1976 Intake Manifold Installation
Thread Starter
Burning Brakes
Joined: Jun 2003
Posts: 1,079
Likes: 1
From: Niagara Falls ON
1976 Intake Manifold Installation
I am obviously missing something. I put an original intake manifold on last year. I noticed some coolant leaking so I did the job again. Everything seemed fine for the season until the end when I noticed oil pressure drop. Upon further inspection some of the bolts on the intake manifold had come loose. I tightened them down and then the pressure came back up.
Today I noticed the pressure was low so I thought it was the same problem. When I looked I could see some coolant leaking near one of the bolts at the front.
I tightened everything to spec from the GM manual. I cleaned all of the surfaced before putting it on. I used the correct sealant around the water jackets. Did I miss something? Should I use thread lock around the bolts? Should I use a sealant on the bolts at the water jackets?
What am I missing?
Today I noticed the pressure was low so I thought it was the same problem. When I looked I could see some coolant leaking near one of the bolts at the front.
I tightened everything to spec from the GM manual. I cleaned all of the surfaced before putting it on. I used the correct sealant around the water jackets. Did I miss something? Should I use thread lock around the bolts? Should I use a sealant on the bolts at the water jackets?
What am I missing?
Melting Slicks
Joined: Mar 2001
Posts: 2,175
Likes: 56
From: Clarence N.Y.
Tightening the intake bolts should have no effect on oil pressure.
I've replaced many intakes and didn't have to seal the bolts although
some guys use a thread sealant,it wouldn't hurt.
Something seems weird regards to your situation.
I've replaced many intakes and didn't have to seal the bolts although
some guys use a thread sealant,it wouldn't hurt.
Something seems weird regards to your situation.
Thread Starter
Burning Brakes
Joined: Jun 2003
Posts: 1,079
Likes: 1
From: Niagara Falls ON
I used the proper tightening sequence and the correct torque. Perhaps it is time to purchase another torque wrench.
The original way that I found it was causing a problem was that I heard a whining noise. When I found out it was the intake bolts were loose I was surprised. I tightened them and then I happened to notice that the oil pressure was normal. I assumed that the vacuum leak caused by the loose bolts must have had some sort of relationship. Perhaps I was wrong.
I will take everything apart again, clean it all up again, and borrow a friends torque wrench to make sure that it is all good. Hopefully the third time will be the one.
The original way that I found it was causing a problem was that I heard a whining noise. When I found out it was the intake bolts were loose I was surprised. I tightened them and then I happened to notice that the oil pressure was normal. I assumed that the vacuum leak caused by the loose bolts must have had some sort of relationship. Perhaps I was wrong.
I will take everything apart again, clean it all up again, and borrow a friends torque wrench to make sure that it is all good. Hopefully the third time will be the one.
Pro
Joined: May 2011
Posts: 581
Likes: 5
From: BC
Can't see how there would be a relationship between the intake and the oil pressure other than leaking antifreeze into the oil and you changed oil at the same time you tightened the intake.
What do you know about the history of the engine? If the block had been decked beyond what the stock intake can tolerate you will get a poor fit. I presume it had some other after market intake on it previously. If you still have it compare the two intakes to see if the other intake had been machined to fit the block. Measure the distance across the bottom from side to side at the frt or rear and compare it to the stock one. If it's been machined it will show up there.
Steve g
What do you know about the history of the engine? If the block had been decked beyond what the stock intake can tolerate you will get a poor fit. I presume it had some other after market intake on it previously. If you still have it compare the two intakes to see if the other intake had been machined to fit the block. Measure the distance across the bottom from side to side at the frt or rear and compare it to the stock one. If it's been machined it will show up there.
Steve g
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Burning Brakes
Joined: Jul 2008
Posts: 914
Likes: 10
From: Brooklet Ga.
I have put on a ton of intakes both aluminum and cast iron and never used a torque wrench, mabye I should have but I have never had a problem. I start with the center bolts and alternate sides working toward the ends of the intake. Just start in the center and work your way out. Are the heads both the same could it be possible one head was shaved and the other not.
Thread Starter
Burning Brakes
Joined: Jun 2003
Posts: 1,079
Likes: 1
From: Niagara Falls ON
It is a curse. The engine used to have an aluminum Edelbrock intake. I put an original on so that I could have all of the emissions devices...this part of the world requires it, even on older cars.
