Oil for my 496 BBC

Maybe you guys can help me with this. Plugs aren’t fouling, appear to be burning clean. Have about 4000 miles on them. No oil burning smoke, seems to have good power. Compression test runs 140 to 152.

Rear main seal?

Seriously this requires you to do the due diligence. Go over the engine and check for leaks including the rear main. You have done the compression test.

Trying to diagnose these kinds of things online is usually a futile exercise.
 
Low tension rings (by themselves) won't cause a quart of oil consumption every 150 miles. Something is wrong. Give us some more information about the engine. I'd rather find the cause of your oil vanishing problem than recommend you an oil.

How long ago was it built and how many miles on it since the build?
How is it typically used? (low rpm cruise, stop and go city traffic, drag racing, towing, garage ornament, etc...)
What temp thermostat are you using and what's the typical operating temp?
What's your static and dynamic compression?
Rod and main bearing clearance?
What camshaft exactly?
What oil pump?

Perhaps most importantly... how was the break-in done?

I've seen this once before with a .030" over 454 BBC (460ci) where the "builder" put cheap slugs in it that were .020" shorter than stock and with a -12cc dish. (may have been -15cc, not sure) They were .040-.045" in the hole with a .040" gasket and the typical massive 119 cc combustion chambers of smog era BBC iron heads. The static compression was in the toilet at barely >7:1. To make matters worse, it had a rather hefty cam in it that was ~235-240 @ .050" with a DCR down ~5.5:1. This engine didn't want to idle below 1000 rpm and was an unresponsive turd. He had a similar issue with oil disappearing though it was every 300-400 miles, not 150. When the oil pan was pulled to start investigating, you couldn't see the pistons in the bores due to a black tar (sludge) coating the bottom of the pistons. It was bad enough that you had to scrape it out of the way to see the lock rings on the pins. Running the DCR so low and lugging it caused very high piston temperatures which coked the cheap oil he was using. Same as you, no blue smoke, no oil on the plugs, no external leaks, etc... it was all evaporating and coking around the pistons and cylinder walls. As you probably imagine, this engine had a bad overheating problem as well.

Engine idles well at 650, wicked cam in it but don’t know the brand or specs. No oil in the coolant and doesn’t overheat even at ambient 102. Has side pipes with coal black deposit on the concrete under each pipe. The PCV system is questionable. I tried to duplicate a BB system but I don’t think I did it well So could use some help on that.
The car is a ‘65 Corvette coupe. I did notice one time I had the carb removed that there was a lot of oil underneath the carb in the intake. Not sure who the builder is and doubt they would remember a 20 year old engine.
 
Trying to diagnose these kinds of things online is usually a futile exercise.

We can help, but some detailed information is going to need to start flowing.

152 sounds sounds low, but if it has a large cam it could be fine. 140-152 is good as far as a range. There are calculators that will tell you what you should be looking for but you need all the engine specs to run one.

You'd be surprised (or maybe not) what has been found in professionally built engines.

I did notice one time I had the carb removed that there was a lot of oil underneath the carb in the intake.

That's a clue.
 
I think the dipstick is correct but not absolutely sure. I never let it get below a quart.
 
I drive moderately traveling to and from car shows, cruise ins, etc. Occasional street race. Never over 80mph. Muncie M22W, 3.08 posi.
Yes, has oil leaks, probably from rear main but not enough to account for that much oil, IMO. But you’re right, I need to get that fixed after the holidays.
 
So an 8.1 vortec. Also why is it consuming so much. Do you have blowby when you take the cap off. Have you compression tested it. Has it had regular oil changes or a good flush and the pcv valve? Have you also tried replacing the intake manifold bolts which is a fix gm issued for the 8.1.
Yes, I sealed the intake bolts that passed thru the intake canels.
 
Yes, but not familiar with the modern seals. I have photos of the valve covers off and will post them but Im not home right now. After the holidays Ill post some engine pics.
 
I think the dipstick is correct but not absolutely sure. I never let it get below a quart.
What's the pan capacity 5qt? ( 65 corvette) Dump the oil and put in a pint under the pan capacity then look at your dipstick, This is your new "FULL" line.

Man I would sell that lump and put a hot 327 in there.
BBC and Vette = nope.

BBC are for B and C bodies. thus the Big B & C ;)

good luck and have fun!
 
What's the pan capacity 5qt? ( 65 corvette) Dump the oil and put in a pint under the pan capacity then look at your dipstick, This is your new "FULL" line.

Man I would sell that lump and put a hot 327 in there.
BBC and Vette = nope.

BBC are for B and C bodies. thus the Big B & C ;)

good luck and have fun!
Nope! I eat 327 Vettes!
 
@496BBC
If you rip the intake off, coat both the intake and the heads with some dykem. Lay the intake with the gaskets back on the motor, lightly torque it, make sure it seals correctly.

I can't tell you how many cam in block motors I worked on that either the block or heads were decked and the intake was sucking oil from the valley.
 
@496BBC
If you rip the intake off, coat both the intake and the heads with some dykem. Lay the intake with the gaskets back on the motor, lightly torque it, make sure it seals correctly.

I can't tell you how many cam in block motors I worked on that either the block or heads were decked and the intake was sucking oil from the valley.
Wouldn’t that affect the idle? Also, vacuum. Getting a steady 10” at idle.
 
Wouldn’t that affect the idle? Also, vacuum. Getting a steady 10” at idle.
Not necessarily. It could be such a small mismatch between the heads and intake, it could be happening at the transition between low vacuum, ie on throttle and high vacuum, stepping off throttle. That "shock" between the two extremes could be sucking in the oil.
 
A sleeper oil with little to no VII is Pennzoil 25w50 racing oil.
Not too expensive and should work well in that engine.
 

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If your heads have valve guide bosses that were machined (.530 diameter) for positive umbrella valve seals you could change those out for an inexpensive attempt. At the Chevy dealership we used both the umbrella and O-ring seals especially on the intake valves for better oil control. The prior suggestions about replacing intake gaskets and sealing the intake bolts is also another inexpensive attempt. As mentioned earlier there were crate engines sold even from Chevrolet performance that had oil control issues. I recall those being big blocks and more so the 502s. Those were the low tension rings and sloppy piston clearances. If a high pressure-high volume oil pump was used it can flood the top end and keep the heads-guides flooded with oil. That’s something to look at if you pull the valve covers and fire it up. A stock oil pump is always enough. I imagine the PCV system doesn’t do much with big cam and low vacuum. Have you had the oil cap/breather off at idle? Does it puff out of the breather (blow by-rings)? Just thoughts at random…
 
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Nope! I eat 327 Vettes!
You stated are an old guy and afraid of the power, but now you are go out and eat 327's.

Maybe. Dusting grampa Joey B. in his 3-2-7 and Aviators. What an accomplishment :)

But it's not a muscle car. You took your 'vette to the gym and stuck it's hiney with T-Roni Roid juice.

In all seriousness,
Was this originally a L78 BB car?
 
You stated are an old guy and afraid of the power, but now you are go out and eat 327's.

Maybe. Dusting grampa Joey B. in his 3-2-7 and Aviators. What an accomplishment :)

But it's not a muscle car. You took your 'vette to the gym and stuck it's hiney with T-Roni Roid juice.

In all seriousness,
Was this originally a L78 BB car?
Didn’t have to totally get on it to take that 327 365hp!😋
No, pretty sure it was originally a SB.
 
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