lower intake gasket probs - help diagnose

rockin_rick · Oct 24, 2005

I noticed that my rear lower intake-to-block seal had started leaking, so I removed my lower intake to fix it. I pulled the lower and found a few issues.

1) big split over #2 cylinder. It appears that the top half of the entire left half of the pass side gasket has shifted (racked) a bit to the left.

2) back seal destroyed. It's essentially cut in half.

3) small split over #7 cylinder.

4) oil leaking into middle cylinders at the bottom of the intake runner.

5) oil seeped up into the middle bolt holes (#9-12). You can see in the pics that there is so much that it was running down the gasket after I took off the lower.

Does this appear like I've overtightened the intake, particularally in the middle?

I used gaskasinch on the entire surface of the gasket-to-head side of the gasket and the head. I then used a light coating of ultra black RTV encircling the water ports on the gasket on the intake side of the gasket and the intake. And use the blue rubber end seals that come with the MS93334 gasket set with a tiny bit of RTV at the ends where they meet the 1250's. Never had any probs until now.

When tighening, I orgininally tightened the anti-seize covered threads with a beam torque wrench in the correct pattern to about 15 lb-ft. I tighened them all to 5 to start with and had to go round about 5 times to get them all to 5, then moved up to 10, and same thing, about 5 times around to get them all to 10. Same thing for 15.

I have since re-torqued these bolts in the same meticulous manner about 6-7 different times (every time the upper intake is off, mostly when adjusting valves). Each time, the bolts had apparently dropped to about 10 lb-ft. So I tightened them up. I wonder now if I should have just done this re-torque once (or twice) and let it go? I wonder if I continually squish the gasket each time? I wonder if I squished the lower rubber gasket so much that the inside half got pushed into the lifter valley and the outer half got squished out?

Thanks,
Rick

rockin_rick · Oct 24, 2005

Before removing the lower, I first suspected that I had blown out the rear seal after letting my PCV catch can overfill. I use a catch can from accurate machine works (http://www.accmachtech.com/pcvcatchcans.htm). I didn't realize how fast it would fill up and found it the other day full. It seems that this would cut off the PCV flow or suck up oil. I then at the same time discovered the leaking rear seal.

Could this have caused the crankcase pressure not be vented (through the PCV) and blow out the rear seal? Wouldn't the tube on the filler tube allow pressure to be vented? Can I rule out excessive crankcase pressure causing this?

Thanks,
Rick

these are pass bank pics

rockin_rick · Oct 24, 2005

pic of split over 2 and back seal

rockin_rick · Oct 24, 2005

pics of 6 and 7, with the split over 7

urban96 · Oct 24, 2005

do you still have the little line going from the oil filler to the intake tube still connected? if so then that should be enough to vent crankcase pressure i would think... did it overheat at all?

final5-0 · Oct 24, 2005

Wow Rick!

I looked at all the pics but not really sure what to say.

I have tore down small blocks that used those very same gaskets but did not see the splitting thing like in your pics.

That blue rubber end gasket does kinda look like the manifold cut it in half due to it being very tight.

Grady

dstanggt50 · Oct 24, 2005

I usually have to re torque the lower a couple of times, usually after a 100 miles or so, but after once or twice , they stayed at the same torque specs. If you're using the torque wrench correctly , then if it is loose by about 10 ft lbs, I wouldn't just leave them, I would re tighten. Idt doesn't sound like you overtightened them to me, unless you are using the torque wrench incorrectly. As far as why your gaskets are doing this??, , I would just clean everything off and put new gaskets, and chk the bolts maybe after 50-100 miles.

mo_dingo · Oct 24, 2005

To be honest, I suspect either your torque wrench, or your install....

I bought a click style torque wrench from sears, and it's a 10-70ftlbs one. It makes it really easy to torque bolts to the smaller settings. Trying to get 18 ft-lbs out of my 10-250ft-lb wrench was nearly impossible....But that torque wrench made the last install I did a piece of cake.

Now, you used a sealant all over the head before you layed the gasket down?

Here is what I do. Get 4 5/16-18 studs that are 3" long, and install them at the 4 corners. Only do a couple turns. You don't need them tight, otherwise they will be a pita to remove later. Then lay a thin bead of RTV around the 2 coolant ports at the back of the heads, then lay your gasket down on the studs, then put another thin layer of RTV around the coolant ports. Put a thin layer of RTV on the block & install the "S" seals on the block. Put a 3/16" thick bead of RTV at the 4 corners of the b-to-head joint. Then put a thin layer of RTV on top of the S-seals to fill the voids in the seals.

They lay the intake down on the studs, back them out one by one, each time replacing them w/ a bolt, and install the rest. Tighten them ALL down until they are all snug. Then start with the sequence.

That is how I did mine and my friends, and it worked both times.

The 3/16" thick bead at the corner will fill the void that is left behind. When I say thin, mean just enough to cover the surface. If you take a magazine (i.e. summit) and compress 20 pages together, that is the thickness I mean.

Another thing I should reiterate. The cork gaskets are crap IMO. I like the blue rubber ones from fel pro. Nice pieces. They don't have any adhesive at the bottom, so that is why I like to put a thin bead on both sides, so no matter voids are there when you install the intake, the RTV will seal them.
Scott

RIO5.0 · Oct 24, 2005

From the looks of those gaskets and especially the back seal, my thinking is over torqued..
I use the same seq as you do at those setting, using a 3/8 drive TQ wrench on the intake....as mentioned the big-un is not accurate...
I hit them one time only in stages and leave em alone.. only used the same Fel-Pro kit to...
Your to damn rugged.... Even the rubber around the intake ports looks deformed...amnit:

final5-0 · Oct 24, 2005

For what it is worth ............

I've never used a tq wrench with the intake. Just snug them up to what I feel is about right with a 3/8 ratchet.

With my AFR's and the fact they don' have helicoils in the threads I did not go as tight as I usually do when using iron heads.

Even if using iron heads, it doesn't have to be all that tight.

I looked in my factory Ford service manual and it called for 23 to 25 lbs.

Grady

bimmertech · Oct 24, 2005

final5-0 said:
For what it is worth ............

I've never used a tq wrench with the intake. Just snug them up to what I feel is about right with a 3/8 ratchet.

Grady

i don't use a tq wrench either, iirc the directions that come with afr heads reccomend you not use a tq wrench. a regular craftsman 3/8 ratchet with a single grrr should do the trick.

final5-0 · Oct 24, 2005

bimmertech said:
i don't use a tq wrench either, iirc the directions that come with afr heads reccomend you not use a tq wrench. a regular craftsman 3/8 ratchet with a single grrr should do the trick.

OK ............................ I just gotta ask

That .......... single grrr

Is that a German kinda thing you picked up at work

Grady

rockin_rick · Oct 25, 2005

I don't know if I feel comfortable with setting them goudentight , as I don't think I have a good feel for what is proper tightness for the lower. I obviously have a fear of leaving the lower too loose, as I'm pretty sure now that this was caused from overtightening.

I'm pretty sure that I am using my torque wrench correctly, and it's pretty new and in great condition/babied. It's a Craftsman 44690 3/8" 0-75 ft-lb beam style.

I wonder if I should only torque them down and then retorque them once (or twice). I wonder if I tightened them down, then from expansion it "compressed" the gaskets, then the bolts appeared "loose". Then I tightened them down again, and then same thing - metal expansion and gasket compression and loose appearing bolts. Then more tightness, more compression, etc... like I said, I did retorque these about 6 times. I wonder if they should be normally a bit looser (about 10) and then when you have the expansion, it effectively increases the torque to 15ish.

Rick

final5-0 · Oct 25, 2005

Rick

I've found you have to go over the entire sequence of bolts around 4 to 6 times until they all take the same anount of tightness when putting the intake on for the first time.

I check em again after a couple of heat cycles and usually find two or three a little loose and the rest seem ok.

That has been my findings for what it is worth.

Grady

bimmertech · Oct 25, 2005

final5-0 said:
OK ............................ I just gotta ask

That .......... single grrr

Is that a German kinda thing you picked up at work

Grady

na, think of it as a grunt, like grrrrr.

one grrr is a slight grunt, 2 grrrr is a medium grunt.

divit250r · Oct 25, 2005

If the heads had been milled, and the intake hadn't, would that cause something like this? I remember looking at a diagram of how much material had to be removed from the intake versus what was removed from the heads, but it's been a few years ago. Just thought maybe something like that could cause this problem.

Scott

rockin_rick · Oct 25, 2005

Usually when I recheck mine, almost all of them are "loose".

I was thinking, when I tighten #3 (the one that the heater tubes bolts onto), I lift the tube up out of the way, thus 'torqueing' the entire manifold - lifting the rear and pushing the front down into the valley. Perhaps coincendently, the front pass side was the side that had #2 split and looked like the gasket had been shifted laterally forward (sorta).

Is this how everyone else handles the heater tubes?
Should I remove it (what a pain) before torquing the lower?

Rick

rockin_rick · Oct 25, 2005

The heads haven't been milled, and are box stock AFR 1402's.

The intake I'm not sure of as it was used.

Thanks for the ideas.

Rick

bimmertech · Oct 25, 2005

rockin_rick said:
Is this how everyone else handles the heater tubes?
Should I remove it (what a pain) before torquing the lower?

Rick

i know this sounds strange, but what i did on mine is stack 2 washers inside the little bracket the stud goes through on the heater tube. what this does is allow you tighten the stud using the top nut thus avoiding any such problems. yeah the tube maybe a ever so slightly loose, but it isnt goin anywhere.

lower intake gasket probs - help diagnose

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