Looking for some diagnostic help with the engine in my '73. The previous owner had the engine built about 18,000 miles ago per the list below my signature.

The engine is using both coolant and oil. Approximately 1 quart of oil per 1,500 miles and about 1/2 gallon of coolant every 1,000 miles. Both appear to be getting worse.

There does not appear to any oil in the coolant and there does not appear to be any coolant in the oil.

No external leaks.

When I first noticed the issue, the engine would produce a bit of white smoke when cold, if the engine was in park and revved fairly high. Now I can get a bit of white smoke at any engine temperature if in park and revved high. Don't notice any smoke during routine driving.

Haven't noticed any black smoke other than if I do a lot of city driving and then take it out on the highway and "blow it out" I get a little black smoke at first and then it goes away.

Engine runs strong and I haven't noticed any other issues.

The engine was dyno tuned back in 2008 and the compression test at that time was excellent. The tuner said the motor was very healthy at that time. I've pretty much babied the car so the engine has only seen fairly normal city and highway driving with a bit of spirited driving from time to time.

I'm aware that I could be looking at a head gasket problem but I've also been told that it could be an intake gasket and/or an angle mismatch between the intake and heads.

Is there a way to figure out the problem before taking apart the engine? What would a pressure test show?

Just looking for advice and comments to help me make a decision as to what comes next. I've done a lot of bolt-ons but have never taken an engine apart. Will likely have a mechanic look at this but I wanted to educate myself before trying to find a mechanic.

At first I wanted to fuel inject this engine but I am now leaning toward an LS swap. I do know someone who will buy the existing engine if I can sort out the coolant and oil use.

Appreciate any help.

DC

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In case it helps, here is what I know about the engine (N.O.M.) which was built about 18,000 miles ago:

Engine was built to be roughly the equivalent of the early '70's LT1 engines. I had it dyno tuned back in 2008 and the tuner calculated power at the crank to be about 330 HP.

Block: 1973 350 ci w/ 4-bolt mains (CE block)
Heads: Camel Hump Heads – 2.02 intake valves.
Exhaust valves may be 1.60 but not sure.
cc is not known at this time.
Hardened valve seats with 3 angle valve grind
Cam: Crane 967601 BluePrint Hydraulic Lifter Camshaft
RPM range 2000 – 5600
Duration @ 0.050” lift: 222/222
Valve lift: 0.447”/0.447”
Replaces GM 350 HP 3863151
Intake: Holley Contender Dominator II Model 300-36
Carb: Holley 650 w/ Vacuum Secondaries
Choke: Electric
Crank: Forged and balanced, standard stroke
Timing Chain: Edelbrock Performer
Pistons: TRW L2490F-30 Forged Pistons
Exhaust: Sanderson Cast Headers model QP1000 into 3” exhaust w/ turbo mufflers
Ignition: GM HEI
Fuel Pump: Stock mechanical
Transmission: TH400

 

Rent or buy a cooling system pressure tester and dont forget to check the cap.
Buy a coolant hydrocarbon test kit to check for an internal leak into the cooling system.

 

If you notice white smoke, it does point to head gasket -- OR could be intake gasket leak or mis-match. I agree you could try a pressure test, but it's not an overly complicated motor to pull intake, and then heads, with the motor in the car. If the motor only has around 18K and you like it for the most part, why even toy with the idea of swapping if the possible solution is head or intake gaskets?

Depending on how you drive it, 1500 miles per quart isn't healthy oil usage, but some would argue not horrible, either. If driven hard a good portion of the time, or depending on oil weight, ring gap, how the cylinders were finished and broken in, etc. it isn't necessarily true that a motor shouldn't need a quart before an oil change. There could be various reasons for that, and addressing the other issue may solve or partially solve the oil usage issue. OR, they may be completely unrelated.

No coolant in the oil, it is probably going out the tail pipes. You don't notice when you're moving because you're moving - and it's steam for the most part.

If it were me, I would check the entire motor out for evidence of external coolant leaks (is the water pump seeping, and it blows onto exhaust or under motor, and basically evaporating? - could be the case). I would run your hands around the pump, look all around the radiator, hoses, intake, etc. If everything is dry and intact, I would tear into the intake and heads and replace gaskets.

 

 

Definitely no external leaks

I do need to do this again. Last time I pulled them I had a different carb that was running very rich and all the plugs looked too much the same to tell anything else.

DC

 

I would do the coolant pressure test first, then pull a valve cover and look for excessive water in oil which will look like a dirty milk shake, losing both oil & coolant sounds like intake sealing issue, could be as easy as a bad intake gasket or mis-matched head/intake surface

 

i had put 186 fuelie heads on when i had my motor rebuilt years ago for the extra compression.
i was using oil, badly fouling the plugs, and coolant was disappearing as well, thought it was just coming out the overflow hose, but i didn't link the 2.
vette sat for 7mths whilst i had family problems.
when i decided to fix the oil problem, took heads off, turns out valve guides were worn out, the oil usage,
and the heads were cracked in 3 chambers, hence the coolant usage.
1 cyl bore had damage from water sitting in it for that time.
ended up ditching the the old cast iron and went modern alli heads.

 

Your oil consumption is not excessive so you really only have a coolant problem. As others suggested, pressure test rad but you may as well remove your intake and heads and inspect for signs of leakage. It's not that difficult on a sbc.

 

well that sux.

oil amount is not too bad.

you didn't mention blue smoke.

a little black smoke can be corrected.
rich.

now the coolant loss.
could be head gasket allowing over pressure of rad and
spitting out coolant.
more likely if you are sure it is not is a cracked head.

all this was already said if you read close.

 

and you need to find out asap as water
will bend a connecting rod and
then you won't know until the motor
gets real sloppy

 

It's easy to crush the intake gasket between the coolant and intake ports creating an internal leak (coolant into intake), so that would be my first candidate to check.

Like others mentioned, 1qt oil/1,500 miles is not ideal, but also not excessive. Unless it gets worse I wouldn't worry about it.

 

I did pull the valve covers awhile back. Everything looks good up top.


You are now the second person who has told me about cracked heads like mine. I wonder if that is a common problem with these heads?

Yeah, it looks like I need to head down that road. Remodeling the house right so it may be summer time before I get a chance.

Thanks zwede. Maybe I'll take some time and pull the intake before I do anything else.

It's been mentioned to me a couple of times that there could be a mismatch between the heads and intake mounting surfaces. Can anyone tell me how best to check for such a mismatch?

Thanks everyone. Appreciate the help.

DC

 

Arent the water ports in the intake on the passenger rear and driver front side of the engine?(or other way round?)
id pull the plugs closest to these ports. Burning water results in a squeeky clean plug. Or pull the intake anyway as thats the least you ll need to do, if its the HG you need to remove it anyway.

 

How did you check this? Did you remove your oil drain plug to see if any coolant flowed out ahead of the oil?

 

If you were getting liquid coolant in bottom of oil pan the oil would be grey milkshake. Try running a high concentration of antifreeze. Then stand behind the car whike running. I can smell head gasket problems in cars on the road in front of me sometimes.

 

After you remove the intake, examine the gasket and the mating surfaces of the head and intake and you will be able to see how everything lines up, and if it was sealing correctly.

 

Cracked cylinder head or head gasket problem...

 

Yes. During the last oil change, I also placed a small amount of first draw and last draw oil in separate glass containers and let them sit for a few days to see if there was any separation of water and oil. There was nothing obvious.

I now check the dipstick frequently. If it's bad enough, it becomes pretty easy to see coolant in the oil on a dipstick.

I did the same glass container test with some coolant taken from the radiator via a Mity-Vac. Again, nothing obvious.

I probably should run both tests again as the problem does seem to be getting worse.

DC


DC

 

going until oil and coolant mix is adding to your problems.

keep driving short trips and risk more trouble,
drive long and make it fail hard and risk more trouble.

heads have to come off.

 

It won't fix itself. Pull the intake, and check the gaskets. Find zilch? Pull the heads. At worst, get a valve job and reassemble.