911! In need of help

[JamesDean305]

Please help!! I recently bought an 86 g.n! The car was not running when i had bought it. The car had been sitting for quite some time. When the car is started it sounds like it is missing rlly bad and wont stay running unless i give it gas. I have replaced the coil, module, plugs (ngk 2771), wires (accel 8.5), fuel injectors (60 lbs), w/ matching chip, fuel pump(Walbro 255), crank sensor, and cam sensor When i got the car the trunk was filled full of misalliances parts. So, the cam sensor i used was on that was in the trunk. I had bought the cam sensor setting tool and followed the direction to the tee when installing. I believe it was installed correctly. Yesterday i did a compression test a found some strange readings.. cyl 1 had 55 psi, cyl 2 had 55 psi, cyl 3 had 60 psi, cyl 2 had 55 psi, cyl 4 had 50 psi, and cly 6 had 60 psi! cyl 1,5,2 and 6 where fouled out just after a cppl time starting, and cly 3 and 4 where good just with what seamed a lot of gas on them when pulled. Blown Head Gasket? Bad cam sensor??

 

[SHADOWII]

Are you sure...

those compression readings are correct? If so they are very low. Did you check the c/r after the engine was warm?

 

[JamesDean305]

I cant keep the car running long enough to reach ideal temp. im pretty familiar w/ sbc but this is my first T.R. Whats the c/r?

 

[JamesDean305]

duh! Compression readings....

 

[SHADOWII]

You got it..

my personal preferance is a min. of 130, some like 120. Mine at present are 153-160. the oil could be from bad valve seals, but w/that low a compression, either the valves aren't closing all the way or the rings are shot. Typically, a blown h/g will be between two cyl's or blown into the intake or exh. side. pull the dip stick and check the oil for water or anti-freeze in it. the oil will look milky if mixed.

 

[JamesDean305]

I thought The C/r readings where extremly low myself. I recently changed the oil and it looked old but good. I've heard if the rings are shot you can put a little oil in the clyinder and it will temperarely bring the cylinder back. have you ever heard of this??

 

[SHADOWII]

yes, it will raise the comp. level.

 

[turbofabricator]

A leak down tester will show you a better picture.

Remove the valve covers and loosen the rocker shaft bolts about a full turn. Start engine and see if it runs better. (temporarily with the valve covers still off) If so, it has too much lifter pre-load and not closing the valves. If that is the case, then it's time for either adjustable push-rods or measure and buy the correct length. If by chance the car came with roller rockers, you're in luck, just re-set lifter pre-load and you're on your way. (providing there is enough adjustability left in the adjusters) Roller rocker require a .100" shorter push rod than stock. Or you can use a Small Block Chevy lifter to accomplish the same thing IF it has a flat tappet cam.

 

[Heg87t]

Did you change the fuel filter also? What's the fuel pressure now?

Is the check engine light on when running?

Did you replace the vacuum lines? Any loose connections after the MAF sensor or intercooler?

 

[JamesDean305]

Thanks, that was my next move of choice. And i dnt beilive it has roller rockers. I had the vavle covers off when i set the timing and they seam to be stock. I dnt knw if it has a flat tappet cam either because i havent went that far into the motor. The car kinda got passed around tryning to figure out whats wrong. Thanks again I will check tonight if the valves seem to be stuck open.

 

[JamesDean305]

Yes, I change the fuel filter. I set the regulator at 38 psi and i believe it hit 43 w/ the vaccum line off. I also went threw the vaccum lines and they seemed to be ok. I checked the MAF sensor conections and it looked pretty good. I also made sure that my intercooler pipeing was tight and secure. I was thinking that the cam sensor i installed was faulty simple because of the shape the plugs where in when i pulled them. I guess that could be frm bad rings. Im going to check the valves tonight and see if they might be stuck open because when i happen to keep it running i do get a back fire frm the exhaust

 

[JamesDean305]

also I dnt believe the check ingine light is on. I can check to make sure

 

[Heg87t]

also I dnt believe the check ingine light is on. I can check to make sure

If the light is on pull the code and see where it leads you.

 

[turbofabricator]

If it's popping it still might be a bad cam sensor adjustment. VERY common to get it wrong. Loosen it and rotate about 1/8 turn then start and see if it runs better. If worse, turn back 1/4 turn the other way, (1/8 back to original, then an 1/8 more.) If it runs better, then you'll know it's the cam sensor setting.

Still be best to start over with the sensor setting. You MUST make sure that #1 cyl. in at 25* AFTER top dead center (ATDC) Make a mark that is 1.5" counter clockwise from the factory TDC mark. (looking at the front of the motor) That mark is what you line up to on the zero mark of the plastic timing indicator. The #1 cylinder is the drivers side front. (just in case you are a Ford man and are use to the passenger side being #1)

 

[JamesDean305]

I was thinking that could be it to. When i set the cam sensor before i used the casper cam sensor setting tool witch lights up a red L.E.D light when your on the money but i guess i could be still a cppl degrees off. I spoke w/ a friend at Harper racing in Ft.lauderdale Fl and thought that C/r where extremley low and that my rings where stuck.

 

[gunslinger]

Almost everyone seems to be ignoring the obvious....it has low compression. Since it is equally low in every hole, it's likely a mechanical issue. Pull the timing cover off, and see if the chain jumped a tooth. If not, the rings are likely stuck in their grooves, and the engine will have to come out and apart anyway.

 

[chadly]

Almost everyone seems to be ignoring the obvious....it has low compression. Since it is equally low in every hole, it's likely a mechanical issue. Pull the timing cover off, and see if the chain jumped a tooth. If not, the rings are likely stuck in their grooves, and the engine will have to come out and apart anyway.

Agree. Very low compression.

 

[JamesDean305]

Thats a rlly good point! W/ the way its runing it sounds as if the timimg is off. Thanks for the positive info

 

[HelloBozos]

First starting

I was thinking that could be it to. When i set the cam sensor before i used the casper cam sensor setting tool witch lights up a red L.E.D light when your on the money but i guess i could be still a cppl degrees off. I spoke w/ a friend at Harper racing in Ft.lauderdale Fl and thought that C/r where extremley low and that my rings where stuck.

http://www.turbobuick.com/forums/engine-tech/342086-how-set-cam-sensor-first-start.html

Read this above...it takes couple read's to get it right,It's pretty much fail proof if fallow to the letter.

Enjoy!

 

[SuperCPA]

If it still has the original timing gears and chain, I would highly recommend changing it out for a new non plastic gear & chain set anyway. The original set is prone to cracking and loosing teeth.