Lapping piston rings
 

I was sorting thru old Car Craft magazines and I found an article from 1974 about Herman Chapman and a tool he built for lapping rings, using comet cleanser, and a piece of glass , does anyone still do this ?, or do todays rings not need this ?

Re: Lapping piston rings
 

Today, you just pay Total Seal $100.00 each for them to do it. The old way sounds much cheaper.

Re: Lapping piston rings
 

Any chance of scanning and posting the article? If not, what issue is it in? The old school tricks for stock eliminator are fascinating.

Rick Thomason
GTOMayhem

Re: Lapping piston rings
 

I remember a Hot Rod magazine article on Dave Boertmans 1969 Chevy Biscayne N/SA 350/255 engine. They went through the motor and how it was built, a very technical article. Quite honestly at that point it was hard for me too understand but it was a start. You don't find technical atricles like that today in car magazines anymore, "just order a crate motor" or call somebody (engine builder) seems to be the norm. Just my 2 cent.

Will Lamprecht 65 Impala I/SA

Re: Lapping piston rings
 

My understanding is that rings are "lapped in" during the manufacturing process. The rings are mounted on a mandrel/fixture and "stroked" through a hardened liner/cylinder.

My experience shows that cylinder wall finish, hone finish, is a vital key to a good seal.

Also, precision piston ring grooves are vital.

Re: Lapping piston rings
 

Herman showed me his lapping setup. It was a piece of aluminum round stock that had a recess machined into it that was .061 deep for 1/16" (0.625) rings. When he ordered the pistons for Super Stock motors (BRC, generally...some Venolias), he spec'd the ring grooves at .061. The ring would go into the aluminum holder and he put some Comet mixed with parts cleaner solvent on a big piece of thick plate glass and rubbed the fixture in a circular pattern, checking the fit of the ring to the groove as he went.He had the same holder for the .043 rings..probably some others as well.

On the Stocker pistons with the 5/64 grooves, he would tighten up the ring lands by lightly dimpling them with a small punch and lap the rings to the now-tighter grooves.

With the advent of CNC equipment, the need for a lot of this is gone.

Anyway, that's how I remember the process.

Re: Lapping piston rings
 

Good point, Will. Many people are so overwhelmed with the technical part of building engines that they believe that the "high tech" referenced in marketing of services and products is the only source of a competitive engine. So the vast majority of racers "buy" the work and the parts, and the expense goes up (again!). Or people get discouraged because of the cost to the point that they do not participate. Then the sources of information go away since demand diminishes and people do not want to jeopardize their livelihood.


If you can change your mindset to be satisfied with "competitive" not "ET killer", that is the first step to having the inspiration to do your own engine work. After a few serious builds and intense striving for information and skill, it is amazing how much you understand. You then have a reference base of knowledge that helps you to glean more information from everything you read, even advertisements.


Another good article to read is the one about Wade Owens 283 engine:http://www.hotrod.com/how-to/engine/...tor-283-chevy/


I personally want to encourage you. I follow your threads and posts and I sense that you are doing so many things right. Keep it up and never be shy to ask questions.


In reference to the lapping of piston rings, there is some benefit to that. Some companies offered the tools for sale if I remember correctly. The additional piece of understand that needs to go with that is that as you lap the rings, you take material off and so the ring gets thinner. Then the clearance increases for the ring land and sealing efficiency sealing suffers. It is the same effect as wear from running the engine. So, you either start with a thicker ring, or you narrow the ring land. In old days, we would press the piston top to compress the top ring land (not too cool) or machine the piston for some items called "ring land restorers" (looked like radial spacers that fit into a specially machined groove at the top or bottom of the ring land and were made of some hard spring steel). Sealed Power/Speed Pro sold the spacers and a specially shaped tool to fit a lathe. It worked okay and was even legal in Stock eliminator with OEM pistons. Today, I might be inclined to order my pistons with thinner ring lands.


Dwight Southerland

Re: Lapping piston rings
 

The article on Scott burton's car in high performance Pontiac is another good one.
I made a couple of chapman's ring tools years ago and still use them. all rings have a torsional twist as they are compressed into the bore. Chapman's lapping process "seated" the bottom of the ring and made it flat.
I used perfect circle's manulathe years ago to save worn piston grooves. A simple device that worked very well. Ron.

Re: Lapping piston rings
 

The magazines forget there is a new 16 year old guy "born every minute" . They haven't seen the articles of the 1960's on good engine building or blue printing etc.
A new article would also serve to increase the interest of younger guys as they could actually learn and become more interested in the technology of Drag Racing.
Car Craft, Super Stock Magazines also covered these topics and today there is only one Hot Rod. Unfortunately by popularizing bizarre paint, or factory topics basics is being lost to the general public.

Re: Lapping piston rings
 

Car Craft November 1974, I will try to scan it