Hawghead

High all,

Just bought my first Cutlass, a 1969 Supreme Holiday Coupe, the P/O did a lot of work on it (based on the stack of receipts I got with the car) but unfortunately he had passed away before I bought the car, and I'm unable to ask him any questions. Some basics about the car. It's a 350 with I'm guessing a Turbo 350 (haven't had a chance to crawl under it and verify that yet) headers, 4 barrel aluminum manifold and Edelbrock carb. According to some of the shop paperwork I have it's been rebuilt with supposedly 10.5 to 1 pistons, a Lunati Cam (specs unknown, does have a little lope at idle.) and the heads had "larger 350 valves installed" with some mild porting work done to them. (why any one would bother with 3A casting heads I don't understand)
The issues I have are first the oil pressure. When first started pressure is about 40 psi at idle and and about 50 psi at 1200 rpm. As the engine heats up pressure starts to drop across the board. When full warmed up (205-210 deg.) pressure has dropped to about 8-10 at idle (750 rpm) and about 35 at 2500 rpm. Now even with the low pressure at idle, it comes up to about 30 psi as soon as you crack the throttle. On the day I brought it home it was over 90 degs. out and I got stuck in afternoon rush hour traffic. Temp climbed up to 215 while stopped and oil pressure was barely off the bottom peg. Even then I didn't hear any knocks, or lifter rattle. I'm not sure if this is indicative of bearing clearance, or oil pump problems and was thinking of trying an oil change with Brad Penn straight 40W and a Wix filter and see if that helps. Thoughts?

Second is the temperature, not sure if it's out of line but it's a little higher then I like, especially on these hot days at long stop lights. I understand most 350s used a 195 degree thermostat and was considering changing it to a 180. Thoughts?

Thanks for your time, looking forward to your input.
Scott

Octania

I thought the thermostat was used to set the operating temperature, not adjust for overheating. Frankly, 215 is not really overheating if your cap holds pressure OK. I think 240F is the boiling point for pressurized coolant. It seems to me that if you are not comfy with 215 stuck in traffic, then perhaps enhancing airflow at idle such as the shrouded clutched 6 or 7 blade fan the factory used, would help. What is your current fan setup? Is your radiator small [thin, 2- or 3-row] and/or clogged from years of scale buildup?


Some models also have a thermal vacuum switch which shoots full vacuum to the distributor in the event of high coolant temps, which greatly helps alleviate heating issues. Many times, these get disconnected because the owner has no clue what it does, and they think they are "getting rid of smog crap".

Get yourself on Wildaboutcars.com [free]
Get the factory CSM Chassis Service Manual [paper copies or CD also available (ePay)]
Read it

70cutty

I know this sounds stupid, but have you checked your oil level??

The first I would've done is crawl under take a look at everything and change the oil before driving around.

jaunty75

You could try a seance.

CutlassDad

Yes, the the 'stat sets the temperature, up to the cracking temp[(180 deg for our example), but at 205- 210 degrees the 'stat is fully open. With the thermostat fully open, the coolant temp is determined by coolant flow, radiator airflow, the engine load, and the air temp entering the radiator.

When idling in traffic, the engine heat load is low.Tthere will be some heat from the trans cooler (if equipped). Coolant flow from a good W/P impeller and airflow from a shrouded fan are the best ways to improve this.

Hawghead

The fan setup is a 6 blade flex fan with the factory shroud. Unfortunately I think it's only a 2 core radiator. The good new is that when I had the cap off and up to temperature the flow through cores was excellent, the coolant was clean and I couldn't see any scale build up at all. Additionally when I took the cap off with it running and up to temp, there was no pressure built up. I may be a little over concerned about the temperature after all.

Yeah I did check the oil level and it was fine, I'm changing the oil today.

CutlassDad

Does the coolant temp come down when the car is driven?

oldcutlass

Your temps are fine. What gauge are you using for the oil pressure readings? I would double compare the readings with an aftermarket mechanical gauge.

Oldsmaniac

My, 2 cents, your temp gauge may be off as you should be building pressure in the hoses and you say you are not. Oldsmobiles engines in stock form were not known for high oil pressures. The gauge readings you have seen are about normal for a stock oiling system. Yes oil thins when hot and thus the oil pressure lowers.

Sugar Bear

I wouldn't go to straight 40 weight unless it was used only in hot weather and on long trips. Try a 15W-40 or a 20W-50. Those oil pressures are not concerning, the engine may have been built with slightly more bearing clearance than normal to allow for more oil in the bottom end.

A 180 stat would be fine, as correctly stated by previous posters a properly operating thermostat only sets the minimum operating temeperature.

Hawghead

Yes temp does come down to the 200-205 range when moving down the highway at about 2500 rpm. It does start to come up a little 205-210 as cruise rpm reaches toward 3000. (Don't know speed the speedo doesn't work.)

The car has a set of autometer gauges installed, both the oil pressure and the temp are mechanical gauges. I did notice that the line from the engine to the gauge has a lot of air pockets in it. (when the engine is shut off, didn't notice when the engine was running) should that line be bled to remove the air, or would it just drain off when the engine was shut off? (Been a long time since I've had a car with aftermarket gauges in it.)

When I said it's not building pressure I meant the one time I took the radiator cap off at temp to observe the coolant flow through the radiator, I didn't get any coolant trying to flow out past the cap as I opened it. When the cap was open the coolant level was below the level of the cap a couple of inches so that the first two rows of tubes were exposed and as I said earlier there was good solid streams of coolant flowing through the tubes and I couldn't see any clogging or scale build up and the coolant looked like new antifreeze.

The plan was just to use the 40 weight for the summer, I'd switch to a lighter oil during the colder months. Although this is strictly gonna be a fair weather driver not a daily driver (I couldn't afford the gas ) This car is strictly for driving for the purpose of having fun, not as a means to get from point A to point B.

Anyway I'm probably just being a little paranoid about the temperature and the oil pressure, probably a side effect of to many decades of driving cars without proper gauges and being blissfully ignorant of was is going on with the engine. I'm just going to clean it up a little and drive it and have fun for awhile before I tear it down to parade rest and build the street and highway cruiser I want.

Thanks for all your input I really appreciate it.
Scott

70cutty

As far as the bubbles go in the gauges, you are fine, the line is pressurized and that's how it reads not by the amount of oil that goes through it.

rustyroger

Oil needs to get round the engine asap after startup, straight 40 isn't good for this. 10w40 should be fine for regular street use, you will be changing it regularly won't you?.


Roger.

johnnyjaws

make sure your belts are all tightend to the right specs

Hawghead

Well changed the oil, filter and the thermostat. Good news is oil pressure is up across the board, still lower than I like at hot idle (8-10 pounds) but 30 psi around town and 48-50 at highway speed. I'm guessing the low idle pressure is just a stock pump that's seen better days, and/or bearing clearances getting a little loose. I'm sure the motor could use a rebuild but I'm not going to bother until I can build a 455 for it.

Still hotter that the hubs of Hades here but temps are better with an observed max of 210 at a long stop light and 190 down the highway. Probably due more to a fresh coolant change than anything else.

Now the bad news, as I was pulling into the driveway I smelled something odd not oil or coolant but more chemical. Then the smoke started pouring out from under the hood. Shut the car off and opened the hood and saw smoke just pouring out of the alternator. I had replaced the valve cover gaskets yesterday and when I went to start the car this morning the battery was dead. I figured I had left something on when I last ran it and drained the battery. I replaced the battery and when I started the car after changing the oil and thermostat everything was fine. The valve cover on the passenger side sits very close to the rear of the alternator and when I put the valve cover back on I could have knocked something out of place.

Anyway I'm obviously going to have to change the alternator, should I also change the voltage regulator at the same time as a matter of pay me now or pay me later and to ensure that something in the regulator didn't go and cause the problem with the alternator. Anything else I should check while I'm at it?

Thanks for your help,
Scott

Sugar Bear

About the pressure at idle, what is the idle speed? The readings you are getting are not concerning, the lower pressure may be indicative of a higher volume (a good thing) due to bearing clearance on the higher side of the specification. If the readings stay where they are and the engine sounds good, forget about it and drive the car A LOT

About changing the regulator at the same time as the alternator? Yes, change it with a quality replacement at the same time.

Hawghead

Yeah I'm gonna stop worrying about the oil pressure, it just that it's lower at idle then any other car I've seen. But I'm just going to drive it until it dies and then but a 455 with 4 speed in it. Oh to answer your question idle speed is 750 in gear and 800 in neutral.

Thanks,
Scott

rustyroger

Unless you beat it like a ginger step child that might take a while.


Roger.

brown7373

First of all, 200-210 is not too high. According to the 1972 Service Manual, the engine coolant light does not come on until the temp reaches 248 degrees (258 on Toronado). Pure water boils at 247 with the proper pressure cap, and proper coolant mix raises the boiling point further. 1969 may be slightly different, but not much.


Just because you see good flow, doesn't mean you don't have a restricted radiator. The bottom is where the sediment gathers, not the top, and it would be the lower tubes that become restricted. Only way to check that is to remove the tanks.


The operating temperature has nothing to do with the thermostat opening, except for very short runs. Once the thermostat is open, it is open. I don't believe there is any difference in the opening size of a 160 compared to a 195. If you don't have enough cooling capacity to keep it at 160, or 180 or 195, it will rise to where you do have enough cooling capacity. Cooling capacity is a function of the radiator, water pump, pressure cap, coolant mixture and air flow. Most people feel the clutch fan is the most effective to move air.

Oldsguy

I would suggest replacing the flex fan with a stock fan. Also, make sure that your hot wire to the coil is not 12 volts, that should be a resistor wire which lowers the voltage and protects the coil from boiling over like yours did.