Slant Six Forum
https://www.slantsix.org/forum/

Intake Manifold leak
https://www.slantsix.org/forum/viewtopic.php?t=43256		 Page 1 of 1
Author:  diy_darryl [ Sat Jan 15, 2011 7:20 pm ]
Post subject:  Intake Manifold leak
Bought a NOS exhaust manifold from Charrlie_S for a good price.

I went with a felpro gasket (which I now regret) for $12.00 because I didn't want to spend $70 for a RemFlex or Aussie set.

Now the damn intake is leaking! I tried overtorqueing it to 15 ft/lbs and now it runs pretty much okay but still has a pretty good leak as starting fluid sprayed around the intake runners speeds up the engine pretty good.

Not going to torque it any more. Now I have to tear it back down and get the good gaskets on order.

Lesson learned!

It's such a pain in the a$$ to do that I am really wishing I would have bought the right gaskets the first time.

If you are on the fence like I was.....just spend the extra money for the peace of mind!!!!!
Author:  4speed [ Sat Jan 15, 2011 7:39 pm ]
Post subject: 
As a temp fix you could try RTV over the leak if it is small and local, wait until it dries and see how it goes.
Author:  Joshie225 [ Sat Jan 15, 2011 9:26 pm ]
Post subject: 
Measure the thickness of the intake and exhaust manifold flanges where they are machined for the triangular washers. The intake should be a little thicker than the exhaust so it has more clamping load. It could be that the intake has been surfaced a couple times and is thinner than the exhaust manifold. Also, the manifold shouldn't be any more than .008" from flat. Further, the two manifolds need to be bolted together loosely until the manifolds are tight to the head.
Author:  diy_darryl [ Sun Jan 16, 2011 8:48 am ]
Post subject: 
Followed the procedure and bolted the intake and exhaust loosely together until the assembly was torqued to the head.

The intake is original and exhaust is new.

There was an extremely slight problem on one end with the surface alignment gauging with a straightedge. So there was some warping but it seemed insignificant.

Taking it out today, if it will perfectly align with the three bolts removed I might be able to fix it by enlarging the 3 mounting holes in the intake to allow a little more wiggle room. But then again it is such a pain I might as well wait for the $$$$ gaskets so I don't have to tear it down 3 times. :shock:
Author:  ceej [ Sun Jan 16, 2011 9:25 am ]
Post subject: 
Since you will have it off, take it to your local machine shop and have the manifolds surfaced.

With flat clean surfaces, you can about get the thing to seal with spit and a thick piece of paper. (Not that you would want to, just sayin') :lol:

Once it is trued up, the quality gaskets will seal things admirably.

My stuff get's machined when it's off if there are any problems.
I use the cheap gaskets that come with kits, and don't have leaks. Exceeding ~12# torque will cause issues with manifold cracking if you run the stock exhuast. It needs to float on there as the engine heats and cools. That's the reason for the torque spec being so low. After a couple heat cycles, check the torque again. It will loosen up, and you'll want to retorque it.

2¢

CJ
Author:  diy_darryl [ Sun Jan 16, 2011 9:48 am ]
Post subject: 
Yes, I was concerned about the manifold not being able to float when I torqued up to 15 ft/lbs but I was desperate. :oops:

Now a DUMB question......

I don't understand the triangle washers. I was told to install with the dimple out (facing the nut). All I am installing is a regular nut here. It seems there isn't much 'meat' for the nut to grip when torqued.

Should the dimple face the head leaving the flat surface for the nut to grab?

And the next DUMB question.......

If I have the intake/exhaust machined as a unit I assume they will be already bolted together at full torque, then installed while still solidly bolted together so the surfaces remain true?
Author:  hantayo13 [ Sun Jan 16, 2011 10:29 am ]
Post subject: 
dimple out


take manifolds apart ..exhast needs to be thinner than intake
Author:  diy_darryl [ Sun Jan 16, 2011 5:23 pm ]
Post subject: 
Apparently there are slight dimensional differences between the old exhaust manifold and the new one.

Enlarged all three mounting holes in the intake by quite a bit to get the flanges to line up correctly. Looks much better with a straightedge on it now but will still wait for the RemFlex gaskets to come in that I ordered today.

I placed the intake manifold back on the old exhaust manifold for a test fit and it lined up perfectly before I enlarged the holes. Not sure why the exhaust manifold dimensions are slightly different?????

Also the intake flanges are the same thickness (or even slightly thinner) as the exhaust flanges. It has probably been machined in the past.
Author:  Doc [ Mon Jan 17, 2011 9:29 am ]
Post subject: 
Image
Page 1 of 1 All times are UTC-08:00
Powered by phpBB® Forum Software © phpBB Limited
https://www.phpbb.com/