I am building a restoration big block engine with closed chamber heads, and have been advised to to chamfer the edge of the combustion chamber, the edge of the bore, and the sharp edges of the piston domes to reduce the chances of having hot spots there.

What do you all use to do this? A fine file? Emery cloth? Cratex wheels? Something else?

Thanks!

 

I haven't in iron yet but the process is the same. If this is your first time I would consider using hand tools vice power tools (air grinder or dremel).

If you had the bore machined just knock any flash off, but more than likely the process took care of it. if not use soem 80 grit sanding cloth. This area is very important to getting a good combustion and maintaining a seal with the top ring.

Same thing for the cylinder heads. Though I've used a dremel and air grinder, a sanding cloth will allow you to take your time and not get into trouble.

The piston I wouldn't use any thing other than sanding cloth. Dremel (with a de-burring or cutting tools) will auger into the Al as it will skip and make divits.

In these cases make sure you clean up. All the sand grit has a way of getting into everything.

 

As for iron chambers: Make an exact scribe from bore with the head mounted on the bare block. round and polish the chamber to fit the bore. on the quench side round the sharp edge to the chamber with hand sanding. This promotes flame travel to the far edge of the bore
. Before the valves are installed round and polish out the venturi above the valve seats. Use tulip valves like Manley race flows with the undercut stems. Have a head shop grind the seats to have minimal valve protruding into the chamber.

Then if you really want to do it take a pick punch and dimple the chamber like a golf ball around the intake side of the chamber. It is an old iron head trick to keep the fuel atomized because of the poor chamber shape

Aluminum x-fers heat so smoothing the edges is not a big deal because they will be covered with carbon/oil with deposit within a 1000 miles anyway

 

For use on the engine block bores, a "ridge reamer" is the tool to perform this function. It`s a rental tool in most parts houses. Necessary to cut the ridge to prevent breaking rings when replacing the pistons. Just a normal procedure when rebuilding blocks...

 

Go here and get the porting kit - it has all the rolls you need to clean up the chambers. Many of the low-end aftermarket heads can really benefit from a little chamber clean-up - just breaking the sharp edges will help. Note that the right way to do this is to get some junk valves to protect the seats and valves...you WILL slip, and you don't want to take out a brand new valve or seat.

http://www.sa-motorsports.com/

I'll respectfully (very respectfully) disagree with Gkull on approach - a head gasket will have a significantly larger opening (for example, SBC gaskets are typically 4.133) than the bore - the approach I'd recommend for marking the bore on the head is to assemble the head to the bare block and mark from below...this is one of those things that if you're going to do it - you'll be doing a lot of mock-up Generally I'd say that unless you're trying to make > 1.4 HP/CID your better off to just gently break any sharp edges and call it good. The dimple thing is new to me; I'm interested in more background. I generally figure if I don't see something like that in an aftermarket head, then I'm agnostic

With respect to Ironcross, a ridge reamer is NOT used to chamfer the bores. Every shop I know of will use a cone like these:

http://www.goodson.com/store/templat...6e31d1882c7e8e
http://www.goodson.com/store/templat...6e31d1882c7e8e

IMHO, you'd be best off to have the machine shop clean this stuff up for you - a slip of the Dremel and you're going to have a Bad Day. If your machine shop didn't chamfer the bores and break all the sharp edges (including doing a chamfer on head bolt holes) then they owe you a little work - it's mandatory IMHO.

 

'billa' is correct, but the ridge has to be removed to insure there is no issue getting the pistons back in. However the cone he expressed that is used in some shopa can bevel the bores. Actually if the block needed boring the boring machine could be used to do that proceedure too.

 

Ironcross, I agree - I read that the engine work was already complete and the block just needed the edge broken. Boring/honing would remove any ridge present.

For removing pistons, I also generally advise against using a ridge reamer. The pistons and rings are going to be replaced anyway, and a broken ring/piston is no big deal...but a ruined bore from an improperly used reamer is...and I see it all the time

 

I second that billa

I've seen a ton of blocks that were ruined by a shade treer with a k-mart ridge reamer

 

More commonly refered too as.'Do-it-Yourselfers"...

 

I'll admit to some confusion about this response...so let me lay out what I'm saying:

• There is no reason to use a ridge reamer to get used pistons out during teardown and a number of reasons not to.
• If the block is bored, there will be no ridge for reinstallation.
• If you are reinstalling pistons and there is a ridge, then you're making a mistake - the ridge is indicative of bore wear and the block needs to be bored.
• Finally, what we're talking about here is breaking the sharp edge of the bore after a block deck cut. This is always (always) done with the sanding cones I referenced. There is no way to do this with a boring machine.

 

Apparently you have never used a boring bar. It`s a simple proceedure to use the cutter to champer the tops of the bores as you finish boring the cylinder. Why screw around with sandpaper.

 

You can do it with the boring machine but why? It is faster with a cone and, if you are using a tapered ring installer (and you should), you only need a very small chamfer; just enough to break the edge.

Too large is just a waste of compression and most of the jobs I have seen done with a boring bar bit are way too deep.

 

OK, I generalized for a broad audience. I have never seen a Level 4 shop that does this. I have used a boring bar, thanks.

Why use sandpaper? Because it's quick, works and is dirt cheap.

Is it standard practice at your shop to do this?

 

Hit the end of the sparkplug hole also, it can be sharp around the edges and get hot. Watch the threads.