MAY have jumped time, it would explain alot.


The hard start, low cylinder PSI etc.

One tooth could have done it.


ALso what is MAP voltage at idle and cruise? Check the little seal where it goes in the intake.

David

96capricemgr

iTrader: (1)

I don't care what alldata says 98psi is HALF of what a stock LT1 should have. Maybe it is a typo and they left a 1 off the front of that number, who knows but they are wrong.

FASTFATBOY

iTrader: (23)

How many times did the engine spin over during the test? I was always taught 5 revolutions. You can watch the needle jump on the gauge 5 times....this insures you go through the entire 4 stroke cycle.


David

ATAY383

we watched the gauge spin like 4 times...

pyronotic138

iTrader: (1)

soo. tomrwo i am going to change o2 sensors. dont have any good way to check time on it. unless someone out there knows of a way. the map sensor voltage i will check. i have a question also. the torque convertor is a stock one on 700r4. if the torque convertor shitted out would that couse the loss of engine. the reason being i think. 1st gear floored shifts at about 6250. then hits 2nd and goes to about 2600 ish and climbs really really slow. almost like the drivetrain is working against the motor more than it should be. ??????????/

FASTFATBOY

iTrader: (23)

Uncap this car and go run it. With what you just posted could be clogged exhaust.

David

ATAY383

i will on friday because today i am getting the car worked on and tommorow the head gaskets are getting put on.

pyronotic138

iTrader: (1)

wel we decided to pull the motor out on it today. we noticed that 3 of the header bolts from whoever did the gaskets last crossthreaded the **** outa the heads. sooo we are going to fix it right. what would help people figure out whats up with this thing. i can run a datamaster but i need to know what the hell to do on it for everyone. i used it once on my car and didnt know what the hell i was looking at. also i checked the o2s and they are fine. tested good. soo that leavs us one step closer. or just one sensor less to worry about for now.

pyronotic138

iTrader: (1)

aynone think the torque convertor could be making this thing feel powerless. the car used to be able to spin through 4th gear. now the car has trouble spinning off the line. let me know. ???

beeker82

3 pages and no one has mentioned the opti yet?

onephatZ28

iTrader: (8)

Good point