Ram Air Formula

Has anyone encountered this problem before on a stone stock LT1? Unless a previous owner had head gaskets replaced and wanted the heads milled, I've never seen this before. Intake was pulled do to the typical oil leak. However, the glue and everything else screamed factory installed. The intake gaskets themselves were covered front and back with oil. Oil was also on top of the manifold where the bolts are at. All this made me think this isn't going to be a normal oil fix. So I dropped the intake without gaskets onto the engine and it's resting on the front and rear ridges not the heads. Should be an easy enough fix once the intake gets milled, but none of this seems normal. I've definetely not seen it all before so I thought I'd ask. Thanks

zr1fred

There is no front or rear gaskets, just RTV and the two side gaskets. As long as the bolt holes line up there is no problem.

Ram Air Formula

I know there was no front or rear gaskets, but everything I have ever known is that the intake should rest on the heads when no intake gaskets are present. If not, then you are essentially pulling and bending the intake down to meet the heads when you torque it down. This is not good. Has this somehow changed with the LT1s and why have I not seen this issue before on LT1s?

Thanks

Corvette Kid

Something is certainly not kosher here. Either the heads have been shaved significantly or someone tried to true the port flanges on the intake and got carried away, or both. Although not always, machinists will often mark a head how much it's been cut. But with the heads on the engine and if they're marked at all, the marks may be covered up by something or otherwise difficult to see. Whatever the case, someone definitely screwed up royally here.

5abivt

Is there a gap between the manifold and the heads when the manifold is sitting on the block? Do the bolt holes not line up? I can't imagine how rtv would seal the manifold though if it was resting on the heads and not the block.

MarkBychowski

Try setting it on with the gaskets in place (even if you use the old gaskets) and see if it still sits on the front and back edges. If it does, there's definitely a problem. Having the gaskets in place will lift the manifold more than just the thickness of the gasket since they're at an angle.

STL94LT1

The oil on the intake gaskets was probably because the intake bolts came loose. I saw this on a high mileage LT1 TA. I'm betting once the new intake gaskets are in place, the intake will have a small amount of clearance to the block.

Ram Air Formula

The bolts where tight and sealed with sealant. If the gaskets are in place the manifold does not rest on the block. The bolt holes line up now without the gasket or with the gasket. There is clearence between the heads and intake now without the gaskets. I will drop the new gaskets in place and see if there is still a gap. I seriously doubt it though.

Like I said, this appears to be the first time this intake has been removed. My friend has had the car for the last 70k miles and it's at 114k now. He hasn't had anything done to it involving the heads or intake. So if anything was done, it was done in the first 40k and nothing else was done. Everything on this car is stock. It's very weird to me. I feel simply milling the front and rear of the intake will solve the problem as that's a normal operation if heads have been milled, but why is it having to be done in the first place has me scratching my head and asking am I missing something else.

Carpenter

I totally agree with your conclusion Formula.

I'd mill the manifold front/back as req'd to have zero tolerance heads to block. The gaskets would raise the intake off the block probably 1/8" which I'd personally believe RTV would work fine (providing it was started up AFTER the RTV was cured).

Sounds like one of those 'mystery' GM screw-ups.

cv67

JAKE

What size gap are we talking about? Slide some feeler gauges in the gap and post what you find.

Jake

Ram Air Formula

With the intake resting on the block, there is between .016 and .020 between the intake and heads.

hexane

When putting on the intake couldn't you prevent the intake bolts from loosening by using lock washers?

JAKE

I believe FelPro sells intake manifold gaskets that are extra thick. I believe they are .060 thicker and there may be others even thicker than that.

They may be able to solve your problem the least expensive way.

Jake

Ram Air Formula

Yeah, I am trying to find those gaskets if they exist. I know they have them for SBC but I don't know about LTs. Anyone have a part number for extra thick gaskets?

Ram Air Formula

1284 is the felpro part number for a .060 thick intake gasket. Barnette Performance here in ATL is a fantastic company. Man I love these guys. The guy found it in less than a minute. part number ms95580 is an OEM replacement gasket. The type you would get at say autozone. This number 1284 is Felpro's racing line. I'll have it in a day and can let y'all know if it fixes the problem.

Ram Air Formula

Well, I just checked the factory gaskets and they are .060 thick already so these Felpros won't do anything for me. ARGH this is annoying.

Slalom4me

How thick is a stock LTx intake gasket?

I believe the standard thickness of the GEN 1 SBC intake gasket is 0.060".
I have an intake that has been milled on the flanges and use 0.120"
gaskets to compensate.

.

Slalom4me

Sorry, Slalom4me types too slowly.

I have checked for 0.120" LTx gaskets and so far, have drawn a blank.

.

hexane

Couldn't you just stack intake gaskets? I know I had a choice between using the Felpro paper gaskets and the metal layer gaskets. The metal ones just felt more logical for all around use. I'd think the paper gaskets would leak and dissolve over time, especially near the coolant areas.