oil pressure drop at temp?

Thinking about it, those that get nervous about oil pressure should never put a gauge on a small block Mopar. With a stock pump, you're unlikely to see much over 45 psi no matter how high you rev it. And idle, well, it depends on the engine. 15 at hot idle isn't uncommon. Officially, 6 psi is plenty. A lot of people say that as long as the lifters aren't clattering at idle, it's fine even if the gauge says 0. I've personally seen the one in my Jeep down at 7 psi with the oil good and hot, engine sounded perfectly normal (and the pressure came right back up with some rpm).

what's cool, is below 10psi the gauge flashes and tells you that it's single digits. Had that happen a few times as it almost dies around 200-300rpm. These dakota Digital guages are friggin awesome. Analog gauge with digital displays for cool stuffs.

curtis73 wrote: 20 psi at idle is perfectly normal. Most low oil pressure sensors trip the light at 12-15psi

Most of the old idiot lights were more like half that, and the owner's manual would tell you the light flickering on a hot day with a sump full of SAE30 was acceptable.

Sounds normal too me. My car idles at 15 psi hot (800rpm) but carries 40psi of oil pressure at cruise rpm. (2400)

I'm still changing the oil tomorrow night. Signed up for my first event of hte season earlier. June 18th.

in 1979 Fiat stopped equipping their cars with oil pressure gages. Too many cars went back for repairs for "low oil pressure" over the years. Basically they would start with 45ish psi and once warmed up, would idle with 10. Perfectly normal for the Twin cam, but it freaked people out, so the gage went away and was replaced with an idiot light.

It's a SBC. If it isn't rattling, it's got plenty of oil pressure.

Back in the AC VW Type 3 days, when they had the automatic transmission and some miles, the oil light would blink.

After checking with a gauge to be sure, the fix was to install the sender from the 36 hp. engine, it was adjustable. Just told the customer we installed a new sender

Always said, if your pressure is good on the highway, don't worry about the idle pressure.

New problem: alt charging at 14.6v at idle. 16.5v at cruising speed (2700 rpm). I'm thinking larger pulley? Or new alt.

Also.... likely needs a new thermostat. Climbs to 210-ish before coming back to 180-ish first time it warms up.

New alt, or regulator at least if its external. Should never get that high regardless of pulley or amperage, regulator should pull that voltage down.

Thermostat isn't out of whack, sounds like every American V8 that I've ever had, Rover too. Wouldn't worry about it.

Bad alternator or maybe bad wiring, they'll run wide open if the sense wire is disconnected (should either be connected to the big B+ terminal or run back to the + post on the battery). A pulley won't fix this. Don't forget to check the battery water level, it will likely be low from the overcharging.

Definitely not bad wiring. There isn't an old piece of wire left in the truck. So likely a fried regulator.

Just checked the price of an alternator. I am still laughing. $30 for a reman.

Yeah, Delco starters and alternators are pretty much consumables and priced that way too. I'd spend the extra money on a lifetime one from your preferred parts store, then when it inevitably pops a year or three later you don't have to buy one again. Make sure it turns smoothly and have it tested before leaving.

The TBI 350 in my 88 C20 does the same. I run 10-40 in the (Florida) summer, 10-30 in the winter, non-synthetic with a qt of Wynn's oil treatment. Cruise when hot is about 30 to 35 PSI.

Miles are unknown, somewhere beyond 350,000. Odometer broke years before I got the truck, reads 242k.

I've had it for 8 years, and it burns 1/2 quart between the​ twice yearly changes. Puff of blue smoke from the worn guides at startup, which I've decided to ignore.

So what's the problem again? Sounds good to me.

It's almost like you've never owned an old-school small block before

In reply to BrokenYugo:

Yep. I remember that from my 3 years at the zone. I still have a starter on warranty with them when this one bites it.

This is my first OLD school. All my previous GM small blocks at least had TBI.

also... this was the easiest alternator pull I've ever done. I think it literally took longer to find my long ratchet than it did to pull it. Love this old stuff.

Is it for sure not the wiring? It sounds like the sense wire from the battery post to the regulator is AWOL or otherwise non-functional. Although that could, I guess, be an internal fault on that circuit.

The sense wire loops from the post back to the plug. I checked both ends of it to make sure and it was reading the same ridiculous high voltage. The bearings in this one are a little noisy anyway so I'm ok spending $34 for a new Lifetime warrantied one. Call it insurance.

Also am hedging my bets and sticking a quart of rotella in with this oil change. I know it's likely overkill, but I am not ready to rebuild the motor from a wiped cam. As much as I'd love to do it.... the wife would likely have my head on a platter.

pres589 wrote: Is it for sure not the wiring? It sounds like the sense wire from the battery post to the regulator is AWOL or otherwise non-functional. Although that could, I guess, be an internal fault on that circuit.

Also makes me wonder if it's a 3-wire alternator with a 1-wire harness.

-Hans

WEll, it kinda looks like a junk yard alternator so who knows what it was from. it was wired the same before I replaced everything, but it was using the only remaining "working" gauge in the original cluster. With as hacked as everything was under there I wouldn't have trusted it to be right much.

I love this... I walked into Advance to pick up my order and they give me $105 back for cores. In reality, I bought an alternator, 8 spark plugs and a belt for $57, and the rest was refunded.