Banjo Posted September 17, 2018 Report Share Posted September 17, 2018 (edited) While waiting for some paint to dry at the weekend, I thought I'd better replace the manifold gasket on my 5K engine, currently on the engine stand, for my distributorless project. I've not had this engine apart before, but like almost everyone who has worked on a K series engine, I know this is a weak point in the design. So off with the manifold, & "sure as eggs", those tell tale black sooty marks on the head facing, at the centre, indicate it has been blowing by. Twenty minutes with a sharp knife edge & a soft wire rotary wheel, on the hand drill, & the result looked like this. Now most; if not all K Series engines, were fitted with manifold "bolts", to tighten the manifold to the head. These are well known for coming loose. Most people tighten them up a couple of times a year. However, as the steel bolt, is screwing into an aluminium head, and that head becomes "softer" over the years, the danger of stripping the threaded holes in the head, becomes more likely. For that reason, I always replace the bolts with steel manifold studs, which results in the steel stud only ever being screwed into the head once. The manifold studs are a generic stud 10mm dia. x 1.25 by 40-41mm long. I saw some of these exact size, on a rack in an auto store, labelled as suitable for a Gemini. Available pretty much anywhere. I picked up a set, complete with nuts for under $ 20. Clean the threads out in the head, with a final tap, or an old 10mm x 1.25mm bolt with a hacksaw cut down the length of one side. Put a bit of Loctite, or similar, on the thread, and screw into the head. If it is a bit tight, & you haven't got a stud remover/insertion tool, then two (2) nuts, tightened back to back, on the outer end of the stud, will do the trick. Your head should then look like this. The original Toyota two (2) piece gasket is not the way to go. This is what, they look like. The one (1) piece gasket is thicker & better made for this arduous application, and are made by several gasket manufacturers, like Durapro, Permatex etc. They are often described as an "extractor gasket". All have the identication EMS30 in their part number somewhere. The current price is around the $20 mark +/- a $ 1 or so. It will be the best $ 20 investment you do for your K Series engine. The manifold nuts are most commonly, deep, heavy duty, & of brass construction, so they don't bind & rust onto the manifold threaded steel studs, with all that intense heat. Before you refit the manifolds, run a straight edge across their mating faces, & make sure the mating surfaces of both manifolds have no air gaps between manifold & the straight edge. (A 200mm S.S. ruler is usually pretty good tool for this application) You will also need some heavy very thick washers, with a 10mm hole, to clamp across the gaps between the aluminium inlet manifold, & cast steel exhaust manifold. Do not fit the manifold without these, or be tempted to use ordinary washers. If you do have issues sourcing some, you could always recover the capitive washers, fitted to the bolts you removed, or I think once, I used some head bolt washers, which were the correct size, which were really nice & thick. Once you refit the manifold & tighten them up, run the engine until it reaches operating temperature, then after it has cooled down a bit, retighten them. Some people like to put a bit of loctite on the outer thread for the nuts, but I've never found it necessary to do this. Retighten the nuts after a week or so, & you should never have another manifold gasket issue. Cheers Banjo Edited April 19 by Banjo 2 Quote Link to comment Share on other sites More sharing options...
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