1998 Vortec 5.7 Intake Gasket... Help!

Bt Doctur

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This Intake Manifold Gasket Set Fits the Following:Warehouse: C
VehicleEngine
• (96) 1996 GMC K15005.7L V8
• (96) 1996 GMC K15005.0L V8
• (97) 1997 GMC K15005.7L V8
• (97) 1997 GMC K15005.0L V8
• (98) 1998 GMC K15005.7L V8
• (98) 1998 GMC K15005.0L V8
• (99) 1999 GMC K15005.7L V8
• (99) 1999 GMC K15005.0L V8
 

Bt Doctur

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Vortec Intake Gasket
Got this from another site


Looks like I may be into an [COLOR=blue !important][COLOR=blue !important]intake [COLOR=blue !important]gasket[/COLOR][/COLOR][/COLOR] change on my fresh RHS Vortec Pro Torker headed 355. Numbers 6 and 8 plugs are oil fouled and I've been using a lot of oil, about 1 quart for every 500-1000 miles.
The current gasket is a FelPro MS90131.
RHS recommends their own RHS 1707 [COLOR=blue !important][COLOR=blue !important]Intake[/COLOR][/COLOR] manifold gasket, 2.09" X 1.28" port, .060" thick.
For what it's worth, the FelPros worked without any problems at all, even re-used , on the OEM Vortecs.
I'm guessing these RHS castings are different enough in that perhaps a thicker intake gasket is needed. I have no dimensions for the FelPro part.
Does anyone have any other recommendations?
 

300sflyer

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I have ordered a Felpro 1255 gasket set, and I should have it by tomorrow. I will report back, once I see how it fits on both the head and the intake.
 

Volphin

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First off, check the intake with a straightedge. It may need to be machined flat for better sealing. Second, use a higher quality gasket. Yes, there are many different types of gaskets for the same intake. The best one you can buy, OEM or otherwise, is the Fel-Pro MS98000T. It will have some parts in the kit you will not need, but it is a steel core gasket with rubber sealing surfaces. Nothing gets by these, and I have used them in racing applications.

I have seen oil consumption from the intake manifold before, but not on a Chevy 5.7L. Some intakes, like the MOPAR 5.9L beer barrel intake have a bolted on plenum with a flimsy gasket. Failures of this gasket would cause oil loss from a vacuum leak in the lifter valley. It is so common on them that many MOPAR enthusiasts installed a solid M1, single plane manifold to rid themselves of the issue forever. So the oil loss from scavenging the lifter valley is NOT common, but not unheard of either.
 

300sflyer

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Found this picture of the MS 98000 laying next to the 1255. I'm worried the MS 98000 will still leak in that corner, as it looks as though the port sizes are the same as stock. The 1255 ports are smaller and tapered to match the heads.

Intakegasket002.jpg
 
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300sflyer

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So I have the 1255 gasket set, and it fits perfectly on both the heads and the intake. :)

Now the question is, do I go with the vortec bolt torque specs at 18 fp, or the non vortec torque specs at 35 fp, or somewhere in between? I'm leaning towards 35 fp, as the 1255 is a paper gasket.

What do you think?
 
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funk6294

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I just did mine with the paper and went with the 35 ft/lbs. I can't remember where I read it but I thought the paper gasket utilized a higher torque.
 

Volphin

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Vortec manifolds are torqued in 3 stages, and nowhere near those values. You are way over tightening! Too much is worse than too little.

The first stage is 27 in-lbs, the second is 106 in-lbs and the final is 133 in-lbs. I usually don't go over 144-150 in-lbs. (Around 12 ft-lbs)
I'm telling you you need to use the 98000. It is a better design. Don't get so hung up on the ports. It's what we certified techs use to seal up stubborn 5.7L intakes from their tendency to leak coolant.
 

Volphin

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Here is the torque sequence for your manifold. Follow it to the T.
 

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300sflyer

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Vortec manifolds are torqued in 3 stages, and nowhere near those values. You are way over tightening! Too much is worse than too little.

The first stage is 27 in-lbs, the second is 106 in-lbs and the final is 133 in-lbs. I usually don't go over 144-150 in-lbs. (Around 12 ft-lbs)
I'm telling you you need to use the 98000. It is a better design. Don't get so hung up on the ports. It's what we certified techs use to seal up stubborn 5.7L intakes from their tendency to leak coolant.

Can't use the 98000. I put one over the intake, and it misses the inner bottom corners just like the Felpro 90131. No choice but to use the 1255.
 

Volphin

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Hmmm. You sure someone hasn't swapped the wrong manifold on it? Have you owned it since new?
 

Bondo

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Ayuh,.... Sure is odd, the way the ports are off so much,.....
 

300sflyer

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Ayuh,.... Sure is odd, the way the ports are off so much,.....

Indeed it is... If there was just a bit more material in the corners of that casting, all would have been fine. The engine is back together, and is running again. I ending up torquing the bolts to 22 fp. Had to do it a few times before the gasket stopped compressing.
 
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Forbes210

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I got similar problem as far of oil usage after my heads were redone. Did new seals fixed an issue? Thanks.
 

300sflyer

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If you start your own thread, stating all of the details, you will have more people trying to help you out with your engine.
 

Forbes210

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I did some time ago and I'm still trying to find the problem. I was just wondering if the intake seal was the problem in your case and if new seal helped with oil consumption. Thanks anyway.
 

300sflyer

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In my case it was the intake gasket that was not sealing properly, and it was sucking oil from the lifter gallery. A different intake gasket solved the problem.
 
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