Torque sequence for L98 intake?
Thread Starter
Instructor
Joined: Apr 2007
Posts: 155
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From: Fern Creek Kentucky
Torque sequence for L98 intake?
After failing at my first attempt to replace a leaking intake gasket, I have to decided to seek the expert opinion of this forum. My faulty repair ended in a oil leak at the rear of the intake apparently along the "china wall". I used a Haynes manual for the torque amount and sequence, but I am not totally sold that they are correct. After reading other suggestions on this forum, for my next attempt, I will be be using right stuff sealer and not rtv. I will also torque the bolts down at 10 lb increments until I reach 35 ft/lbs. I will then wait 24 hours for the sealer to cure and then re-torque. Is there a consenses on the forum for ***** punching the china wall surface and rear intake surfaces to give the sealer somewhere to bite? I will follow to the advice of the forum this time although as a machinest the thought of purposely damaging smooth metal goes against all of my training even though the recommendation seems to make sense.
Le Mans Master
Joined: Aug 2007
Posts: 8,735
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From: WV
Im sure others will have a different answer for this because everyone has a favorite way to do it but here goes..First off Right stuff is good but its a rubber not a RTV. It works great and I beleave it sticks better than RTV. Next, Yes dimpling the china walls helps,I did it to mine and I know people that have had problems in the past that it has helped. Just use a pointy punch and put a dimple about every 1/2 inch all along the wall. Also when you put the sealer on the china wall run it about 1/2 inch up onto the head at bought ends, this helps seal.As far as torque sequence,I looked at 2 different sources and got 2 different answers. I finally just started at the center and worked my way out while moving from one side to the other and this has worked for me. Now this is where others will differ on opinions. I do not retorque after the sealer has set up for 24 hours, this can break the seal that has formed and make it leak. Torque up to specs and don't retouque. Last but not least, use sealer on the bolts,sometimes when you have a leak it is coolant coming up through the threads of the bolts..Good Luck this time. WW
Last edited by WW7; Apr 6, 2008 at 10:20 AM.
Racer
Joined: Sep 2007
Posts: 375
Likes: 18
From: Lawrenceville Georgia
The one thing I will add is this: mating surface on block and intake have to be to 100% free of any oil residue. Use a carb. cleaner or brake cleaner, these work good. No sealer will adhere to a greasy surface. Good luck.
Joel
Joel
Thread Starter
Instructor
Joined: Apr 2007
Posts: 155
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From: Fern Creek Kentucky
Thanks for your input. I went from a small coolant leak in the front to a major oil leak in the rear when I decided to fix the leak when I had to replace the injectors. Did you use rtv or right stuff?
Thread Starter
Instructor
Joined: Apr 2007
Posts: 155
Likes: 32
From: Fern Creek Kentucky
I learned about that mistake 25 years ago the hard way. If I do nothing else correct, my mating surfaces are always clean and dry after a good acetone wipedown.
Racer
Joined: Sep 2007
Posts: 375
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From: Lawrenceville Georgia
Joel
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Joined: Dec 2000
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From: SE NY
Cruise-In II Veteran
I run very coarse sand paper along the china wal top as well as along the mating surface under the intake base. Then I wipe with brake parts cleaner.
I lay two beads of black RTV along each of the front & rear china walls, trailing a little up onto the heads gaskets.
Then I drop the base down onto the engine with NO fore/aft motion once it has touched the RTV.
Per my '88 FSM the snug sequence is as follows:
..........3..4
o-o----o-o----o-o
<front
o-o----o-o----o-o
..........2..1
My torquing (25-45 lb-ft) sequence is as follows:
8..7.....9.10...11.12
o-o----o-o----o-o
<front
o-o----o-o----o-o
2..1.....3..4.....5..6
Once the base is torqued to spec I walk away for 24-48hrs, depending on temp.
I lay two beads of black RTV along each of the front & rear china walls, trailing a little up onto the heads gaskets.
Then I drop the base down onto the engine with NO fore/aft motion once it has touched the RTV.
Per my '88 FSM the snug sequence is as follows:
..........3..4
o-o----o-o----o-o
<front
o-o----o-o----o-o
..........2..1
My torquing (25-45 lb-ft) sequence is as follows:
8..7.....9.10...11.12
o-o----o-o----o-o
<front
o-o----o-o----o-o
2..1.....3..4.....5..6
Once the base is torqued to spec I walk away for 24-48hrs, depending on temp.
Thread Starter
Instructor
Joined: Apr 2007
Posts: 155
Likes: 32
From: Fern Creek Kentucky
How course of sandpaper do you use? after 24-48 hours, do you then re-torque? Also, don't you think that 25-45 spec is a big difference? Also how wide of rtv bead do you make and why 2 thin ones verses one thicker one.
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Le Mans Master
Joined: Aug 2007
Posts: 8,735
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From: WV
I just checked my Auto Repair Reference Service site and it says the RTV should be one bead of sealent 3/16 " thick and almost as wide as the wall. Also let me add, if using RTV its a good idea to let it set until it just starts to skin over or starts to get a little dull looking before you lay your manifold down on it , that way it doesn't just push all the RTV out. If you let it start to get a little tacky first it will compress it, not squish it all out ..I believe the sandpaper I used was around 80 grit or so. And lastly, the torque on a 89 vette is (35 lbs) ... the 25-45 lbs is for a 85-88 vette and when you get to a 90 vette the torque gets real crazy, with some bolts at 35 lbs and some at 45 lbs.... WW
Last edited by WW7; Apr 5, 2008 at 09:27 PM.
Team Owner
Joined: Dec 2000
Posts: 90,675
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From: SE NY
Cruise-In II Veteran
How course of sandpaper do you use? after 24-48 hours, do you then re-torque? Also, don't you think that 25-45 spec is a big difference? Also how wide of rtv bead do you make and why 2 thin ones verses one thicker one.
Yes I retorque after 24-48hrs.
I used 35lb-ft as the torque spec.
I once got a leak on the rear wall with only one bead of RTV. I feel there is less chance of a void if two beads are used. The beads are wide enough to nearly cover the top of the wall.
BTW, soon as the beads were laid down onto the china wall tops I carefully lowered the intake base into position on the fresh RTV.
Le Mans Master
Joined: Aug 2007
Posts: 8,735
Likes: 412
From: WV
I think it was like 40 grit and I laid some paper towels in the valley to catch any grit and debris.
Yes I retorque after 24-48hrs.
I used 35lb-ft as the torque spec.
I once got a leak on the rear wall with only one bead of RTV. I feel there is less chance of a void if two beads are used. The beads are wide enough to nearly cover the top of the wall.
BTW, soon as the beads were laid down onto the china wall tops I carefully lowered the intake base into position on the fresh RTV.
Yes I retorque after 24-48hrs.
I used 35lb-ft as the torque spec.
I once got a leak on the rear wall with only one bead of RTV. I feel there is less chance of a void if two beads are used. The beads are wide enough to nearly cover the top of the wall.
BTW, soon as the beads were laid down onto the china wall tops I carefully lowered the intake base into position on the fresh RTV.
Its like I said at the begining of this thread, everyone has there own way of doing this. Its real hard to tell someone there way is wrong when it has worked for them over the years...
WW
Last edited by WW7; Apr 6, 2008 at 10:25 AM.
Team Owner
Joined: Oct 2004
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From: altered state
St. Jude Donor '05
Everyone has a different way...so take them as you may.
I never use a torque wrenchwith anitseize as imo it change the reading and result in a stripped thread. Personally I never go more than 25, maybe 30 lbs. Good and snug (maybe a touch past) in increments, thats about it. Retorque
I never use a torque wrenchwith anitseize as imo it change the reading and result in a stripped thread. Personally I never go more than 25, maybe 30 lbs. Good and snug (maybe a touch past) in increments, thats about it. Retorque
Thread Starter
Instructor
Joined: Apr 2007
Posts: 155
Likes: 32
From: Fern Creek Kentucky
Only thing I know for sure it that my way did not work. The beauty of this forum is that you get so many good ideas and learn from your own failures and those of your brothers. Thanks to all for your input.
