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Dan693

Big Twin Head Sanding and Tappet Needed

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Dan693

I'm rebuilding a K-482 twin and wondering if it's a good idea to wet sand the heads before re-assembling.

They don't appear to be warped but are 40+ years old so I thought about wet sanding them with some emery paper on a pane of glass.

Not too much just enough to get the gasket surface nice and shiny.

 

Also looking for a valve tappet for the 482. Part of the skirt is broken off on one of them which makes me a little nervous about what damage it did inside the engine.

A few chips of it in the oil pan so I'm hoping no big damage.

 

Thoughts?

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KC9KAS

I think I used some 600 grit wet sanding paper to make sure one of my heads were nice & flat.

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The Tuul Crib

 I would. Put the  600 grit on a perfectly flat surface maybe  some thick glass and wet it down very well. Then take the head and do a circular motion. Repeat as needed until   Surface looks clean .

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Marv

I always do. 

Marv

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Dan693

Nice advise gentlemen. That's why I come here.

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Sarge

One of the best investments I ever did in tools was to buy a used machinist's straight edge for checking heads and block decks, intake manifolds, etc. Tolerance of less than .0002" total on it's 24" length makes for some truly flat work. I also had bought a very heavy 7075 aluminum drop that is 2-1/2"x5"x20"L and had it surface ground to .0003" tolerance - that is my flattening platen on the bench and been using it the last 20yrs. I also picked up some flat gauges that go down to .0005" for re-checking my work after flattening a cylinder head. When I built custom Weber carb work/manifold adapters/plates and did intake flow work all this stuff was necessary - really pays off now as I can use it for other things such as working on these small engines. 

 

The point? Not all pieces of glass are truly flat - find a thick (at least 3/8"), tempered table top or door off a piece of furniture and take it to a machine shop. Keep it under 24" square and it should be rigid enough to hold it's shape, smaller, of course, is always better. If you ask nicely, most machinists will check a surface while you wait - but it has to be a rigid piece or you are wasting their time. Might get surprised, I've seen a lot of pieces that are off nearly .010" in less than 18" square, not good. Most small engine head tolerances are .003-.005" maximum, so that doesn't work. Glass is not always flat, folks - you must check your work when done cutting the surface back to spec. Simple 18" machinist's grade straight edges are not that expensive, might want to invest into one. Also, for a truly and amazingly cheap flat surface to work with - check into getting a granite surface plate - once in a while industrial suppliers will have free shipping sales, 18" square surface plates can be had very cheap and it's always the shipping that is a killer.

 

As a great, occasional surface flattening plate - either one is an excellent size to get a diy'er started

 

granite surface plate

granite surface plate #2

 

machinist straight edge

 

Getting a cylinder head within a tolerance of .003" across a typical 8"-10" length is not all that easy. Yes, most glass is pretty "flat" - but it's not as flat as one would think. Many engine shops now have gone to surface grinding belt machines to accommodate cylinder heads due to a much easier design versus surface grinders and time-consuming setup procedures. Basically, these are a very precision belt sander. For those shops, cutting a small engine cylinder head is a treat compared to man-handling a 125lb diesel head - so they will do them quickly and pretty cheap too. Don't ignore a local engine shop - doing small jobs is something these guys don't mind - it's a quick buck and gives them a break from the more tedious stuff.

 

Sarge

 

 

 

 

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Dan693

Thanks for that info. I thought where can I get a granite flat surface and how much?

I have a habit of getting a hundred bucks too death.

Lucky I have a good machine shop and may just have them do the heads.

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953 nut
10 hours ago, Dan693 said:

where can I get a granite flat surface and how much?

Just go to any cabinet shop or counter top shop. They have sink cutouts stacked up all around the place that you can get for little or nothing.

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