Exhaust Manifold Gaskets

Rick · Post by **Rick** » Tue Sep 07, 2010 2:40 pm

I'm going to replace my exhaust elbows this winter on my 454's. Should I replace the Exhaust Manifold Gasket as a precaution and clean everything up ? Or leave Exhaust Manifold alone ? The reason I ask is a local mechanic (who's a pretty good one) told me that it's common for Exhaust Manifold Gaskets to fail. So I'm thinking of just pulling the whole thing out of there. Rick Ticket 85 SF Merc 454 MPI's Falmouth, MA

franklyprice · Post by **franklyprice** » Tue Sep 07, 2010 4:32 pm

Rick, I seem to remember you having a hell of a time getting those bolts off the last time. I would think that would be the main reason to do the gaskets now, exercise those bolts before they rust into the manifold. Otherwise I don't recall those gaskets going bad very often as long as the bolts are tight.

Rick · Post by **Rick** » Wed Sep 08, 2010 3:06 am

Thanks Frank, That's another good reason ! I used Stainless bolts with anti-seize this last time around, hope they come out a little easier. Rick Ticket 85 SF Merc 454 MPI's Falmouth, MA

CB35 · Post by **CB35** » Wed Sep 08, 2010 4:40 am

The anti-seize is ok; but stainless bolts? Man that is a big mistake. Stainless is way to soft. I really hope the anti-seize works or you are going to be drilling and cleaning threads. If anything use grade 8 bolts. Never had a grade 8 I could not remove.

Donmystic1 · Post by **Donmystic1** » Wed Sep 08, 2010 4:58 am

I just did mine two days ago but not to replace the gaskets which were fine. I needed to tighten the three inner bolts on the valve covers as I had a minor oil leak on those gaskets. Make sure that you screw in guides starting at bolts holes #2,5 and 7. let the manifold slide down the guide after you disconnect the water hoses. Then you are need an assortment of different length bolts to pull the manifold back to the block using the guides to line up the bolts holes in the block. I would also check your valve cover gaskets while you are at it.

sbeer · Post by **sbeer** » Wed Sep 08, 2010 6:11 am

Getting those bolts out can be a pita. What I did was dremal the heads off with a cutting wheel, slide the manifold down on the studs and use a pair of vise grips to pull the studs out of the head. There is nothing worst than having to drill out a broken bolt. Of course try and remove with the right tools first but usally the exhaust manifold bolts get frozen in place. Good luck, Mike

Rick · Post by **Rick** » Wed Sep 08, 2010 6:26 am

I've been there Mike and Capt'n Lobsta helped me big time. Charlie I really hope that the anti-seize worked ! I don't know what grade the bolts are but I bought them at a Merc dealer and they thought these were the cure for corroded bolts. One of those deals that sounded great at the time. So as soon as I get winterized in November I'll try to free all of them. Rick Ticket 85 SF Merc 454 MPI's Falmouth, MA

h2ojst · Post by **h2ojst** » Wed Sep 08, 2010 7:28 am

There are a couple of tricks that I have found that actually work on the manifold bolts. The first is to use hardened steel studs with stainless nuts and washers. The other trick is to cut the gaskets between the exhaust ports. This stops the water from collecting between the gasket & the head and corroding the heck out of everything. The studs make for easy assembly & dissassemby. I use copper coat spray on the gaskets. Just slide them on the studs & then slide the manifolds in place. Works great. Joe Tomaini 1988 Sportfish Attitude Adjustment II Fort Lauderdale, FL

Rick · Post by **Rick** » Wed Sep 08, 2010 11:17 am

Really interesting Joe, nice trick on the cutting of the gaskets. Do you free up the studs when changing the manifold ? Rick Ticket 85 SF Merc 454 MPI's Falmouth, MA

h2ojst · Post by **h2ojst** » Wed Sep 08, 2010 12:27 pm

I loctite (stud & bearing mount-red) the studs in place & then every now & then I spray CorrosionX on the nuts & various other steel parts & I've never had a problem removing anything. I swear by my CorrosionX. Joe Tomaini 1988 Sportfish Attitude Adjustment II Fort Lauderdale, FL

CB35 · Post by **CB35** » Thu Sep 09, 2010 4:54 am

Stainless steel bolts are all soft compared to high grade steel bolts. A grade 8 steel bolt has a yield strength of 130,000 psi. A 302 or 316 stainless steel bolt has a yield strength of 65,000 psi. Never oh no never use stainless bolts when you want something to stay in place. That is where high torque is required. Heads, manifolds, shaft couplings. I had a buddy once that had one of those plastic shaft savers let go during a shaft tournament. A local mechanic recommended he replace them with stainless bolts. Outside of using them for head bolts shaft couplings is probably the second worse place to use stainless steel. I do like the idea of grade 8 studs and ss nuts; but I have never had any trouble getting grade 8 bolts out of heads and manifolds.

Rick · Post by **Rick** » Thu Sep 09, 2010 6:50 am

I hope that they're grade 8....will you typically see a numer "8" on the bolt somewhere Charlie ? Rick Ticket 85 SF Merc 454 MPI's Falmouth, MA

CB35 · Post by **CB35** » Thu Sep 09, 2010 6:44 pm

No a steel bolt will have 6 dash marks on the bolt head. No ss bolt even comes close to grade 8 steel boats. Cheap Chinese bolts are really soft by the way.

h2ojst · Post by **h2ojst** » Fri Sep 10, 2010 5:06 am

Charlie, Check out arpbolts.com. I think you'd be very surprised how strong their stainless bolts and studs are. Over 170,000 psi, which is actually harder than a grade 8. This is the only company that machines their own bolts & then hardens them. I've used their SS head bolts & other goodies on my race & show engines & they are really tough. They're not cheap and you must use their anti-gaul lube when torqueing. These are obviously not your off the shelf stainless bolt, which, as you say, are way too soft for most anything on an engine except accessories. Joe Tomaini 1988 Sportfish Attitude Adjustment II Fort Lauderdale, FL

Rick · Post by **Rick** » Fri Sep 10, 2010 7:10 am

Very cool Joe, but now I don't have a clue what to use the next time around with the manifolds ! The problem with those steel bolts is that they rust....and rust quick. Once I pull the bolts I have out of there (if they come out), I'm going to get in touch with those headbolts.com guys are see what they say. Rick Ticket 85 SF Merc 454 MPI's Falmouth, MA