94 4.0 lower intake question


tbunch

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Still new here and I need a little more help ASAP. this motor is still out on the stand and nearly ready to go back in. I just torqued the heads and lower intake back on, in order and in the alternating sequence described in multiple threads and manuals, I've done many a lower intake gasket and I know how to do them, but...

For some reason it seems the intake is not sitting correctly between the heads. On the gasket surface, where the valve covers will sit, there are 4 areas where the lower intake meets the heads. 3 of these 4 are prefectly level, but the 4th is not. the head sticks up about 1/16th of an inch and I'm concerned it may cause the valve cover to leak.

On top of that, the lower intake seems like its not seating all the way down. I put silicon in the valley on both ends and normally I feel like the lower intake squishes that silicon out when you tighten it down, but mine is basically just resting on top of the silicon bead. It has enough silicon that it wont likely leak, but it doesn't seem right.

I'm strongly inclined to remove and re-do the lower intake and lay on a thicker bead of silicon for extra security, but since the heads and LIM are torqued together in an alternating pattern and it has never been heat cycled, am I safe to remove and re-do just the LIM without causing further issues? I'm not about to remove the heads again, but I want this as right as possible.

Anyone else ever have problems doing one of these? I did it once before on this same truck with the engine in the vehicle and it went fine and never leaked so maybe I'm over thinking it, but I cant help feeling its not sitting right.

Thanks in advance!
 


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RonD

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I no longer put the heads on with intake as specified.

I install and torque down heads first, then add the lower intake afterwards.
Never had any issues over the years, and it has been years and quite a few 4.0l OHVs.

Couple of things I would do, I add some sealant around both sides of intake gasket where the 4 coolant passages are, the 4 corners, thin coat.
And I use Lock-tite on the lower intake bolts.

The intake bolts are only tighten to 9 to 11ft/lb so not high torque

The earlier 4.0ls had an issue with the lower intake bolts loosening up, I think that issue is where the heads and intake tighten sequence came from.


Valve cover surface should be smooth at all 4 corners, I would pull the intake and check why that is not the case on that 1 corner
 

tbunch

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Excellent, that's exactly what I was looking to hear, I figured as much since I've done others without the alternating torque, with the heads on there already and loctite is a must.
Ill pull it off and see whats going on. Hopefully the gasket isn't ruined from torquing it down!
Thanks!
 

tbunch

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In conjunction with this same question, the gasket type I have currently is the metal/rubber fel-pro but I also have a Fel-pro one-piece composite, it kinda looked like crap compared to the metal one, but if the metal one if messed up after I remove the LIM have you ever used a composite type? will it leak? Id rather not spend another 60 bucks on a 3rd one of these if I don't have to.
 

cdxhizors

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I re-used my intake gaskets both upper and lower after about 500 miles. I had a slight coolant leak and tore it apart and rebuilt it. Definitely recommend rtv around the coolant passages as Ron suggested. For reference I have the metal and rubber fel pro lower intake gaskets.
 

RonD

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Yes, +1, reuse the intake gasket, very low torque compression on that gasket
 

tbunch

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Awesome, thanks for all the feedback everyone, ill pull it apart, figure out the issue and get it done right.
 

RonD

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Give a close look at lower intake passenger front and driver's rear coolant passages, that's where the flow is, and that's where electrolysis eats away at the aluminum.
That is why these spots are common leak points on cooling system.

Changing coolant every 2 years keeps PH high so less chance of electrolysis.
 

tbunch

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Very true, I changed this out the first time due to that and had no leakage afterwards, the passages were not corroded, just a deteriorated gasket that caused a major exterior leak. Its only getting re-done this time as part of the re-build. Which makes it all the more strange that it sits funny. I had one head marked with a bolt when they went to the machine shop and advised the shop which was which. I know the heads are interchangeable, but if he possibly mixed them up I suppose its possible that would cause incorrect seating, I seriously doubt it though. Guess we will see shortly.
 

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Just a thought. Were the heads machined, and if so, was 1 warped? You can deck a warped head and get it to seal, but the rest of the head will still be warped. Had a 2.0 pinto that the head cleaned up fine, but the cam would shave a slight bit of babbitt on install from the head being warped (ohc motor). Intake could be warped, alternatively.

Again, just a thought. Start simple, and let us know how it goes!
 

tbunch

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Good thought, I thought the same. I pulled everything apart last night and checked the ports on the head and the manifold with a straightedge in every direction and couldn't find any gapping so I felt good that the heads (and intake) were straight. I then test fitted it dry with the gaskets in place multiple times to see why it wasn't sitting far enough down. From what I could tell one of the locating tabs on the manifold gaskets was bent upward allowing the gasket to sit lower in the valley, the trailing edge of the rubber was getting stuck under the manifold preventing it from seating. This seems to be why I had such a gap at the valley ends.
I probably could have gotten a warranty replacement on the gasket, but since it was an online purchase and I can't wait another 2 weeks without the motor running I threw on the composite fel-pro. I still have my doubts about it, but it did allow the manifold to seat correctly. I also beaded extra silicon at the valley ends for extra insurance and around the coolant ports. When all was said and done i feel much better about it now.

The gasket surface where the valve cover sits still seems off ever so slightly, but the uneven surface is the same at all 4 corners, and when I say uneven it's probably within a few thousandths of an inch, little extra silicon and some gasket sealer and I'm feeling good I should get some mileage before any seepage.

Thanks again for all the input!
 

jeremysdad

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Glad you got it sorted out!
 

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permetex sealant ? hi tac? what type? for lower ..... locktite what type for bolts ? I assume blue
 


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