Low compression

[garncarz]

I recently performed a compression test on my CA78. The results were suboptimal: While warm 89 psi on the right and 94 on the left cylinder. The valves passed a basic leak test (filled the head with water and blew compressed air through the ports.) My question is: without a bore micrometer, how do I tell whether I need to replace just stock sized rings or that an overbore, bigger rings and bigger pistons are in order?

Thanks.

[G-Man]

1) You can use a new piston ring placed at various places in the bore and measure the gap between the ends.

The bottom of the bore wears least, the top most. Comparing top with bottom indicates wear.

2) Alternatively, measure the clearance between the piston skirt at the top and bottom with a feeler gauge. You must do this with the lower part of the skirt as the piston is tapered toward the top. Same comparison as above.

3) take the cylinder barrel it to a good machine shop and get them to measure it for you.

G

I recently performed a compression test on my CA78. The results were suboptimal: While warm 89 psi on the right and 94 on the left cylinder. The valves passed a basic leak test (filled the head with water and blew compressed air through the ports.) My question is: without a bore micrometer, how do I tell whether I need to replace just stock sized rings or that an overbore, bigger rings and bigger pistons are in order?

Thanks.

[garncarz]

thank you.

[garncarz]

I am looking for a good machine shop in the Central PA area that can hone the cylinders and reseat the valves. I figure that while I have the cylinders off I might as well get the valves looked at, too.

Also, does anyone have the appropriate part number for stock size rings for this '66 CA-78?

Thanks in advance.

[LOUD MOUSE]

13012-275-000 ............lm

I am looking for a good machine shop in the Central PA area that can hone the cylinders and reseat the valves. I figure that while I have the cylinders off I might as well get the valves looked at, too.

Also, does anyone have the appropriate part number for stock size rings for this '66 CA-78?

Thanks in advance.

[LOUD MOUSE]

What do you expect with reset the valves?. ......................lm

I am looking for a good machine shop in the Central PA area that can hone the cylinders and reseat the valves. I figure that while I have the cylinders off I might as well get the valves looked at, too.

Also, does anyone have the appropriate part number for stock size rings for this '66 CA-78?

Thanks in advance.

[garncarz]

Hi Ed,

With respect to the valves, I want to be sure they seat correctly and the guides are in good shape. If not, repair/replace. Thanks for the ring part number.