SBC keeps blowing out intake gasket, need help

I've had the intake off the engine 3 times and it keeps blowing out the rear intake gasket, resulting in a nasty oil leak.

I'm running an older Offenhauser intake and I'm beginning to think that it could be warpped.

I'm not an engine expert at all but I would think that there should not enough pressure in the valley under the intake to push the gasket and seal out like that.

Another problem could be the valve covers that i'm using.

They are the old California Customs originally for an older down draft apllication.

At some time, someone drilled holes in the sides for a breather and a pcv but there is not a baffle inside of them.

Could this create a problem of too much pressure under the intake ?

Any ideas would be greatly appreciated.

 

Do not use the end gaskets put a bead of rtv on the frt and back. This is a common problem

 

Not all chevy intakes are created equal. Take a careful look at how the rear of the intake is configurated compared to the block. I think you will find that the angle is different.

 

I'd say that you probably don't have the crankcase vented right but it also may be that the heads and manifold aren't matching up right due to one or the other due to some reason or an other. See 61 bone's comment.

You have an intake with no fill/breather tube an you have valve covers with small holes for the breather/pcv valve (you do have a pcv valve hooked up I hope?)

The crankcase has to be vented so that the pressure and fumes that build up can get out and if it isn't vented properly it will often vent it's self at the gasket that is easiest to push out.

 

You need to have a way for the inside of your motor to breath. Yes, there is pressure that builds up under your intake. You need a breather of some sort,either in the intake or valve covers.

 

are you running a PCV?
i think i see something that you might be running crank case ventilation..but not sure.

also..dont use those rubber S nakes they give you in the gasket kit..they suck..or in your case,.. blow!

get a good thick bead of RTV on there and let it just tac up a bit..than put on the manifold and let it sit on there with out torque on the bolts. just hand tighten the intake bolts down slight ly..than after the RTV has almost set up completely..torque the sucker down as the normal torque and the normal sequence..works for me everytime

 

I throw end gaskets away and use rtv as mentioned above also.

 

If you are sure it is not coming from the oil pressure sending unit, use only the rtv like has already been said.

 

All good suggestions. You need to vent the motor. A breather in either or both valve covers is common. I never use the end gaskets. Run a nice bead of RTV, and carefully set the manifold straight down into position. Torque and tighten in sequence specified

 

Try the RTV method. Do not use the stock rubbers. Put a good amount on each end of the block. You might want a buddy to help you sit the manifold on straight down Torque manifold evenly. Remove excess RVT on the outside to be neat. Give it about 48 hours to set up to be safe. Good luck.

 

Those end gaskets are such a joke even GM quit using them. None of the newer engines have them.

 

I have a pcv intalled on the right side and a breather cap on the left.
Does anyone see a problem with the fact that the Valve covers are not baffled?

 

X50 on the RTV. I haven't used the rubber gaskets of over 30 years and it's been that long since I've had a rear intake leak.

Frank

 

Let us know the outcome.

 

Funny, I use those end gaskets with success. I like the ones that come in the kits now that have the little nubs that fit in the holes on the rail and the tabs that hold it in place. I put some RTV on both sides of it and set her down. Easy - no fuss - no muss. I think the gap is just too big to rely on the RTV but I know it works. I've done it both ways.

 

tudor goes both was ha ha!Just kidding.I use those gaskets to with rtv.no problems.Maybe your oil pressure line is broken or cracked,maybe loose. just an idea.they go through heat cycles witch makes them brittle if it is plastic.

 

almost certainly the gasket. like eveyone has said RTV or RTV and seal.Ii would put baffles in those valve covers if I were you though. otherwise the vaccum line on the pcv side will suck all of the oil out and run it through your carb.

 

I use the gaskets but glue them to the block using 3M weatherstrip adhesive, aka gorilla snot and give that time to set up. I've yet to have one blow out on me. I also use a dab of it on the gaskets at the corners where the heads, block and manifold meet up.

Bob

 

X2 never a problem.

 

With that said, as said many times ditch the end gaskets and use RTV only.

 

Were the heads milled on that engine? There's a limit to that if its done because it changes the distance between the cylinder heads (brings them closer together) This can cause leaks in intake manifold gaskets ,sometimes making it possible for oil to get sucked into combustion chambers and gives the appearance that the engine is burning oil.Head milling beyond a certain amount will change the relationship between an intake manifold and the mating surface of the heads it should lay against,also at front and back of the block in the valley. Any competant engine machine shop should be able to advise you on the allowable amount for head planing. It may not be this but its something thats worth consideration. It does happen. ,,good luck with chasing down your problem

 

x2 i had a problem like this to much pressure in the motor and it did the same thing just blew oil everyplace

 

I say just send me the intake and that should cure the problem, LOL

 

these are all good tips! but...even rtv will not work unless the surface is clean! not even paint, ive seen the paint stuck to the bead of rtv and nuthing stuck on the block so use a wiz wheel or sand off any paint before you apply rtv...also i usually dimple the intake and block sealing surface with a punch so the dimples grab the rtv! hope this will help!

 

All GM block after 79 were never assembled with end rubbers. All GM dealerships were sent bulletins to stop using them and use RTV only. Later Chevy blocks were widened on the top to give a larger surface for the sealant, none of the later blocks will even accept the end rubbers. Throw them away, using them in 1955 was a bad idea and still is today.

 

right stuff the crap out of it.. but be forewarned.. that shit works so damn well it will make it damn near impossible to get the intake back off...

 

What he says times 2 on the punch thing..............................

 

i am with nortin did you mill the heads at all? Knuck from indiana.

 

I've always wire-brushed the crap out of all surfaces and wiped them down with lacquer thinner. And let the gasket set up so it can't be moved when tugged on.

I like the dimple idea, have to file that away in the cranium.

Bob

 

You are a victim of corporate greed my friend