Ridge Reamer?

[meadowbrook]

Hi, my 50 Meadowbrook’s original engine broke piston number 4 and since oil pressure has been excellent and a measurement of the cylinder bores and visual inspection shows I can still use standard size pistons and the walls are glass smooth, I am only honing and replacing pistons and rings.

I was able to remove the pistons by unbolting the bearing caps, removing the head and pushing the rods up. 
 

There was some resistance to pushing the piston up but they came out. I’m assuming there is a minimal if any ridge , and only carbon buildup there.

 

Is there a measurement to determine the need of a ridge reamer?

 

Any brand of pistons to avoid? Napa provides them .

[Sniper]

there is an argument against using ridge reamers.  Aggressive use of one can necessitate a bore job instead.

 

If it's just carbon clean it out with something less aggressive.

 

If there is indeed a metal ridge there you will need to remove it or the possibility of the new rings hitting it and cracking exists, just be careful not to cut too far.

[Loren]

Generally you use a ridge reamer BEFORE you take the pistons out.

The so called ridge is the place in the bore where the rings start and stop.

The top ring gets rounded on its edge and as it rocks in the bore it wears the "ring lands" (or grooves) in the piston. This causes them to recede in the bore a little. The results are that a groove in the bore forms. When you go to remove the pistons the rings hit that ridge (I have heard them called "cylinder ledges" as well) and they break the rings when forced.

Needless to say you might want to change the pistons if that has happened. If you change pistons you might as well bore the block. A caution: some machine shops will bore a block to pistons they have on hand....not what is required....so suddenly an engine that needs a .010 overbore gets a .060 overbore. I've taken to supplying the pistons rather than buying them from the machine shop thereby removing that temptation. But you have to have the means to accurately measure the block to guess what size you need.

The idea behind removing the ridges (besides getting the pistons out safely) is to remove the "dull" radius worn area which will encounter the new sharp piston ring thus breaking it on the first rotation of the engine. The problem is as I see it that unless you are real careful and have a good sharp reamer the area you're working on is the place in the bore that sees the maximum pressure. Not done perfectly and you will lose a lot of pressure to blow by.

If you're doing a "used car lot" rebuild, go ahead on. If you plan on keeping the car then do a real rebuild with properly fitted pistons. A ring and valve job is not a rebuild, it is a kind repair as the engine still has old worn cylinder bores and certainly doesn't have the compression of a new engine.

Just my humble opinion.