Oil Pressure

[Paddywhack]

Hi all, new here. Just picked up an '86 coupe that needs minor work, but is still driveable. One of the questions I have is on the oil pressure. Oil pressure guage reads 42 to 52 most of the time, but when accellerating it sounds like there is no oil getting to the rockers. The car is also pinging heavily under a load. Never a problem starting though. Any thoughts on these matters will be greatly appreciated. Like I said, I'm new to this, comming over from the Tri-Five Forum. Traded my '57 for the vette and its a whole different ballgame under the hood now! ;help

 

[grumpyvette]

first obvious thing thats mandatory is youll want to temporarly install a second oil pressure gauge to verify the current pressure readings and ID bet the current gauge or sensor are DEFECTIVE and need replacing.

ideally youll want to install a good quality oil filter and do an oil change with a decent 10w30 oil like MOBILE 1 or HAVOLINE,SHELL,TEXECO etc, and have about 20 psi at 750 rpm idle speed (once the engines up to operateing temp of about 200F and see the gauge pressure hit 60 psi by 5500rpm, if it doesn,t youll want to evalueate the pressure and decide if you need top rebuild or replace components
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92687

keep in mind the (valve train rattle) might be the sound of DETONATION, in th cylinders so Id swap to HIGH TEST GAS and back off the ignition advance to see if that reduces or completely eliminates the sound

 

[Hib Halverson]

42 to 52 psi is more than adquate oil pressure, however, if you think there's problem there, do what "grumpyvette" suggests and validate that with a scond, known-good gauge.

As for the noise while accelerating that sounds like rockers, it's highly unlikely that's the source. If you had a valvetrain problem that made noise, it would be there all the time, regardless of acceleration, decel. or just cruising.

I suspect that noise is something else and, since you say it's pinging under heavy load, I'm going to guess the engine is detonating at lighter loads as well.

First, I'd fill the gastank with premium unleaded then road test. If the noise persists, I'd check the timing. Then, I'd check to make sure EGR is functioning properly. After that, I'd make sure EST is functional. Lastly, just after you turn on the key, do you see the check or service engine light coming on then going off at "bulb check"?

As for it being a whole new ball game....well, it may not be as new as you think. The engine is that 87 is still a Gen 1 Small-Block V8 and computer controls or not, an engine that's suffering detonation when it shouldn't be is still approached in about the same way, ie: try to pinpoint the cause of the detonation and fix it.

One thing that will be different is to sucessfully service/maintain a C4 Vette you must have the factory service manual. That may have not been true with the Tri-5.

 

[Paddywhack]

Thanks Grumpy, I did change the oil and filter, Shell 10 W 30. I will pick up the second guage, Harbor Freight actually just opened up around here recently. Hib, ran a couple of tanks of hi test, didn't notice any difference. The service engine soon light does come on occasionally while driving. I'll check the egr and the rest. Any Ideas on why the idle is fine around 700 sometimes and other times its up around 1400 or so? Thanks again guys

 

[Hib Halverson]

If the service light is coming on, the first thing to do is find out why. Please pull the code(s) and post them.

When the idle is unstable that means either there's a mechanical problem with the throttle linkage or the TB which prohibits the throttle from fully closing or the engine controls cannot control the idle. If the latter, there's more evidence there's a problem.