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Does anyone know what the specs are for the valve guide clearance on the 21 HP Intek (331877 0939 B1)? It is from a Craftsman Rider about 6-7 years old. I have not put a dial indicator on them yet but they are pretty loose!! I was burning oil BAD before I decided to rebuild. I believe the head gasket was blown between the piston and pushrod chamber so this may be where the majority of the oil was getting into the combustion chamber. Do people knurl the guides to tighten them up? I know that is what we did 30 years ago in high school when rebuilding an engine.

Thanks!

Jeff

Ben a long time since you were in high school I would guess.
Knurl the piston, knurl the valve stem ( not easy ) but knurling a guide would only be done if the guide was slipping in the head.

Inteks have a fubdamental faw in the design ( copied off the Vanguard when better materials were used ) where thers is insufficient clamping pressure on the head gasket between the pot & push rod tunnel.
I have never needed to touch the valves save fitting a new seal on the inlet.
However I always have to touch up the head which you will find has gone hollow at the bridge between the pot & tunnel.
Really annoying, and extra .020" thickness on the head would have added enough stiffness to fix this but B & S ignored this problem & continue to do so.

This manual might help you out.

https://doc-0o-5o-docs.googleuserco...253/*/0B6NaqjIxWV1ySkZjTTA5TGltZEE?e=download

Bertsmobile1, How do you "touch up the head"? I am almost sure my head gasket was blown there!

Jeff

jmartin99 said:

Bertsmobile1, How do you "touch up the head"? I am almost sure my head gasket was blown there!

Jeff

Click to expand...

You check it very carefullt with a strait edge .
Usually they go hollow at the bridge between the pot & tunnel so you have to lap the head to get it flat.
A couple of sheets of wet & dry on a sheet of glass wit the hose running on the water slowly to was away the cut debris.
Gentle circular motion till all the surface that the gasket sits on is the same colour.
Otherwise it will blow the new gasket in no time flat.

My 24 hp Intek . Cannot buy valve guides only complete heads. Poor man's straight edge-your table saw machined surface. Look for a "light band" or ""rocking"if the head is warped. I once levelled a set of header flanges with a long Sears file. A new sharp one is also the poor man's surface mill. Use blue marker pen accross the head surface and stroke one way. Keep cleaning the swarf (aluminum filings) from the file teeth. A .001" feeler should not fit when done. Good luck.

Wet or Dry Paper on Plate Glass is the best way to assure flat. level as said above.

Walt Conner

What grit sand paper do you recommend?

Thanks!

Jeff

jmartin99 said:

What grit sand paper do you recommend?

Thanks!

Jeff

Click to expand...

Start with 400 then go to 600 to polish as surface appears true.

Walt Conner

Walt, Won't such fine paper load up terribly . Also the surface finish on an aluminum head to mate to a head gasket is not polished. Sounds good for a chisel. Just sayin'...

motoman said:

Walt, Won't such fine paper load up terribly . Also the surface finish on an aluminum head to mate to a head gasket is not polished. Sounds good for a chisel. Just sayin'...

Click to expand...

Yes it will which is why you do it near a tap with a hose drizzling water onto the paper and lift the paper regularly to was it and the face you are truing.
I use 240 then 320, mainly because I have 5000 sheets of 320 zinc sterate paper ( plasterers paper ) Bought at clearing sale for about 5c / sheet.

600 is probably a bit fine.
The shop I get some parts from uses a fly cutter in a mill.
They do so many of them they made a jig.
Odd, some never give a peep of head gasket problems while others it is almost seasonal maintenance.

Berts, To clarify for newbie home mechanics. The water dribbling clears the "swarf" (metal grains) from the abrasive paper so that it can continue to cut. Need your opinion on warped heads...are they typically softened and therefore likely unlikely to hold valve seats and guides tight? motoman

motoman said:

Berts, To clarify for newbie home mechanics. The water dribbling clears the "swarf" (metal grains) from the abrasive paper so that it can continue to cut. Need your opinion on warped heads...are they typically softened and therefore likely unlikely to hold valve seats and guides tight? motoman

Click to expand...

Haven't seen any warped heads and if I did it would be a no brainer replacement .
They erode &/or distort at the bridge.

If you want a ten page thesis on why this happens pm me & I will ( eventually ) get back to you.
Basically it is bad design allowing the alloy to flow upwards between the two bolts on the push rod tunnel which could have been fixed easily but wasn't for some pig headed reason probably made at board room level.
The fact that some do & some don't is most likely due to subtle differences in the chemical composition of the alloy which will vary a little from batch to batch and within an actual pour as silicon in particular burns out of the metal.
This has led to all sorts of myths like inteks on Toros are better than Inteks on AYP's but it is most likely a random selection as to which engines got what heads from which pours & at what time in the pour and even what alloy had been in the furnace immediatly prior to the heads.
Aluminium silicon alloys used in cast heads on air cooled engines actually harden with age.
In order to softem the head would need to be solution heat treated which means getting up to around the 300-400 deg C mark and staying there for a long time.
The Aluminum - Silicon- Copper - Manganese -Iron alloys used in die cast water cooled car heads is a different matter.

While some spots on the head can ge quite hot momentarily the heat is conducted away very quickly so very rarely gets above a critical level.
People who do not understand heat flow through metals see combusion temperatures and tables of heat treatment temperatures and jump to totally wrong conclusions.

I liken it to welding.
The temperature of an oxyflame is around the 2000 deg C mark.
Aluminium melts at around 700 deg.
So why does the entire head not melt when you weld ?
Because heat gets conducted away which is why you need to preheat aluminium to oxy weld it properly.
For the exact opposite reason you also have to preheat cast iron before you weld it or it will crack.