manifold not sealing

steve4speednova · 04-28-2011, 09:35 AM

I have a big block chevy 396, with 401 heads and 359 manifold.I'm geting oil in the intake port, and seeing it on the plugs.useing mr.gasket #110 gaskets. the angles on head and manifoild seem to be ok. any ideas out there thanks.

Bob Pagano · 04-28-2011, 10:12 AM

Check the front and rear rail, if it contacts the block it will hold your intake up and it will suck oil. In most cases they need to be trimed.

Alan Roehrich · 04-28-2011, 10:25 AM

I use Mr. Gasket 5828 intake gaskets on our 427/425 Stock engine, with 401 heads, and a 359 intake.

As Bob said, I had to radically mill the ends of the intake, and on at least one of the blocks. I'm pretty sure I took 0.080" off the ends of the intake.

If you put the intake on the engine, with the gaskets, when you tighten the intake, there needs to be at least 0.060" between the ends of the intake and the block.

Take a new set of gaskets, with the block and heads clean, and install them, with no sealer anywhere. Tighten the intake down as you would to install it. Let it sit for an hour or so. Check the clearance on the ends. Then remove the intake, and check to see how well the intake gasket is imprinted on both sides. You should see a good solid imprint, on both sides, of the intake flange and the head flange. Pay particular attention to the bottom of the ports.

When used on the closed chamber engines, in Stock and Super Stock, the 401 heads are angle milled a fair amount, and then flat milled. It would be easy to miss getting the right amount of material removed from the intake flange of the head, and/or to miss correcting the angle.

Harry 6674 · 04-28-2011, 10:47 AM

I have taken the block end rails down a touch so I'm free to change intakes without modifying them.

Floyd Staggs · 04-29-2011, 08:08 AM

I had the same issue, had to completely cut the manifold. Took .100 off each end and then milled the sides to make them flat. Sucking oil causes severe detonation.

chris ok · 05-01-2011, 04:05 PM

do the intake rockers stud bolt hole in head go thru to intake port? if so use teflon tape and some indian head sealant on the stud threads. just another possible cause.

Alan Roehrich · 05-01-2011, 04:42 PM

Yes, the stud bosses are open to the intake ports.

04-28-2011, 10:12 AM	#2
Bob Pagano VIP Member Join Date: Jun 2002 Location: New Holland, PA Mooresville,NC Posts: 1,163 Likes: 232 Liked 16 Times in 11 Posts	Re: manifold not sealing Check the front and rear rail, if it contacts the block it will hold your intake up and it will suck oil. In most cases they need to be trimed. __________________ Bob Pagano A/SA

04-28-2011, 10:25 AM	#3
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,066 Likes: 1,487 Liked 1,630 Times in 378 Posts	Re: manifold not sealing I use Mr. Gasket 5828 intake gaskets on our 427/425 Stock engine, with 401 heads, and a 359 intake. As Bob said, I had to radically mill the ends of the intake, and on at least one of the blocks. I'm pretty sure I took 0.080" off the ends of the intake. If you put the intake on the engine, with the gaskets, when you tighten the intake, there needs to be at least 0.060" between the ends of the intake and the block. Take a new set of gaskets, with the block and heads clean, and install them, with no sealer anywhere. Tighten the intake down as you would to install it. Let it sit for an hour or so. Check the clearance on the ends. Then remove the intake, and check to see how well the intake gasket is imprinted on both sides. You should see a good solid imprint, on both sides, of the intake flange and the head flange. Pay particular attention to the bottom of the ports. When used on the closed chamber engines, in Stock and Super Stock, the 401 heads are angle milled a fair amount, and then flat milled. It would be easy to miss getting the right amount of material removed from the intake flange of the head, and/or to miss correcting the angle. __________________ Alan Roehrich 212A G/S

04-28-2011, 10:47 AM	#4
Harry 6674 Senior Member Join Date: Dec 2006 Posts: 589 Likes: 0 Liked 0 Times in 0 Posts	Re: manifold not sealing I have taken the block end rails down a touch so I'm free to change intakes without modifying them.

04-29-2011, 08:08 AM	#5
Floyd Staggs VIP Member Join Date: Feb 2006 Location: Cucamonga, CA Posts: 1,521 Likes: 138 Liked 223 Times in 98 Posts	Re: manifold not sealing I had the same issue, had to completely cut the manifold. Took .100 off each end and then milled the sides to make them flat. Sucking oil causes severe detonation. __________________ Floyd Staggs 787 SST

05-01-2011, 04:05 PM	#6
chris ok Senior Member Join Date: Jul 2002 Location: Long Island, New york Posts: 591 Likes: 127 Liked 46 Times in 29 Posts	Re: manifold not sealing do the intake rockers stud bolt hole in head go thru to intake port? if so use teflon tape and some indian head sealant on the stud threads. just another possible cause.

04-28-2011, 09:35 AM	#1
steve4speednova Junior Member Join Date: Jul 2009 Posts: 57 Likes: 0 Liked 0 Times in 0 Posts	manifold not sealing I have a big block chevy 396, with 401 heads and 359 manifold.I'm geting oil in the intake port, and seeing it on the plugs.useing mr.gasket #110 gaskets. the angles on head and manifoild seem to be ok. any ideas out there thanks.

05-01-2011, 04:42 PM	#7
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,066 Likes: 1,487 Liked 1,630 Times in 378 Posts	Re: manifold not sealing Yes, the stud bosses are open to the intake ports. __________________ Alan Roehrich 212A G/S