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I recently replaced the starter on my 87 F-250 w/460. In the process I had to take the header off to get the old one out and the new one in. Since I had one off already i decided to take the other off and replace both gaskets. When I went to put them back on i found that after I had put in the new gaskets and tightend all the bolts the headers still leaked and later found that the flanges werent even butted up against the head. The bolts are all as tight as they can go and i can't figure out why the headers wont seal.
its not the old gasket, I scraped it all off. and the bolts worked fine before. They do look like they could be warped but their fairly new and Still look ok.
Look at the header flange,my Douy Thorley header flange does not go up aganist the head.The tubes stick out just that much,but have a 1/4 machained? flat oval.They seal very good ,no leaks.
Need thicker gaskets?
Try torqueing the bolts from the center toward both ends, but if you have the headers off lay a straight edge accross them and see how much their warped. Ford's tolerance for their own manifolds is .010 inch-any more than that and they need replaned. If your careful, lay the headers accross a flat piece of glass and see how much gap you have all around. Are you sure they wern't leaking before you took them off? Sometimes it helps to chase the threads in the head with a tap to get rid of rust and crud and then use compressed air to blo em out. If your headers have the 3/8 flange it is fairly common for them to warp, which is why Banks uses 5/8. Another option that sometimes helps is to use new hardware.
I think ill take the bolts off and clean out the threads, checking the flange for straightness is a good idea but those things are impossible to get out.
For what it is worth, I managed to install exhaust gaskets on the wrong sides a while back. And can they go on upside down? Good luck and hope it is an easy fix. Alex
like aboss said make sure the gaskets aren't backwards, they only work one way, they go on either way but if wrong the leak pretty good.
I have to double up the gaskets to my hookers to seal at the flanges now they've been off a couple of times and the flange is warped now. only way it seals is to double up the gaskets on them.
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