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Navigator Engine Rebuild

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Can anybody Help. I am rebuilding a Navigator engine and would like to know what is the gap between the barrel and the cylinder heads i.e. spigot height as the heads have been skimmed and at the moment there is a big gap many thanks.

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hello  well there should no gap between barrel surface top and the mating surface of the two-cylinder heads   and the copper gasket I use Heldite gasket sealer  it works well  no leaks  and a good seal  and it comes with a small brush to apply  in the bottle screw top  look on eBay for heldite  gasket compounds  come in 400ml tins  with a screw top,  and you can use Heldite without any gaskets  but all surfaces must be very clean   

             yours   anna j 

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Hi Duncan, the Navigator and Jubilee originally had spigots on the top of the barrels which fitted into grooves machined in the heads.   At some point in 1964 the spigots were removed from the barrels and the heads machined to suit without the spigots.  If I understand your description I am guessing you have a later set of heads and an earlier set of barrels which I suspect wouldn't be compatable without machining.    If you send us photos of both it would help the diagnosis!   Nick   

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Hi Duncan,

I agree with Nick. You perhaps have a late Navigator head (just skimmed) and an earlier barrel assembly. You need to get a later barrel which is about the same height as the old barrel plus spigot height. 

As a young man with an exploded 1965 Navigator I went to Taylor Matterson in London for spares. On the counter were 'bargain' Navigator barrel and piston assemblies for £15.00 (It was worth something then). Back home I observed the bargain barrels had a spigot at the top. The originals did not. A trip to a machine shop soon had the spigots flush with the top of the barrels.

But now the pistons stuck out of the top of the barrels at TDC. The head sat about 2mm lower than it had done before. The pushrods were now too long. The headsteady wouldn't fit. The pistons hit the head.

So, the hard way, I discovered the late Navigator had a taller barrel with no upper spigot, and a reduced height cylinder with no spigot location feature.

Faced with this problem today, and with a lot more experience, I might consider making an alloy plate, same thickness as the height of top spigot, and same shape as cylinder base gasket. Added below cylinder it will lift the barrel but will play murder with the geometry and support of the cam followers.

You can't mix old and new. The later Navigator parts are much rarer than earlier parts. This may suggest your best course of action is to find a pair of early heads.

Peter

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The difference is 2mm. The spigots were 2mm tall - & they WERE NOT removed. The barrels were always 2mm taller, and then the spigots were machined down from the top.

At some point in 1963/64, it was decided to stop cutting out these spigots (initially on the Electra) and thus to maintain compression & rocker geometry, 2 mm had to be removed from the head.

You cannot mix the two types - except with the help of a 2mm spacer on top of an (early) spigotted barrel, & a later milled head. Very messy.

 

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