Is it even possible to have a completely leakless 350?

[BabyBlueChevrolet]

My 350 leaks from the breather, pcv line, carburetor (?), front and back manifold end seals, valve covers (despite getting new covers and gaskets). Admittedly the manifold end seals are my fault when i replaced the manifold, but from what Ive read these engines will leak oil pretty much no matter what. Anyone got a perfectly dry, leakless engine?

 

[Rusty Nail]

Mine don't leak.
It is a one piece RMS engine though which I think helps a great deal. It IS completely possible to seal a 2 piece engine rear main but that requires a competent and experienced builder.

Try to tune for more engine vacuum (mixture and advance) and buy a new PCV valve , that will help a bunch. The "rattle test" ain't no good. That little c-hair spring loses tension quickly in heat cycles and contributes towards leaking.. I believe the service interval is only three oil changes or similar. I change mine every two, they're cheap and make engine vacuum.

Sounds to me like you need to re-install the intake manifold first!

Spend some time under the hood with a vacuum gauge and see how high you can get that number.

Hope ths helps!

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[PrairieDrifter]

Felpro blue gaskets and super clean things. As well as permztex's the right stuff. The rear main is probably what people fail at the most, or the China walls. The rear main 2 pieces need to be staggered and a small bit of the right stuff between them. People usually don't use enough rtv on the China wall.

Also, wore out covers. This hurts a lot of people. Especially valve covers, if you don't get those sealed properly it is the biggest mess maker of them all. The 40 year old covers get old.

With felpro blue silicone gaskets and some nice cast or billet aluminum valve covers there's no more flex to be had from the covers, and no more engine bathing leaks. Same goes for oil pan or timing cover, most people don't center the front main seal, there is play where the timing cover will bolt down, but not the seal contact on the crank snout.

Basically, quality covers gaskets and sealant, yes an old(healthy) engine can be leak free.

 

[rusted nuts]

Sounds like Your engine is wore out and is blowing compression past the Rings thereby Blowing air and oil out of engin anywhere it can.

 

[GTX63]

I have a 1974 C10 with a 350 2bbl that has never been out of the truck. My wife wouldn't let me park it on the driveway if it leaked. Yes, the motor is 5 decades of grease, but nothing liquid.
I have a 1980 K15 that has a very slight ooze from the passenger side cork valve cover gasket. Maybe a drip a week.
Yes, I have had the ones that needed diapers, but it is possible to have an anteeky truck that doesn't leak.

 

[ChuckN]

Felpro blue gaskets and super clean things. As well as permztex's the right stuff. The rear main is probably what people fail at the most, or the China walls. The rear main 2 pieces need to be staggered and a small bit of the right stuff between them. People usually don't use enough rtv on the China wall.

Also, wore out covers. This hurts a lot of people. Especially valve covers, if you don't get those sealed properly it is the biggest mess maker of them all. The 40 year old covers get old.

With felpro blue silicone gaskets and some nice cast or billet aluminum valve covers there's no more flex to be had from the covers, and no more engine bathing leaks. Same goes for oil pan or timing cover, most people don't center the front main seal, there is play where the timing cover will bolt down, but not the seal contact on the crank snout.

Basically, quality covers gaskets and sealant, yes an old(healthy) engine can be leak free.

This right here. I even used the steel core blue silicone Felpro oil pan gasket on mine.

On my old ‘54, the 327 was a nightmare, mostly from the valve covers. For the life of me, I could not get the old stamped tin chrome covers to seal, even with light pressure ( I used Phillips head screws to tighten). A lot of folks over tighten them.

I can be pretty hamfisted, so I got some cast aluminum Edelbrock covers, used the Felpro blue steel core gaskets, and that solved the issue.

The ends of the intake manifold….the guys on Engine Masters etc use a bead of Ultra Grey or Ultra Black on them, so I threw away the rubber gaskets on mine and used that stuff instead. Best thing I ever did.

IMHO, is it possible? Yes. Do most of them leak somewhere at some point? Yes. Best of luck to ya!

 

[PrairieDrifter]

When you want something to seal up, you use permatex's right stuff. But in general anything permatex or 3m you can't go wrong with. I used the blue silicone gaskets on the pan as well. Yep no gaskets just rtv on the china wall.

Also you need to take note of bolts that pass through into oil galleys and water passages, such as the intake, water pump, oil pan, some misc bolts and plugs on the block. They need some either Teflon paste in water or rtv in oil on the bolts or those will seep over time.

Basically you have to know all the little odds and ends and do it properly with quality stuff or you can learn the hard way over time lol.

 

[SquareRoot]

I am at one of the most satisfying points in my relationship with my truck. After recently completely rebuilding the NV4500 trans, 205 T-Case and both axles, I find myself looking under it every time I walk past it as a matter of habit. However, since I've owned it, this is the FIRST time the driveway has remained spotless for over a month now! That in itself seems to be the biggest accomplishment.

 

[PrairieDrifter]

I have the Holley muscle series

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[PrairieDrifter]

I am at one of the most satisfying points in my relationship with my truck. After recently completely rebuilding the NV4500 trans, 205 T-Case and both axles, I find myself looking under it every time I walk past it as a matter of habit. However, since I've owned it, this is the FIRST time the driveway has remained spotless for over a month now! That in itself seems to be the biggest accomplishment.

I. Hate. Leaks.

My biggest battle has been power steering fluid at this point. The pump, the hoses, the gearbox, the second gear box, the new hoses, the resealed gearbox seeps a little(Just needed everything to seat and settle in). I've finally got it sorted other than the pump, I haven't touched it because it's pretty quiet and works great, just barely ever so slightly seeps.

Knowing your old truck is sealed up good, especially the engine is a GREAT feeling.

 

[fast 99]

Kind of disagree. Yes, older design small blocks can be leak free....... for a while. However, with age or high miles haven't ever seen it. Have tried everything I could think of. At some point before the motor is worn out it will leak.

GM has made improvements in sealing. Examples are valve covers, oil pan rail/gasket and 1-piece rear main on Vortec. Those engines are much better at keeping the oil inside.

It's my guess the EPA had some input on engine oil leaks. A lot of manufacturers changed sealing designs about the same time.

 

[PrairieDrifter]

Plenty plenty of new cars dripping oil, from all places, we really haven't come that far, the cam in block pushrod v design is still in use. That being said new vehicles are less prone. But the newer they get the worse they've gotten. So many new cars with this water oil just leaking it no problem.

Pretty sure we were still using rope seals into the 60's. Probably later in the ag world.

 

[squaredeal91]

Check blow by status

 

[rusted nuts]

Yes after

Plenty plenty of new cars dripping oil, from all places, we really haven't come that far, the cam in block pushrod v design is still in use. That being said new vehicles are less prone. But the newer they get the worse they've gotten. So many new cars with this water oil just leaking it no problem.

Pretty sure we were still using rope seals into the 60's. Probably later in the ag world.

Yes after 100, oooor 200, 000 miles. Back in the late 50s early 60 engines were wore out and leaking oil at 50,ooo

 

[scrap--metal]

Pretty sure we were still using rope seals into the 60's. Probably later in the ag world.

My dad used to have a '77 Lincoln that still used a rope seal. That's what he told me anyway. I believe it coming from Ford too.

Kind of disagree. Yes, older design small blocks can be leak free....... for a while. However, with age or high miles haven't ever seen it. Have tried everything I could think of. At some point before the motor is worn out it will leak.

I agree with @fast 99 . At some point its just going to become a leaker. When I read your post I thought, how many miles before I expect it to become a leaker?

Back in the late 50s early 60 engines were wore out and leaking oil at 50,ooo

50,000 was the number that came to my mind for a SBC. Regasketing things at that point should fix it, but it'll be more than valve cover gaskets.