Replace Both head gaskets?
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Replace Both head gaskets?
My '86 351W developed a spark knock on the passanger side. The number 6 and 7 pistons had 25# compression. Upon pulling the head, the head gasket between those two pistons had burned out, causing spark knock and excessive power loss. I have the passanger side striped down. Should I replace the other head gasket as well? The exhaust manifold came apart on the pass. side and I'm afraid to bust up the other one too. Exhaust manifolds run 100$ a side around here. One other thing about the head, Should I have the machine shop mill down the head? It is cast iron not aluminum. I know its important to machine aluminum heads but cast iron too? It looks like its in good shape if I lay a scale on edge and check for flatness.
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From: Destin/Ft. Walton Beach,
You most likely know this, but yes, do replace both head gaskets. You'll kick yourself in the **** if it goes out on you later. If your exhaust manifold breaks from you simply removing it, don't you think that you needed a new one anyway? You can check your head if you have a precision straight edge. Not a framing square or whatever. Put the straight edge against the head in several places, and try to slide a small feeler gauge between the two. If you don't have these tools, I would take both heads to be checked at a machine shop. I've learned my lessons the hard way. Trying to save a little time or money now by not doing it the right way, usually ends up costing you much more time and money in the future.
Last edited by stevef100s; Mar 27, 2005 at 10:49 AM.
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Thanks for the advise. The other head comes off tommorrow, regardless of exhaust manifold risks. I used a small 6" Starrett machinist scale and the feeller gauge won't go in. Thinking the head is in good shape. Your righ about doing it right the first time. Pay me know or pay me more later. It's like having the patience to wait overnight for the penetrating oil to work in and try it in the morning. At 30 I'm still learning the hard way.
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Whats the dope on torqueing the head gaskets. The Chilton specifies three torques increments up to 112ft/#s. Do I need to run the engine then check to torque again? I'm getting conflicting info from my old man and the manual? What a pain to retoque a 351. Exhaust manifold and valve cover gaskets come off again?
