I have rebuilt the carb and redone the in take.....I have had to take it off once to replace the front seal between the intake and the block and it blew out again yesterday. As soon as it gets warm it starts pissing through. What is happening?....the torgue is at 30 ft lbs. I have a brand new craftsman (digital) torque wrench....could it be off?
Thanks,
Jeff

 

Where is your PCV?
edit-your blowing your front seal because you DONT have a PCV valve.

 

No PCV....just a draft tube down the back. I will check to make sure.
By the way it is a 68 small b lock....

 

pcv port on front of carb is capped off, pcv valve needs to be installed in one of the valve covers. the pressure is going to get out and thats the easiest way. if not there then the crankshaft seals.

 

Hmmm forgot about the draft tube.It might not be enough.I think they still had a PCV system to create negative pressure.Take your oil cap off and put your hand over the opening while the engine is running if you feel much positive pressure then its going to be tough to keep a seal in place.....are you using the old rubber style seal?

 

You need a complete PCV venting system. Just as an example, the pic shows my 1967 with the crankcase vent tube at the back of the block and the PCV valve in the oil fill spout. The former connects to the base of the air cleaner and the latter to the carb. I believe in 1968 the PCV was re-located to a valve cover hole with rubber grommet. That is your best option.

 

Paul is correct
the 327 blocks vented differently than the 350 blocks
The 327 blocks used a vent tube at the rear of the block that went into the air cleaner housing for fresh air intake into the block but than still needed an "exhaust" side of the system to release the vapors and pressure. In older models (pre '65) they simply uses a venter cap on the oil fill tube. In '65 they went to a 90º fitting with a measured orifice on the carb that connected via a hose to the oil fill tube to bring the vapors back into the carb to be burnt off in the combustion chamber. Starting in '66 they added an actual PCV valve inserted into the oil fill tube and than ran the hose to the carb. The PCV valve replaced the '65 measured orifice 90º fitting used in '65.

here is a pic from my '65 showing the rear vent tube at the back of the block and the hose from the oil fill tube to the 90º fitting on the carb.



(sorry for the messy motor, this pic was while I was doing disassembly to clean up the motor and engine bay a few years ago)

since your car doesn't have the front oil fill tube but you do have the real vent tube, you need to add a PCV valve so you have the pressure and vapor release for the "exhaust" side of the system. All you have now is the air intake side. The system will build up pressure and can cause the seals to fail as you are experiencing.

 

The aftermarket one I took off had a pcv in the oil filler tube....I will put that back on. I did not know the port at the front of the carb was for PCV. As for the vent tube...I looked and could not see one. There is a flat spot on th block behind the distributor (i beleive that's where my Dad's 62 has it), but no outlet...where would it be located on a 68and where should it go to?
Thanks for the help guys...this is all trial and error for me....I am glad the gasket sets only cost $12.00 and my son and I can now switch these out in a total of 1/2 an hour.
Thanks again!!!

 

You might want to consider using a bead of super blue rtv in place of the little rubber gaskets.

 

if your motor is a 327 motor it will have the rear vent.
Here is a better pic to show where it is on the block. As you can see it's directly behind the oil tube fitting for the oil pressure gauge.



the tube shown screws into the vent hole on the block. Than it connects to the air cleaner housing to get in fresh air.

 

Those rubber gaskets for the front and rear block rails tend to shift during installation of the intake and when they do they leak.
You are better off ditching them and using RTV for the front and rear block rails. People all have their "favorites" and I like the Permatex Ultra-Cooper RTV myself.

Try to put the RTV down on each rail in one continuous bead, and I like to extend it up onto the head and go around the end water jacket ports. also, in the corners where the block rails meet the heads is a common leak area so I put a slightly thicker bead i those corners. Let the RTV set up for 5-10 minutes before dropping the intake down.
One thing to be careful of is that you don't make the RTV bead TOO thick as this will cause it to ooze out and if it oozes into the lifter valley it can find it's way into the oil galleries and plug them up, not allowing the oil to get thru, not a good thing. This isn'r something to be overly concerned about but it is a valid issue so just be sure not to get too carried away when putting down the RTV.

You also have an iron intake which is much heavier than the aluminum intakes and that makes it more difficult to lay down during installation without having to shift it to get it aligned, etc. A good tip is to use a cut off broom handle stuck in the block's distributor hole, than lower the intake down onto the block by sliding it down the broom handle with the handle doing thru the distributor hole in the intake. This allows you to drop the intake in perfect alignment without having to shift it after it's down, moving the gaskets or messing up the RTV bead.

Here is an example from when I was doing my '78 motor

 

Here is a picture...it is an early 68...I beleive april It ....is a 327..where else could it be?>

 

Jeff

my apologies. Your pic with no vent hole in the block threw me as I assumed (we all know what happens when you do that!) that the '68 327 blocks would be the same as earlier 327 blocks. I guess they are different although why they would change them for one year only when they were coming out with the new 350 block in '69 is beyond me. Maybe the '68 327 is the "new" block but they didn't make it a 350ci until the next year? I don't know.
I researched and found that in at least one instance in '68 Chevy had three motors, a 302, a 327, the other a 350, with the same block casting number #3914678. The 302ci was used for the Z28 Camaro.
They must have used that block in 327 configuration for the Vette and the 350ci must have been used for larger application vehicles.
Based on this I'll guess (may be wrong) that since the same block casting is being used as a 350ci that it's the new block design so there wouldn't be a rear vent in the block.
Lookling at pics of other '68 engine pics they all showed NO rear vent tubes and had the breather and PCV valves in the valve covers as did other motors after '67.

That means what I told you before was completely incorrect so I'm sorry.

What you need to do is simple than.
install a PCV valve in the drivers side valve cover and run the hose to the connection on the carb.
Install the breather tube on the passenger side valve cover and run it to the air cleaner housing for fresh air intake.

here are some pics as examples if you want to take a look

http://www.proteam-corvette.com/cars/203X.htm
This link should take you to their 68-72 inventory cars. They have a couple of '68 SB cars and pics show the engine bay.

here is another. Scroll down to the engine pic
http://www.contes.com/68blueMAR.htm

sorry about the confusion in my earlier posts. I learned something from this post.....never realized the '68 327 motors were different than the '63-67 327 motors and that it was based on the new block castings.
there is no rear vent because the new castings had completely different oil galleries and ventilation than the older blocks.

EDIT:
something else to keep in mind...... you removed the oil fill tube which was still standard it look like on the '68 327 so if you want to keep it off you will have to go with different valve covers that allow both a PCV and oil fill on the drivers side and the hole for the breather tube on the passenger side.
If you choose to reinstall the oil fill tube, you still need to have the holes in the valve covers on each side, drivers side for the PCV and passenger side for the breather tube. You can see this in the pics i linked to

 

Don't appolagize brother ...........it is great because I have now figured it out. I have never had this car running the way it should in the past 3 years I've owned it. I am getting closer and closer. If I keep the one vent in the filler tube....should the other go in the passenger side valve cover or does it matter.

 

But you are showing the distributor hole????

 

And where the oil gauge hooks up......

 

Paul
look at the flat spot behind the oil pressure line fitting. on an older 327 block the vent tube hole would be there.

 

it looks like the '68's didn't use the oil filler tube for the PCV valve like the '66 and 67's did.
PCV valve in the drivers side valve cover and breather tube in the passenger side valve cover

 

I am trying to go back to original....hence the carb and intake change...so I will read up on how to install the ports for the PCV on both valve covers.
Thanks evryone!!!

 

But that has nothing to do with PCV??