Smoking 390
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Smoking 390
alright so I’ve completly rebuilt my 360 into a 390 and it ran ok for the first bit then started spewing dark smoke out the tail pipe so I pulled it apart and found the intake gasket was leaking oil into the cylinders and a broken push rod. So I fixed all that and drove it for a week and it worked great but tonight started it started blowing blue again. So I’m not sure where to go with it now. It’s got 74 truck heads and early 60s four barrel intake.
Cargo Master
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I don't know if it's a mismatch or not. Whether it is or not, Krewat might be on to something. When installing intake on heads for first time always have to check intake fit with a BHJ fixture (if you got one) or hillbilly method is to check fit by laying wax string on the heads and then dry fitting the intake. (Probably find a youtube). Doesn't hurt to check angles with some type of protractor ...should be around 135 degrees.
Broken push rod? At the least verify the rods aren't rubbing the intake anywhere in their full range of motion...it's easy to miss.
Broken push rod? At the least verify the rods aren't rubbing the intake anywhere in their full range of motion...it's easy to miss.
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Probably not a mismatch. While he didn't elaborate, I'm assuming he's referring to an iron intake. The heads and the intake would both be a low-riser port.
While there could be an intake to head interface issue, that normally would occur where the heads were heavily cut. Same for the intake. You most often see this with aftermarket intakes. But that's not universal. It also could be using the wrong intake gasket, such as a medium riser gasket on a low riser port. And you can't overlook intake manifold alignment. These are not simple intakes to install. They can be installed out of alignment, which causes pushrod rubbing and gasket leaks. What caused the bent pushrod?
And It may have more to do with the intake gasket type being used. When you pulled the intake, was there any damage to the gaskets? The Felpro Print-o-seals have a very bad reputation for distorting in use and leaking. I did two sets before going to a traditional fiber gasket.
While there could be an intake to head interface issue, that normally would occur where the heads were heavily cut. Same for the intake. You most often see this with aftermarket intakes. But that's not universal. It also could be using the wrong intake gasket, such as a medium riser gasket on a low riser port. And you can't overlook intake manifold alignment. These are not simple intakes to install. They can be installed out of alignment, which causes pushrod rubbing and gasket leaks. What caused the bent pushrod?
And It may have more to do with the intake gasket type being used. When you pulled the intake, was there any damage to the gaskets? The Felpro Print-o-seals have a very bad reputation for distorting in use and leaking. I did two sets before going to a traditional fiber gasket.
Hotshot
Joined: May 2003
Posts: 11,141
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From: south louisiana
It is. Those heads have medium riser style ports and the intake has taller low riser ports. Shouldn't be a problem as far as leaks go, unless he used the shorter gaskets meant for the heads, if there are such gaskets made. He may not have retorqued the bolts several times until the gaskets fully compressed.
Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
Probably not a mismatch. While he didn't elaborate, I'm assuming he's referring to an iron intake. The heads and the intake would both be a low-riser port.
While there could be an intake to head interface issue, that normally would occur where the heads were heavily cut. Same for the intake. You most often see this with aftermarket intakes. But that's not universal. It also could be using the wrong intake gasket, such as a medium riser gasket on a low riser port. And you can't overlook intake manifold alignment. These are not simple intakes to install. They can be installed out of alignment, which causes pushrod rubbing and gasket leaks. What caused the bent pushrod?
And It may have more to do with the intake gasket type being used. When you pulled the intake, was there any damage to the gaskets? The Felpro Print-o-seals have a very bad reputation for distorting in use and leaking. I did two sets before going to a traditional fiber gasket.
While there could be an intake to head interface issue, that normally would occur where the heads were heavily cut. Same for the intake. You most often see this with aftermarket intakes. But that's not universal. It also could be using the wrong intake gasket, such as a medium riser gasket on a low riser port. And you can't overlook intake manifold alignment. These are not simple intakes to install. They can be installed out of alignment, which causes pushrod rubbing and gasket leaks. What caused the bent pushrod?
And It may have more to do with the intake gasket type being used. When you pulled the intake, was there any damage to the gaskets? The Felpro Print-o-seals have a very bad reputation for distorting in use and leaking. I did two sets before going to a traditional fiber gasket.
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So I used gel pro gaskets I checked to make sure they would seal on both the head and the intake but I did notice the intake had much bigger openings than the heads. I torqued them down properly but didn’t go back in to do it after I had run it.
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Hotshot
Joined: May 2003
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From: south louisiana
Did you use the Print-O-Seal gaskets or the Permatorque Blue ? The Print-O-Seal's are just as the abbreviation suggests: P.O.S.
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Hotshot
Joined: May 2003
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From: south louisiana
The intake ports are deeper than the head ports on the 74 heads. If you used a gasket that fit the heads and not the intake, then that could be a problem. Been awhile since I messed with an FE so I'm not sure if they make two different sized port gaskets.
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Yes, they make gaskets specifically for these head styles: The 427 heads: SOHC, Tunnel Port, High Riser, Medium Riser, and Low Riser. There is also a gasket for the 428CJ. And of course, the passenger car port -which, as was pointed out is not a low riser- is similar to a low riser, but has different port dimensions and is by far the most common port.
Hotshot
Joined: May 2003
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From: south louisiana
Yes, they make gaskets specifically for these head styles: The 427 heads: SOHC, Tunnel Port, High Riser, Medium Riser, and Low Riser. There is also a gasket for the 428CJ. And of course, the passenger car port -which, as was pointed out is not a low riser- is similar to a low riser, but has different port dimensions and is by far the most common port.
Cargo Master
Joined: Dec 2015
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From: Harned, Ky
Most all of the gaskets sets now have the low riser intake gasket, it will seal low riser, medium riser, CJ heads and intakes.
High riser, tunnel port and SOHC each have their own special gaskets.
Never really had a problem getting intakes to seal on FE engines no matter what gasket I used, but I have always applied a thin coat of sealer (RTV, High Tack, Copper Coat) to the gasket as well.
I've never seen a intake out of alignment so bad that it would cause the push rods to rub
High riser, tunnel port and SOHC each have their own special gaskets.
Never really had a problem getting intakes to seal on FE engines no matter what gasket I used, but I have always applied a thin coat of sealer (RTV, High Tack, Copper Coat) to the gasket as well.
I've never seen a intake out of alignment so bad that it would cause the push rods to rub
Cargo Master
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A broken pushrod sure stirs the imagination on the how it happened and what else got beat up.
Cargo Master
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From: Harned, Ky
Agree! Some aftermarket intakes have smaller push rod tunnels, and larger push rods may require additional clearance, but neither of those is caused from an alignment issue.
I am also wondering what caused the broken push rod.
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So I never did figure out the broken push rod but I kept driving the truck trying to get it tuned and my problems were getting worse. It was smoking out the tailpipe so bad I thought I was going to have to stop driving it. Every second plug was black and crusty and every other was burning white. It would backfire into the carb all the time under all driving conditions. So bad so that it blew the diaphragm in my vacuum advance. It had no power and it was driving me nuts. So one day I got bored and found the dimensions of a #90 Holley jet and made two out of metal on my lathe. I put them in the heads and before I got to the end of my street all my problems were gone.... so all I can assume is that it was flooding the heads with oil and getting up under the umbrella style valve seals and sucking down into the combustion chambers.