Oil pressure (buying my first vette).

[xlwhellraiser]

Hi, I was checking out 85 L98 vette and the oil preassure was weird. Two previous owners were both over 50 and the current owner claims that the motor has been re-built by the previous owner.

The preassure guage drops down to 18PSI at idle (albeit check engine light was on). However, once you give it gas the PSI would rocket to about 65-68PSI. I know that 65PSI is very good pressure, but 18 at idle seems weird.

The vette has 140K miles on it, and no leaks and in great condition. Its gold too.

I was just wondering if this is right??? It doesn't seem right to me.

Also, I have a choice between 84 vette with 81K on it that needs few gaskets, mainly due to sitting, and a set of tires for 4700, or this one for 5500.
What do you think>???

Oh, and there was another one that has re-built engine, and tranny for 6000 (170K on the odometer). All of them have around 35PSI at idle too.

????
Thanks.

 

[c4c5specialist]

HI there,
Too low.
Allthebest, c4c5

 

[G Winter]

It is possible that when the engine was rebuilt that the cam bushings were not replaced. I have seen those kind of oil pressure results from that.There are many diff ideas of what an engine rebuild is. Some will throw rings, bearings and a valve job in it and call it a rebuild.:ugh

Glenn

 

[3dale1]

18 is a little low in my opnion, but I have seen some good running, high mileage V-8's with less than that at idle that are fine.

I think that you should give extra consideration to whichever car you are thinking about that is overall the cleanest of the 3 (esp paint and interior) and not so much weight on the engine. If you can get the 84 with 81,000 for 4K, that sounds interesting. however, don't be afraid of the 85 with the mileage if it's a nicer car; there are lots of SBC's, crates, and used L-98's out there.

I like my 85; its been flawless since I bought it 2 years ago. Everything works well, and though it could use a few things (like most) it's been great. It holds 29-35 at idle, and 53 plus cruising, assuming the guage and sending unit work right.

AND FWIW, I paid 4100 for mine. Good luck, and let us know more about the cars you're looking at!

 

[vader86]

18-20psi at idle, if the engine is hot, is fine.

 

[xlwhellraiser]

Well, the corvette is gold and the guy is asking 5500 for it. Its in pristine condition, the shifts are firm and the oil was always cooler than the temperature. the temp was 205 and the oil was 195. He told me that he drove the car with that low of a preassure for three years now. Albeit, he only put 3K miles on it in those three years.
The engine starts up fine, although it takes a bit to start it. I know L98's and this one took a bit longer than I like to start.

The 84 C4 's paint is kinda flat compared to other ones, and it has a little oil leak on the pan, and needs a new radiator. It was the only corvette that ran at 195 the whole time I tested it. All the rest of them ran at 205-235.

The gold one has a bit of a shake when put in gear.
The rest of the 84's I drove did not have that, hence the mileage.


The 84 corvette with 81K felt like it needed a tune up, and was slow. The l98 felt better, but it did not seem to feel that much faster.

Its funny, I just sold my 89 firebird with a 305 TBI that was built for more horses, and the 305 felt much faster then all the corvettes I drove. How's that??? I am sure its just a different feel when you drive the vette, and you don't really notice that you're hauling butt.

All in all, I am torn between the 84 with 81K on the odometer, or the imaaculate 85 with 140K.
I'd rather put 60K on a car, than start up with that much, but if the motor was re-built then we'd be OK.


How can I find out if the motor was built???? What can I look at??

 

[Vettefan87]

HI there,
Too low.
Allthebest, c4c5

Ditto on that...When I had my motor rebuilt the first time...or second...I noticed my oil pressure get down that low and before long I had bearing knock.

 

[xlwhellraiser]

Sorry, I forgot to mention that once I get on the gas the preassure gets to about 65 plus.

Is that good???


I've had countless chevy's and have heard about low oil preassures at idle, and how OK they are.
I've noticed that the car idled a bit lower at around 550RPM, maybe thats why the low preassure. If idle increased I know the oil preassure would.

Man, am I picky or what???:crazy

 

[Vettefan87]

Well I would have this type of oil pressure when the oil temp was around 170ish, not when the motor was entirely hot. Right now my oil pressure will not drop under 38, that is with the oil hot, and the car idling.
​

 

[3dale1]

550 idle in drive is good.

Few obvious quick things you could look for on the motor that aren't truly indicitave of a rebuild but may lead you to believe it is are good quality headers, roller rockers, better intake system, clean gasket tabs, and receipts if you haven't asked yet. I'm sure the current owner knows the prior owners name, the one who did the rebuild. Call him too.

I like your choice of the words pristine and immaculate.....go for the 85. From your posts it sounds like you like the gold, too.

 

[xlwhellraiser]

Well. I'd rather have a vette with better oil preassure.

I am going to throughly look at that 84 with 81K tommorow.

So, if you guys want to give me some pointers about what I should look on in a vette???

What things usually go wrong, and what is the usual oil preassure.

 

[MoeJr]

My 84 has 93k on it. Going down the highway I have 55-60 psi oil pressure. At hot idle just getting off the highway it will dip to 19 psi. 18 psi is fine for that car. Rule of thumb is 10 psi per 1000 rpm.

Like I said in a previous post. Don't let that 84 with 81k scare ya. Get the TB's balanced and it will be a different car.

 

[xlwhellraiser]

When I give it gas it goes up to 65 PSI. What do you think about that???


Tommorow I am checking out the 84 corvette, and I'll report with results.

 

[MoeJr]

65 psi like that is not a problem.. Here in the fall and winter on cool to cold mornings my 84 will hit over 70 psi. Had the car almost 4 years and have had no engine problems.