Advice on Engine Build: Coolant Pressure

[Gatez]

Ok I'm doing a SBC swap on an 85' Regal and I have a problem with a lot of pressure in the coolant system. After about 5-6 minutes of firing it up I get a coolant geyser coming out of the radiator. Now I'm pissed cause I'm thinking I did something wrong with the head gasket. I go through, break it back down and there is coolant in #7 and #8. So its my luck that coolant has entered on both sides of the engine. I checked the head gaskets ( Fel-Pro permatorque ) and there were no signs of blowing out anywhere. I looked at the block and cylinder walls with not a sign of cracking. I also check the heads for any sign of cracking with nothing visible. The block is a 79' and the heads are 84'. They both were machined but at different times by different places. I also am using ARP hex head bolts torqued to 65lbs.

I am also using an aftermarket summit racing intake manifold with fel-pro intake gaskets.

I went ahead and tried another set of the Fel-Pro head gaskets with the same end results. SOB!!

What the hell am I doing wrong? What things should I have checked to find out where the problem is?

 

[Phoenyx]

Faulty thermostat?

 

[rccktmn2]

There are only a few things that can cause coolant in the cylinders, 1. blown head gasket. 2. blown intake gasket. 3. cracked block. 4. cracked head, that is considering that the head and block coolant holes line up with no problems. If you can pressure test the cooling system and check for leaks, take a bore scope into the cylinder throught the spark plug hole and look around to see where the coolant is coming from. The other option that you have is to take the block and heads to the machine shop and have them check for cracks, sometimes cracks cant be seen by the naked eye. Just about any reputable machine shop will check for cracks before doing any machine work. Good luck!

 

[Gatez]

I did notice something about the intake manifold gaskets. They look just like they came out of the package even though I have torqued them down twice. The one on the left side slides right off when I take the manifold off. They don't look compressed like the head gaskets or exhaust manifold gaskets.

Could it be they aren't thick enough or the aftermarket intake manifold has some problem?

The intake bolts line up fine and I torque them to 30lbs..

 

[rccktmn2]

The intake manifold gaskets should at least look like they were torqued down. If they are sliding around when the intake is put on maybe your not getting a good enough seal around the coolant passages. Try the right stuff from permatex around your coolant passage holes. Make sure everything is clean and dry before you use it, I usually use it on all coolant passages and have had no problems since. The other thing that comes to mind is the head bolts. I think the headbolts on a chevy 350 go through the water jackets of the block so you could have coolant working it's way up the bolts and into the combustion chamber but if you used the arp lube thats in the kit it should be ok. Your local gm parts dept also sells a tablet that is made to stop coolant leaks, it's like the bars stop leak stuff at the parts stores but alot better, I've used it also and had no problems afterwards. I think I would defintately start at the intake if the gasket doesn't look right. Also check the angle of the heads against the intake to make sure there isn't a big gap between your intake and heads that is preventing the gasket from getting the torque and not just the bolt.

 

[Gatez]

I wonder if I could use some plastigauge or something similar to check if the gasket is getting pressed.

 

[Coveted]

if the gasket isnt squished from it being torqued on, the intake is probabaly warped.

 

[Blake442]

If your heads or intake were milled down at all, you'll need to run thicker gaskets to compensate for the difference.

 

[megaladon6]

x2 on the thicker gaskets due to milling. the other thing is to double check that the intake still lines up properly. also make sure that the block, head, and intake surfaces are dead flat.
and find out if the head gaskets require a certain finish level on the block surface. some of the fel-pro MLS gaskets need a very fine and specific finish.

 

[TRX]

The end gaskets are usually some sort of cork-based "composition" material. Sometimes they are quite hard. The factory intakes have plenty of clearance between their end surfaces and the block, but many aftermarket intakes have much less. The end gaskets can then keep the intake from sitting down properly.

Most builders lay a pencil-sized bead of silicone across the top of the block before setting the intake down. It works best if you let the silicone dry until it's just barely tacky before you put the manifold on.

If it's a brand new intake manifold, at least one manufacturer has had problems with pinhole leaks between the water passages and the intake runners. While the manifold is off look up the runners with a flashlight and see if anything is visible there.