351 lower intake question
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Tuned
Joined: Aug 2007
Posts: 287
Likes: 1
351 lower intake question
1988 F250 351
Any tips on how to get the lower intake to seal better? After 10,000 on the rebuilt (crate) my lower intake is starting to leak back and front. I just had a new clutch put in and the trans shop said the back of the block was wet under the galley location. I used black RTV instead of the cork gaskets when I reinstalled the lower. The engine runs great and the leak isn't bad (yet), but if I have to do it this winter I'd appreciate any input. When I originally installed the lower, the right (driver's) side took an unusally long time to torque up to specs. I always wondered if the mating surface on the old lower was not matching the rebuild block correctly.
Thanks
Any tips on how to get the lower intake to seal better? After 10,000 on the rebuilt (crate) my lower intake is starting to leak back and front. I just had a new clutch put in and the trans shop said the back of the block was wet under the galley location. I used black RTV instead of the cork gaskets when I reinstalled the lower. The engine runs great and the leak isn't bad (yet), but if I have to do it this winter I'd appreciate any input. When I originally installed the lower, the right (driver's) side took an unusally long time to torque up to specs. I always wondered if the mating surface on the old lower was not matching the rebuild block correctly.
Thanks
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
I don't know why everybody is so afraid of cork gaskets? The solution is simple, clean the mating surface and glue the cork on there with contact cement, then apply RTV in the corners and a light bead along the top and you will never have a leak again.
Elder User
Joined: Feb 2007
Posts: 690
Likes: 1
From: Madison Ohio
Biggest problem I ever had with intake gaskets was the first motor I ever rebuilt. a 390 BB. Made the mistake of installing a high vol. oil pump on new a kind of tight crank and rod bearings. Then drove in the plug on the end of the pump to up vol and pressure even higher.
In the winter and engine cold I would peg the 100 PSI oil gauge. This just kind of pushed the valley gaskets out, and was hell on all the other gaskets too. Live and learn! 
Thread Starter
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Tuned
Joined: Aug 2007
Posts: 287
Likes: 1
I have no abject fear of using cork gaskets but when I picked up the rebuild gaskets at a local speed shop, the owner told me to toss the cork and use RTV instead or face having leak problems. Never having done a 351 before I took his advice - obviously the cork plus the RTV would have been better.
What about the possibility of the lower manifold mating surface being warped? I had to torque the right (driver's) side bolts many more times than the left side while doing the crisscross pattern to get then to spec. I remember it seemed kind of odd to have to do this.
What about the possibility of the lower manifold mating surface being warped? I had to torque the right (driver's) side bolts many more times than the left side while doing the crisscross pattern to get then to spec. I remember it seemed kind of odd to have to do this.
Elder User
Joined: Feb 2007
Posts: 690
Likes: 1
From: Madison Ohio
I have no abject fear of using cork gaskets but when I picked up the rebuild gaskets at a local speed shop, the owner told me to toss the cork and use RTV instead or face having leak problems. Never having done a 351 before I took his advice - obviously the cork plus the RTV would have been better.
What about the possibility of the lower manifold mating surface being warped? I had to torque the right (driver's) side bolts many more times than the left side while doing the crisscross pattern to get then to spec. I remember it seemed kind of odd to have to do this.
What about the possibility of the lower manifold mating surface being warped? I had to torque the right (driver's) side bolts many more times than the left side while doing the crisscross pattern to get then to spec. I remember it seemed kind of odd to have to do this.
I ended up scrapping the stock intake and picking up a summit intake & carb package.
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Thread Starter
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Tuned
Joined: Aug 2007
Posts: 287
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Is there any way to check for trueness of the surface of the lower? I'm not a machinist but it would seems tough to do with the mating surface (the head) not out of the truck to measure against.
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