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One Piece Manifold Gasket - K Series


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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 by Banjo
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I do recall once reading a post on here by Altezzaclub, quite a few years ago, where he came across this issue, & described it in great disgust !

If I can find it, I'll put the link here.  It was beautiful !   Almost as good as his  comment about the cow treading on his bonnet, or eating a K series engine.

It is a bummer of a design,  but once you've done this mod, with care, the issue is eliminated.  I'm sure it is exacerbated, in some instances, by some leaving the exhaust pipe support bracket off, which bolts onto the bellhousing, about where the starter motor sits. The omission, would create potential movement of the manifold flange.


I posted this for new timers to Rollas, & hopes it saves a few headaches for some.

Cheers Banjo

Edited by Banjo
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One of the difficult items to work on, in a K series motor is the starter motor, but with the manifolds off, it is easily accessible.  The starter motor can pose an issue like the manifold bolts, as the rear flange section of the starter motor, that the holding bolts screw into, is aluminium. Now the starter motor produces high torque, so you certainly want these bolts never to come loose, & if you are like me, you make sure you tighten them up well & truly.  Unfortunately, this can result is stripping the thread in the aluminium flange.  Now if the bottom mount thread strips, it is not really a great issue, as you just drill the thread section out, & fit a longer bolt, with washers & nuts on the accessible rear of the flange.  However, it is invariable the top thread that strips, & this technique cannot be used, so the only real option is to put in an oversized bolt & rethread it, which is a real pain, or another starter motor. 

While you've got the manifolds off, it is very easy to remove the starter motor & fit the same size manifold studs to the starter motor, just as I have described above with the head.  This results in the uninstalling & installing of the starter motor, never causing any damage to the aluminium threads on the starter motor.  Again, clean out the threads, & add some Locktite to the stud thread, & fit to the starter motor proper, as depicted below.




Use some nice flanged 10mm x 1.25 nuts, again with some Loctite, & you can rest assured, you won't have starter motor mount issues in the future.


Cheers Banjo 

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Nope Si.   Should have !  Last time I looked you said they were all gone. That was about 4 odd years ago.  Have you done a rerun of the copper ones, or intend to do one again ?


Cheers Banjo

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My bmw 6clr engine has a 2 piece exhaust gasket and a 3 (!!) Piece inlet gasket. But cross flow engine so somewhat acceptable. 

I spent a good few hrs cursing at the 2 piece setup on the 4k back in the day. I never did change to 1 piece but that looks like a superiour setup that is for sure.



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