Intake Gasket or Head Gasket?

[shane72_383]

So i've asked this question somewhat before and thought i had fixed it but not anymore. Ok, my truck is leaking a little oil where the intake bolts to the head on one spot in the front. And while its running you can see it blowing bubbles in the oil. Also the top of the valve covers (chrome) have "milk" on them but there isn't any on the dipstick. Also, it is sometimes hard to start after its ran for a while and warms up, it acts like the battery is dead and a jump start fixes it. So whats the deal? is it head gasket or intake gasket or heads or what? I thought i fixed this a while back but no such luck. The radiator is also losing water. I don't understand with it being a rebuilt motor with maybe 100 and all new gaskets and a new Edelbrock Performer intake that it would be doing this. Any help is greatly appreciated, kinda need my daily driver. Thanks Shane

[dave2953]

The leak from the intake could be attributed to trash in the threaded boss or the threads of the bolt that don't allow it to tighten properly. As far as the radiator losing water, have you noticed any white smoke or coolant leaks? I would think if you were leaking coolant internally you would notice it in the oil, although I'm not certain about this. The milky residue on the valve covers could just be condensation from the motor. Is it around the breather or PCV?

[Longhorn Man]

is there a proper PCV system installed?

[cfinance]

What torque setting did you use for the intake manifold bolts when installing the new Performer? Did you clean out the intake bolt holes in the block before mounting the new intake? How did you clean them? Did you use new bolts?

I'm partly asking because I've got a new RPM Air Gap I'm prepping to install, but am hesitant to use a tap & die to clean out the holes (never used one before and don't want to screw up). The manual warns that gunk in the bolt holes can give bogus torque readings, leading to possible leaks like what you're describing. I suppose that old bolts can do the same.

[lilpup69chevy]

wow i've never used a torque wrench for intake bolts, and yet i've never had an intake leak, just start from the inside bolts and work your way out, and another thing a fairly easy way to check for an intake leak is to spray some carb cleaner around where the suspected area is if you notice a change in the idle you found your problem

[bobthecop]

Your battery problem could be a hot starter, is there a heat shield between the starter and exhaust?? Also could be timing is off. Btw what type of truck and what exhaust are you running??

[ridge runner]

wow i've never used a torque wrench for intake bolts, and yet i've never had an intake leak

Not a good idea, this is a good way to warp or crack the manifold.

[Longhorn Man]

while that's true... I never use one either, and I do it for a living

[shane72_383]

Its a 383 stroker in a 72 chevy custom deluxe. Longhorn Man whats the deal on the PCV system your the only one i've ever heard this from and im not sure i understand some more explaining is appreciated. Thanks Shane

[Longhorn Man]

One one valve cover, you should have the PCV (Positive Crankcasr Ventilation) valve. On the other velve cover, either a tube going to the inside of the air filter, or a breather that is open to the elements. (The former is better, but seldom used in performance aplications)
The valve sucks acidic fumes caused by blow by, and as a natural byproduct of the combustion process, and it puts it into the intake charge, where it is burned with the incoming intake charge. This also removes condensation too. On top of that, any positive pressure inside the crank case...which can, and will blow out gaskets, is just placed in the intake charge as well, and a negitive pressure (vacume) is left in there whicvh helps improve ring sealing.
This is one emissions control item that is well worth the time and effort, and has no performance issues that I am aware of.
From an emissions/legal stand point, I think all (light duty) trucks since 69, and all cars since 65 are required (per federal law, regardles if your state enforces it) to have this... not that this matters to 75% of the ppl on here...just a FYI on that part. (info is for gas powered engines, not diesels)

[67ChevyRedneck]

I have a set up like Longhorn Man mentions. I have an old school breather (circled in first pic) and a PCV set up on the DS to the carbs full vacuum port (PCV circled in green, hose to carb in blue.)

Hope this helps.

[BarryB]

You said you are using an Aluminum Intake and cast iron heads. If so you would probablly need to go with an intake gasket set for this set up. reason Being the two type of metals heat up and cool down differentlly. And if a standard intake gasket is used, It tends to cause a leak. Might not be your problem. But that is where I would check first. Check out The Mr Gasket Ultra seal. Part # MRG- 5820. That was from the summit Racing catalog. They run close to 14 bucks.

[cfinance]

Sure hope I'm not about to step on any toes, but...

The Edelbrock installation flyer that came in the box of my RPM Air-Gap intake manifold provides a bolt torque sequence and recommends using a torque of 25 ft/lbs (top attachment).

My old Haynes manual (1967-1987 Chevy truck) recommends 30 ft/lbs for small block V8 and V6 intake manifolds (bottom attachment). This page has a bunch more torque specs in case it helps anybody else out there.

I'm a mechanical newbie and I don't trust myself as much as others with more experience, so I go a bit overboard with research sometimes. But that has worked for me and has been a fun way to learn. Anyway, hope this helps and gives you more ideas to consider toward solving your leak question.

[71/454]

Curious how the 383 was built. 400 block with 350 crank? I don't remember too much on the configuration of the 383 but I am told that the 400 heads have a bad habit of cracking, if they were 400 heads may explain this. Or if it is a 400 block and someone put 350 heads on it and didn't drill the steam holes in the head to match the block, I would think one may blow a head gasket. Sorry if this causes more questions than answers. My friend had a motorhome with a 400 and a cracked set of heads.

[BarryB]

Hey 71/454. A 383 stroker is a 400 crank in a .030 overbored 350. with 350 rods.
Most heads that came on 400's were the 882's. These heads are notorious for cracking anyways. just bad design or bad castings. Dunno but it is hard to find a good used set not cracked.

[shane72_383]

My 383 isn't set up that way. Its a 350 block .30 over with an aftrmarket crank setup to use 5.7" rods and 383 pistons. The heads are just plain jane 1.94's.

[shane72_383]

Longhornman, i have friends and have personally owned engines that have no PCV system and don't have this problem. A friend has a 350 with cam Edelbrock performer intake and Edelbrock carb, and no PCV and has never had this problem. Not tryin to step on your toes im just trying to figure it out.

[Longhorn Man]

does he have breather(s) on it? That is enough to keep from spitting out gaskets, but not enough to vent all the toxic acidic fumes.
A properly operating PCV system is a win/win situation.

[71/454]

Barry B. I was pretty sure that was how they were made. Curious would it work the other way? I'm sure A friend of mine said it has been done either way but the ratio of 400 to 350 stuffmade it more common the other way plus the aftermarket cranks they make now

[fastwillie 696969]

and another thing a fairly easy way to check for an intake leak is to spray some carb cleaner around where the suspected area is if you notice a change in the idle you found your problem

i wont use carb cleaner to check for intake manifold leaks if you get that spray around any hot spark like a hei distributor
you want to use is propane fuel instead

[BarryB]

Hey Shane72 383, I too, put in an aftermarket crank in my stroker. Anyways what type of Intake gasket did you use ??

71/ 454, You can put a 350 crank in a 400. But you are destroking it. And you would have a 377 ci. Not sure of why they would do that. maybe fro getting higher RPM's haven't gone that route yet.

[bowtiebreece]

I have a 400 with a intake gasket leak as well. Both of my valve covers have breathers and no PCV. do you think not having the PCV caused the intake gasket to blow?

[Slammed70]

Originally Posted by cfinance

Sure hope I'm not about to step on any toes, but...

The Edelbrock installation flyer that came in the box of my RPM Air-Gap intake manifold provides a bolt torque sequence and recommends using a torque of 25 ft/lbs (top attachment).

My old Haynes manual (1967-1987 Chevy truck) recommends 30 ft/lbs for small block V8 and V6 intake manifolds (bottom attachment). This page has a bunch more torque specs in case it helps anybody else out there.

I'm a mechanical newbie and I don't trust myself as much as others with more experience, so I go a bit overboard with research sometimes. But that has worked for me and has been a fun way to learn. Anyway, hope this helps and gives you more ideas to consider toward solving your leak question.

Your Edelbrocks an aluminum intake compared to the factory cast iron one though too.