How to Install Piston Rings in a Relieved Block

[Chuck Kuntz]

I've installed a lot of rings in flatheads but never in a relieved block before. What is the secret? Standard band type compressor won't work. I suppose I could chamfer the top of the cylinder to make it easier but would rather not. This is a factory relief. Thanks for any help on this.
Chuck

[Mart]

I just use a normal compressor. Mine is thin enough to go down the bore enough in that area. Just take extra care and watch that area like a hawk.

Mart.

[Bored&Stroked]

I use a normal "band type" ring compressor - and I align the ring gaps to NOT be in the relieved area. Also, you will see that sometimes a ring wants to pop-out a bit and hang up on the edge of the relief. This is common!

Do not just try to force it - as you'll probably break a ring. What I use is a wooden paint stir stick - and with a small rubber hammer I tap on the stick (which is placed where the ring is popping out) and push the ring back in. I then continue to use the rubber handled end of my 2 lb hammer to tap on the top of the piston and watch and the rings slide by the relief.

Also, prior to assembly (during porting/relief operations), I put a small radius on the edge of the relief - this helps to reduce the ring hang-up and also reduces the amount of cuts and scrapes to my dang hands!

Here are some pictures and babble from a recent build:

Relief-PushingOilringBack copy.jpg

Relief-OilRingIssues copy.jpg

[JWL]

The method I used for many years was to modify my ring compressor to follow the contour of the block. It doesn't have to be a perfect fit, just close enough to prevent ring hangups.

[Ronnie]

Easy fix x 2 ^^^


R

[Chuck Kuntz]

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I got them installed but a paint stick was too thick. I ground a slight radius on a thick bladed screw driver tip and that worked well. Three piece bottom oil ring was the only challenge. Never too old to learn something new. Thanks to all that responded.
Chuck

[supereal]

Be sure that the top piston ring is not exposed at top dead center. This is due to an overzealous attempt to "relieve" the block. Last year a customer brought in a very nice T Bird he bought on line. It wouldn't run well, so we pulled the heads. At the top of the stroke, the whole side of the ring was exposed in the place where the block was ground down! Porting and relieving was popular among hot rodders years ago, but for street use they were misplaced.

[Pete]

Besides JWL's method which will work on any bore size, you can make a dedicated compressor from a piece of cylinder sleeve the SAME ID AS THE ENGINE BORE. You fit the bottom edge exactly to the relief and taper the inside.
The advantage of this type is, there is no tendency for the compressor to slide down the bore and pinch a ring.

The top ring should end up at least .200 below the edge of the relief.

[frnkeore]

Originally Posted by Pete

The top ring should end up at least .200 below the edge of the relief.

That would mean custom pistons only, for relieved blocks? My factory Ford pistons, have the first ring at .250, below the edge of the crown.

[Pete]

Originally Posted by frnkeore

That would mean custom pistons only, for relieved blocks? My factory Ford pistons, have the first ring at .250, below the edge of the crown.

I wouldn't put a cast piston in a demo motor driven by an electric motor.