david068513

iTrader: (2)

I have a 1992 z28 with vortec intake and heads. The back of the Intake by the firewall on the passenger side has a vacuumn leak where the intake meets the block. There is no gasket there only rtv holds it so would it be ok to just reCh back there and rtv it or do I need to take it apart and do it?

HF_monster

Id say remove the intake and replace the gaskets from what you wrote sounds like a leak in the lifter valley no telling which port it could be coming from but it must be a heck of a leak?

david068513

iTrader: (2)

There never is a gasket there. Its just rtv. It's the back of the intake where it meets the block to the left Of the distributor.

Sparkytfl

I had a ton of trouble with that too. Instructions say to use a 1/4in thick bead of sealer, but really the gap is more like 3/8 or 1/2. Thats like four beads on top of each other. Even on my second try I still didnt trust that it sealed, so I ended up just squeezing more out and spreading it along the space after it was already installed. On the front too, but the front was easier to get to. Worked just fine. Its definitely worth a try before dealing with removing the whole thing. Just degrease it real well so you can be sure your second layer of silicone will stick to the original layer and to the block and intake. Maybe do another layer after that. Remove the tube for the oil pressure sensor so you can get it into the space behind it. Then do the carb cleaner leak-check once its done and running.

HF_monster

sorry I must have misunderstood I thought you said it was a vacuum leak if its just an oil leak yeah clean the area good and spread some more silicone and you should be good like Sparkytfl said.

ASE doc

Actually, if your cylinder seal is good, you may get vacuum at a leak in this area. The vacuum is introduced to the crankcase by your PCV valve. Under load, im sure your vacuum leak turns to an oil leak. The area in question opens up to the lifter valley. These are called the "manifold end seals" and if you're having trouble sealing them with RTV, your first mistake is using RTV. Permatex makes a product called "Right Stuff" especially for areas such as the end seals. It is much heavier than RTV and forms a much better seal. Find it at your local parts store. BTW, once the manifold is torqued down, these gaps generally close up to about a 1/16".

david068513

iTrader: (2)

It's a vacumn leak. I put a smoke machine on it and it comes from there. It was causing it not to idle and stall in gear.

I haven't tried RTV I was asking if it's ok to try it there since it seals with a liquid sealer and not a gasket.

HF_monster

you need to pull the intake and find the cause of the leak at this point Id say the work is well worth it to make sure you dont have a cracked intake manifold or intake port on the head it could be just a bad gasket. siliconing the intake is not going to fix the problem with stalling and not idleing

are you running a vortec intake or a 12 bolt intake?

david068513

iTrader: (2)

there isn't a gasket there though. there never was. there is no gasket for this spot and it is all a liquid sealer.

It's a SD vortec intake.


btw its a 96 vortec block

HF_monster

you should be OK with the liquid sealer if the area is clean try that first but if the idle and stalling issue dont stop Id take the intake off and check everything.

ASE doc

Note that I edited my earlier post. Im sorry, I wasn't thinking. I've seen vacuum leaks at intake end seals before. There's not much oil at that spot and at idle, with good cylinder seal(no blow by), you will get vacuum. However, you hadn't said before thaty you had a stalling, no idle issue. Sounds more like a sucked in manifold gasket. Did you say there was no gasket, even at the manifold to head port opennings? That is highly unusual.

I am with HF on this. You need to pull the intake and see what's up. Fixing the end seal leak will not solve your drivaility issue. You are obviously losing vacuum at one or more runners.

ASE doc

The 96 Vortec takes RTV at the end seals. Of course it has typical intake gaskets. Youve sucked a gasket and will need to replace it. Again, use Right Stuff in place of RTV for the end seals. I have used this method for some time and after years of service have had no leaks on several SBC V8s, Vortecs and gen 1s.

david068513

iTrader: (2)

ok thanks
there is no gasket in the area we were talking about not that area.
how could it have sucked a gasket? are you sure? what if I seal that leak and it fixes the issue would it mean it didn't suck the gasket?

ASE doc

Intake gasket failure unfortunately isnt that uncommon. I see it every so often. The top and bottom of an intake gasket has a thin strip of gasket material which is held in place by pressure between the manifold and head. When inlet pressure spikes overcome the pressure holding the gastket in place, the gasket will collapse and get sucked into the runner. Thus creating an inlet air, or vacuum leak. The solution might be to use a good quality, heavier bodied gasket like Felpro and for added insurance, coating the gasket around the runners with Edelbrock's Gasket Sinch. Gasket Sinch is an anti slip adhesive intended to prevent gaskets from slipping out of place. Its perfect for your situation. And remember the Right Stuff for your end seals. Also be sure to use Permatex Ultra Black rtv around your coolant passages so they dont end up leaking. I dont recommend using Right Stuff on the coolant passages because its so thick.

ASE doc

One last point, be sure to double check the fitment of the gaskets. They should surround the runner with a thin strip of head/manifold mating surface visible inside each gasket openning. Port matched heads/manifolds will have less surface showing but the gasket should still not prodrude into the runner. A gasket that doesnt fit completely outside the runner is more likely to be sucked in.